1 00:00:04,370 --> 00:00:02,090 okay welcome everyone again to the 2 00:00:07,610 --> 00:00:04,380 University of Washington astrobiology 3 00:00:09,830 --> 00:00:07,620 programs fall seminar series today's 4 00:00:12,950 --> 00:00:09,840 speaker is a saurian Abbott from the 5 00:00:16,519 --> 00:00:12,960 University of Chicago joining out his 6 00:00:19,310 --> 00:00:16,529 PhD in 2008 is that right from Harvard 7 00:00:21,560 --> 00:00:19,320 spent a year there as a postdoc and then 8 00:00:24,349 --> 00:00:21,570 went to use Chicago is a TC Chamberlain 9 00:00:28,370 --> 00:00:24,359 postdoctoral fellow and after two years 10 00:00:31,189 --> 00:00:28,380 as a postdoc there became faculty and so 11 00:00:33,440 --> 00:00:31,199 now he is an assistant professor so 12 00:00:35,479 --> 00:00:33,450 Dorian's going to speak for about 50 13 00:00:38,049 --> 00:00:35,489 minutes or so then we'll take questions 14 00:00:40,819 --> 00:00:38,059 from the audience both near and far 15 00:00:42,410 --> 00:00:40,829 whoever's in there remote you can type 16 00:00:44,779 --> 00:00:42,420 your questions into the Adobe Connect 17 00:00:46,760 --> 00:00:44,789 chat room and we'll read those the crowd 18 00:00:48,950 --> 00:00:46,770 that's here and today's a little bit 19 00:00:51,680 --> 00:00:48,960 special and easy and pretty sharp at 20 00:00:54,200 --> 00:00:51,690 four because I'll more shields general 21 00:00:55,970 --> 00:00:54,210 exam is immediately following this event 22 00:00:57,979 --> 00:00:55,980 in the same room so I also hope that you 23 00:00:59,900 --> 00:00:57,989 all will say and listen to Omaha talk 24 00:01:01,939 --> 00:00:59,910 about the runaway greenhouse okay take 25 00:01:05,990 --> 00:01:01,949 the blade Orion okay thank you for 26 00:01:09,530 --> 00:01:06,000 coming nice to be standing oh no it just 27 00:01:11,870 --> 00:01:09,540 rotated really so if you have a question 28 00:01:13,880 --> 00:01:11,880 please interrupt me well I'm going 29 00:01:16,160 --> 00:01:13,890 because we might run out of time at the 30 00:01:18,350 --> 00:01:16,170 end I'll try to end early but I feel 31 00:01:20,480 --> 00:01:18,360 free to interrupt so I can be talking 32 00:01:23,600 --> 00:01:20,490 about alleble zone and you've got this 33 00:01:26,240 --> 00:01:23,610 is a picture of alleble zone based on 34 00:01:29,690 --> 00:01:26,250 serve classic casting concept and so 35 00:01:32,300 --> 00:01:29,700 this is different masses of stars star 36 00:01:34,910 --> 00:01:32,310 likes on less massive and this is 37 00:01:37,069 --> 00:01:34,920 distance from the star and the happy 38 00:01:39,170 --> 00:01:37,079 blue area is habitable zone where you 39 00:01:41,450 --> 00:01:39,180 can sustain liquid water at the surface 40 00:01:43,850 --> 00:01:41,460 and at the inner edge in Apple's own is 41 00:01:47,030 --> 00:01:43,860 moist free house or runaway greenhouse 42 00:01:50,389 --> 00:01:47,040 depending and at the outer edge you have 43 00:01:51,889 --> 00:01:50,399 either co2 compensation or increase in 44 00:01:54,289 --> 00:01:51,899 rayleigh scattering due to co tube so 45 00:01:56,780 --> 00:01:54,299 that you too can no longer cause warming 46 00:02:00,319 --> 00:01:56,790 and the assumption is that anywhere in 47 00:02:01,940 --> 00:02:00,329 here if you move the planet out further 48 00:02:04,700 --> 00:02:01,950 from the Sun and it wants to cool down 49 00:02:06,770 --> 00:02:04,710 at the co2 will adjust through silicate 50 00:02:08,869 --> 00:02:06,780 weathering feedback continental feedback 51 00:02:10,490 --> 00:02:08,879 and get as high as it needs to be keep 52 00:02:12,710 --> 00:02:10,500 you in the Hubble so that's consumption 53 00:02:13,730 --> 00:02:12,720 and that's important because if you 54 00:02:16,040 --> 00:02:13,740 don't include that 55 00:02:18,340 --> 00:02:16,050 Chemical feedback and so it's not 56 00:02:21,950 --> 00:02:18,350 included in this early paper by harsh 57 00:02:23,450 --> 00:02:21,960 what you find is a bubble zone if you 58 00:02:26,030 --> 00:02:23,460 don't include that feedback but you do 59 00:02:29,540 --> 00:02:26,040 include the positive feedbacks of ISIL 60 00:02:31,070 --> 00:02:29,550 veto and moisture a green ops feedback 61 00:02:32,990 --> 00:02:31,080 just an increase in moisture and wear 62 00:02:37,790 --> 00:02:33,000 green owes you get a habitable zone 63 00:02:40,430 --> 00:02:37,800 that's something like maybe point 05 64 00:02:42,950 --> 00:02:40,440 2.18 use so something like an order of 65 00:02:45,140 --> 00:02:42,960 magnitude smaller ten times smaller so 66 00:02:47,690 --> 00:02:45,150 this why Abbott was own depends on 67 00:02:49,250 --> 00:02:47,700 silicate whether it came back and what 68 00:02:51,170 --> 00:02:49,260 I'm interested in and when we talk about 69 00:02:54,560 --> 00:02:51,180 today is what if you start changing the 70 00:02:56,930 --> 00:02:54,570 land fraction of the planet what can we 71 00:02:58,970 --> 00:02:56,940 say just adjust in general terms about 72 00:03:01,550 --> 00:02:58,980 what that's going to do the habitable 73 00:03:03,230 --> 00:03:01,560 zone and there are a lot of 74 00:03:05,660 --> 00:03:03,240 uncertainties a lot of like and drink 75 00:03:06,770 --> 00:03:05,670 Martin's aspects and this problem so 76 00:03:08,480 --> 00:03:06,780 what I'm going to do is I'm going to try 77 00:03:12,710 --> 00:03:08,490 to state the assumptions that I'm making 78 00:03:13,880 --> 00:03:12,720 and see where they need it may turn out 79 00:03:15,050 --> 00:03:13,890 that some of those assumptions are 80 00:03:17,900 --> 00:03:15,060 correct and some of the things that are 81 00:03:20,870 --> 00:03:17,910 based on those assumptions what won't be 82 00:03:23,000 --> 00:03:20,880 correct but I think the appropriate way 83 00:03:25,220 --> 00:03:23,010 to proceed when you have a problem that 84 00:03:27,020 --> 00:03:25,230 time constrained at least you can do is 85 00:03:29,750 --> 00:03:27,030 say what you're assuming and see where 86 00:03:32,630 --> 00:03:29,760 that takes you and the co-authors are 87 00:03:36,530 --> 00:03:32,640 Nick Cowan was one of yours for a few 88 00:03:39,920 --> 00:03:36,540 years ago yes that's five year mostafa 89 00:03:44,990 --> 00:03:39,930 northwestern and Francesca who 90 00:03:45,980 --> 00:03:45,000 is on faculty receive Chicago okay so 91 00:03:48,710 --> 00:03:45,990 this is just sort of an outline of 92 00:03:51,580 --> 00:03:48,720 loading the Ajanta low first just 93 00:03:54,350 --> 00:03:51,590 introduction to weathering and 94 00:03:56,960 --> 00:03:54,360 weathering the cabinet on continental at 95 00:04:02,930 --> 00:03:56,970 the sea floor then this is the meat of 96 00:04:07,520 --> 00:04:02,940 the top do you know why that happened 97 00:04:13,580 --> 00:04:07,530 tie it didn't like gross oh how we need 98 00:04:15,590 --> 00:04:13,590 to reassure the body but I go back so 99 00:04:17,150 --> 00:04:15,600 actually I think the most important part 100 00:04:20,270 --> 00:04:17,160 is how it will off the club in Adobe 101 00:04:22,670 --> 00:04:20,280 Connect sorry it can you reach we share 102 00:04:26,330 --> 00:04:22,680 a couple different limits that are 103 00:04:27,830 --> 00:04:26,340 instructive for the behavior of the full 104 00:04:29,240 --> 00:04:27,840 model and those of 105 00:04:30,790 --> 00:04:29,250 that's the part of this that I believe 106 00:04:32,990 --> 00:04:30,800 that I would put the most certainty on 107 00:04:36,590 --> 00:04:33,000 at least if you believe the assumptions 108 00:04:38,629 --> 00:04:36,600 that I make in the limits that cake so I 109 00:04:43,129 --> 00:04:38,639 think that's that's something so pay 110 00:04:45,050 --> 00:04:43,139 attention to that and then this water 111 00:04:47,420 --> 00:04:45,060 world self arrest idea this is where the 112 00:04:49,040 --> 00:04:47,430 wild things are in the sock or in for 113 00:04:50,950 --> 00:04:49,050 having issues with the online part I 114 00:04:57,710 --> 00:04:50,960 think we get here me know when a 115 00:05:01,219 --> 00:04:57,720 two-second sickness or quit out yeah so 116 00:05:03,800 --> 00:05:01,229 the waterworld self arrest part that's 117 00:05:06,290 --> 00:05:03,810 the more specula sort of an interesting 118 00:05:10,100 --> 00:05:06,300 idea and I'd be interested in here put 119 00:05:13,430 --> 00:05:10,110 any with things about it she's it on huh 120 00:05:14,990 --> 00:05:13,440 ok I also forgot to mention that the 121 00:05:16,670 --> 00:05:15,000 paper describing this work is on my 122 00:05:21,830 --> 00:05:16,680 website if you want to look at that 123 00:05:23,629 --> 00:05:21,840 after this this this section 124 00:05:25,250 --> 00:05:23,639 observational prospects probably i'm 125 00:05:27,610 --> 00:05:25,260 going to have to skip given the given 126 00:05:32,240 --> 00:05:27,620 that it has to be a short seminar and 127 00:05:34,510 --> 00:05:32,250 then just some some more general issues 128 00:05:36,920 --> 00:05:34,520 about see for weathering outer edge of 129 00:05:38,719 --> 00:05:36,930 albums that i'll introduce this term c 130 00:05:40,879 --> 00:05:38,729 for weathering in a second this last 131 00:05:41,810 --> 00:05:40,889 section so everything up here then i'm 132 00:05:44,060 --> 00:05:41,820 going to tell you i'm not going to show 133 00:05:46,070 --> 00:05:44,070 any sensitivity tests but this is all 134 00:05:49,270 --> 00:05:46,080 stuff that is very robust to changes and 135 00:05:53,270 --> 00:05:49,280 model parameters this last section is 136 00:05:54,950 --> 00:05:53,280 parts that are not so robust and the non 137 00:05:55,909 --> 00:05:54,960 robust aspects of them is actually 138 00:05:57,890 --> 00:05:55,919 what's interesting i should probably 139 00:06:01,750 --> 00:05:57,900 stop believing this round it's going to 140 00:06:04,190 --> 00:06:01,760 get distracting and so that's something 141 00:06:06,110 --> 00:06:04,200 that's another sort of speculative part 142 00:06:07,670 --> 00:06:06,120 and apart with another aspect of 143 00:06:10,279 --> 00:06:07,680 weathering at the sea floor that could 144 00:06:12,020 --> 00:06:10,289 be important for for how ilysm okay 145 00:06:14,800 --> 00:06:12,030 introduction everyone probably knows 146 00:06:18,219 --> 00:06:14,810 about this you have a balanced 147 00:06:20,870 --> 00:06:18,229 maintaining the co2 in the atmosphere 148 00:06:24,230 --> 00:06:20,880 along time scales and carbon cycle you 149 00:06:27,379 --> 00:06:24,240 have outgassing of co2 into the 150 00:06:29,690 --> 00:06:27,389 atmosphere ocean system and you normally 151 00:06:30,710 --> 00:06:29,700 have the silicate weathering i'm not 152 00:06:32,270 --> 00:06:30,720 gonna spend too much time on this 153 00:06:33,650 --> 00:06:32,280 because i think everyone knows this on 154 00:06:36,080 --> 00:06:33,660 the continent that responds to 155 00:06:39,100 --> 00:06:36,090 temperature and co2 so higher 156 00:06:41,439 --> 00:06:39,110 temperature high co2 it runs faster 157 00:06:44,920 --> 00:06:41,449 which is a negative feedback 158 00:06:46,420 --> 00:06:44,930 so choose I just keep talking yeah you 159 00:06:49,510 --> 00:06:46,430 can keep talking they can hear you and 160 00:06:53,439 --> 00:06:49,520 it can see walking around but they can't 161 00:06:54,760 --> 00:06:53,449 see the spot it since the issue okay but 162 00:06:57,040 --> 00:06:54,770 to do a statement the thing that I'm 163 00:07:00,219 --> 00:06:57,050 going to talk about that's not in most 164 00:07:11,409 --> 00:07:00,229 habitable zone pictures is weathering 165 00:07:12,820 --> 00:07:11,419 that can happen at the seafloor so I'm 166 00:07:14,739 --> 00:07:12,830 going to be changing I'm going to be 167 00:07:15,969 --> 00:07:14,749 trying to take into account weathering 168 00:07:17,800 --> 00:07:15,979 that can happen at the sea floor so 169 00:07:19,989 --> 00:07:17,810 removal obscure to from the ocean 170 00:07:28,959 --> 00:07:19,999 atmosphere system happening at the sea 171 00:07:31,179 --> 00:07:28,969 floor where you could out yeah basalt is 172 00:07:33,070 --> 00:07:31,189 exposed at the mid-ocean ridge and then 173 00:07:36,070 --> 00:07:33,080 you have hydrothermal systems and 174 00:07:38,649 --> 00:07:36,080 seawater working into them salt reacting 175 00:07:40,089 --> 00:07:38,659 with the basalt carbonizing it removing 176 00:07:42,610 --> 00:07:40,099 carpet promotion atmosphere system 177 00:07:45,489 --> 00:07:42,620 that's eventually buried in a similar 178 00:07:48,519 --> 00:07:45,499 way how the calcium carbonate that's 179 00:07:50,739 --> 00:07:48,529 precipitated from continental weathering 180 00:07:53,800 --> 00:07:50,749 is buried and set in the sediment that 181 00:07:55,329 --> 00:07:53,810 eventually into mental and so I'm going 182 00:07:57,969 --> 00:07:55,339 to try to add the sea floor weathering 183 00:08:00,159 --> 00:07:57,979 into this picture of what sustains 184 00:08:03,519 --> 00:08:00,169 palpable zone and then see what happens 185 00:08:07,360 --> 00:08:03,529 as you change the land fraction and how 186 00:08:08,980 --> 00:08:07,370 the hobbled zone result responds okay so 187 00:08:11,019 --> 00:08:08,990 first of all I just want to say 188 00:08:20,019 --> 00:08:11,029 something about the continental 189 00:08:22,089 --> 00:08:20,029 weathering something to keep rolling so 190 00:08:24,909 --> 00:08:22,099 I'm going to report the camera at spring 191 00:08:36,579 --> 00:08:24,919 so it isn't quite as you normally would 192 00:08:37,959 --> 00:08:36,589 ok that's it I'm is good to me ok so so 193 00:08:40,170 --> 00:08:37,969 this is this paper by these French guys 194 00:08:42,309 --> 00:08:40,180 and what they're doing is they're 195 00:08:43,659 --> 00:08:42,319 plotting they look at a bunch of 196 00:08:45,040 --> 00:08:43,669 different rivers each of these dots as 197 00:08:47,410 --> 00:08:45,050 rivers I'll explain what the little dot 198 00:08:49,600 --> 00:08:47,420 the different colors of things mean and 199 00:08:51,189 --> 00:08:49,610 what they're doing is they look at the 200 00:08:53,390 --> 00:08:51,199 runoff which is sort of like the total 201 00:08:55,610 --> 00:08:53,400 amount of precipitation the hit that 202 00:08:56,690 --> 00:08:55,620 catchment area and its flow you know the 203 00:08:58,610 --> 00:08:56,700 amount of water is flowing out in the 204 00:09:01,310 --> 00:08:58,620 river and they plot the chemical 205 00:09:03,680 --> 00:09:01,320 weathering great images they're plotting 206 00:09:06,350 --> 00:09:03,690 basically what we want to know for the 207 00:09:07,490 --> 00:09:06,360 content of the weather which can see is 208 00:09:10,490 --> 00:09:07,500 there's some sort of reasonable 209 00:09:12,890 --> 00:09:10,500 correlation between precipitation or 210 00:09:14,420 --> 00:09:12,900 runoff and chemical weathering great and 211 00:09:16,400 --> 00:09:14,430 then down here they're doing the same 212 00:09:22,130 --> 00:09:16,410 thing with the mean annual temperature 213 00:09:23,240 --> 00:09:22,140 and it was the question no and what you 214 00:09:25,040 --> 00:09:23,250 can see when they do its function of 215 00:09:27,650 --> 00:09:25,050 temperature is that there seems to be a 216 00:09:30,950 --> 00:09:27,660 correlation except for these ones where 217 00:09:33,530 --> 00:09:30,960 there isn't a correlation is it runoff 218 00:09:35,690 --> 00:09:33,540 is that that rainfall number ya like 219 00:09:38,930 --> 00:09:35,700 like how much water so humming out in 220 00:09:41,870 --> 00:09:38,940 the river you know like help what's the 221 00:09:44,420 --> 00:09:41,880 rivers flow okay so it's not rainbow 222 00:09:46,700 --> 00:09:44,430 millions I go integrated in the cat 223 00:09:48,620 --> 00:09:46,710 integrated over the catchment rainfall I 224 00:09:51,130 --> 00:09:48,630 think that was the River alpha loss that 225 00:09:53,450 --> 00:09:51,140 divided by the area of the catchment uh 226 00:09:55,400 --> 00:09:53,460 yeah I think that's what that's what 227 00:10:02,740 --> 00:09:55,410 we're talking about that exactly so 228 00:10:07,220 --> 00:10:05,960 okay so about great so obviously this is 229 00:10:09,860 --> 00:10:07,230 supposed to be a function of both these 230 00:10:13,370 --> 00:10:09,870 things so the situation could exist 231 00:10:15,140 --> 00:10:13,380 where you have low runoff and that's 232 00:10:17,090 --> 00:10:15,150 what caused it and even if the 233 00:10:19,040 --> 00:10:17,100 temperature is high enough that you 234 00:10:21,890 --> 00:10:19,050 don't have enough run off to get the 235 00:10:23,660 --> 00:10:21,900 value of of of weathering that you would 236 00:10:25,790 --> 00:10:23,670 expect and so there may be some of that 237 00:10:28,430 --> 00:10:25,800 going well but you also have the Amazon 238 00:10:31,250 --> 00:10:28,440 which has a high runoff having a below 239 00:10:33,740 --> 00:10:31,260 what you would expect a value of 240 00:10:35,120 --> 00:10:33,750 chemical weather and so the point is 241 00:10:37,970 --> 00:10:35,130 that there's a bunch of things can 242 00:10:40,010 --> 00:10:37,980 affect this and it's and it's not sort 243 00:10:44,920 --> 00:10:40,020 of a dead-on one-to-one correlation and 244 00:10:47,780 --> 00:10:44,930 if you go in the new update of how to 245 00:10:49,640 --> 00:10:47,790 build a habitable planet by line here 246 00:10:51,860 --> 00:10:49,650 and grow period they have a scale where 247 00:10:55,280 --> 00:10:51,870 they sort of there's a qualitative 248 00:10:56,960 --> 00:10:55,290 ranking of all the theories that they go 249 00:10:59,240 --> 00:10:56,970 through they sort of present the 250 00:11:00,920 --> 00:10:59,250 evidence and then they and then they and 251 00:11:05,030 --> 00:11:00,930 then they rank them on a scale of 0-10 252 00:11:06,140 --> 00:11:05,040 and so they gave they give the big bang 253 00:11:08,240 --> 00:11:06,150 theory or nine point nine 254 00:11:12,230 --> 00:11:08,250 and they give theory of nucleosynthesis 255 00:11:14,870 --> 00:11:12,240 and stars and and they give the silicate 256 00:11:16,970 --> 00:11:14,880 weathering a six and that's important 257 00:11:19,310 --> 00:11:16,980 because that's what ever anyone talks 258 00:11:20,930 --> 00:11:19,320 about the habitable zone they're talking 259 00:11:22,700 --> 00:11:20,940 about silicate weathering feedback and 260 00:11:25,280 --> 00:11:22,710 the evidence we have that this is 261 00:11:26,990 --> 00:11:25,290 functioning on earth is only a six and 262 00:11:28,310 --> 00:11:27,000 that's the lowest value of anything that 263 00:11:32,510 --> 00:11:28,320 they're willing to put into their 264 00:11:33,770 --> 00:11:32,520 textbook so this is something there's 265 00:11:36,070 --> 00:11:33,780 still a lot of interesting problems to 266 00:11:38,180 --> 00:11:36,080 work on with this that's what I'm saying 267 00:11:40,400 --> 00:11:38,190 now the other hand sea floor whether 268 00:11:42,350 --> 00:11:40,410 that this is what I'm talking about when 269 00:11:44,270 --> 00:11:42,360 I talk about see available you have some 270 00:11:46,400 --> 00:11:44,280 basalt that you took from from the ocean 271 00:11:48,980 --> 00:11:46,410 ocean basement and it's got a little 272 00:11:51,230 --> 00:11:48,990 craft sitting and into these cracks 273 00:11:52,970 --> 00:11:51,240 there's a hydrothermal circulation and 274 00:11:55,220 --> 00:11:52,980 there's a percolation into them of 275 00:11:58,250 --> 00:11:55,230 seawater and then it reacts with the 276 00:12:00,980 --> 00:11:58,260 basalt and it precipitates out 277 00:12:03,200 --> 00:12:00,990 carbonates and so you can see these 278 00:12:04,850 --> 00:12:03,210 veins so these are these are considered 279 00:12:05,960 --> 00:12:04,860 younger ones the fair ones and the older 280 00:12:08,240 --> 00:12:05,970 ones are thicker ones and they can 281 00:12:10,420 --> 00:12:08,250 eventually merge together and the idea 282 00:12:12,800 --> 00:12:10,430 is you can store a huge amount of carbon 283 00:12:15,020 --> 00:12:12,810 in the ocean result and then it can get 284 00:12:18,380 --> 00:12:15,030 subducted later and if you look at these 285 00:12:20,660 --> 00:12:18,390 reactions in the laboratory and crush up 286 00:12:22,310 --> 00:12:20,670 a bunch of basalt that you reacted with 287 00:12:24,830 --> 00:12:22,320 seawater of different temperatures and 288 00:12:26,990 --> 00:12:24,840 different in this case they're changing 289 00:12:29,570 --> 00:12:27,000 the pH which corresponds to changing the 290 00:12:33,890 --> 00:12:29,580 co2 you see a strong function of 291 00:12:35,270 --> 00:12:33,900 temperature and pH you see that the 292 00:12:37,820 --> 00:12:35,280 reactions so strong function of 293 00:12:40,190 --> 00:12:37,830 temperature pH and so in theory you 294 00:12:42,140 --> 00:12:40,200 could build a negative feedback on 295 00:12:43,700 --> 00:12:42,150 climate based on that you know the 296 00:12:45,710 --> 00:12:43,710 temperature could increase could 297 00:12:47,180 --> 00:12:45,720 increase the ocean water temperature 298 00:12:48,950 --> 00:12:47,190 increase the bottom of the ocean 299 00:12:52,130 --> 00:12:48,960 temperature and eventually you could 300 00:12:53,990 --> 00:12:52,140 increase see slow weathering and and 301 00:12:57,310 --> 00:12:54,000 ameliorate the climate change that were 302 00:12:59,450 --> 00:12:57,320 resulting that but the problem is that 303 00:13:03,080 --> 00:12:59,460 there are a number of reasons to think 304 00:13:04,940 --> 00:13:03,090 that these laboratory changes are not 305 00:13:06,770 --> 00:13:04,950 what you're actually going to see if you 306 00:13:09,460 --> 00:13:06,780 do this in the real system and in 307 00:13:11,390 --> 00:13:09,470 particular you had these really crappie 308 00:13:14,840 --> 00:13:11,400 correlations when you go measure in the 309 00:13:17,150 --> 00:13:14,850 river but you get the same sort of 310 00:13:19,460 --> 00:13:17,160 relationship if you if you crush up the 311 00:13:19,940 --> 00:13:19,470 right types of rocks in the lab and so 312 00:13:22,010 --> 00:13:19,950 there are 313 00:13:26,360 --> 00:13:22,020 complicating factors that can mess this 314 00:13:28,730 --> 00:13:26,370 up even more so this the surface 315 00:13:30,290 --> 00:13:28,740 temperature is a lot different from the 316 00:13:32,420 --> 00:13:30,300 temperature that these reactions feel 317 00:13:35,350 --> 00:13:32,430 and in particular most of these 318 00:13:38,150 --> 00:13:35,360 reactions at the sea floor are happening 319 00:13:40,580 --> 00:13:38,160 they're happening maybe 500 meters to a 320 00:13:43,640 --> 00:13:40,590 plum they're down into the basalt at 20 321 00:13:45,530 --> 00:13:43,650 to 40 Celsius and that temperature what 322 00:13:47,840 --> 00:13:45,540 determines that temperature is probably 323 00:13:49,580 --> 00:13:47,850 the heat flux from the interior and not 324 00:13:51,470 --> 00:13:49,590 the upper boundary condition to that 325 00:13:53,300 --> 00:13:51,480 system which is the temperature at the 326 00:13:55,550 --> 00:13:53,310 bottom of the ocean and so the standard 327 00:13:57,560 --> 00:13:55,560 assumption when people consider the sea 328 00:13:59,860 --> 00:13:57,570 floor weather is to assume that there's 329 00:14:03,680 --> 00:13:59,870 no dependence on the surface temperature 330 00:14:07,850 --> 00:14:03,690 and based on these type of laboratory 331 00:14:10,280 --> 00:14:07,860 measurements to assume that that the 332 00:14:11,650 --> 00:14:10,290 dependence on co2 is eat and so this is 333 00:14:16,820 --> 00:14:11,660 kind of a classic paper on the subject 334 00:14:18,980 --> 00:14:16,830 caldera men 1995 and this just shows 335 00:14:21,200 --> 00:14:18,990 yeah he has a number of these different 336 00:14:23,840 --> 00:14:21,210 boxes to simulate different processes 337 00:14:26,600 --> 00:14:23,850 atmosphere ocean system and then down to 338 00:14:27,920 --> 00:14:26,610 the to the seafloor weathering and when 339 00:14:30,740 --> 00:14:27,930 he gets out of the bottle into the 340 00:14:33,260 --> 00:14:30,750 pendants of co2 of seafloor weathering 341 00:14:35,000 --> 00:14:33,270 in this case shown here and silicate 342 00:14:37,400 --> 00:14:35,010 weathering out men what you can see is 343 00:14:39,230 --> 00:14:37,410 you've got to get the co2 extremely high 344 00:14:42,920 --> 00:14:39,240 to get much changes at all in the 345 00:14:44,720 --> 00:14:42,930 seafloor weather so most people have 346 00:14:47,960 --> 00:14:44,730 considered this problem have concluded 347 00:14:50,000 --> 00:14:47,970 that c4 weathering should have very weak 348 00:14:52,130 --> 00:14:50,010 or no dependence but surface temperature 349 00:14:54,230 --> 00:14:52,140 of the planet and a weak dependence on 350 00:14:55,510 --> 00:14:54,240 the co2 the pudding and that's those are 351 00:14:59,060 --> 00:14:55,520 the assumptions I'm going to make you 352 00:15:01,340 --> 00:14:59,070 now it's possible that in certain cases 353 00:15:02,720 --> 00:15:01,350 those assumptions could be wrong it's 354 00:15:04,600 --> 00:15:02,730 also possible to those that some things 355 00:15:09,320 --> 00:15:04,610 are wrong on current so in particular 356 00:15:11,930 --> 00:15:09,330 this type of work is based on 5 to 10 357 00:15:13,790 --> 00:15:11,940 cores down into the result so it's not 358 00:15:18,320 --> 00:15:13,800 like there's a huge sample what's going 359 00:15:21,830 --> 00:15:18,330 on down there but that's what I'm you 360 00:15:23,120 --> 00:15:21,840 too soon okay okay so I just argued that 361 00:15:26,690 --> 00:15:23,130 the weathering could be very different 362 00:15:28,220 --> 00:15:26,700 on the Continental weathering and sea 363 00:15:30,620 --> 00:15:28,230 floor weather could behave very 364 00:15:32,840 --> 00:15:30,630 differently at the same time we have 365 00:15:33,890 --> 00:15:32,850 numerical simulations that suggests that 366 00:15:37,430 --> 00:15:33,900 plants in 367 00:15:39,140 --> 00:15:37,440 halibel zone of stars like the Sun could 368 00:15:41,450 --> 00:15:39,150 have vastly different quantities of 369 00:15:43,250 --> 00:15:41,460 water delivers them so by orders of 370 00:15:46,550 --> 00:15:43,260 magnitude so you could have clinic to 371 00:15:49,310 --> 00:15:46,560 end up you know very dry right around 372 00:15:51,730 --> 00:15:49,320 the hospital zone or planets that end up 373 00:15:54,800 --> 00:15:51,740 very wet these colors sorry indicate 374 00:15:57,590 --> 00:15:54,810 this is a wet planet drypoint it's a log 375 00:16:00,200 --> 00:15:57,600 and then this is earth somewhere in this 376 00:16:02,210 --> 00:16:00,210 range so you can have planets 10 to 100 377 00:16:04,790 --> 00:16:02,220 times wetter 10 200 times drive in 378 00:16:08,810 --> 00:16:04,800 abbeville and this is also by someone 379 00:16:11,060 --> 00:16:08,820 your program created so they so at the 380 00:16:13,490 --> 00:16:11,070 same time that weathering the weathering 381 00:16:16,040 --> 00:16:13,500 of planets could have a strong 382 00:16:17,300 --> 00:16:16,050 dependence on how much land you have we 383 00:16:20,090 --> 00:16:17,310 could expect a habitable zone planets 384 00:16:23,000 --> 00:16:20,100 but at least at the delivery level have 385 00:16:25,490 --> 00:16:23,010 vastly different amounts of of land 386 00:16:27,380 --> 00:16:25,500 exposed and so what I want to do is I 387 00:16:29,090 --> 00:16:27,390 want to try to make a stab at this 388 00:16:31,280 --> 00:16:29,100 problem and I want to see what the 389 00:16:33,920 --> 00:16:31,290 effect of changing the land fraction on 390 00:16:37,430 --> 00:16:33,930 when it is it turns into every behavior 391 00:16:39,020 --> 00:16:37,440 and with the metabolism and so I can be 392 00:16:42,440 --> 00:16:39,030 considering things ranging from water 393 00:16:45,230 --> 00:16:42,450 world to something with maybe like 394 00:16:47,450 --> 00:16:45,240 ninety percent of the planet covered by 395 00:16:51,260 --> 00:16:47,460 land and I'm not going to be considering 396 00:16:52,970 --> 00:16:51,270 a completely land planet so the 397 00:16:55,010 --> 00:16:52,980 complement of what I'm talking about 398 00:17:00,020 --> 00:16:55,020 today is this augment paper where they 399 00:17:01,810 --> 00:17:00,030 talk about a dry clinic and these are 400 00:17:04,910 --> 00:17:01,820 some of the assumptions that I'm making 401 00:17:07,250 --> 00:17:04,920 so the first thing is I want to plan it 402 00:17:09,620 --> 00:17:07,260 that's geologically active so let's say 403 00:17:10,880 --> 00:17:09,630 plate tectonics to make it simple maybe 404 00:17:13,630 --> 00:17:10,890 there's something else that works like 405 00:17:17,180 --> 00:17:13,640 plate tectonics that can release co2 and 406 00:17:19,550 --> 00:17:17,190 Mary carbonates that you create I don't 407 00:17:21,790 --> 00:17:19,560 want a carbon planet so silicate rocks 408 00:17:25,280 --> 00:17:21,800 get these these types of things working 409 00:17:28,100 --> 00:17:25,290 I want a large reservoir of carbon and 410 00:17:30,170 --> 00:17:28,110 carbonate rocks so I can build up large 411 00:17:32,050 --> 00:17:30,180 amounts of co2 if I need to going 412 00:17:35,390 --> 00:17:32,060 further out in the habitable zone and 413 00:17:38,510 --> 00:17:35,400 this is important when I say Waterworld 414 00:17:40,880 --> 00:17:38,520 in this talk I could mean one metre of 415 00:17:43,160 --> 00:17:40,890 water above the highest topography I 416 00:17:46,220 --> 00:17:43,170 couldn't mean you know ten kilometers of 417 00:17:47,360 --> 00:17:46,230 water 20 kilometers of water but I 418 00:17:49,340 --> 00:17:47,370 definitely don't me 419 00:17:51,530 --> 00:17:49,350 thousand kilometers with all kinds of 420 00:17:53,330 --> 00:17:51,540 strange license under pressure at the 421 00:17:55,670 --> 00:17:53,340 bottom of the ocean I'm talking about 422 00:17:57,230 --> 00:17:55,680 something that looks like hers but maybe 423 00:17:59,390 --> 00:17:57,240 has ten times as much water to those 424 00:18:02,450 --> 00:17:59,400 ducks that's a water world in the 425 00:18:03,680 --> 00:18:02,460 context of this time this is not that 426 00:18:06,230 --> 00:18:03,690 important and I already talked about 427 00:18:11,980 --> 00:18:06,240 this assumption assume that that is 428 00:18:15,500 --> 00:18:11,990 alive or not ah not explicitly anywhere 429 00:18:18,530 --> 00:18:15,510 not explicitly Edward this is the depth 430 00:18:21,890 --> 00:18:18,540 of the ocean another so the depth of the 431 00:18:24,620 --> 00:18:21,900 ocean couldn't come into play for 432 00:18:27,799 --> 00:18:24,630 example if you had I'm kind of trying to 433 00:18:29,870 --> 00:18:27,809 get rid of that it's a problem by saying 434 00:18:32,930 --> 00:18:29,880 small water fractions suppose you added 435 00:18:35,360 --> 00:18:32,940 a 200 kilometer deep ocean you could 436 00:18:37,880 --> 00:18:35,370 have so much pressure that it could make 437 00:18:39,530 --> 00:18:37,890 this you to cut off co2 outgassing if 438 00:18:40,669 --> 00:18:39,540 you could have the facts like that but 439 00:18:43,070 --> 00:18:40,679 I'm not considering those texts 440 00:18:46,010 --> 00:18:43,080 appointments so I'm taking something 441 00:18:49,430 --> 00:18:46,020 like Earth and the only thing I want to 442 00:18:51,830 --> 00:18:49,440 toggle is the amount of water it happens 443 00:18:53,540 --> 00:18:51,840 and I that it has on the surface and I 444 00:18:59,150 --> 00:18:53,550 only want to toggle that within maybe an 445 00:19:01,580 --> 00:18:59,160 order magnitude each way ok this is the 446 00:19:04,820 --> 00:19:01,590 meat of the top so the next maybe 10 447 00:19:08,510 --> 00:19:04,830 slides if you need to take a nap wait 448 00:19:14,120 --> 00:19:08,520 till after those are done pay attention 449 00:19:16,610 --> 00:19:14,130 now now don't ya so ok so there can be 450 00:19:19,400 --> 00:19:16,620 some equations please don't take a nap 451 00:19:21,770 --> 00:19:19,410 yet because that dr. what is important 452 00:19:25,730 --> 00:19:21,780 about this time but I tried to put in 453 00:19:26,900 --> 00:19:25,740 some diagrams and stuff too ok so now 454 00:19:28,340 --> 00:19:26,910 I'm going to tell you about the actual 455 00:19:30,169 --> 00:19:28,350 model that I'm using how am I 456 00:19:33,830 --> 00:19:30,179 calculating whether calculating weather 457 00:19:37,160 --> 00:19:33,840 grades so I'm basing it on this wack is 458 00:19:40,160 --> 00:19:37,170 wack paper from 1981 the content of 459 00:19:43,070 --> 00:19:40,170 weather so W hell that's that's whether 460 00:19:45,110 --> 00:19:43,080 it on land and this is this is all the 461 00:19:46,549 --> 00:19:45,120 dimensions full stuff and so it's going 462 00:19:48,770 --> 00:19:46,559 to depend on precipitation which I'm 463 00:19:50,299 --> 00:19:48,780 going to be a function of pressure it's 464 00:19:52,850 --> 00:19:50,309 going to have some power law depends on 465 00:19:54,140 --> 00:19:52,860 co2 which I'm calling fee here and an 466 00:19:58,550 --> 00:19:54,150 exponential dependence on temperature 467 00:20:00,169 --> 00:19:58,560 based on an arena state relationship sea 468 00:20:01,130 --> 00:20:00,179 floor whether I'm pulling this in 469 00:20:03,260 --> 00:20:01,140 caldera 470 00:20:04,940 --> 00:20:03,270 is basically going to be a power-law 471 00:20:07,460 --> 00:20:04,950 dependence on the proton concentration 472 00:20:09,200 --> 00:20:07,470 in the ocean no dependence on 473 00:20:10,640 --> 00:20:09,210 temperature so that's actually important 474 00:20:12,320 --> 00:20:10,650 what's going to come these are the 475 00:20:14,210 --> 00:20:12,330 standard assumptions the only difference 476 00:20:16,810 --> 00:20:14,220 the only main difference that some 477 00:20:19,280 --> 00:20:16,820 people will use is instead of using 478 00:20:21,770 --> 00:20:19,290 making a function of the proton 479 00:20:23,240 --> 00:20:21,780 concentration in the water they'll make 480 00:20:26,960 --> 00:20:23,250 it a function of the total dissolved 481 00:20:30,050 --> 00:20:26,970 inorganic carbon it turns out that when 482 00:20:31,730 --> 00:20:30,060 you do that the only difference when 483 00:20:34,010 --> 00:20:31,740 you're related to co2 is just changing 484 00:20:35,390 --> 00:20:34,020 that exponent so still give you a 485 00:20:37,070 --> 00:20:35,400 slightly different exponent but not very 486 00:20:39,980 --> 00:20:37,080 much it's not not an important 487 00:20:41,870 --> 00:20:39,990 difference when I combine these I get 488 00:20:43,850 --> 00:20:41,880 this relationship for weathering so 489 00:20:46,610 --> 00:20:43,860 again this is a zero dimensional picture 490 00:20:48,950 --> 00:20:46,620 of the weathering on the planet non 491 00:20:53,330 --> 00:20:48,960 dimensionalized everything so one unit 492 00:20:56,450 --> 00:20:53,340 of t wiggle is t 1 unit of key no wiggle 493 00:21:01,550 --> 00:20:56,460 is equivalent to tu units of T wiggled 494 00:21:03,830 --> 00:21:01,560 of the dimensional quantity and then so 495 00:21:05,750 --> 00:21:03,840 this this is the sea floor whether Bart 496 00:21:08,330 --> 00:21:05,760 the Continental weathering part comes in 497 00:21:10,280 --> 00:21:08,340 here this is important gammas the land 498 00:21:11,960 --> 00:21:10,290 fraction i'm making a particular 499 00:21:15,170 --> 00:21:11,970 assumption for how the land fraction is 500 00:21:18,020 --> 00:21:15,180 going to scale is going to scale with 501 00:21:20,090 --> 00:21:18,030 how the continental weathering is going 502 00:21:23,270 --> 00:21:20,100 to scale with land fraction this 503 00:21:25,340 --> 00:21:23,280 assumption corresponds to just growing 504 00:21:27,680 --> 00:21:25,350 to just growing yourself some water 505 00:21:29,750 --> 00:21:27,690 pocket if you imagine the continent 506 00:21:31,880 --> 00:21:29,760 growing in different ways you might have 507 00:21:35,390 --> 00:21:31,890 like a square root dependence if it's 508 00:21:37,100 --> 00:21:35,400 the area if it's the perimeter rather 509 00:21:38,450 --> 00:21:37,110 than the area of the continent that's 510 00:21:40,400 --> 00:21:38,460 important for the sea floor weathering 511 00:21:42,710 --> 00:21:40,410 which it might be the comments all 512 00:21:45,620 --> 00:21:42,720 broken up in that doesn't end up 513 00:21:49,040 --> 00:21:45,630 affecting the results very much and this 514 00:21:50,600 --> 00:21:49,050 data 0 term it says if you put all your 515 00:21:55,190 --> 00:21:50,610 parameters that their standard value 516 00:21:56,630 --> 00:21:55,200 this goes to 1 this goes to one if land 517 00:21:58,790 --> 00:21:56,640 fraction is equal to the value and 518 00:22:01,760 --> 00:21:58,800 current earth this goes to 1 this goes 519 00:22:04,760 --> 00:22:01,770 to 1 and beta 0 is your estimate for how 520 00:22:06,440 --> 00:22:04,770 much sea floor weathering happens as a 521 00:22:08,330 --> 00:22:06,450 fraction of the total weather in current 522 00:22:10,100 --> 00:22:08,340 earth and our best estimate is that it's 523 00:22:12,110 --> 00:22:10,110 about twenty-five percent of total 524 00:22:14,990 --> 00:22:12,120 weathering on current earth but there's 525 00:22:16,580 --> 00:22:15,000 an uncertainty of probably roughly 100 526 00:22:20,660 --> 00:22:16,590 not so it's probably between zero and 527 00:22:23,360 --> 00:22:20,670 fifty percent and then this assumption 528 00:22:25,220 --> 00:22:23,370 if you have a closed system gap I'm 529 00:22:27,650 --> 00:22:25,230 calling the outcasts in gamma the big 530 00:22:29,600 --> 00:22:27,660 gambler little gammas land fraction big 531 00:22:31,790 --> 00:22:29,610 game is outgassing it's never going to 532 00:22:33,800 --> 00:22:31,800 come back in for the rest of the top 533 00:22:35,840 --> 00:22:33,810 because I'm just going to assume there's 534 00:22:38,840 --> 00:22:35,850 some constant outgassing that doesn't 535 00:22:41,030 --> 00:22:38,850 depend on where the planet is in the 536 00:22:42,230 --> 00:22:41,040 hobbles own or anything else surface 537 00:22:44,390 --> 00:22:42,240 temperature of the planet is going to 538 00:22:46,280 --> 00:22:44,400 set that to a constant and the constant 539 00:22:50,690 --> 00:22:46,290 outgassing has to equal the weather so 540 00:22:52,910 --> 00:22:50,700 that's how you get a closed system ok so 541 00:22:55,280 --> 00:22:52,920 to solve this you need a couple you need 542 00:22:56,600 --> 00:22:55,290 a weathering so I need to solve I need 543 00:22:58,520 --> 00:22:56,610 to write down equations that I can solve 544 00:22:59,780 --> 00:22:58,530 for temperature in co2 so I need 545 00:23:02,030 --> 00:22:59,790 something for weathering a weather 546 00:23:05,300 --> 00:23:02,040 relationship which was big gamma equals 547 00:23:07,420 --> 00:23:05,310 the weathering function of of P and T 548 00:23:10,420 --> 00:23:07,430 and then I need some sort of climate 549 00:23:12,950 --> 00:23:10,430 model and so this is my client wall so 550 00:23:15,140 --> 00:23:12,960 any of my friends I don't think any of 551 00:23:17,630 --> 00:23:15,150 them were here so atmosphere and climate 552 00:23:20,990 --> 00:23:17,640 here would probably take me out back and 553 00:23:25,010 --> 00:23:21,000 shoot me for this but this is my climate 554 00:23:27,730 --> 00:23:25,020 model it's zero dimensional and what it 555 00:23:30,200 --> 00:23:27,740 is is we have incoming solar radiation 556 00:23:32,600 --> 00:23:30,210 we have an OB know that can reflect and 557 00:23:34,630 --> 00:23:32,610 then we have the outgoing of red a 558 00:23:37,490 --> 00:23:34,640 mission to space so I have one equation 559 00:23:44,720 --> 00:23:37,500 take us from the Alpha the Omega of 560 00:23:46,880 --> 00:23:44,730 climate I'm going to do is I cake first 561 00:23:50,900 --> 00:23:46,890 they non dimensionalize my red a mission 562 00:23:53,210 --> 00:23:50,910 to space and then I expand it so if I 563 00:23:55,940 --> 00:23:53,220 non-dimensionalize this I just set this 564 00:23:59,120 --> 00:23:55,950 to a non dimensionalize everything by 565 00:24:00,680 --> 00:23:59,130 the current insulation and so I'm left 566 00:24:03,920 --> 00:24:00,690 it on this side is a quarter 1 minus 567 00:24:06,950 --> 00:24:03,930 alpha and so I expand around that so in 568 00:24:08,660 --> 00:24:06,960 the base climate I just need to have my 569 00:24:10,160 --> 00:24:08,670 outgoing mission to space equal the 570 00:24:15,020 --> 00:24:10,170 absorb radiation that's what this term 571 00:24:16,520 --> 00:24:15,030 means and then I capture this is if I 572 00:24:17,810 --> 00:24:16,530 increase the temperature the planet I'm 573 00:24:20,600 --> 00:24:17,820 going to want to admit more radiation 574 00:24:23,300 --> 00:24:20,610 spaced and I capture all of that physics 575 00:24:25,850 --> 00:24:23,310 in this one parameter and if i increase 576 00:24:28,430 --> 00:24:25,860 the log of the co 2 i'm in a bit less 577 00:24:30,620 --> 00:24:28,440 radiation space and i calculate 578 00:24:32,420 --> 00:24:30,630 I capture all that physics in this one 579 00:24:35,930 --> 00:24:32,430 perimeter so only have two parameters 580 00:24:38,660 --> 00:24:35,940 for the radiation scheme I grab those 581 00:24:42,050 --> 00:24:38,670 parameters from rape your hunger it's 582 00:24:44,030 --> 00:24:42,060 kind of book where he used a radio to 583 00:24:47,510 --> 00:24:44,040 connect them all and calculates their 584 00:24:49,160 --> 00:24:47,520 value and when I'm left with when i plug 585 00:24:51,260 --> 00:24:49,170 this back in is this for the climbing 586 00:24:52,670 --> 00:24:51,270 wall so I have a simple climate model 587 00:24:56,870 --> 00:24:52,680 and what you should know about it is if 588 00:24:58,880 --> 00:24:56,880 i increase the insulation s volume the 589 00:25:03,290 --> 00:24:58,890 amount of radiation that from this star 590 00:25:04,730 --> 00:25:03,300 that the planet is hit with i can deal 591 00:25:06,350 --> 00:25:04,740 with that either by increasing 592 00:25:11,150 --> 00:25:06,360 temperature by an appropriate amount of 593 00:25:15,290 --> 00:25:11,160 units regulated by this mega one or i 594 00:25:18,410 --> 00:25:15,300 can deal with it by decreasing the co2 595 00:25:20,210 --> 00:25:18,420 and so in the standard silicate 596 00:25:21,800 --> 00:25:20,220 weathering feedback you get some 597 00:25:23,600 --> 00:25:21,810 combination of both to increase the 598 00:25:26,480 --> 00:25:23,610 insulation you increase the temperature 599 00:25:28,160 --> 00:25:26,490 some and you decrease the co2 some and 600 00:25:29,660 --> 00:25:28,170 that's why they temperature didn't 601 00:25:30,980 --> 00:25:29,670 increase as thought as much as you 602 00:25:34,790 --> 00:25:30,990 thought it might what happened to Sigma 603 00:25:38,180 --> 00:25:34,800 Theta reform yeah that's that's right 604 00:25:42,200 --> 00:25:38,190 there now it turns out that if you 605 00:25:45,170 --> 00:25:42,210 linearize if you linearize roughly 606 00:25:48,560 --> 00:25:45,180 between let's say minus 10 Celsius to 40 607 00:25:51,080 --> 00:25:48,570 Celsius you might think sigma t to the 608 00:25:54,170 --> 00:25:51,090 fourth is going to deviate fairly far 609 00:25:56,870 --> 00:25:54,180 from a linearization but because of the 610 00:25:59,090 --> 00:25:56,880 water vapor feedback it actually looks 611 00:26:00,410 --> 00:25:59,100 that the actual function isn't Sigma to 612 00:26:01,700 --> 00:26:00,420 do the fourth it actually looks more 613 00:26:04,700 --> 00:26:01,710 linear so it makes us a better 614 00:26:06,950 --> 00:26:04,710 approximation and that's not to say I'm 615 00:26:08,720 --> 00:26:06,960 really defending you know bottling all 616 00:26:10,730 --> 00:26:08,730 of climate in 20 dimensions and doing 617 00:26:15,800 --> 00:26:10,740 this but that's Sigma to you that's 618 00:26:19,250 --> 00:26:15,810 worth okay this this is an important 619 00:26:21,380 --> 00:26:19,260 equation so what I do it I kick them all 620 00:26:23,030 --> 00:26:21,390 and what I'm interested in the most 621 00:26:26,870 --> 00:26:23,040 important quantity for the rest of this 622 00:26:29,390 --> 00:26:26,880 is D tds so how much does surface 623 00:26:30,710 --> 00:26:29,400 temperature of the planet rather explain 624 00:26:32,540 --> 00:26:30,720 what those are I should have put some 625 00:26:33,590 --> 00:26:32,550 little things explaining with these how 626 00:26:35,420 --> 00:26:33,600 much the service temperature of the 627 00:26:37,010 --> 00:26:35,430 planet can respond to changes in 628 00:26:39,350 --> 00:26:37,020 solutions you could get insulation 629 00:26:41,450 --> 00:26:39,360 changes and stars warming up with time 630 00:26:42,010 --> 00:26:41,460 getting more luminous and you could get 631 00:26:43,810 --> 00:26:42,020 insulation 632 00:26:45,820 --> 00:26:43,820 changes because you're going further 633 00:26:47,650 --> 00:26:45,830 further from the star or closer to the 634 00:26:49,660 --> 00:26:47,660 star but what's important for the 635 00:26:52,000 --> 00:26:49,670 habitable zone is that this value be as 636 00:26:53,770 --> 00:26:52,010 small as it possibly can be and the 637 00:26:55,390 --> 00:26:53,780 limit that this 40 and you could just 638 00:26:57,250 --> 00:26:55,400 move the planet anywhere you wanted and 639 00:26:59,200 --> 00:26:57,260 the surface temperature wouldn't care so 640 00:27:01,240 --> 00:26:59,210 if you started in the Hubble zone you'll 641 00:27:03,060 --> 00:27:01,250 always be the Hamilton but we want this 642 00:27:07,630 --> 00:27:03,070 to get small as it possibly can be and 643 00:27:10,870 --> 00:27:07,640 this term right here this is the climate 644 00:27:13,570 --> 00:27:10,880 sensitivity if you don't have any 645 00:27:16,030 --> 00:27:13,580 changes in co2 so every unit of 646 00:27:17,410 --> 00:27:16,040 insulation change gets converted into a 647 00:27:19,450 --> 00:27:17,420 temperature change this is the maximum 648 00:27:22,270 --> 00:27:19,460 you can get for the Clemson student 649 00:27:24,910 --> 00:27:22,280 external forcing and this term describes 650 00:27:26,620 --> 00:27:24,920 any weather and feedbacks we're going to 651 00:27:30,700 --> 00:27:26,630 change in the co2 in order to keep the 652 00:27:35,890 --> 00:27:30,710 temperature in a smaller range so we 653 00:27:37,630 --> 00:27:35,900 want that to be low and after writing 654 00:27:39,700 --> 00:27:37,640 down the complicated weathering 655 00:27:42,820 --> 00:27:39,710 memorization I'm going to simplify here 656 00:27:44,200 --> 00:27:42,830 because the explicit form of those terms 657 00:27:46,240 --> 00:27:44,210 doesn't matter for i'm going to say in 658 00:27:48,040 --> 00:27:46,250 the next two slides and so i'm going to 659 00:27:50,770 --> 00:27:48,050 do is I'm going to say the total weather 660 00:27:52,810 --> 00:27:50,780 is equal to some function of the land 661 00:27:56,140 --> 00:27:52,820 pratchett time to the Continental 662 00:27:59,320 --> 00:27:56,150 lettering which is a function of co2 and 663 00:28:01,600 --> 00:27:59,330 temperature plus some function on the 664 00:28:03,550 --> 00:28:01,610 land fraction time to the ocean weather 665 00:28:07,210 --> 00:28:03,560 which is a function of co2 and the 666 00:28:10,060 --> 00:28:07,220 temperature it's pretty hard to cook up 667 00:28:12,730 --> 00:28:10,070 a parameterization where this gamma 668 00:28:14,710 --> 00:28:12,740 function is somehow inside here so this 669 00:28:17,590 --> 00:28:14,720 is a very safe assumption that you can 670 00:28:18,970 --> 00:28:17,600 separate these variables out and all I'm 671 00:28:21,700 --> 00:28:18,980 going to require about these functions 672 00:28:23,200 --> 00:28:21,710 is that if you have a water world you 673 00:28:25,840 --> 00:28:23,210 can't have any continental weather and 674 00:28:27,820 --> 00:28:25,850 if you have and when planet you can't 675 00:28:32,050 --> 00:28:27,830 have any seeds for weathering so I think 676 00:28:33,580 --> 00:28:32,060 those are basic safe assumptions and now 677 00:28:36,190 --> 00:28:33,590 and now is when you when you should wake 678 00:28:41,620 --> 00:28:36,200 up so these two slides that you should 679 00:28:43,810 --> 00:28:41,630 pay extra attention sleep so most people 680 00:28:45,070 --> 00:28:43,820 think that c4 weather is independent of 681 00:28:46,600 --> 00:28:45,080 surface temperature that's something 682 00:28:48,520 --> 00:28:46,610 that more work should be done on but 683 00:28:50,140 --> 00:28:48,530 that's that would that sort of the null 684 00:28:53,080 --> 00:28:50,150 hypothesis right now that's what people 685 00:28:55,390 --> 00:28:53,090 think and so what I'm going to show here 686 00:28:55,840 --> 00:28:55,400 is that if that's true that a water 687 00:28:57,430 --> 00:28:55,850 world 688 00:28:59,320 --> 00:28:57,440 and have known climate stabilizing 689 00:29:00,909 --> 00:28:59,330 weather and feedback and therefore is 690 00:29:04,000 --> 00:29:00,919 going to have a much smaller navigable 691 00:29:06,669 --> 00:29:04,010 zone so that has direct implications for 692 00:29:10,360 --> 00:29:06,679 planets being detected today it's the 693 00:29:13,720 --> 00:29:10,370 way I do that is I take this last I take 694 00:29:16,840 --> 00:29:13,730 this equation and I differentiate with 695 00:29:20,289 --> 00:29:16,850 respect to s and we remember that w is 696 00:29:24,039 --> 00:29:20,299 equal to a constant so the DDT of this 697 00:29:25,570 --> 00:29:24,049 equation has to be zero and you get you 698 00:29:26,860 --> 00:29:25,580 just sort of move the terms through and 699 00:29:28,779 --> 00:29:26,870 this is what you get when you 700 00:29:33,220 --> 00:29:28,789 differentiate the weather with respect 701 00:29:38,440 --> 00:29:33,230 to s and I'm going to be considering 702 00:29:40,270 --> 00:29:38,450 Waterworld so f of gamma equals zero 703 00:29:43,240 --> 00:29:40,280 past equals zero so this term is gone 704 00:29:47,080 --> 00:29:43,250 and I've constructed that by 705 00:29:49,990 --> 00:29:47,090 construction the sea floor wondering 706 00:29:52,600 --> 00:29:50,000 whether oceans wo doesn't depend on 707 00:29:55,510 --> 00:29:52,610 temperature so that's the basis umph 708 00:29:58,810 --> 00:29:55,520 shin and so this term goes away and what 709 00:30:00,700 --> 00:29:58,820 you're left with is that defeat es 710 00:30:02,890 --> 00:30:00,710 changes in co2 as you change the 711 00:30:04,270 --> 00:30:02,900 installation have to be zero and so the 712 00:30:07,419 --> 00:30:04,280 physical picture you shop in your mind 713 00:30:09,970 --> 00:30:07,429 is if the if the weathering of the 714 00:30:11,740 --> 00:30:09,980 planet can only depend on co2 you've got 715 00:30:13,659 --> 00:30:11,750 a certain out gassing rate and you're 716 00:30:15,730 --> 00:30:13,669 going to have to keep putting out more 717 00:30:19,360 --> 00:30:15,740 and worse into until you until you've 718 00:30:21,270 --> 00:30:19,370 got your your weather and high enough to 719 00:30:24,549 --> 00:30:21,280 balance the co2 that you help guests and 720 00:30:27,159 --> 00:30:24,559 only then can you stop outgassing co2 721 00:30:29,529 --> 00:30:27,169 and you'll just build up to some events 722 00:30:32,230 --> 00:30:29,539 high co2 value maybe it's point one Mars 723 00:30:33,640 --> 00:30:32,240 maybe it's 10 bars something high and 724 00:30:35,529 --> 00:30:33,650 it's just going to stay there it doesn't 725 00:30:38,950 --> 00:30:35,539 care the co2 doesn't care what you do 726 00:30:41,470 --> 00:30:38,960 about the where the planet is relative 727 00:30:43,029 --> 00:30:41,480 to the star what the insulation is and 728 00:30:45,250 --> 00:30:43,039 so you can have no weather and feedback 729 00:30:47,940 --> 00:30:45,260 and so that's why you get physically 730 00:30:52,060 --> 00:30:47,950 while you get the CD s equals zero and 731 00:30:54,039 --> 00:30:52,070 so what that means is your DTS your 732 00:30:57,190 --> 00:30:54,049 climate sensitivity to external forcing 733 00:30:59,440 --> 00:30:57,200 is just equal to its maximum value that 734 00:31:00,760 --> 00:30:59,450 it can take as long as there's no 735 00:31:02,919 --> 00:31:00,770 positive I'm assuming there's no 736 00:31:04,990 --> 00:31:02,929 positive feedback weathering feedback so 737 00:31:07,960 --> 00:31:05,000 you just get the maximum possible value 738 00:31:09,200 --> 00:31:07,970 every unit of s goes into a unit 739 00:31:10,970 --> 00:31:09,210 increase of tea 740 00:31:12,860 --> 00:31:10,980 and this is the change you get in the 741 00:31:14,720 --> 00:31:12,870 habit though so here's here's deserves 742 00:31:16,880 --> 00:31:14,730 schematic picture what's going to happen 743 00:31:19,880 --> 00:31:16,890 you go from colliding with some land a 744 00:31:22,070 --> 00:31:19,890 lot of ocean some sort of relatively 745 00:31:24,230 --> 00:31:22,080 wide album zone like this and now all of 746 00:31:25,789 --> 00:31:24,240 a sudden on the water world these are 747 00:31:29,000 --> 00:31:25,799 your habitable zone limits so it's an 748 00:31:30,500 --> 00:31:29,010 order of magnitude smaller and so all of 749 00:31:37,370 --> 00:31:30,510 that follows just from these basic 750 00:31:39,139 --> 00:31:37,380 assumptions the second thing I'm going 751 00:31:40,960 --> 00:31:39,149 to consider is I'm going to say what if 752 00:31:43,340 --> 00:31:40,970 see for weathering to the constant 753 00:31:46,130 --> 00:31:43,350 what's going to happen to this to this 754 00:31:47,960 --> 00:31:46,140 climate weather and feedback the reason 755 00:31:51,409 --> 00:31:47,970 that I'm considering that limit there 756 00:31:54,260 --> 00:31:51,419 are two reasons the first is we saw from 757 00:31:56,210 --> 00:31:54,270 from the caldera word the sea floor 758 00:31:58,940 --> 00:31:56,220 weather in is that week has a weak 759 00:32:02,360 --> 00:31:58,950 dependence on co2 and its peak enough 760 00:32:04,250 --> 00:32:02,370 then this limit is a pretty good 761 00:32:06,200 --> 00:32:04,260 description of the full model which I'm 762 00:32:08,649 --> 00:32:06,210 going to show us so it's an instructive 763 00:32:12,950 --> 00:32:08,659 limit to consider the second reason is 764 00:32:14,720 --> 00:32:12,960 there's a possibility that that c4 765 00:32:17,149 --> 00:32:14,730 weathering is actually limited by the 766 00:32:19,789 --> 00:32:17,159 circulation ocean water and hydrothermal 767 00:32:21,980 --> 00:32:19,799 vents through the basalt and if that's 768 00:32:23,690 --> 00:32:21,990 the case then it doesn't really care 769 00:32:24,980 --> 00:32:23,700 about the co2 or temperature at all so 770 00:32:29,720 --> 00:32:24,990 there is a physical limit where this is 771 00:32:30,919 --> 00:32:29,730 actually correct we don't know currently 772 00:32:35,060 --> 00:32:30,929 people think that that's not the case 773 00:32:40,610 --> 00:32:35,070 but it's possible that's kid okay so 774 00:32:41,630 --> 00:32:40,620 what happened in this limit so I said 775 00:32:43,810 --> 00:32:41,640 that the sea floor weather and his 776 00:32:50,149 --> 00:32:43,820 confidence that knocks these terms out 777 00:32:52,610 --> 00:32:50,159 and then right away because I assume 778 00:32:54,320 --> 00:32:52,620 that that the land fraction function was 779 00:32:56,570 --> 00:32:54,330 separable which is the safe assumption 780 00:33:00,200 --> 00:32:56,580 you're left with this and so you can 781 00:33:01,880 --> 00:33:00,210 solve for D feed ES and plug it in to 782 00:33:04,130 --> 00:33:01,890 the pds and you get something that has 783 00:33:06,320 --> 00:33:04,140 no dependence on gamma so there's just 784 00:33:13,610 --> 00:33:06,330 no dependence on the land fraction left 785 00:33:15,139 --> 00:33:13,620 and what this means is so if you go to a 786 00:33:17,419 --> 00:33:15,149 clinic with more land to a play with 787 00:33:19,669 --> 00:33:17,429 less than you're definitely you've got 788 00:33:21,740 --> 00:33:19,679 if the land fractioning if the land 789 00:33:23,120 --> 00:33:21,750 weathering is is the dominant term and 790 00:33:24,950 --> 00:33:23,130 you go to 791 00:33:26,780 --> 00:33:24,960 with less wind you're going to get a 792 00:33:28,880 --> 00:33:26,790 higher co2 you're going to get a higher 793 00:33:31,430 --> 00:33:28,890 temperature but you're not going to get 794 00:33:33,380 --> 00:33:31,440 a higher change in temperature as you 795 00:33:35,330 --> 00:33:33,390 change the insulation so you'll get a 796 00:33:37,310 --> 00:33:35,340 small shifting and where the habitable 797 00:33:39,380 --> 00:33:37,320 zone exists so it's going to shift 798 00:33:43,280 --> 00:33:39,390 outwards a bit but the width is going to 799 00:33:45,230 --> 00:33:43,290 stay the same and so this is a 800 00:33:47,960 --> 00:33:45,240 relationship that holds up in the full 801 00:33:49,990 --> 00:33:47,970 model so the basic picture that you can 802 00:33:53,330 --> 00:33:50,000 construct just from the simple examples 803 00:33:58,370 --> 00:33:53,340 is that a water world a very narrow 804 00:34:00,350 --> 00:33:58,380 alleble zone and a and and planets that 805 00:34:02,120 --> 00:34:00,360 have some Lin should so show weak 806 00:34:04,550 --> 00:34:02,130 dependence of their habitable zone of 807 00:34:06,860 --> 00:34:04,560 land fraction which is the powerful 808 00:34:08,960 --> 00:34:06,870 result because what it means is that the 809 00:34:12,560 --> 00:34:08,970 previous habitable zone theory should be 810 00:34:14,869 --> 00:34:12,570 robust in these cases which has been 811 00:34:18,320 --> 00:34:14,879 drive without any explicit reference to 812 00:34:21,830 --> 00:34:18,330 what the land fraction is okay more meat 813 00:34:23,480 --> 00:34:21,840 this is the this is the full model 814 00:34:25,970 --> 00:34:23,490 results so I'm not considering my 815 00:34:28,430 --> 00:34:25,980 bicycle limits anymore I've gone back to 816 00:34:31,700 --> 00:34:28,440 the complete law and what I'm showing 817 00:34:34,190 --> 00:34:31,710 here is imagine the evolution of a 818 00:34:36,139 --> 00:34:34,200 planet like Earth these are different 819 00:34:38,540 --> 00:34:36,149 land fractions as a function of 820 00:34:40,940 --> 00:34:38,550 insulation here I've just plotted for a 821 00:34:43,190 --> 00:34:40,950 star like the Sun what time these would 822 00:34:44,480 --> 00:34:43,200 be these are my non dimensional 823 00:34:50,030 --> 00:34:44,490 variables in here I turn them back into 824 00:34:52,220 --> 00:34:50,040 visible log co2 in bars and this is the 825 00:34:54,290 --> 00:34:52,230 temperature and I just sort of draw the 826 00:34:56,659 --> 00:34:54,300 kind of rough habitable zone limits 827 00:34:58,850 --> 00:34:56,669 where moist green odds might be where a 828 00:35:01,190 --> 00:34:58,860 snowball might be this is some other 829 00:35:04,040 --> 00:35:01,200 people's I needed it I don't think it's 830 00:35:05,840 --> 00:35:04,050 all that useful of where floorset 831 00:35:07,040 --> 00:35:05,850 business might shut up because there 832 00:35:08,540 --> 00:35:07,050 could be other types of life that don't 833 00:35:11,840 --> 00:35:08,550 need there are other types of life that 834 00:35:15,230 --> 00:35:11,850 don't need to Lucis I want you can see 835 00:35:19,370 --> 00:35:15,240 is as you increase the insulation so 836 00:35:20,960 --> 00:35:19,380 you're going your plan is the star is 837 00:35:23,180 --> 00:35:20,970 aging where you're going closer to the 838 00:35:26,150 --> 00:35:23,190 star you get increases in temperature 839 00:35:28,040 --> 00:35:26,160 but but they're ameliorated by the fact 840 00:35:30,050 --> 00:35:28,050 that the co2 is decreasing and so that's 841 00:35:32,390 --> 00:35:30,060 the silicate weathering feedback and as 842 00:35:34,700 --> 00:35:32,400 we increase the interaction like this 843 00:35:36,810 --> 00:35:34,710 you get higher temperatures but you 844 00:35:39,300 --> 00:35:36,820 still get a 845 00:35:41,310 --> 00:35:39,310 tds this slope that's about to say and 846 00:35:45,450 --> 00:35:41,320 say your howl zone is just shifting 847 00:35:48,390 --> 00:35:45,460 rather than shrinking or expanding now 848 00:35:50,340 --> 00:35:48,400 if we put on top of that a planet where 849 00:35:52,980 --> 00:35:50,350 we set the land fraction is zero and you 850 00:35:56,940 --> 00:35:52,990 can no longer do any land whether you 851 00:35:59,580 --> 00:35:56,950 get a much more rapid increase in to the 852 00:36:02,190 --> 00:35:59,590 moist greenhouse and the reason is this 853 00:36:04,050 --> 00:36:02,200 is what I was describing before the co2 854 00:36:06,210 --> 00:36:04,060 just builds up until its height up to 855 00:36:07,440 --> 00:36:06,220 balance the outgassing so the weather 856 00:36:09,990 --> 00:36:07,450 and get tired of balance the outgassing 857 00:36:12,000 --> 00:36:10,000 and sticks at that I body value in this 858 00:36:14,940 --> 00:36:12,010 case it's like six bars of seven bars 859 00:36:17,100 --> 00:36:14,950 co2 and so you just rapidly go into the 860 00:36:20,250 --> 00:36:17,110 moisture you know state and so what that 861 00:36:28,620 --> 00:36:20,260 means is you get a much narrower however 862 00:36:30,630 --> 00:36:28,630 rules and habitable zone okay so I just 863 00:36:33,480 --> 00:36:30,640 want to say something about why that's 864 00:36:36,660 --> 00:36:33,490 happening in the model basically what 865 00:36:40,230 --> 00:36:36,670 I'm plotting here forget about what B is 866 00:36:43,200 --> 00:36:40,240 is the scaling of of co2 in the wac 867 00:36:45,450 --> 00:36:43,210 primer ization the point is it looks you 868 00:36:47,640 --> 00:36:45,460 get a similar picture at both of these 869 00:36:49,200 --> 00:36:47,650 potential values and feet which might be 870 00:36:51,900 --> 00:36:49,210 different because of the affected land 871 00:36:55,980 --> 00:36:51,910 plants but the idea is this is the 872 00:36:58,350 --> 00:36:55,990 insulation level modern higher lower 873 00:37:00,810 --> 00:36:58,360 this is the land fraction so this is ten 874 00:37:02,850 --> 00:37:00,820 percent one percent one hundred percent 875 00:37:05,640 --> 00:37:02,860 and you can see there there are these 876 00:37:07,500 --> 00:37:05,650 broad regions where dt bf's this this 877 00:37:09,690 --> 00:37:07,510 climate sensitivity to external forcing 878 00:37:11,880 --> 00:37:09,700 parameter is roughly constant in both 879 00:37:13,770 --> 00:37:11,890 cases and they tend to happen when the 880 00:37:15,660 --> 00:37:13,780 planet is warmer and the planet might be 881 00:37:18,240 --> 00:37:15,670 warmer because you make the land 882 00:37:19,970 --> 00:37:18,250 fraction smaller or it might be warmer 883 00:37:23,460 --> 00:37:19,980 just because you increase the insulation 884 00:37:25,860 --> 00:37:23,470 and so why does that happen well we can 885 00:37:30,180 --> 00:37:25,870 write down in the full model what key 886 00:37:32,250 --> 00:37:30,190 tds is it's this value you get with no 887 00:37:34,530 --> 00:37:32,260 weather and feedback time something 888 00:37:36,060 --> 00:37:34,540 that's always between 0 and 1 which 889 00:37:38,880 --> 00:37:36,070 describes the weather and keep that if 890 00:37:42,540 --> 00:37:38,890 there's no seas for weathering then this 891 00:37:44,100 --> 00:37:42,550 term equals 0 and you get sort of this 892 00:37:47,820 --> 00:37:44,110 term describes the land weather and 893 00:37:49,950 --> 00:37:47,830 feedback and this kind of annoying term 894 00:37:50,700 --> 00:37:49,960 is the one that comes into the sea floor 895 00:37:52,320 --> 00:37:50,710 weather 896 00:37:54,750 --> 00:37:52,330 but what you can see and this is 897 00:37:56,820 --> 00:37:54,760 critical is there's this ego minus T and 898 00:37:58,890 --> 00:37:56,830 so anything that gets temperature more 899 00:38:00,720 --> 00:37:58,900 than you know 10 degrees 20 degrees 900 00:38:03,839 --> 00:38:00,730 warmer than today is going to kill this 901 00:38:05,550 --> 00:38:03,849 term even if it's you know even if it's 902 00:38:08,370 --> 00:38:05,560 just 10 degrees you get this term 903 00:38:12,329 --> 00:38:08,380 totally killed and you end up in a limit 904 00:38:14,640 --> 00:38:12,339 where dgds is just equal is constant and 905 00:38:18,390 --> 00:38:14,650 that actually is a very good description 906 00:38:19,440 --> 00:38:18,400 of all of those planets problems over it 907 00:38:22,230 --> 00:38:19,450 so this is an actuation of 908 00:38:24,870 --> 00:38:22,240 mathematically of why in the model you 909 00:38:29,240 --> 00:38:24,880 get those constant DTD esas and those 910 00:38:35,670 --> 00:38:29,250 lied alleble zones for such large 911 00:38:37,710 --> 00:38:35,680 interaction ridge okay this the part is 912 00:38:40,050 --> 00:38:37,720 talk with where the wild things are so 913 00:38:43,890 --> 00:38:40,060 this is the more speculative stuff and 914 00:38:45,990 --> 00:38:43,900 be interested in your comments on it so 915 00:38:50,370 --> 00:38:46,000 I just said that I just made an argument 916 00:38:52,050 --> 00:38:50,380 that I just made an argument that a 917 00:38:54,510 --> 00:38:52,060 water world is not to be attractive 918 00:38:57,300 --> 00:38:54,520 place to look for life other than the 919 00:38:58,560 --> 00:38:57,310 problems biologists might have that it's 920 00:39:01,079 --> 00:38:58,570 not going to be a place with a light 921 00:39:02,280 --> 00:39:01,089 apples over and so now I'm going to talk 922 00:39:05,280 --> 00:39:02,290 about something that might be able to 923 00:39:07,859 --> 00:39:05,290 save water world's attention and so the 924 00:39:10,950 --> 00:39:07,869 idea is if if the water world get such a 925 00:39:14,010 --> 00:39:10,960 high co2 that it puts itself into a 926 00:39:15,570 --> 00:39:14,020 moist greenhouse cape and their water 927 00:39:17,490 --> 00:39:15,580 and the stratosphere is being broken 928 00:39:20,670 --> 00:39:17,500 apart and hydrogen escaping and you're 929 00:39:23,250 --> 00:39:20,680 losing oceans of water what if you reach 930 00:39:25,710 --> 00:39:23,260 a point as you decrease your water 931 00:39:28,230 --> 00:39:25,720 levels where you start to expose some 932 00:39:29,880 --> 00:39:28,240 type of some sort of wind it might be 933 00:39:33,570 --> 00:39:29,890 the salt it doesn't really matter what 934 00:39:36,089 --> 00:39:33,580 it is and then you can engage these land 935 00:39:37,620 --> 00:39:36,099 weathering feedbacks that are a strong 936 00:39:39,300 --> 00:39:37,630 function of temperature and are going to 937 00:39:41,520 --> 00:39:39,310 be extremely rapid if you're in a moist 938 00:39:45,150 --> 00:39:41,530 Reno of state is it possible that you 939 00:39:48,660 --> 00:39:45,160 could decrease the co2 fast enough to 940 00:39:52,500 --> 00:39:48,670 stop arrest this water loss while you 941 00:39:57,740 --> 00:39:52,510 still have a partially exposed land and 942 00:40:00,630 --> 00:39:57,750 some amount of ocean so there's some t0 943 00:40:02,670 --> 00:40:00,640 the time it takes to initially expose 944 00:40:03,700 --> 00:40:02,680 the continent that's going to depend on 945 00:40:07,390 --> 00:40:03,710 how much water is in 946 00:40:09,630 --> 00:40:07,400 let it and for some very moist water 947 00:40:15,099 --> 00:40:09,640 world but it's not t0 is going to be 948 00:40:17,650 --> 00:40:15,109 potentially infinitely large but for a 949 00:40:21,250 --> 00:40:17,660 planet where t0 is small enough and you 950 00:40:23,620 --> 00:40:21,260 essentially exposed confident it's going 951 00:40:25,930 --> 00:40:23,630 to take you know the time scale for this 952 00:40:28,120 --> 00:40:25,940 water loss to occur it depends a lot of 953 00:40:30,849 --> 00:40:28,130 parameters for example it's going to 954 00:40:32,920 --> 00:40:30,859 probably be longer on a super earth but 955 00:40:34,750 --> 00:40:32,930 for South planet like Earth 100 million 956 00:40:37,990 --> 00:40:34,760 years as a good time skip keep in mind 957 00:40:39,880 --> 00:40:38,000 Hank where's the weathering feedbacks we 958 00:40:42,099 --> 00:40:39,890 have reason to believe that they're more 959 00:40:43,960 --> 00:40:42,109 like they have been more like on at the 960 00:40:45,849 --> 00:40:43,970 scale of 10 million years and there are 961 00:40:48,070 --> 00:40:45,859 some things that could mess this up and 962 00:40:50,470 --> 00:40:48,080 make it take longer but it's reasonable 963 00:40:53,500 --> 00:40:50,480 to believe that at least some planets 964 00:40:55,990 --> 00:40:53,510 you could have a short time skill to 965 00:40:57,910 --> 00:40:56,000 draw it out co2 and for example we have 966 00:41:00,190 --> 00:40:57,920 in Earth's history the snowball earth 967 00:41:04,599 --> 00:41:00,200 where we think the co2 was built up to 968 00:41:08,010 --> 00:41:04,609 immense gongs maybe a tenth of a bar of 969 00:41:10,930 --> 00:41:08,020 co2 and on a very short time scale 970 00:41:13,750 --> 00:41:10,940 10,000 years 100,000 years after the 971 00:41:15,160 --> 00:41:13,760 snowboarder that all that seemed to was 972 00:41:17,560 --> 00:41:15,170 able to be drawn on the atmosphere 973 00:41:19,450 --> 00:41:17,570 through mother so it could be in fact a 974 00:41:20,710 --> 00:41:19,460 very short time scale but it's 975 00:41:22,930 --> 00:41:20,720 definitely reasonable that's under 10 976 00:41:25,720 --> 00:41:22,940 million years so what the combination of 977 00:41:27,190 --> 00:41:25,730 these means is it looks like it's at 978 00:41:29,349 --> 00:41:27,200 least possible if you could have a 979 00:41:31,300 --> 00:41:29,359 situation that you're reducing water and 980 00:41:33,790 --> 00:41:31,310 voice greenhouse to expose some kind of 981 00:41:35,500 --> 00:41:33,800 continent or LED and that stops the 982 00:41:38,079 --> 00:41:35,510 water loss because you engage weather 983 00:41:41,680 --> 00:41:38,089 then weathering and so it's a mechanism 984 00:41:44,950 --> 00:41:41,690 that water world's could turn into into 985 00:41:47,230 --> 00:41:44,960 planets that have steph planets that 986 00:41:49,240 --> 00:41:47,240 have a more robust weather and feedback 987 00:41:51,060 --> 00:41:49,250 on a wider Howl's OH and the way it 988 00:41:53,740 --> 00:41:51,070 would look in that diagram again 989 00:41:56,890 --> 00:41:53,750 insulation temperature is your cooking 990 00:41:58,839 --> 00:41:56,900 along as the moist greenhouse you're 991 00:42:00,579 --> 00:41:58,849 cooking along as a lot of Rome who hit 992 00:42:03,099 --> 00:42:00,589 the moist greenhouse and then on a 993 00:42:05,800 --> 00:42:03,109 geologically very short time scale you 994 00:42:07,900 --> 00:42:05,810 go through that but stop it at the 995 00:42:10,120 --> 00:42:07,910 tapenade and then you go through as a 996 00:42:11,600 --> 00:42:10,130 planet that has you know thirty percent 997 00:42:14,450 --> 00:42:11,610 fifty percent 998 00:42:17,500 --> 00:42:14,460 mater water as a lighthouse so it's a 999 00:42:20,810 --> 00:42:17,510 way that the water world can save itself 1000 00:42:24,380 --> 00:42:20,820 running out of time so I'm going to skip 1001 00:42:26,240 --> 00:42:24,390 this observational stuff we can talk 1002 00:42:28,850 --> 00:42:26,250 about it later if anyone wants to I just 1003 00:42:30,770 --> 00:42:28,860 want to make one quick point this is 1004 00:42:32,150 --> 00:42:30,780 what it means this is the bottom line if 1005 00:42:33,920 --> 00:42:32,160 the stuff I'm saying is correct in your 1006 00:42:36,680 --> 00:42:33,930 astronomer this is what it means with 1007 00:42:42,020 --> 00:42:36,690 you point one and I'm assuming that your 1008 00:42:43,700 --> 00:42:42,030 villain Ted really strong so if you if 1009 00:42:45,820 --> 00:42:43,710 you if you think the planet has some 1010 00:42:48,260 --> 00:42:45,830 sort of land fraction then you're happy 1011 00:42:50,990 --> 00:42:48,270 it doesn't matter how much you've got a 1012 00:42:52,820 --> 00:42:51,000 wide habitable zone the the previous 1013 00:42:56,390 --> 00:42:52,830 scaling is derived for where the hobbles 1014 00:42:57,470 --> 00:42:56,400 onus is should be roughly right if you 1015 00:43:00,290 --> 00:42:57,480 think you're dealing with the water 1016 00:43:02,000 --> 00:43:00,300 world that you're not happening because 1017 00:43:04,100 --> 00:43:02,010 it should have a very narrow habitable 1018 00:43:05,330 --> 00:43:04,110 zone and things that can find that you 1019 00:43:11,570 --> 00:43:05,340 might think are in the habitable zone 1020 00:43:14,420 --> 00:43:11,580 are unlikely to be actually there your 1021 00:43:15,890 --> 00:43:14,430 guy Nick Cowan has to work on how you 1022 00:43:18,860 --> 00:43:15,900 could estimate in the infraction I'm not 1023 00:43:21,710 --> 00:43:18,870 going to go into that and then I have to 1024 00:43:24,140 --> 00:43:21,720 skip these ones and I just want to make 1025 00:43:26,420 --> 00:43:24,150 a couple brief points about sea floor 1026 00:43:28,040 --> 00:43:26,430 weathering and the outer edge of the 1027 00:43:29,810 --> 00:43:28,050 habitable zone and then I'll go to a 1028 00:43:33,800 --> 00:43:29,820 question so they do it like two more 1029 00:43:35,480 --> 00:43:33,810 minutes okay so everything I told you 1030 00:43:36,950 --> 00:43:35,490 before we're sir bust when I changed 1031 00:43:38,960 --> 00:43:36,960 things in the model now I'm going to 1032 00:43:42,920 --> 00:43:38,970 tell you something that is not robust so 1033 00:43:44,450 --> 00:43:42,930 I this was what my c for weathering 1034 00:43:47,140 --> 00:43:44,460 parameterization looking good there was 1035 00:43:52,340 --> 00:43:47,150 some constant and then there was some 1036 00:43:55,580 --> 00:43:52,350 exponential powering of co2 of feet okay 1037 00:43:58,340 --> 00:43:55,590 so we can imagine a second we get the 1038 00:44:00,680 --> 00:43:58,350 most possible that the seafloor 1039 00:44:03,320 --> 00:44:00,690 muttering can impose a limit on the co2 1040 00:44:04,610 --> 00:44:03,330 that the planet can attain and the way 1041 00:44:06,350 --> 00:44:04,620 you can imagine this happening is 1042 00:44:09,440 --> 00:44:06,360 imagined you start going to a lower 1043 00:44:13,300 --> 00:44:09,450 lower insulation so low that that the 1044 00:44:15,920 --> 00:44:13,310 temperature and future dependencies of 1045 00:44:17,960 --> 00:44:15,930 the land whether and just shut Lynch 1046 00:44:20,300 --> 00:44:17,970 whether or not there's no longer anyway 1047 00:44:21,950 --> 00:44:20,310 land weathering and now you have to 1048 00:44:25,370 --> 00:44:21,960 balance all your outgassing with sea 1049 00:44:28,010 --> 00:44:25,380 floor weather and if you have a strong 1050 00:44:29,870 --> 00:44:28,020 it's on co2 you won't need to increase 1051 00:44:31,820 --> 00:44:29,880 this year to very much to do that if you 1052 00:44:34,100 --> 00:44:31,830 have a weak dependence on co2 got to 1053 00:44:35,870 --> 00:44:34,110 crank the co2 way up and you'll have not 1054 00:44:39,550 --> 00:44:35,880 very much of a limit on this suture you 1055 00:44:43,070 --> 00:44:39,560 can get but it turns out that it's it's 1056 00:44:44,990 --> 00:44:43,080 exquisitely highly dependent on what 1057 00:44:47,500 --> 00:44:45,000 value you choose for him so for example 1058 00:44:51,950 --> 00:44:47,510 I chose that of one-third which 1059 00:44:53,660 --> 00:44:51,960 corresponds to what caldera did if you 1060 00:44:56,300 --> 00:44:53,670 change any two points and when I did 1061 00:44:59,240 --> 00:44:56,310 that the maximum co2 I could build up on 1062 00:45:02,960 --> 00:44:59,250 my planet + love seven dollars if i 1063 00:45:04,730 --> 00:45:02,970 change that 2.5 which is totally within 1064 00:45:07,970 --> 00:45:04,740 the error bars all of a sudden i can 1065 00:45:09,860 --> 00:45:07,980 only get a tenth of a bar of co2 before 1066 00:45:14,540 --> 00:45:09,870 see for weather and chokes you off and 1067 00:45:16,160 --> 00:45:14,550 that's critical because if you look at 1068 00:45:20,180 --> 00:45:16,170 the outer edge of the habitable zone so 1069 00:45:22,520 --> 00:45:20,190 for example in this Lisa 581 system I'm 1070 00:45:24,350 --> 00:45:22,530 not plotting the planet but nobody knows 1071 00:45:27,500 --> 00:45:24,360 if it's there or not but applauding only 1072 00:45:29,330 --> 00:45:27,510 planets that we think are there there is 1073 00:45:31,370 --> 00:45:29,340 this planet I don't think anyone argues 1074 00:45:34,930 --> 00:45:31,380 with that this planet that somewhere 1075 00:45:39,680 --> 00:45:37,460 GCM calculations suggest you need 1076 00:45:42,050 --> 00:45:39,690 something like 10 bars to make this 1077 00:45:43,760 --> 00:45:42,060 plated habitable of co2 well if sea 1078 00:45:46,130 --> 00:45:43,770 floor weathering limits you so that you 1079 00:45:47,540 --> 00:45:46,140 can only generate a tenth of a bar then 1080 00:45:49,790 --> 00:45:47,550 you're not going to be able to keep that 1081 00:45:53,540 --> 00:45:49,800 guy habitable at least with the classic 1082 00:45:57,950 --> 00:45:53,550 mechanism of just increasing the co2 so 1083 00:46:01,400 --> 00:45:57,960 that's why this is important and their 1084 00:46:04,550 --> 00:46:01,410 stuff I never wrap up but basically 1085 00:46:06,830 --> 00:46:04,560 clip-ins on they have made similar 1086 00:46:08,570 --> 00:46:06,840 arguments for early Earth and they find 1087 00:46:11,870 --> 00:46:08,580 that if you have a stronger relationship 1088 00:46:14,030 --> 00:46:11,880 of seafloor weathering on co2 it gets a 1089 00:46:16,190 --> 00:46:14,040 lot harder to keep to get to see you're 1090 00:46:21,470 --> 00:46:16,200 too high on early Earth fake em son 1091 00:46:23,930 --> 00:46:21,480 problem and Geon woo here considered 1092 00:46:26,480 --> 00:46:23,940 this problem for the snowball and he 1093 00:46:28,670 --> 00:46:26,490 actually found that sea floor weathering 1094 00:46:30,410 --> 00:46:28,680 in his model was so high that he could 1095 00:46:32,510 --> 00:46:30,420 only get a couple tenths of a bar of co2 1096 00:46:34,580 --> 00:46:32,520 and that was potentially a problem for 1097 00:46:36,590 --> 00:46:34,590 escaping from the snowball so there's 1098 00:46:38,980 --> 00:46:36,600 clearly some uncertainty in terms of the 1099 00:46:41,900 --> 00:46:38,990 sea floor wedding prayer 1100 00:46:43,730 --> 00:46:41,910 but suppose we find out that it's strong 1101 00:46:45,440 --> 00:46:43,740 that there's a strong dependence on co2 1102 00:46:47,960 --> 00:46:45,450 this could really kill the outer edge of 1103 00:46:50,240 --> 00:46:47,970 the album ilysm I'm gonna skip this one 1104 00:46:53,120 --> 00:46:50,250 and that one okay so there's a loss 1105 00:46:59,089 --> 00:46:53,130 slide so these are the take-home 1106 00:47:01,849 --> 00:46:59,099 messages but first is that a planet that 1107 00:47:04,220 --> 00:47:01,859 has some sort of land fraction something 1108 00:47:06,410 --> 00:47:04,230 between a few percent and ninety percent 1109 00:47:09,920 --> 00:47:06,420 or something like that we should have a 1110 00:47:11,299 --> 00:47:09,930 robust y habitable zone if previous 1111 00:47:12,769 --> 00:47:11,309 comment below and furious correct of 1112 00:47:14,809 --> 00:47:12,779 course if the silicate weathering idea 1113 00:47:17,539 --> 00:47:14,819 is correct we should have a robust white 1114 00:47:19,940 --> 00:47:17,549 alleble zone that could shift around a 1115 00:47:21,079 --> 00:47:19,950 little based on the land fraction and if 1116 00:47:22,910 --> 00:47:21,089 you're doing more than a zero 1117 00:47:25,099 --> 00:47:22,920 dimensional model you know based on how 1118 00:47:28,099 --> 00:47:25,109 these continents break up but it should 1119 00:47:29,630 --> 00:47:28,109 show a strong dependence however if what 1120 00:47:31,250 --> 00:47:29,640 we think we know about the seafloor 1121 00:47:34,460 --> 00:47:31,260 weathering and cottonelle weathering is 1122 00:47:36,319 --> 00:47:34,470 correct we can show with a simple 1123 00:47:39,079 --> 00:47:36,329 mathematical model we can show that 1124 00:47:42,319 --> 00:47:39,089 implies that a water world is going to 1125 00:47:44,299 --> 00:47:42,329 have no weather and feedback and a very 1126 00:47:47,539 --> 00:47:44,309 narrow habitable zone those are the 1127 00:47:49,549 --> 00:47:47,549 gentle messages and if you enjoyed this 1128 00:47:52,069 --> 00:47:49,559 I have another talk on snow lovers on 1129 00:47:58,430 --> 00:47:52,079 Thursday I don't know where this 1130 00:48:06,650 --> 00:47:58,440 building is wherever a JJ is so thank 1131 00:48:08,120 --> 00:48:06,660 you for example you Dorian for 1132 00:48:09,710 --> 00:48:08,130 persevering through all of our technical 1133 00:48:16,069 --> 00:48:09,720 issues so we have time for a couple 1134 00:48:19,339 --> 00:48:16,079 questions yeah serious we're super all 1135 00:48:21,200 --> 00:48:19,349 living doesn't happen I mean like worlds 1136 00:48:25,400 --> 00:48:21,210 where you have sediments to completely 1137 00:48:27,740 --> 00:48:25,410 cover everything and good mean the 1138 00:48:29,809 --> 00:48:27,750 surface phenomena right yeah you have to 1139 00:48:32,569 --> 00:48:29,819 be able to get the hydrothermal 1140 00:48:36,500 --> 00:48:32,579 circulations to the salt yeah but it's a 1141 00:48:38,539 --> 00:48:36,510 dumb there are situations yeah i mean ii 1142 00:48:42,890 --> 00:48:38,549 none of those sediments you know yeah if 1143 00:48:45,500 --> 00:48:42,900 you really have to well so i'm sure the 1144 00:48:48,190 --> 00:48:45,510 answer is yes i'm sure you could 1145 00:48:50,930 --> 00:48:48,200 construct examples but at least on earth 1146 00:48:52,700 --> 00:48:50,940 a lot of this important 1147 00:48:54,380 --> 00:48:52,710 for weathering is happening near mid 1148 00:48:56,630 --> 00:48:54,390 ocean ridge yeah there's not much 1149 00:48:57,710 --> 00:48:56,640 sediment and then eventually it's 1150 00:48:59,089 --> 00:48:57,720 getting covered with sediment and 1151 00:49:01,819 --> 00:48:59,099 there's probably less action happening 1152 00:49:04,579 --> 00:49:01,829 for the last 20 30 40 million years 1153 00:49:08,839 --> 00:49:04,589 budget gets dragged over and seductive 1154 00:49:12,290 --> 00:49:08,849 like Mars wouldn't object if you 1155 00:49:16,250 --> 00:49:12,300 promotional todd's got a fifties the 1156 00:49:18,020 --> 00:49:16,260 other x + well so yeah one of my issue 1157 00:49:20,630 --> 00:49:18,030 assumptions of course list that would 1158 00:49:23,329 --> 00:49:20,640 you want to be active so if you don't 1159 00:49:25,250 --> 00:49:23,339 ask you to be an outcast you know if you 1160 00:49:28,160 --> 00:49:25,260 watch my thing you also go down soon to 1161 00:49:29,809 --> 00:49:28,170 being upright so it's not for any of 1162 00:49:36,770 --> 00:49:29,819 these apples that I guess are going to 1163 00:49:38,540 --> 00:49:36,780 work in that case so we have the ave 1164 00:49:40,309 --> 00:49:38,550 toilet paper on dry papers yeah right 1165 00:49:42,589 --> 00:49:40,319 right but they got to have a phone to 1166 00:49:44,120 --> 00:49:42,599 expand in both wrists yeah and here when 1167 00:49:47,569 --> 00:49:44,130 you're going from a small amount of plan 1168 00:49:49,309 --> 00:49:47,579 to get help is to move out so gently at 1169 00:49:50,750 --> 00:49:49,319 some point you should small enough quite 1170 00:49:52,550 --> 00:49:50,760 a large enough fraction of land that 1171 00:49:54,589 --> 00:49:52,560 then you kind of give to the op amp Anna 1172 00:49:56,329 --> 00:49:54,599 silk did you sort of explore when that 1173 00:49:58,520 --> 00:49:56,339 happened like oh yeah I've also need two 1174 00:50:01,309 --> 00:49:58,530 different strictly visit holiday but 1175 00:50:03,819 --> 00:50:01,319 actually a very important point is my 1176 00:50:07,550 --> 00:50:03,829 climate model is little rinky dinky and 1177 00:50:09,620 --> 00:50:07,560 i'll be at all put all of their effort 1178 00:50:11,150 --> 00:50:09,630 into their bottom lock so first they 1179 00:50:13,430 --> 00:50:11,160 brought a movie and zindies mannequin 1180 00:50:15,230 --> 00:50:13,440 how to read and they worked really hard 1181 00:50:17,569 --> 00:50:15,240 a radius convective model from the inner 1182 00:50:19,940 --> 00:50:17,579 edge but they never actually do any 1183 00:50:22,700 --> 00:50:19,950 explicit calculations of whether where I 1184 00:50:24,920 --> 00:50:22,710 put all my effort so we're actually kind 1185 00:50:26,630 --> 00:50:24,930 of looking at different different 1186 00:50:30,380 --> 00:50:26,640 aspects of the problem other than the 1187 00:50:31,370 --> 00:50:30,390 different land and ocean direction we're 1188 00:50:35,030 --> 00:50:31,380 looking at different aspects of the 1189 00:50:40,069 --> 00:50:35,040 problem they are considering how the 1190 00:50:41,839 --> 00:50:40,079 climate out any weather and feedback I'm 1191 00:50:43,910 --> 00:50:41,849 considering the weather in the feedback 1192 00:50:45,950 --> 00:50:43,920 and so you never got any of your cases 1193 00:50:48,859 --> 00:50:45,960 they expand handles them at the Internet 1194 00:50:51,559 --> 00:50:48,869 as you've changed line pressure no okay 1195 00:50:54,859 --> 00:50:51,569 I didn't know a question from safe 1196 00:50:57,710 --> 00:50:54,869 online crowd so chicken grease truck has 1197 00:50:58,880 --> 00:50:57,720 a comment yep item it soon has performed 1198 00:50:59,740 --> 00:50:58,890 calculations of clutter the block 1199 00:51:02,530 --> 00:50:59,750 earth-like 1200 00:51:04,720 --> 00:51:02,540 orbiting low-mass stars yeah who's like 1201 00:51:06,610 --> 00:51:04,730 geography and found that the atmospheric 1202 00:51:09,430 --> 00:51:06,620 co2 strongly depends on whether 1203 00:51:13,360 --> 00:51:09,440 substellar point downing water or land 1204 00:51:17,770 --> 00:51:13,370 yeah publishes he received system yeah 1205 00:51:20,170 --> 00:51:17,780 exactly okay so that's in the class so i 1206 00:51:22,030 --> 00:51:20,180 assume zero dimensions so i can't 1207 00:51:24,280 --> 00:51:22,040 consider a problem like that what what 1208 00:51:25,810 --> 00:51:24,290 he's saying is if i move it's 1209 00:51:28,210 --> 00:51:25,820 essentially into two dimensional issue 1210 00:51:30,550 --> 00:51:28,220 whether i move my son my continents 1211 00:51:31,840 --> 00:51:30,560 under the sun or out of the Sun and a 1212 00:51:33,430 --> 00:51:31,850 related issue is how I break my 1213 00:51:36,610 --> 00:51:33,440 continents up and all of those things 1214 00:51:40,450 --> 00:51:36,620 could have could definitely out of facts 1215 00:51:45,190 --> 00:51:40,460 and in a case in a case where you have a 1216 00:51:46,510 --> 00:51:45,200 huge asymmetry in the forcing where you 1217 00:51:48,340 --> 00:51:46,520 have all of your installation on one 1218 00:51:50,260 --> 00:51:48,350 side and on the other and you would 1219 00:51:52,330 --> 00:51:50,270 expect spatial heterogeneity needs to be 1220 00:51:55,690 --> 00:51:52,340 more important and this is an example of 1221 00:51:59,280 --> 00:51:55,700 that are you going to draw it on the co2 1222 00:52:02,080 --> 00:51:59,290 if you put them put the land underneath 1223 00:52:03,850 --> 00:52:02,090 okay a few quick announcements so next 1224 00:52:05,470 --> 00:52:03,860 week we have Boswell Ling who's going to 1225 00:52:07,570 --> 00:52:05,480 be speaking he's on sabbatical here 1226 00:52:10,060 --> 00:52:07,580 we're not broadcasting that talk for the 1227 00:52:12,520 --> 00:52:10,070 online people joining us online in two 1228 00:52:14,020 --> 00:52:12,530 weeks please join us for professor David 1229 00:52:16,270 --> 00:52:14,030 brain who's going to be talking about 1230 00:52:17,710 --> 00:52:16,280 whether or not plant planetary magnetic 1231 00:52:19,810 --> 00:52:17,720 fields matter for planetary habitability 1232 00:52:22,090 --> 00:52:19,820 that is going to be broadcast so a 1233 00:52:23,920 --> 00:52:22,100 problem I'd people join us for that home 1234 00:52:25,720 --> 00:52:23,930 was general exam immediately follows 1235 00:52:27,940 --> 00:52:25,730 this I'm going to be taking Dorian out 1236 00:52:29,980 --> 00:52:27,950 to dinner tonight and if interested in 1237 00:52:31,930 --> 00:52:29,990 joining please come speak to myself or 1238 00:52:33,910 --> 00:52:31,940 maybe Vicki because I'm gonna have to 1239 00:52:37,210 --> 00:52:33,920 jump out here so maybe she can help was