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clouds they seem so simple when they

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appear darker we pack an umbrella when

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they're nowhere in sight we pack extra

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sunscreen

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either way we look to clouds for more

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information than you might realize but

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for all that they can tell us they

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actually remain quite mysterious

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especially when it comes to how they

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impact the climate the question is

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because clouds are produced by the

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climate how will a changing climate

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impact clouds and conversely clouds have

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an impact on our climate so how will

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changing clouds affect a change in

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climate welcome to clouds 101

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like all good Mysteries this one begins

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with a sophisticated scientific concept

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Earth's radiation budget

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delicate balance between the sun's

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radiant energy that reaches Earth and

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the radiant energy that flows from Earth

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back out to space about 30 percent of

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the sun's incoming energy essentially

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the light and heat we're familiar with

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is reflected back to space by gaseous

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molecules in the atmosphere tiny

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particles called aerosols land snow and

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ice surfaces and by clouds the remaining

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energy from the Sun roughly 70 percent

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is absorbed by the planet

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most of this absorbed energy heats up

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Earth's surface while the rest is

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absorbed in the atmosphere by gas

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molecules clouds and aerosols

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so heat can be both absorbed and

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reflected by clouds we'll come back to

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this later

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heat is also separately emitted by Earth

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into space in the form of thermal

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infrared radiation which is the kind of

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heat humans can only see through night

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vision goggles

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for Earth's temperature to remain

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constant the absorbed solar radiation

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and outgoing thermal infrared radiation

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must balance one another if the Earth

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system is changed either through natural

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phenomena like volcanic activity or

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through unnatural phenomena like humans

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burning fossil fuels an imbalance in

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Earth's radiation budget occurs and as a

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result the Earth's temperature

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eventually increases or decreases to

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restore an energy balance

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in recent decades satellite and surface

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measurements clearly show an energy

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imbalance taking place that's been

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increasing over the past 150 years the

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large rise in carbon dioxide emissions

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which accumulate in the atmosphere has

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created an enhanced greenhouse effect

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this means that energy from the Sun

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still easily reaches Earth but Earth's

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thermal infrared radiation has a harder

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time getting out into space this has

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caused a decrease in how much heat earth

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sheds consequently we have observed a

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rise in Earth's Global mean surface

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temperature an increased melting of snow

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and sea ice sea level rise and more

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extreme weather events so that brings us

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back to the mystery of clouds long-term

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effects on climate

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here's what we know so far clouds impact

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the radiation budget in two ways by

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reflecting solar radiation back to space

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which leads to a cooling effect on the

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climate

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and by absorbing heat emitted from below

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the clouds that would have otherwise

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escaped to space if the clouds weren't

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present leading to a warming effect

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which of these effects dominates in any

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given location depends upon the cloud

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type high altitude clouds are typically

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thinner and colder than low clouds

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allowing for more solar radiation to

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pass through them and reach Earth's

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surface and because they're cooler they

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emit less thermal infrared radiation to

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space so they have a net warming effect

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on the climate clouds at low altitudes

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on the other hand are generally thicker

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and reflect more solar radiation back

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out to space

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they're also typically warmer so they

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emit more thermal infrared radiation and

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therefore have a net cooling effect on

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the climate

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Earth can respond in ways that leads to

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further warming for example as

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temperatures increase we see snowpack

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and sea ice melting away in polar

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regions a loss of white surfaces that

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reflect the solar radiation that means

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darker colored land and oceans Left

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Behind absorb more solar radiation and

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so more heat is added to the climate

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system

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this cycle of more heat more melt and

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more absorption of solar radiation is

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called a feedback cycle

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and it doesn't end there

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a feedback cycle also happens with

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clouds climate models predict a decrease

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in low altitude cloud coverage over the

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globe as the climate warms since low

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clouds are the highly reflective type a

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decrease in low cloud coverage means

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more heat will be added to the Earth's

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system leading to further warming

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and clouds impact the climate in another

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way too through the water cycle

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producing rain and snowfall

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water at Earth's surface evaporates

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providing the atmosphere with a supply

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of water vapor depending on the air

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temperature and atmospheric pressure the

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air Can Only Hold so much water vapor

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until it becomes saturated when that air

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is saturated with water vapor cools the

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water vapor turns back into liquid water

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droplets and forms clouds

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when these droplets or ice crystals

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accumulate that is what we call a cloud

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when the droplets or ice crystals within

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the cloud grow to be large enough they

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eventually fall to the ground or ocean

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as rain snow or hail

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this brings us back to the mystery at

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hand

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because clouds both reflect and absorb

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energy from the Sun impacting both ends

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of the radiation balance and play a

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massive role in the water cycle any

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changes in clouds will result in a

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change in our climate

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but clouds are also produced by our

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climate so any change in climate will

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result in a change in clouds

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as you probably now realize the

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relationship between clouds and the

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climate is incredibly complex and NASA

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is on a mission to understand it

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using NASA's earth-observing Fleet of

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satellites like Calypso and instruments

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like Ceres and Modis scientists have

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been collecting vital data on clouds to

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be able to precisely model their

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behavior a key ingredient to unraveling

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the mystery of clouds lies in the

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collection of global accurate

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multi-decado climate data records of

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cloud properties and their influence on

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Earth's radiation budget

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once we can accurately and fully

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understand the physics of clouds through

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observations that data can then be used

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to help improve climate and weather

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models so we can better prepare for the