Cloud forcing

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Cloud forcing

Cloud forcing (sometimes described as cloud radiative forcing) is the difference between the radiation budget components for average cloud

Cloud

A cloud is a visible mass of Drop or frozen crystals floating in the Celestial body atmosphere above the surface of the Earth or another planetary body....
conditions and cloud-free conditions.

Much of the interest in cloud forcing relates to its role as a feedback

Feedback

Feedback describes the situation when output from an event or phenomenon in the past will influence the same event/phenomenon in the present or future....
process in the present period of global warming

Global warming

Global warming is the increase in the Instrumental temperature record of the Earth's near-surface air and the oceans since the mid-twentieth century and its projected continuation....
. All global climate model

Global climate model

A General Circulation Model is a mathematical model of the general circulation of a planetary atmosphere or ocean and based on the Navier-Stokes equations on a rotating sphere with thermodynamic terms for various energy sources ....
s used for climate change projections include the effects of water vapor

Water vapor

Water vapor or water vapour , also aqueous vapor, is the gas phase of water . Water vapor is one Phase of the water cycle within the hydrosphere....
and cloud forcing.

Clouds increase the global reflection of solar radiation

Albedo

The albedo of an object is the extent to which it diffusely reflects light from the Sun. It is therefore a more specific form of the term reflectivity....
from 15 to 30%, reducing the amount of solar radiation absorbed by the Earth by about 44 W/m².

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Encyclopedia

Cloud forcing (sometimes described as cloud radiative forcing) is the difference between the radiation budget components for average cloud

Cloud

Feedback

Global warming

Global climate model

Water vapor

Albedo

Greenhouse effect

The greenhouse effect refers to the change in the steady state temperature of a planet or moon by the presence of an atmosphere containing gas that absorbs and emits infrared....
of clouds which reduces the outgoing longwave radiation

Outgoing longwave radiation

Outgoing Longwave Radiation is the energy leaving the earth as infrared radiation at low energy. Earth's radiation balance is very closely achieved since the OLR very nearly equals the Shortwave Absorbed Radiation received at high energy from the sun....
by about 31 W/m². Thus the net cloud forcing of the radiation budget is a loss of about 13 W/m² . If the clouds were removed with all else remaining the same, the Earth

Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
would gain this last amount in net radiation and begin to warm up. These numbers should not be confused with the usual radiative forcing

Radiative forcing

In climate science, radiative forcing is defined as the change in net irradiance at the tropopause. "Net irradiance" is the difference between the incoming radiation energy and the outgoing radiation energy in a given climate system and is thus measured in Watts per square meter....
concept, which is for the change in forcing related to climate change

Climate change

Climate change is any long-term significant change in the expected patterns of average weather of a specific region over an appropriately significant period of time....
.

Without the inclusion of clouds, water vapor alone contributes between 36-70% of the greenhouse effect on Earth. When considering water vapor and clouds together, the contribution is between 66-85%. The ranges come about because there are two ways to compute the influence of water vapor and clouds: the lower bounds are the reduction in the greenhouse effect if water vapor and clouds are removed from the atmosphere leaving all other greenhouse gases unchanged, while the upper bounds are the greenhouse effect introduced if water vapor and clouds are added to an atmosphere with no other greenhouse gases. The two values differ because of overlap in the absorption and emission by the various greenhouse gases. Trapping of the long-wave radiation due to the presence of clouds reduces the radiative forcing of the greenhouse gases compared to the clear-sky forcing. However, the magnitude of the effect due to clouds varies for different greenhouse gases. Relative to clear skies

Sky

The sky is the part of the atmosphere or of outer space visible from the surface of any astronomical object. It is difficult to define precisely for several reasons....
, clouds reduce the global mean radiative forcing due to CO₂

Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
by about 15% , that due to CH₄

Methane

Methane is a chemical compound with the molecular formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees....
and N₂O

Nitrous oxide

Nitrous oxide, commonly known as "laughing gas", is a chemical compound with the chemical formula Nitrogen2Oxygen. At room temperature, it is a colorless Flammability gas, with a pleasant, slightly sweet odor and taste....
by about 20% , and that due to the halocarbon

Halocarbon

Halocarbon compounds are chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms resulting in the formation of organofluorine compounds, organochlorine compounds, organobromine compounds, and organoiodine compounds....
s by up to 30%. Clouds remain one of the largest uncertainties in future projections of climate change by global climate models, owing to the physical complexity of cloud processes and the small scale of individual clouds relative to the size of the model computational grid.