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Information about Climate Commitment Studies

Climate commitment describes the fact that climate reacts with a delay to influencing factors ("climate forcings") such as the presence of greenhouse gases. Climate commitment studies attempt to assess the amount of future warming that is "committed" under the assumption of some constant level of forcings. The "constant level" often used for illustrative purposes is CO2 doubling or quadrupling; or the present level of forcing.

Basic idea

If a perturbation - such as an increase in greenhouse gases or solar activity - is applied to the climate system the response will not be immediate, principally because of the large heat capacity of the oceans.
As an analogue, consider the heating of a thin metal plate (by the sun or by a flame): the plate will warm relatively quickly. If a thick metal block is heated instead, it will take much longer for the entire block to reach equilibrium with the imposed heating because of its higher heat capacity.
Land only stores heat in the top few meters. Ocean water, by contrast, can move vertically and store heat within the ocean's depth (convection). This is why the land surface is observed to warm more than the oceans. It also explains the very large difference in response between
  • "equilibrium" climate prediction runs in which only a shallow ocean is used and it is assumed that the climate has come to equilibrium and
  • "transient" climate prediction runs in which a full ocean is used and the climate is out of balance.
Note that "commitment" can apply to variables other than temperature: because of the long mixing time for heat into the deep ocean, a given surface warming "commits" to centuries of sea level rise from thermal expansion of the ocean. Also once a certain threshold is crossed, it is likely that a slow melting of the Greenland ice sheet will commit us to a sea level rise of 5m over millennia.

Models

Main article: global climate model
Recent models forecast that even in the unlikely event of greenhouse gases stabilising at present levels, the earth would warm by an additional 0.5-1 °C by 2100, a similar rise in temperature to that seen during the 20th century. As ocean waters expand in response to this warming, global sea levels would mount by about 10 centimetres during that time. These models do not take into account ice cap and glacier melting; a better estimate might be double or triple this value [1].

History

This is by no means a new idea, the concept is discussed in the IPCC TAR [2] and in the SAR in 1995.

External links

References

  • Meehl G. A., et al. Sciencexpress, 10.1126/science.1106663 (2005).
  • Wigley T. M. L., et al. Sciencexpress, 110.1126/science.1103934 (2005).
Greenhouse gases are components of the atmosphere that contribute to the greenhouse effect. Without the greenhouse effect the Earth would be uninhabitable;[1] in its absence, the mean temperature of the earth would be about -19 °C (-2 °F, 254 K) rather than the present
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Perturbation may refer to any of numerous concepts in several fields:
  • A verb in the English language, meaning to annoy or disturb (Example: "Tim and Matt were perturbing James.

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Solar variations are changes in the amount of radiant energy emitted by our Sun. There are periodic components to these variations, the principal one being the 11-year solar cycle (or sunspot cycle), as well as fluctuations which are aperiodic.
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Climate is the average and variations of weather over long periods of time. Climate zones can be defined using parameters such as temperature and rainfall.
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Earth's oceans
(World Ocean)
  • Arctic Ocean
  • Atlantic Ocean
  • Indian Ocean
  • Pacific Ocean
  • Southern Ocean
An ocean (from Ωκεανός, Okeanos
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thermodynamic equilibrium when it is in thermal equilibrium, mechanical equilibrium, and chemical equilibrium. The local state of a system at thermodynamic equilibrium is determined by the values of its intensive parameters, as pressure, temperature, etc.
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Convection in the most general terms refers to the movement of currents within fluids (i.e. liquids, gases and rheids).

Convection is one of the major modes of heat and mass transfer.
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Execution in computer and software engineering is the process by which a computer or virtual computer carries out the instructions of a computer program. The term run is used almost synonymously.
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Transience means passing with time. Something which has the property of transience is said to be transient, or often simply a transient or transient state.
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General Circulation Models (GCMs) are a class of computer-driven models for weather forecasting, understanding climate and projecting climate change, where they are commonly called Global Climate Models.
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For other uses, see Model.


An abstract model (or conceptual model) is a theoretical construct that represents something, with a set of variables and a set of logical and quantitative relationships between them.
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This article or section relies largely or entirely upon a .
Please help [ improve this article] by introducing appropriate of additional sources. ()
This article has been tagged since December 2006.
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An ice cap is a dome-shaped ice mass that covers less than 50 000 km² of land area (usually covering a highland area). Masses of ice covering more than 50 000 km² are termed an ice sheet.
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glacier is a large, slow moving river of ice, formed from compacted layers of snow, that slowly deforms and flows in response to gravity. Glacier ice is the largest reservoir of fresh water on Earth, and second only to oceans as the largest reservoir of total water.
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Tar is a viscous black liquid derived from the destructive distillation of organic matter. Most tar is produced from coal as a byproduct of coke production, but it can also be produced from petroleum, peat or wood.
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SAR may stand for:
  • (in microbiology) A naming convention for uncultured bacteria first found in the Sargasso Sea (see SAR11)
  • (in pharmacology and computational chemistry) structure-activity relationship
  • In plant disease resistance Systemic acquired resistance

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