20 Facts About Climate sensitivity

Climate sensitivity is a measure of how much Earth's surface will cool or warm after a specified factor causes a change in its climate system, such as how much it will warm for a doubling in the atmospheric carbon dioxide concentration.

In technical terms, climate sensitivity is the average change in global mean surface temperature in response to a radiative forcing, which drives a difference between Earth's incoming and outgoing energy.

Climate sensitivity is a key measure in climate science, and a focus area for climate scientists, who want to understand the ultimate consequences of anthropogenic global warming.

Two primary types of climate sensitivity are the shorter-term "transient climate response", the increase in global average temperature that is expected to have occurred at a time when the atmospheric CO2 concentration has doubled, and "equilibrium climate sensitivity", the higher long-term increase in global average temperature expected to occur after the effects of a doubled CO2 concentration have had time to reach a steady state.

Climate sensitivity is typically estimated in three ways: using direct observations of temperature and levels of greenhouse gases taken during the industrial age, using indirectly-estimated temperature and other measurements from the Earth's more distant past, and computer modelling the various aspects of the climate system with computers.

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Climate sensitivity is a measure of how much temperature change a given amount of radiative forcing will cause.

Economics of climate change mitigation depend greatly on how quickly carbon neutrality needs to be achieved, climate sensitivity estimates can have important economic and policy-making implications.

Scientists are uncertain about the precision of estimates of greenhouse gas increases on future temperature since a higher climate sensitivity would mean more dramatic increases in temperature, which makes it more prudent to take significant climate action.

The uncertainty in climate sensitivity estimates is entirely from the modelling of feedbacks in the climate system, including water vapour feedback, ice–albedo feedback, cloud feedback, and lapse rate feedback.

Climate sensitivity is approximately the same whatever the reason for the radiative forcing .

When climate sensitivity is expressed as the temperature change for a level of atmospheric CO2 double the pre-industrial level, its units are degrees Celsius .

Equilibrium climate sensitivity is the long-term temperature rise that is expected to result from a doubling of the atmospheric CO2 concentration .

Common approximation to ECS is the effective equilibrium climate sensitivity, is an estimate of equilibrium climate sensitivity by using data from a climate system in model or real-world observations that is not yet in equilibrium.

Climate sensitivity has been defined as the short- or long-term temperature change resulting from any doubling of CO2, but there is evidence that the sensitivity of Earth's climate system is not constant.

Two most common definitions of climate sensitivity specify the climate state: the ECS and the TCR are defined for a doubling with respect to the CO2 levels in the pre-industrial era.

The effect of any change in climate sensitivity is expected to be small or negligible in the first century after additional CO2 is released into the atmosphere.

The IPCC supplementary report, 1992, which used full-ocean circulation models, saw "no compelling reason to warrant changing" the 1990 estimate; and the IPCC Second Assessment Report stated, "No strong reasons have emerged to change [these estimates], " In the reports, much of the uncertainty around climate sensitivity was attributed to insufficient knowledge of cloud processes.

Authors of the 2007 IPCC Fourth Assessment Report stated that confidence in estimates of equilibrium climate sensitivity had increased substantially since the Third Annual Report.

Climate sensitivity can be estimated using the observed temperature increase, the observed ocean heat uptake, and the modelled or observed radiative forcing.

The average estimated climate sensitivity has increased in Coupled Model Intercomparison Project Phase 6 compared to the previous generation, with values spanning 1.