New method improves long-term climate change projections
It’s a well-known fact that the amount of CO2 in the atmosphere affects the Earth’s climate. However, despite this certainty, it’s still difficult to calculate these effects accurately. In global climate model experiments, scientists double atmospheric CO2 and record the long-term increase in temperature this causes. Known as equilibrium climate sensitivity, this temperature increase is important because an accurate estimate helps scientists to make better predictions of how different emission scenarios will affect the future climate. However, “accurate estimations of equilibrium climate sensitivity are hard to come by,” according to a paper published in the journal ‘Geophysical Research Letters’. This is “mostly due to the lengthy computation times needed to fully equilibrate modern global climate models,” the paper explains. An efficient way to obtain accurate projections of future climate change is proposed in the paper that presents the results of research carried out with support from the EU-funded TiPES project. The authors, all from project partner Utrecht University, the Netherlands, discuss their method of improving global warming estimations from complex climate models. Even when taking advances in computer technology into account, realistic climate models will take increasingly longer to simulate the effects of global warming far into the future. As stated in the paper, “it takes a very long time before all processes in a climate model are fully settled—especially in state‐of‐the‐art, more and more detailed models—and, in practice, settling all is simply not feasible.” The solution is to estimate climate sensitivity using limited model data, which can be problematic since the climate system involves “many processes that behave on vastly different time scales.”
More observables, improved estimates
Conventional equilibrium climate sensitivity techniques most often make use of two measurable properties called observables: global mean surface temperature and top‐of‐atmosphere radiative imbalance (caused because Earth absorbs more heat than it emits). The solution the authors propose is a new estimation technique that can capture the very slow processes better than conventional techniques. Called multicomponent linear regression, the method provides better estimates for equilibrium climate sensitivity and can also be used to develop extensions of climate sensitivity into the future by incorporating other observables such as precipitation or ocean heat transport. “What we did, was add another observable on top of the two traditional ones. That is the idea. If you use additional observables, you will improve estimates over longer time scales. And our work is proof that this is possible,” explains lead author Dr Robbin Bastiaansen in an article posted on the ‘Phys.org’ website. The results of this study will help to further the goals of the TiPES (Tipping Points in the Earth System) project. The key objective is to provide better assessments of the climate system’s tipping points and to make sure that they are included in climate projections. The 4-year project ends in August 2023. For more information, please see: TiPES project website
Keywords
TiPES, climate, equilibrium climate sensitivity, climate model, global warming