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Sensitivity Study: Recent Past Predicts Future Warming

04.01.2016 16:31 Age: 2 yrs

Examination of Earth's recent history is the key to predicting global temperatures says a team of NASA researchers looking at the sensitivity of the climate to CO2 increases. They calculated the temperature impact of different variables including greenhouse gases, natural and manmade aerosols, ozone concentrations, and land use changes based on historical observations from 1850 to 2005 using a massive ensemble of computer simulations

Click to enlarge. On December 7, 2015, the Moderate Resolution Imaging Spectroradiometer on NASA's Aqua satellite captured this image of eastern China being inundated by thick smog, seen in gray. The previous day in Beijing, the Chinese government issued a first-ever “red alert” for the city, which resulted in school and factory closures and the forcing of motorists from the roads. The new NASA study argues that smog and other aerosols and climate drivers do not necessarily behave like carbon dioxide, which is uniformly spread throughout the globe and produces a consistent temperature response; rather, each climate driver has a particular set of conditions that affects the temperature response of Earth. Courtesy: NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response and Adam Voiland



Climate sensitivity to doubled CO2 is a widely used metric for the large-scale response to external forcing. Climate models predict a wide range for two commonly used definitions: the transient climate response (TCR: the warming after 70 years of CO2 concentrations that rise at 1% per year), and the equilibrium climate sensitivity (ECS: the equilibrium temperature change following a doubling of CO2 concentrations). Many observational data sets have been used to constrain these values, including temperature trends over the recent past, inferences from palaeoclimate and process-based constraints from the modern satellite era. However, as the IPCC recently reported, different classes of observational constraints produce somewhat incongruent ranges. Here we show that climate sensitivity estimates derived from recent observations must account for the efficacy of each forcing active during the historical period. When we use single-forcing experiments to estimate these efficacies and calculate climate sensitivity from the observed twentieth-century warming, our estimates of both TCR and ECS are revised upwards compared to previous studies, improving the consistency with independent constraints.


Implications for climate sensitivity from the response to individual forcings by Marvel, K., G.A. Schmidt, R.L. Miller, and L. Nazarenko published in Nature Climate Change, doi:10.1038/nclimate2888

Read the abstract and get the paper here.


NASA news release here.