Earth's recent history may predict global temperatures

Climate change over the last 150 years may estimate future global temperatures, a NASA study has found.

According to a new NASA study published in the journal Nature Climate Change, to quantify climate change, researchers need to know the Transient Climate Response (TCR) and Equilibrium Climate Sensitivity (ECS) of Earth.

TCR is characteristic of short-term predictions, up to a century out, while ECS looks centuries further into the future, when the entire climate system has reached equilibrium and temperatures have stabilised.

As part of that calculation that depended on the measurements of important climate drivers, such as carbon dioxide, the researchers have relied on simplifying assumptions when accounting for the temperature impacts of climate drivers other than carbon dioxide, such as tiny particles in the atmosphere known as aerosols.

But the assumptions made to account for these drivers are too simplistic and result in incorrect estimates of TCR and ECS, said Gavin Schmidt, a climate scientist and director of NASA's Goddard Institute for Space Studies (GISS) in New York, who is also a co-author of the study.

"The problem with that approach is that it falls way short of capturing the individual regional impacts of each of those variables," he said, adding that only within the last 10 years has there been enough available data on aerosols to abandon the simple assumption and instead attempt detailed calculations.

Earlier NASA calculated the temperature impact of each of variables like 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.

However, earlier studies did not account for what amounts to a net cooling effect for parts of the northern hemisphere and the predictions for TCR and ECS were lower than they should have been.

"If you've got a systematic underestimate of what the greenhouse gas-driven change would be, then you're systematically underestimating what's going to happen in the future when greenhouse gases are by far the dominant climate driver," Schmidt said.