New estimate narrows global warming range

U. MELBOURNE (AUS) — Scientists have generated what they say are more reliable projections of how much warmer the planet will be in 2100 due to climate change.

The paper, published in Nature Climate Change, suggests that exceeding 6 degrees warming was now unlikely, while exceeding 2 degrees is very likely for business-as-usual emissions.

Roger Bodman, a postgraduate research fellow at Victoria University, and Professors David Karoly and Peter Rayner from the University of Melbourne’s School of Earth Sciences made their estimates using new methods that combine observations of carbon dioxide and global temperature variations with simple climate model simulations to project future global warming.

Team leader Bodman says while continuing to narrow the range even further was possible, significant uncertainty in warming predictions would always remain due to the complexity of climate change drivers.

“This study ultimately shows why waiting for certainty will fail as a strategy,” he says. “Some uncertainty will always remain, meaning that we need to manage the risks of warming with the knowledge we have.”

The study found 63 percent of uncertainty in projected warming was due to single sources—such as climate sensitivity, followed by future behavior of the carbon cycle, and the cooling effect of aerosols—while 37 percent of uncertainty came from the combination of these sources.

“This means that if any single uncertainty is reduced—even the most important, climate sensitivity—significant uncertainty will remain,” Bodman says.

Karoly says the study reinforced the importance of strong action on climate change.

“Our results reconfirm the need for urgent and substantial reductions in greenhouse gas emissions if the world is to avoid exceeding the global warming target of 2 degrees needed to minimize dangerous climate change,” he says.

Source: University of Melbourne