Regions around the Arctic may have passed a 2°C temperature rise as far back as 2000 and, if emissions rates don’t change, areas around the Mediterranean, central Brazil and the contiguous United States could see 2°C of warming by 2030.
This is despite the fact that under a business as usual scenario the world is not expected to see global average temperatures rise by 2°C compared to pre-industrial times until the 2040s.
New research published in Nature led by Professor Sonia Seneviratne from ETH Zurich with researchers from Australia's ARC Centre of Excellence for Climate System Science (ARCCSS) has quantified the change in regional extremes in a world where global average temperatures have risen by 2°C.
The research shows worldwide warming extremes over land generally exceed the rise in this scenario, in some cases by as much as 6°C.
"We even see starkly different rates of extreme warming over land even when global average temperatures reach just 1.5°C, which is the limit to the rate of warming agreed to at the Paris talks," Seneviratne said.
“At 1.5°C we would still see temperature extremes in the Arctic rise by 4.4°C and a 2.2°C warming of extremes around the Mediterranean basin."
The extreme regional warming projected for Alaska, Canada, Northern Europe, Russia and Greenland could have global impacts, accelerating the pace of sea-level rise and increasing the likelihood of methane releases prompted by the melting of ice and permafrost regions.
Co-author Professor, Andy Pitman, said to keep extreme temperature changes over the Mediterranean below a 2°C threshold, the cumulative emissions of CO2 would have to be restricted to 600 gigatonnes rather than the 850 gigatonnes currently estimated to keep global average temperatures below 2°C.
According to the researchers, if global average temperatures warm by 2°C compared to preindustrial times this would equate to a 3°C warming of hot extremes in the Mediterranean region and between 5.5 - 8°C warming for cold extremes over land around the Arctic.
Most land-masses around the world will see an extreme temperature rise greater than 2°C.
One of the few exceptions is Australia – famously known as a land of droughts and flooding rains. The projections show little difference between global average temperatures and a change in its extreme regional temperatures.
“This might be something peculiar about Australia’s climate, or perhaps it highlights problems with the climate models," Pitman said.
The ARC Centre of Excellence for Climate System Science is the largest university-based climate research centre in the Southern Hemisphere.