Half a degree might not sound like much. But when it comes to the Earth’s climate, this small difference could have a big impact on the planet – that’s the finding of a team of European climate scientists.
The researchers, based in Germany, Switzerland, Austria and the Netherlands, used climate models to predict the effects of a global warming of 1.5°C or 2.0°C by 2100. These are the two temperature limits mentioned in the Paris Agreement, which aims to reduce greenhouse gas emissions and limit the effects of climate change.
The study, presented at the European Geosciences Union’s General Assembly this week, identified a number of places where a temperature difference of just 0.5°C could pose severe problems.
The Mediterranean region, for instance, is predicted to lose fresh water as the climate warms. With a global temperature increase of 2.0°C, the availability of fresh water in the region is estimated to be about 20 per cent lower than in the late 20th Century, compared to 10 per cent in a 1.5°C world.
Meanwhile, in tropical regions, maize and wheat yields were calculated to reduce twice as much at 2.0°C compared to the 1.5°C increase. And according to the study, a 2.0°C increase would also be bad news for sea level rise (the scientists estimate a rise of 50cm by 2100 – 10cm more than for the 1.5°C scenario) and tropical coral reefs (the higher temperature would provide less opportunity for the reefs to adapt to climate change, increasing the likelihood of coral bleaching).
"Some researchers have argued that there is little difference in climate change impacts between 1.5°C and 2°C,” says co-author Jacob Schewe at the Potsdam Institute for Climate Impact Research in Germany. “Indeed, it is necessary to account for natural variability, model uncertainties, and other factors that can obscure the picture. We did that in our study, and by focusing on key indicators at the regional level, we clearly show that there are significant differences in impacts between 1.5°C and 2°C."
The Paris Agreement, which comes into force in 2020, is tasked with pursuing efforts to “limit the temperature increase to 1.5°C above pre-industrial levels”, as well as tackling the impacts of a warmer world.