More fires, droughts and floods predicted

Despite the commitment we have already to global warming, even if we stopped emitting greenhouse gases now the researchers predict that Eurasia, eastern China, Canada, Central America, and Amazonia are at risk of forest loss (up to 30% probability for a global warming of less then 2°C and increasing to more than 60% for a warming of more than 3°C), while the far north, Amazonia and many semi-arid regions will become more susceptible to wildfires.

Less freshwater availability, and with it more intense droughts, are likely to occur in West Africa, Central America, southern Europe and the eastern USA. Other regions, particularly areas north of 50°N, tropical Africa and northwest South America, will be at significant risk of excessive runoff as trees are lost, increasing the chances of flooding as temperatures rise.

The researchers also found that if the temperature increase is more than 3°C, land carbon sinks could release their stored carbon, starting a positive feedback loop that would increase atmospheric carbon dioxide.

Marko Scholze, lead author on the paper published in PNAS this week, said: “Most importantly we show the steeply increasing risks, and increasingly large areas affected, associated with higher warming levels. This analysis represents a considerable step forward for discussions about ‘dangerous’ climate change and its avoidance.”

The team from QUEST (Quantifying and Understanding the Earth System, a project funded by the Natural Environment Research Council and based at Bristol University), with a colleague from the University of Southampton, quantified the risks of climate-induced changes in key ecosystem processes, using novel methods. They gathered results from more than 50 climate model simulations to calculate these risks and then grouped the results according to varying amounts of global warming: less than 2°C, 2-3°C, and more than 3°C.

For each of the temperature groups they show the probability of shifts in forest cover and the areas which exceed the natural variability in wildfire frequency or freshwater supply for the coming 200 years.