for National Geographic News
If overall global warming exceeds 5.5°F (3°C), many parts of the world are likely to see substantially increased risks of drought, floods, and wildfires, climate scientists say.
In addition, there will probably be large-scale changes in vegetation types, a U.K.-based research team reports in tomorrow's issue of the Proceedings of the National Academy of Science.
But if global warming is less than 3.5°F (2°C), the risks of such changes are much lower.
"The most important message from the paper is that with stronger global warming, the risk of severe events becomes much more pronounced," said the study's lead author, Marko Scholze of the University of Bristol's QUEST (Quantifying and Understanding the Earth System) project.
In the past, making climate-change projections has been complicated by the fact that different models produce different answers.
So rather than trying to pick one "best" climate model, Scholze's team looked at the degree to which 52 previous forecasts were in agreement.
The result, Scholze says, is like a weather report.
"[Weather forecasters] don't say, It's likely to rain tomorrow," he said. "They say, There's a 50 percent probability. It's the same with our paper."
"This work isn't brand new science," added Sarah Cornell, science manager of the QUEST program. Rather, she said, "it's a new way of communicating."
With average global temperature increases of more than 5.5°F (3°C), there will be a high probability of droughts along Europe's Mediterranean coastline, the scientists report.
The eastern U.S. would also become prone to severe dry spells.
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