From the Tropics north, warmer summers - and their almost certainly disastrous consequences - within the next few decades are close to being an irreversible consequence of global warming says a new study from Stanford University in the United States of America.
The research is published in the new edition of the journal Climate Change and says warmer summers are on the way unless greenhouse gas concentrations stop increasing.The change will be felt first closest to the Equator, where, say the scientists there will be a "permanent emergence of unprecedented summer heat" within 20 years. The warming trend will move north over the next four decades.
"According to our projections, large areas of the globe are likely to warm up so quickly that, by the middle of this century, even the coolest summers will be hotter than the hottest summers of the past 50 years," said the study's lead author, Noah Diffenbaugh, an assistant professor of environmental Earth system science and fellow at the Woods Institute for the Environment at Stanford.
Diffenbaugh and his co-author research assistant Martin Scherer looked at more than 50 climate models, including those from the past that had been proved accurate by the passage of time.
In the tropics they predict that 70 percent of summers will beat temperature records by 2040. By 2070, this trend will have affected North America, China and Mediterranean Europe are also likely to enter into a new heat regime by 2070, according to the study.
Such speedy climate change will have a massive impact on humans and the natural world with heat waves causing deaths and reducing agricultural output.
"The fact that we're already seeing these changes in historical weather observations, and that they match climate model simulations so closely, increases our confidence that our projections of permanent escalations in seasonal temperatures within the next few decades are well founded," Diffenbaugh said.