Global warming could make southern Spain look like the Sahara Desert if temperatures are not held in check at 1.5 C degrees above preindustrial levels.

A new report in the journal Science titled "Climate Change: The 2015 Paris Agreement Thresholds and Mediterranean Basin Ecosystems" warns that if greenhouse gas emissions continue unabated and global warming reaches or exceeds the 2 C degrees Celsius limit specified in the Paris deal, desertification could overtake many areas around the Mediterranean by the end of the century.  The heat would alter ecosystems in ways not seen in 10,000 years.

The authors came to the conclusion after examining pollen cores found in sediments dating back to the Holocene - the geological epoch that began more than 10,000 years ago, and the last time local temperatures were as high as what could happen with global warming.  They compared the information from past conditions to predictions of future climate and vegetation under different climate change scenarios.

"The main message is really to maintain at less than 1.5 C," said lead author Joel Guiot, palaeoclimatologist at the European Centre for Geoscience Research and Education in Aix-en-Provence, France.  "For that, we need to decrease the emissions of greenhouse gases very quickly, and start the decreasing now, and not by 2020, and to arrive at zero emissions by 2050 and not by the end of the century."