The forecasts, based on new computer models and an analysis of a significant number of extreme heatwaves in the past decade, are more concerning than the findings of the UN panel of climate scientists last year. The report by the Intergovernmental Panel on Climate Change, which compiles scientific research from around the world, stated that it is likely that warm spells or heatwaves will increase in length, frequency, and intensity over most land areas this century. The new study published in the journal Environmental Research Letters predicts that monthly heat extremes in summer currently affect five percent of the world's land area, a number expected to double by 2020 and quadruple by 2040. The tropics will be the most impacted by increased heatwaves, followed by regions such as the Mediterranean, Middle East, parts of western Europe, central Asia, and the United States. Without curbing greenhouse gas emissions, the coldest summer months in many areas by the end of the century will be hotter than the hottest experienced today, according to Dim Coumou of the Potsdam Institute for Climate Impact Research. The IPCC indicates that heat-trapping gases, primarily from burning fossil fuels, are leading to higher temperatures and are likely to result in more severe downpours, heatwaves, floods, and rising sea levels. Nearly 200 governments have agreed to limit global warming to less than 2 degrees Celsius above pre-industrial times and are working towards a deal to reduce greenhouse gas emissions by the end of 2015. Global average surface temperatures have increased by 0.8C since the Industrial Revolution.