Based on climate modelling, the study projects that extreme heat waves like those that hit the United States in 2012 and Australia in 2009 will by 2020 affect about 10 percent of total land area -- double today's figure. By 2040, it would have quadrupled.
But what happens after 2040 can still be influenced by what we decide now. Targets adopted today for curbing greenhouse gas emissions will determine whether the pattern stabilises thereafter, or grows even worse.
Under a low emission scenario, the number of extremes will stabilise by 2040, whereas under a high emission scenario, the land area affected by extremes will increase by one percent a year.
High temperatures and heat waves in the last decade are widely blamed on climate change that occurred over the last 50 years - amounting to global warming of about 0.5 degrees Celsius (0.9 deg Fahrenheit), said the study in the journal Environmental Research Letters.