Global warming will force more than a fifth of the world's population out of the "climate niche" most conducive to human life by 2100 if temperatures continue rising, a new study estimates, articulating the dire toll across many parts of the world in the coming decades if policymakers do not take sharp action to curtail the worst effects of heat.
By the end of the century, nearly 2 billion people could be living with average annual temperatures hotter than 84 degrees Fahrenheit, or 29 degrees Celsius, the maximum level at which the study's authors said was historically conducive to human settlement and habitation.