Countdown to 'thermogeddon' has begun

"There may come a point, if the world warms enough, when parts of the tropics will become so hot and humid that humans will not be able to survive. Models predict that this could start to happen in places in as little as 100 years in the worst case scenario. Now, observations show the process is already under way.

As humidity rises, sweating cools us less, so we suffer heat stress at lower air temperatures. For now, no place on Earth exceeds the human threshold for heat tolerance, with the exception of a few caves like the Naica cave in Mexico. That is thanks to a fortunate natural thermostat: when humid air gets hot, it rises and causes storms that cool things down.

But there is a catch. The point at which air begins to rise - the stability threshold - depends on how warm and moist surrounding air is. Models predict that as the entire tropics warm, the stability threshold will rise."
via New Scientist/read more