For Billions, Earth Could Be Too Hot to Handle in 50 Years

In just 50 years, 2 billion to 3.5 billion people, mostly the poor who can’t afford air conditioning, will be living in a climate that historically has been too hot to handle, a new study says. With every 1.8 degree increase in global average annual temperature from man-made climate change, about a billion or so people will end up in areas too warm day-in, day-out to be habitable without cooling technology, according to ecologist Marten Scheffer of Wageningen University in the Netherlands, co-author of the study. How many people will end up at risk depends on how much heat-trapping carbon dioxide emissions are reduced and how fast the world population grows, the AP reports. Much more from the study:

• Under the worst-case scenarios for population growth and for carbon pollution—which many climate scientists say is looking less likely these days—the study in Monday’s journal Proceedings of the National Academy of Sciences predicts about 3.5 billion people will live in extremely hot areas. That’s a third of the projected 2070 population.
• But even scenarios considered more likely and less severe project that in 50 years a couple of billion people will be living in places too hot without air conditioning, the study said.

• In an unusual way to look at climate change, a team of international scientists studied humans like they do bears, birds and bees to find the "climate niche" where people and civilizations flourish. They looked back 6,000 years to come up with a sweet spot of temperatures for humanity: Average annual temperatures between 52 and 59 degrees.
• Currently about 20 million people live in places with an annual average temperature greater than 84 degrees—far beyond the temperature sweet spot. That area is less than 1% of the Earth’s land, and it is mostly near the Sahara Desert and includes Mecca, Saudi Arabia.
• But as the world gets more crowded and warmer, the study concluded large swaths of Africa, Asia, South America, and Australia will likely be in this same temperature range.
• "It’s a huge amount and it’s a short-time. This is why we’re worried," said Cornell University climate scientist Natalie Mahowald, who wasn’t part of the study.

(More climate change stories.)