The way heat impacts us depends on humidity. New projections of Wet Bulb Temperature in Summer are staggering.
The authors used an index known as Wet Bulb Globe Temperature, a calculation involving not just temperature but humidity, wind chill, sunlight and infra-red radiation: this is used by the US military and by sports scientists to calculate the effect of temperature conditions on human performance, and to indicate the potential hazards of heat stroke and heat exhaustion.
They report in Nature Climate Change that they estimate that environmental heat stress has reduced labour capacity to 90% in the peak months in the last few decades. By 2050, they estimate, this capacity could be reduced to 80% as workers gasp and perspire in the heat.
“Under the highest scenario considered, by 2100 much of the tropics and mid-latitudes experience months of extreme heat stress, such that heat stress in Washington DC becomes higher than present-day New Orleans,” they report.
New Orleans, in such conditions, would be hotter than present-day Bahrain.
If carbon dioxide emissions continue at the highest projection, then by 2200 in the hottest months, future humans will struggle to deliver even 40% of their present productivity.
By 2200, Washington and New York would be hotter and more uncomfortable than present-day Bahrain.
They ... considered only the case of healthy people accustomed to their local climate.
The old, the ill, the very young and the inexperienced, of course, are the most likely to sicken and die in conditions of extreme heat.