Editor TLN
Aug. 25 () –
New research from the University of Washington and Harvard University, both in the United States, offers a series of heat shocks around the world by the end of this century, depending on future greenhouse gas emissionsas published by its authors in the journal ‘Communications Earth & Environment’.
“Record-breaking heat episodes in recent summers will be much more frequent in places like North America and Europe. said lead author Lucas Vargas Zeppetello, who conducted the research as a doctoral student at UW and is now a postdoctoral researcher at Harvard. For many places near the equator, by 2100 more than half the year will be challenging to work outdoors, even if we start to curb emissions.”
“Our study shows a wide range of possible scenarios for 2100 –Add–. This demonstrates that the emissions choices we make now are still important to create a livable future.
The study looks at a combination of air temperature and humidity known as “heat index” that measures the impact on the human body. The National Weather Service defines a “dangerous” heat index such as 39.4º C. An “extremely dangerous” heat index is 51ºand is considered unsafe for humans for any length of time.
“These standards were originally created for people working indoors, in places like boiler rooms, and there was no thought given to conditions that would be found outdoors. But now we are seeing them,” says Vargas Zeppetello.
The study concludes that Even if countries manage to meet the Paris Agreement goal of keeping warming to 2C, crossing the “dangerous” threshold will be three to ten times more frequent by 2100 in the US, Western Europe, China and Japan. In that same scenario, dangerous days could double by 2100 in the tropics, covering half the year.
In the worst case, in which emissions are not controlled until 2100, “extremely hazardous” conditions, in which humans should not be outdoors at any time, could be common in the countries closest to the equator, especially in India and sub-Saharan Africa.
“It’s extremely scary to think about what would happen if 30 or 40 days a year were to exceed the threshold of extreme danger. Vargas Zeppetello warns. These are terrifying scenarios that we still have the ability to prevent. This study shows you the abyss, but it also shows you that we have some agency to prevent these scenarios from happening.”
The study uses a probability-based method to calculate the range of future conditions. Instead of using the four future emissions pathways included in the Intergovernmental Panel on Climate Change reports, the authors employ a statistical approach that combines historical data with population projections, economic growth and carbon intensity -the amount of carbon emitted per dollar of economic activity- to predict the likely range of future CO2 concentrations.
The Statistical Approach “provides plausible ranges for future carbon emissions and temperature, and has been statistically estimated from and validated against historical data”stresses co-author Adrian Raftery, a UW professor of statistics and sociology with an adjunct appointment in atmospheric sciences.
The authors translated the increase in carbon dioxide levels into a series of global temperature increases and then looked at how that would affect the global monthly weather patterns.
“The number of days with dangerous levels of heat in the mid-latitudes will more than double by 2050 says co-author David Battisti, professor of atmospheric sciences at UW. Even for the lowest estimates of carbon emissions and climate response, by 2100 much of the tropics will experience “dangerous” levels of heat stress for nearly half the year.”
The results underscore the need both to reduce future greenhouse gas emissions and to protect the population, especially outdoor workers, against dangerous heat.
