[MCN] Human thermal limits impose human population limits

Lance Olsen lance at wildrockies.org
Mon Jul 29 10:56:50 EDT 2019

Excerpt: Deadly heatwaves are, of course, no stranger to Europeans. The infamous 2003 event claimed as many as 70,000 lives <https://www.sciencedirect.com/science/article/pii/S1631069107003770?via%3Dihub>, and 2010 saw more than 50,000 fatalities <https://science.sciencemag.org/content/332/6026/220.full> in western Russia. Fortunately, lessons were learned and authorities are now much better prepared <https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/801539/Heatwave_plan_for_England_2019.pdf> when heat-health alerts are issued.

But spare a thought for less fortunate communities who are routinely experiencing extraordinary temperatures. In places like South Asia <https://advances.sciencemag.org/content/3/8/e1603322.full> and the Persian Gulf <https://www.nature.com/articles/nclimate2833?platform=oscar&draft=journal>, the human body, despite all its remarkable thermal efficiencies <https://www.ncbi.nlm.nih.gov/pubmed/26184272>, is often operating close to its limits.

And yes, there is a limit.

When the air temperature <https://phys.org/tags/air+temperature/> exceeds 35°C, the body relies on the evaporation of water—mainly through sweating—to keep core temperature <https://phys.org/tags/temperature/> at a safe level. This system works until the "wetbulb" temperature reaches 35°C. The wetbulb temperature includes the cooling effect of water evaporating from the thermometer, and so is normally much lower than the normal ("drybulb") temperature reported in weather forecasts.

Once this wetbulb temperature threshold is crossed, the air is so full of water vapour that sweat no longer evaporates. Without the means to dissipate heat, our core temperature rises, irrespective of how much water we drink, how much shade we seek, or how much rest we take. Without respite, death follows—soonest for the very young, elderly or those with pre-existing medical conditions.

Wetbulb temperatures of 35°C have not yet been widely reported, but there is some evidence that they are starting to occur <https://journals.sagepub.com/doi/abs/10.1177/0309133318776490> in Southwest Asia. Climate change then offers the prospect that some of the most densely populated regions on Earth could pass this threshold by the end of the century, with the Persian Gulf <https://www.nature.com/articles/nclimate2833?platform=oscar&draft=journal>, South Asia <https://advances.sciencemag.org/content/3/8/e1603322.full>, and most recently the North China Plain <https://www.nature.com/articles/s41467-018-05252-y> on the front line. These regions are, together, home to billions of people.

End of excerpt
https://phys.org/news/2019-07-heatwave-human-body-thermal-limits.html <https://phys.org/news/2019-07-heatwave-human-body-thermal-limits.html>

“I just want it to be clear that the mainstream environmental movement has been asking very little of people for decades” said Bea Ruiz, also an organizer with the U.S. national [ Extinction Rebellion ] team. “There’s no element of, ‘We are in an emergency. We all need to do more than what we’re doing.’ There’s a lot of emphasis on positivity and hope.”

“We’re trying to put out there what’s necessary, not what people think is politically possible. And then we’re trying to be part of helping to change what’s politically possible through direct action,” Ruiz said. “We are really, literally, almost out of time, and if we don’t make the reductions that are needed based on the science, we’re going to be in serious trouble. We can’t negotiate with reality.”

Extinction Rebellion’s radical philosophy
July 22 2019

A recent Ambio article by some heavyweights in climate sets out the situation well enough. 

A team including the likes of Will Steffen, Paul Crutzen, Veerabhadren Ramathan, Johan Rockstrom, Marten Scheffer and Hans Joachim Schellnhuber begin the abstract of their article by saying “Over the past century, the total material wealth of humanity has been enhanced …”  

They end it saying,“we risk driving the Earth System onto a trajectory toward more hostile states from which we cannot easily return.”

Their analysis is echoed across the scientists side of the situation. But it doesn’t take a scientist to get the drift of what’s going on. 

Liam Denning is former investment banker, former editor of one of the Wall Street Journal’s most closely read columns —Heard on the Street — and a former columnist for Financial Times. Writing about the Green New Deal for Bloomberg, Denning has come to the conclusion that, “We have built our standard of living on forms of energy that we now know pose a threat to our very existence,” and that, “this is a conversation that is long overdue — and necessarily begins with a shout, not a whisper.”


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