Global Warming Now Pushing Heat into Territory Humans Cannot Tolerate

Our analysis of wetbulb temperatures from 1979-2017 did not disagree with these warnings about what may be to come. But whereas past studies had looked at relatively large regions (on the scale of major metropolitan areas), we also examined thousands of weather station records worldwide and saw that, at this more local scale, many sites were closing in much more rapidly on the 35°C limit. The frequency of punishing wetbulb temperatures (above 31°C, for example) has more than doubled worldwide since 1979, and in some of the hottest and most humid places on Earth, like the coastal United Arab Emirates, wetbulb temperatures have already flickered past 35°C. The climate envelope is pushing into territory where our physiology cannot follow.

The consequences of crossing 35°C, however brief, have perhaps been mainly symbolic so far, as residents of the hottest places are used to riding out extreme heat by sheltering in air-conditioned spaces. But relying on artificial cooling to cope with the growing heat would supercharge energy demand and leave many people dangerously exposed to power failures. It would also abandon the most vulnerable members of society and doesn’t help those who have to venture outside.

The only way to avoid being carried further and more frequently into uncharted heat territory is to reduce greenhouse gas emissions to net zero. The economic slowdown during the coronavirus pandemic is expected to slash emissions by 4-7% in 2020, bringing them close to where global emissions were in 2010. But concentrations of greenhouse gases are still rising rapidly in the atmosphere. We must also adapt where possible, by encouraging simple behavioral changes (like avoiding outdoor daytime activity) and by ramping up emergency response plans when heat extremes are imminent. Such steps will help to buy time against the inexorable forward march of the Earth’s climate envelope.

We hope that our research illuminates some of the challenges that may await us as global temperatures rise. The emergence of unprecedented heat and humidity – beyond what our physiology can tolerate – is just a portion of what could be in store. An even warmer and wetter world risks generating climate extremes beyond any human experience, including the potential for a whole host of “unknown unknowns”.

We hope that the sense of vulnerability to surprises left by COVID-19 invigorates global commitments to reaching carbon neutrality – recognizing the value in preserving conditions that are somewhat familiar, rather than risking what may be waiting in a very novel climate ahead.

Tom Matthews is Lecturer in Climate Science, Loughborough University. Colin Raymond is Postdoctoral Researcher, California Institute of Technology. This article is published courtesy of The Conversation.