expert reaction to the North American heatwave


Record-breaking high temperatures continue in western Canada and parts of the US Pacific northwest.


Prof Richard Allan, Professor of Climate Science, University of Reading, said:

“Weather patterns that produce persistent high pressure systems, cloud-free conditions and dry continental winds can generate summer heatwaves. Climate change is intensifying these heatwaves as greenhouse gas increases raise temperatures and a warmer, more thirsty atmosphere rapidly dries out soils so that more of the sun’s energy heats the ground rather than evaporating water. Heatwaves have clear implications for human health as well as for plants and animals while conditions are often exacerbated by increased risk of fires, droughts and poor air quality as stagnant, sun-baked air traps and increases pollutants.”


Prof Julienne Stroeve, Professor of Polar Observation & Modelling, University College London, said:

“The unusual heat wave in the northwest of the US is caused by a an extremely high sea level pressure anomaly that some research has showed can be linked to the droughts in the West and Arctic sea ice loss. A study in Nature in 2017 showed that sea ice loss leads to persistent atmospheric ridging in the North Pacific, that in turn results in high sea level pressure over the North Pacific that dries out California.”


Prof Richard Betts, Head of Climate Impacts Research, Met Office Hadley Centre, said:

“Weather conditions leading to heatwaves are now happening on top of a background climate that has been warmed by humans adding more greenhouse gases to the atmosphere. So even though heatwaves happen naturally as part of the weather, they are now routinely hotter than they would have been without human-driven global warming. Extreme heat causes a risk to life, especially in places where people are not so used to hot weather so are not prepared to take action to keep cool, as seen in North America at the moment. The warming climate is also increasing the risk of wildfires in many regions around the world by drying out the landscape, including in the Pacific North-West.”


Prof Ilan Kelman, Professor of Disasters and Health, University College London, said:

“This heat wave is unusual, extremely dangerous, and unfortunately not surprising. It is exactly in line with what we expect due to climate change if we do not act, keeping in mind that we do not always have long datasets to be able to calculate how much climate change contributed to these specific temperatures in these specific places. Such terrible heat-related death tolls could be seen not only in western Canada and the USA, but also elsewhere around those countries and around the world from Melbourne to Manama–including London among many other European cities.

“The lethal danger particularly hits people who work outdoors or who do not have, or who cannot afford, indoor temperature control. Especially when it does not cool down sufficiently at night, not even fans help, because they end up just blowing hot air onto people. The deaths attributed to this heat wave is, sadly, just the beginning of what we will see if we do not act on averting climate change while helping people to deal with extreme heat and humidity.

“Heat and humidity combine to be one of the most immediate, dangerous health impacts from human-caused climate change, which we now witness in a horrible manner. We then have knock-on effects on food production, water availability, power outages, and fires, such as Lytton, British Columbia being alight.”



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