Ann Arbor (Informed Comment) – The earth’s atmosphere can make things wet or dry them out depending on the water vapor pressure. When there is a Vapor Pressure Deficit, it dries the earth out. VPD is defined as “a measure of atmospheric water demand defined as the difference between the amount of water vapor in the air and the amount of water vapor that air would hold at saturation.” If there is a lot less water vapor than the atmosphere would normally hold, all other things being equal, you have a bigger deficit. A dry atmosphere also makes the earth beneath it drier. Dry land conditions are conducive to wildfires. The dryness of the atmosphere can also be seasonal. But more than 66% of the summertime vapor pressure deficit in the West has been caused by human activity in burning fossil fuels.
Kristina Dahl et al. conclude that carbon dioxide emissions put out by 88 major carbon producers contributed 48% of the long-term rise in Vapor Pressure Deficit between 1901 and 2021. The paper is published in Environmental Research Letters. Ms. Dahl is the principal climate scientist for the Climate & Energy program at the Union of Concerned Scientists.
We’ve seen massive wildfires in the US and Canadian West in recent years. You might think, well, there have always been wildfires. But how big an area the wildfires burn, the length of the fire season, the number of large fires each season, how high the fires climb up into the hills, and the amount of forested land that burns at “high severity” all vary. All of these measurements of how bad the situation is have increased in the past few decades. So not a random variation. Things have gotten very bad recently, and that needs to be explained.
It’s the 88 companies? It’s the 88 companies.
Some 5 years ago, Tess Riley at The Guardian blamed most of global climate change on 100 companies.
12 News: “Heavy fuels, climate change create uncertainty for Arizona wildfire season”
Dahl and her colleagues concluded that of the blackened earth left behind by forest fires from 1986 to 2021 in the west of the two countries, these 88 companies caused the carbon dioxide emissions that contributed to 37%, over a third, of that burn area. In California, Oregon, Washington State and Vancouver, etc. there has been a big increase in Vapor Pressure Deficit, which in turn has caused more wildfires and contributed to the prolonged Megadrought, which has lasted now for two decades and used to be a once-in-five-hundred years event.
So, no, there haven’t always been wildfires just like the ones we have been experiencing recently. Some 88 companies selling petroleum, coal, fossil gas and cement have made it twice as dry as it would otherwise be, two-thirds drier in summer, and have caused the wildfires to be over a third more destructive than they otherwise would be.
Even before this new study, researchers had established that carbon dioxide and methane produced by Big Oil, Big Coal and Big Cement were responsible for more that 40% of the increasing temperatures around the world, for a quarter of all the world’s sea level rise, and for half of ocean acidification.
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