Wavy jet stream - the picture of radical climate disruption
From heatwaves in the west to floods across the world
Reading time - 4 minutes
It is the picture of a climate in chaos, a wavy and broken jet stream causing hell across the planet. Heatwaves and wildfires in western North America. Floods from Western Europe to Africa to India.
CBS News meteorologist Jeff Berardelli has been doing some of the absolute best connecting of weather extremes to climate disruption on any major media outlet. He tweeted this GIF showing how it’s all connected.
The science has been emerging over the last several years. Scientists are cautious by nature, and the connections between the wavy jet stream and global heating are not 100% nailed down. But they are pretty damned close.
In a 2017 study of the connections led by climate scientists Michael Mann and Stefan Rahmstorf, "We came as close as one can to demonstrating a direct link between climate change and a large family of extreme recent weather events," Mann said. Those include the 2003 European heat wave, 2010 Pakistan flood and Russian heatwave, 2011 Texas and Oklahoma heat wave and drought, and the 2015 California wildfires.
The physical logic is strong. The jet stream is the major weather driver in the Northern Hemisphere. It carries along storms and heatwaves. Those have limited impacts when they move through quickly. But when the jet stream slows down and locks in place, intense heat and rainfall can stay stationary over regions for longer times. The wavy jet stream is the source of the heat domes parking over the North American west and the drenching storms that have devastated places from Germany, Belgium and Switzerland to Lagos, Nigeria and Mumbai, India. (Though media coverage in the western press is emphasizing the European impacts and only lightly covering those in the global south. The map below is only too true.)
The jet stream is driven by the contrast in heat between the north pole and equator. The sharper the contrast, the more defined is the path of the jet stream and the quicker is its movement. But Arctic heating has been diminishing that contrast, and Arctic summer sea ice melt is amplifying the heating. Roughly 90% of solar rays bounce back into space from white ice, while roughly 90% are absorbed in blue oceans.
Jennifer Francis of Woods Hole Research Institute drew the connection back in 2015. Viewing an increase in jet stream waviness, she and fellow authors concluded, “These results suggest that as the Arctic continues to warm faster than elsewhere in response to rising greenhouse-gas concentrations, the frequency of extreme weather events caused by persistent jet-stream patterns will increase.”
Mann and Rahmstorf built off her work with peer-reviewed studies in 2017 and 2018. The 2017 study made the connection with recent weather extremes. In 2018, they found that events which intensify the waviness of the jet stream are likely to increase 50%, from 7.5 a year to 11, if we continue on a business-as-usual increase in climate pollution. Some models which emphasize Arctic heating show a tripling by the end of the century. But if we can keep global heating under 2°C/3.6°F, we can likely avert those increases.
This is why we need dramatic reductions in burning coal, oil and natural gas beginning immediately, as well as in deforestation, another significant source of climate pollution. The emergence of radical impacts demands radical action. Business as usual is done. If we want to leave a world with which our children can cope, when the capacity of humanity and nature to adapt is stressed beyond the breaking point, we need to rise up as people and demand change now.
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