Along With Arctic Ice Loss, GHGs & Aerosols Causing "Stuck" Jet Stream, Extreme Weather

[hatrack]

Greenhouse gases are increasingly disrupting the jet stream, a powerful river of winds that steers weather systems in the Northern Hemisphere. That's causing more frequent summer droughts, floods and wildfires, a new study says. The findings suggest that summers like 2018, when the jet stream drove extreme weather on an unprecedented scale across the Northern Hemisphere, will be 50 percent more frequent by the end of the century if emissions of carbon dioxide and other climate pollutants from industry, agriculture and the burning of fossil fuels continue at a high rate.

In a worst-case scenario, there could be a near-tripling of such extreme jet stream events, but other factors, like aerosol emissions, are a wild card, according to the research, published today in the journal Science Advances.

The study identifies how the faster warming of the Arctic twists the jet stream into an extreme pattern that leads to persistent heat and drought extremes in some regions, with flooding in other areas.

The researchers said they were surprised by how big a role other pollutants play in the jet stream's behavior, especially aerosols—microscopic solid or liquid particles from industry, agriculture, volcanoes and plants. Aerosols have a cooling effect that partially counteracts the jet stream changes caused by greenhouse gases, said co-author Dim Comou, a climate and extreme weather researcher at the Potsdam Institute for Climate Impacts Research and the Vrije Universiteit Amsterdam.

EDIT

https://insideclimatenews.org/news/31102018/jet-stream-climate-change-study-extreme-weather-arctic-amplification-temperature

[mn9driver]

1. I have been observing this directly over the last 30 years.

I spend my working days flying back and forth across North America. The jet streams behave very differently now than they did back then.

It’s now fairly unusual to see a “classic” west to east flow. Based on my personal observations, I think the worst case scenario described in the article is more likely than not.

[nitpicker]

2. From DW

https://www.dw.com/en/how-a-warmer-arctic-could-lead-to-more-extreme-weather/a-46107835

How a warmer Arctic could lead to more extreme weather

Climate experts are concerned we may soon start to see more extreme weather events in the Northern Hemisphere. The culprit? A warmer Arctic, which could potentially disrupt the polar jet stream. Whether it's long-lasting sunshine or rain that drags on for days on end, the Northern Hemisphere is experiencing extended stretches of certain kinds of weather — especially in summer. This brings with it more extreme weather events, from heat waves and droughts that cause crop failures to torrential downpours that can flood major cities.

Climatologists say one reason for the increase of such protracted extreme weather events is due to lingering fast-moving air currents — more specifically the polar jet stream, which has shifted from its usual patterns as a result of rising temperatures in the Arctic and air pollution.

How does a warmer Arctic disrupt the jet stream?

Connecting the dots between higher temperatures around the North Pole and more extreme weather across parts of Europe, North America and Asia seems a little complicated — but it's basically all about the atmosphere. Most of our planet's weather phenomena actually get their start at 8 to 17 kilometers kilometers (4.9 to 10.5 miles) above the ground.

"Huge flows of air are orbiting our Earth in the upper troposphere — we refer to them as planetary waves," explained Joachim Schellnhuber from the Potsdam Institute for Climate Impact Research (PIK). "The evidence is now mounting that mankind is essentially confusing these wind currents," he continued. Fueled by man-made greenhouse gas emissions, such natural circulation patterns are likely to get distorted by global warming, he said.

The waves of air that carry chains of high- and low-pressure areas oscillate from west to east, between the equator and the North Pole. But they can get held in place and slow down, which causes the weather to get stuck in a particular region. This "turns rainfall into flooding, sunny days into heat waves and dry conditions into forest fires," said Schellnhuber.