Changing jet stream, extreme weather linked to humans: study

[applegrove]

https://www.google.ca/amp/www.cbc.ca/amp/1.4043390

Johanna Wagstaffe - CBC News

March 29, 2017 (from Canada but could be applied to tropical storm Harvey over Houston)

"SNIP........


The team of international scientists found that warming caused by greenhouse gases impacts the massive conveyor belts that live in our upper atmosphere. Driven by temperature differences, these giant jet streams transport heat and moisture around the northern hemisphere. 

The Arctic is warming faster than any other region on Earth. As well, land masses warm more quickly than the oceans. These two factors have led to the overall temperature difference between the two — essentially the fuel for these jet streams — to decrease.

As our climate changes, the temperature gradient isn't as strong between the Arctic and the tropics, meaning there isn't as much energy to help move these waves — and weather — along. When these planetary waves get stuck in place, droughts or floods can occur. And it's part of a growing trend that can't just be accounted for by usual variability in the weather, the researchers said.​

The team of researchers analyzed temperature differences between the equator and the poles recorded since the 1870s and reconstructed the changes over time. They found that the frequency of these jet streams stalling out has increased by 70 per cent since the Industrial Revolution, with most of the effects in the past four decades — indicating a clear fingerprint of human activity. 

.........SNIP"

https://www.nature.com/articles/srep45242