Unum
2018-11-04 03:46:36 UTC
https://www.washingtonpost.com/opinions/its-not-rocket-science-climate-change-was-behind-this-summers-extreme-weather/2018/11/02/b8852584-dea9-11e8-b3f0-62607289efee_story.html
A warmer ocean evaporates more moisture into the atmosphere — so you get worse
flooding from coastal storms (think Hurricanes Harvey and Florence). Warmer
soils evaporate more moisture into the atmosphere — so you get worse droughts
(think California or Syria). Global warming shifts the extreme upper tail of
the “bell curve” toward higher temperatures, so you get more frequent and
intense heat waves (think summer 2018 just about anywhere in the Northern
Hemisphere). Combine heat and drought, and you get worse wildfires (again,
think California).
In a study my co-authors and I recently published in the journal Science
Advances, we identified a key factor behind the rise in extreme summer weather
events (such as the ones that played out in summer 2018) that — as we
demonstrate in our study — is not captured by current generation climate
models. Using an alternative approach based on a combination of models and
real-world observations, we showed that climate change is causing the summer
jet stream to behave increasingly oddly. The characteristic continental-scale
meanders of the jet stream (its “waviness”) as it travels from west to east
are becoming more pronounced and are tending to remain locked in place for
longer stretches of time.
Under these circumstances — when, for example, a deep high-pressure “ridge”
gets stuck over California or Europe — we usually see extreme heat, drought
and wildfire. And typically there’s a deep low-pressure “trough” downstream,
stuck over, say, the eastern United States or Japan, yielding excessive
rainfall and flooding. That’s exactly what happened in summer 2018. The spate
of extreme floods, droughts, heat waves and wildfires we experienced were a
consequence of such jet stream behavior.
Our study shows that climate change is making that behavior more common,
giving us the disastrous European heat wave of 2003 (during which more than
30,000 people perished), the devastating 2011 Texas drought (during which
ranchers in Oklahoma and Texas lost 24 percent and 17 percent of their cattle,
respectively), the 2016 Alberta wildfire (the costliest natural disaster in
Canadian history) and yes, the extreme summer of 2018.
A warmer ocean evaporates more moisture into the atmosphere — so you get worse
flooding from coastal storms (think Hurricanes Harvey and Florence). Warmer
soils evaporate more moisture into the atmosphere — so you get worse droughts
(think California or Syria). Global warming shifts the extreme upper tail of
the “bell curve” toward higher temperatures, so you get more frequent and
intense heat waves (think summer 2018 just about anywhere in the Northern
Hemisphere). Combine heat and drought, and you get worse wildfires (again,
think California).
In a study my co-authors and I recently published in the journal Science
Advances, we identified a key factor behind the rise in extreme summer weather
events (such as the ones that played out in summer 2018) that — as we
demonstrate in our study — is not captured by current generation climate
models. Using an alternative approach based on a combination of models and
real-world observations, we showed that climate change is causing the summer
jet stream to behave increasingly oddly. The characteristic continental-scale
meanders of the jet stream (its “waviness”) as it travels from west to east
are becoming more pronounced and are tending to remain locked in place for
longer stretches of time.
Under these circumstances — when, for example, a deep high-pressure “ridge”
gets stuck over California or Europe — we usually see extreme heat, drought
and wildfire. And typically there’s a deep low-pressure “trough” downstream,
stuck over, say, the eastern United States or Japan, yielding excessive
rainfall and flooding. That’s exactly what happened in summer 2018. The spate
of extreme floods, droughts, heat waves and wildfires we experienced were a
consequence of such jet stream behavior.
Our study shows that climate change is making that behavior more common,
giving us the disastrous European heat wave of 2003 (during which more than
30,000 people perished), the devastating 2011 Texas drought (during which
ranchers in Oklahoma and Texas lost 24 percent and 17 percent of their cattle,
respectively), the 2016 Alberta wildfire (the costliest natural disaster in
Canadian history) and yes, the extreme summer of 2018.