“If the same weather persists for weeks on end in one region, then sunny days can turn into a serious heat wave and drought, and lasting rains can lead to flooding.” — Dr. Stefan Rahmstorf.
“The warming of the Arctic, the polar amplification of warming, plays a key role here. The surface and lower atmosphere are warming more in the Arctic than anywhere else on the globe. That pattern projects onto the very temperature gradient profile that we identify as supporting atmospheric waveguide conditions.” — Dr. Michael Mann.
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To say that, for the U.S., it’s been hot out west and stormy in the east this summer is a bit of an understatement. For while the east has seen numerous storms producing local-to-national record rainfall amounts, the west has been baking under heatwaves that appear to have set off one of the worst years for wildfires nationally on record. This is an extreme summer weather pattern that recent scientific studies have linked to human-caused climate change.
Last week, extreme heat baked the U.S. west coast. On Friday, San Francisco hit a record high of 106 degrees (F), striking up to 102 (F) on Saturday. Regions further inland near Eureka hit a Death Valley-like 115 F. 36 million Californians fell under a heat advisory as excessive heat warnings ranged on up the west coast through Oregon, Washington, and British Columbia.
The heat wave — which was just the most recent of many for the region this year — baked hills and valleys covered with new vegetation springing up after unusually heavy winter rains. Setting off a spree of wildfires that has seen very severe burn rates throughout summer.
Los Angeles County in Burbank experienced its largest fire on record Saturday as a massive blaze swept through the hills — igniting 7,000 acres before being tamped down by the oddly northward tracking remnants of a tropical storm drifting through the region on Sunday.
The fire spurred the response of 1,000 firefighters, forced 700 people to evacuate, closed route 210 for a time and consumed three homes. Assisted by the rains and moisture flowing off the remnants of Lidia, firefighters have now managed to contain 30 percent of this particular blaze. But with many more fires continuing to burn throughout the west, the region is far from out of the proverbial woods.
According to the National Interagency Fire Center, 70 large fires continue to burn in the western states of Montana, California, Oregon, and Washington. The vast majority of these fires remain uncontained. And at least two exceed 100,000 acres in size. Smoke from these fires has been cycling into the upper level winds for some time now — with most of the northern U.S. falling under a high altitude smoke plume (see top image above).
In total, more than 7,800,000 acres have burned so far in the U.S. this year. This represents the second worst fire year on record so far compared to the last ten years and may ultimately beat out 2006 as the second worst fire year ever recorded. By end 2006, 9 million total acres had burned. During the worst fire year for the U.S. — 2015 — 11 million acres burned in total. By this time during 2015, nearly 9 million acres had been consumed compared to 2017’s present total near 8 million acres.
These fires are occurring primarily in the west where a persistent high amplitude ridge in the Jet Stream has formed. This ridge keeps enabling heatwaves to bake the region and spike fire dangers. And it’s a weather feature that some scientists are saying is linked to human-caused climate change — which is causing the Arctic to warm, while pulling meridional south-to-north upper level winds into the polar zone and producing a wavier jet stream during extreme weather patterns.
The net effect is to create a kind of Halo of Storms and Heatwaves over the middle and upper latitude regions of the world. Earlier this year, The Scientific American noted:
What we think happens is that when there is a ridge forming in a location where Arctic warming can intensify it, that makes the ridge strong and builds it even farther northward. It creates an even bigger wave in the jet stream. You get a stronger ridge over western North America and a stronger southward dip that is farther toward eastern North America.
A subsequent scientific study lead by Dr. Michael Mann and presented in March of this year found that:
… analysis of both historical model simulations and observational surface temperature data, strongly suggests that anthropogenic warming is impacting the zonal mean temperature profile in a manner conducive to wave resonance and a consequent increase in persistent weather extremes in the boreal summer.
And this is exactly what we’ve seen over the U.S. this summer. A stronger than normal ridge in the west fueling record heatwaves and wildfires and a stronger than normal trough in the east fueling more extreme storms. This is a pattern of juxtapposed extremes. One that appears to be fueled by climate change related factors.
Links:
National Interagency Fire Center
Largest Wildfire in Los Angeles History Burns Amid Record-Setting Heat
Extreme Weather Events Linked to Climate Change’s Influence on the Jet Stream
A Halo of Storms and Heatwaves
