Climate Fingerprints All over Cali Wildfires

November 10, 2018

PBS Newshour from August has perspective from Michael Mann and others.

San Francisco Chronicle:

Much of the heat that’s gripped California and hastened the spread of deadly wildfires recently is due to a strange but familiar shift in the jet stream — one that’s haunted the West with threatening fire conditions in the past and could cause more hot, dry spells in the future, especially with a changing climate.

The jet stream, the river of wind high above the Northern Hemisphere, has been weaker and wavier in the past few weeks, scientists say. Instead of pushing weather systems along as it usually does, it’s allowing the patterns to stagnate.

Not only has this meant searing temperatures for the West Coast, where the hot spot of Death Valley averaged a record 108 degrees last month, but also for Scandinavia and Japan. Norway and Sweden flirted with a rare 90 degrees at the Arctic Circle this week, while the Japanese city of Kumagaya recently landed that nation’s highest-ever temperature: 106. Other places, such as the East Coast, have endured relentless rain, even flooding.

“We’re seeing this mix of conditions across North America and Europe, but they’re all connected,” said Jennifer Francis, a professor at Rutgers University who studies atmospheric circulation. “The weather patterns are just stuck. They’re trapped.”

The shift in the jet stream that’s driving the stagnation, say Francis and other climate scientists, is almost certainly tied to global warming.

It’s just one of the ways that climate change is probably contributing to the spree of fires in California that has killed eight people and destroyed more than 1,000 homes.

California’s fire season, most fundamentally, is saddled with higher temperatures — with or without a heat wave, scientists say. The greenhouse gases emitted from cars, power plants and factories, which trap sunlight and warm the atmosphere, have created baseline conditions that are more hospitable to wildfire. Water loss from soil and plants is generally up while snowmelt and river flows are down.

A study last year by researchers at Columbia University and the University of Idaho found that human-caused warming was drying out forests so much that peak fire seasons across the West have expanded every year by an average of nine days since 2000.

Other factors are influencing wildfire as well, making it difficult to always draw such precise conclusions about the role of climate change. The nation’s longtime policy of wildfire suppression, for example, has created a dangerous buildup of vegetation that’s making fires more intense. Development in rural areas, meanwhile, is increasing the human toll.

Nevertheless, climate researchers and fire experts agree that global warming is having an impact and that the impact will only grow.

Across California this week, more than 12,000 firefighters were battling several major wildfires. The Carr Fire, in Shasta County, has already become the state’s sixth most destructive blaze, leveling 1,067 homes as of Friday. Temperatures were reported to be 113 degrees, at least 13 degrees above average for the week, when the fire tore into the city of Redding.

The Ferguson Fire, to the south, has been burning along the western edge of Yosemite for weeks, prompting a rare shutdown of much of the national park. In nearby Fresno, the mercury has been at 100 degrees or higher every day since July 6, setting a mark for consecutive days of triple-digit heat.

The weak and wavy jet stream behind California’s hot spell has taken hold before. The pattern was firmly established in 2003 when a heat wave killed tens of thousands in Europe, in 2010 when several hundred wildfires ignited in Russia and in 2011 when Texas saw its worst drought in state history.

Research by Michael Mann, a climatologist and geophysicist at Penn State University, suggests that the change in the jet stream is partly the result of warming in the Arctic. When the Arctic gets hotter, the contrast in temperatures between northern latitudes and more southern latitudes is less. That variation causes a disturbance in the atmosphere that shifts the jet stream, Mann said.

“These factors work together to produce the sorts of persistent extreme weather events — droughts, floods, heat waves, wildfires — that we’re seeing across the Northern Hemisphere right now,” Mann said in an email.



6 Responses to “Climate Fingerprints All over Cali Wildfires”

  1. dumboldguy Says:

    This news from August has been superseded by the much worse news of what is going on with fires in CA right NOW. Relatives on the coast SW of SF in Half Moon Bay report that the smoke is so bad that they can’t go outside (not if they want to keep breathing, that is). Town of Paradise has been virtually destroyed.

  2. indy222 Says:

    DOG – south of Half Moon Bay is Santa Cruz, and it’s just as bad here. I don’t even know which fire is responsible.

    Here’s how the right wing financial media (“ZeroHedge”) is spinning it

    • Lionel Smith Says:

      Of course zerohedge is repeating that which has been fed to the CinC (Clown in Chief) which entity has simply repeated it.

      As most of us realise, but the financial wizard goons don’t, and as Jennifer Frances aptly puts it global warming has caused the, in this case polar jet-stream to weaken and get stuck so that some experience atypical lengths of dry spells of increasing severity whilst others get drowned.

      The jet stream weakens because of the effect of the poles warming faster than the tropic. This in turn causes the the air over the Arctic to become warmer, less dense and expand up towards the troposphere. The differential in gravity effect between the Ferrel and polar cells is thus reduced and a weakened jet-stream results.

      The Wikipedia entry is quit clear on this and worth a study for those new, or who don’t get it with the paragraph ‘Description’ has a nice diagram to help with the understanding, ‘Cause’ is of particular interest and ‘Longer-term climatic changes’ being more to the point and I quote:

      Climate scientists have hypothesized that the jet stream will gradually weaken as a result of global warming. Trends such as Arctic sea ice decline, reduced snow cover, evapotranspiration patterns, and other weather anomalies are expected to make the Arctic heat up faster than other parts of the globe. This in turn reduces the temperature gradient that drives jet stream winds, causing the jet stream to become weaker and more variable in its course.

      ‘Longer-term climatic changes’ also has an explanation that explains the current California situation.

      Since 2007, and particularly in 2012 and early 2013, the jet stream has been at an abnormally low latitude across the UK, lying closer to the English Channel, around 50°N rather than its more usual north of Scotland latitude of around 60°N.[not in citation given] However, between 1979 and 2001, it has been found that the average position of the jet stream has been moving northward at a rate of 2.01 kilometres (1.25 mi) per year across the Northern Hemisphere. Across North America, this type of change could lead to drier conditions across the southern tier of the United States and more frequent and more intense tropical cyclones in the tropics. A similar slow poleward drift was found when studying the Southern Hemisphere jet stream over the same time frame.

      I had appreciated this effect by the early 1990s and indeed was asked about it at a job interview for a scientific Officer at the UK Met Office as there were particular anomalies showing up in the year of my application. My blend of aviation related knowledge and engineering experience (including several years on a Naval aircraft trials installation unit) along with recently acquired computer experience and also meteorological understanding were of interest as at that time the Met Office was operating a C-130 for research.

      By the time the offer came through I had accepted a post elsewhere.

  3. John Says:

    Reblogged this on jpratt27 and commented:
    Time to join the #ExtinctionRebellion

  4. shastatodd Says:

    “Climate Fingerprints All over Cali Wildfires”

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: