Extreme Temperature Diary- Wednesday August 25th, 2021/ Main Topic: Another Dire Feedback Loop?…Where There IS Smoke There Is More Drought + Climate Central Western Fire Trends

The main purpose of this ongoing blog will be to track planetary extreme or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials)😉

Main Topic: Another Dire Feedback Loop?…Where There IS Smoke There Is More Drought + Climate Central Western Fire Trends

Dear Diary. Well this one is a new one on me. I spied the following National Geographic article indicating that a new scientific study has found that smoke from wildfires itself inhibits rainfall, creating a dangerous feedback loop reinforcing drought. I was actually under the assumption that smoke nuclei aided the formation of droplets within clouds. I am probably wrong along with many other meteorologists. Evidently chemicals found within smoke keep rain clouds from forming. We have one more reason to get our carbon pollution house in order.

After posting this National Geographic article I will present the latest Climate Central trends on western wildfires, which came in my email in box this morning:


A firefighting helicopter flies past smoke plumes during the Dixie Fire on August 18, 2021, near Coppervale in northern California. As of August 22, the wildfire had burned more than 724,000 acres and destroyed 1,259 structures and was continuing to grow. PHOTOGRAPH BY PATRICK T. FALLON, AFP/GETTY

Wildfire smoke is transforming clouds, making rainfall less likely

A new study finds smoke could be making it harder for clouds to drop rain and alleviate drought, potentially kicking of a “very scary” feedback loop.


Over the summer of 2018, the worst wildfire season the western United States had ever seen sent thick plumes of smoke high into the sky. Atmospheric scientist Cynthia Twohy and her colleagues spent weeks flying a giant C-130 research airplane through the smoke, which was so dense that the light inside the plane sometimes went dusk-dim.

“You couldn’t even see the clouds outside, the smoke particles were so thick,” says Twohy, who works for NorthWest Research Associates, a scientist-owned research organization. All that smoke, she thought, must have an impact on the clouds forming above the West’s scorched surface.

It does indeed, according to a study she and her colleagues published recently in Geophysical Research Letters: Smoke particles make some clouds denser and more tightly packed with tiny droplets—a combination that means the water in them is less likely to fall as rain.

The team didn’t directly link the changes in clouds with the ongoing western drought. But the fear is that in the bone-dry, increasingly fire-prone West, a feedback loop like this could make drought, and so fire cycles, worse.

What’s very clear for now, says Twohy, is that “the reason these clouds are the way they are is because of the smoke particles”—and the way they are makes them less likely to produce rain.

More particles, less rain

Clouds form when water vapor in the atmosphere condenses into droplets around tiny particles floating in the air.

But there’s only so much water in the air, especially during summertime over the arid western U.S. If that little bit of water has only a few sticky particles to grab onto, the water will eventually collect on just those few specks, forming big droplets. But if there are lots of little particles available, the water can spread out, forming a glittering kaleidoscope of tiny droplets.

In a smoke plume, there is no shortage of particles. A fire chews up anything in its path and can shoot the detritus high into the atmosphere: dark, charred bits of organic material; gooey particles of tar; brown ash; and much more. The dark particles often glom together into small clusters about 100 nanometers across—about the size of a piece of fine corn starch—which is exactly the right size for forming cloud droplets.

Back in 2018 Twohy and her colleagues collected cloud droplets directly from the air outside the plane. Sure enough, inside the smoke plumes they found droplets that were about five times as numerous and roughly half the size as in clouds without smoke.

In and of itself, that’s not surprising, though scientists hadn’t previously collected droplets from inside a smoke-changed cloud. But its impacts are potentially bad news, because clouds made up of smaller droplets are less likely to rain—the droplets just aren’t heavy enough to fall to the ground, and instead stay floating in the air.

“When the cloud droplets are too small, it sometimes doesn’t rain,” says Jonathan Jiang, an atmospheric scientist at the Jet Propulsion Laboratory in California.

Smoke squelches rain

Scientists have seen evidence of these effects elsewhere—but not by collecting cloud droplets directly from the air, and not over such drought-plagued land as the western U.S. Fires in the Amazon, southern Africa, and Indonesia, for instance, all kick huge plumes of smoke into the atmosphere, and the fine particles do the same thing there as in the western U.S.—grow clouds that are dense with tiny droplets and stingy with their trapped water.

The fires also affect the atmosphere itself. Smoke particles are dark, so they absorb sunlight, warming themselves and the air around them. Meanwhile, the denser clouds they help form are bright, so they reflect a lot of sunlight, which keeps it from warming the ground.

The upshot is that smoke reduces the temperature difference between the warm ground and the cold air higher up. But that temperature difference is what drives the convective updrafts that form storm clouds.

Scientists estimate that those combined effects­—the suppressed convection and droplets too small to rain­—cut precipitation over smoke-laden parts of central Africa during fire season, potentially kicking off a feedback loop that leads to more fire. The same has happened over Madagascar, which has seen a roughly 20 percent drop in precipitation over the last few decades, in part because of human-induced fires, says Jiang.

In some cases, smoke could do the opposite and intensify precipitation. In parts of the humid Amazon, a complicated set of atmospheric physics means smoke tamps down the lower-level clouds but causes storm clouds to form in the high atmosphere.

But overall, climate models suggest that a smoke-induced drop in rainfall probably happens across much of the planet. What’s concerning, says Jiang, is how all the pieces of the climate change puzzle can push toward worse conditions.

“Think about global warming. Because of the extra heat the wildfires are more frequent. And because they’re more frequent, you get the drier [conditions], which means less precipitation,” he explains.

So the smoke could end up exacerbating the drought and perpetuating its own existence.

A ‘very scary’ feedback loop

Though Twohy and her colleagues didn’t directly link the extra smoke in the air to changes in western rainfall, scientists already know that the West is seeing less rain during fire season than it used to. A 2018 study found that the number of summertime rain days has dropped by about 4 percent per decade since 1979. That has led to an increase in dry vegetation that is ripe for burning. 

And in fact the West has seen a large increase in wildfires and smoke over the past two decades. In 2018, nearly twice as much burned material ended up in the atmosphere than the 20th-century average; in 2020, it was higher by nearly a factor of three.

Though not much rain falls during summer across much of the West in the best of years, that rain matters a lot. “Very often, how big a fire gets relates to when the rain comes to put out the fire,” says Charles Luce, a Forest Service researcher at the Rocky Mountain Research Station in Boise, Idaho.

What the new research suggests is that smoke may help tamp down the rains that put fires out or keep them from starting in the first place. No one yet knows how much of an impact this effect might be having in the western U.S—or the world.

But for the West, which is locked in a two-decades-long drought that rivals any in the last 2,000 years and is facing another year of enormous wildfires and choking smoke, the prospect of another exacerbating feedback loop is “a very scary thought,” says Jiang.



Western Fire Weather Days Increasing

AUG 25, 2021

Climate Central’s new report examines the increase in fire weather days—when weather conditions allow small fires to explode into infernos.

See full multimedia package here >>KEY CONCEPTS | POTENTIAL STORY ANGLES


  • Climate change is worsening wildfires across forested land and lengthening wildfire seasons in the western United States. 
  • Heat, dryness, and wind—the main components of wild fire weather—affect fire behavior. A new analysis from Climate Central shows the frequency of fire weather days are increasing across most of the American West, driven by dryness and heat.
  • Fire weather conditions are causing problems even where fires aren’t burning. When fire weather is in the forecast, utilities may shut  off power to prevent equipment-related ignitions.
  • Smoke from the many wildfires harms people hundreds of miles downwind, especially those with asthma or other health conditions.


Fire Weather Days by Climate Division
*Not available for all locations

Percent Change Western Map

Fire Weather Infographic

It’s already been a brutal year for wildfires, with at least 104 large fires burning across 12 states, including Oregon, Montana, Washington, California, and Idaho. Hot, dry, and windy conditions fueled the intensity of both the Dixie and the Bootleg fires, which have forced evacuations and devastated dozens of communities. 

What is fire weather?
Fire weather generally refers to meteorological conditions that promote the spread of wildfires, although specific definitions of fire weather can vary.  Climate Central’s analysis focuses on three meteorological elements fundamental to fire weather—relative humidity, temperature, and wind. 

  • Relative humidity is a measure of how close the air is to being saturated by water vapor. When humidity levels are very low, the air feels dry and it sucks moisture from the land, leaving vegetation dry and prone to burning. 
  • Hotter temperatures affect humidity of the air and the dryness of the ground. They also have a direct influence on fire behavior, heating the fuels and making them more likely to ignite. 
  • Wind supplies oxygen to a fire, so it burns more rapidly. Wind increases evaporation, drying out the land and providing more fuel for the fire. Wind also carries embers, which help a fire spread. Changes in wind speed or direction can cause a fire to shift, altering the rate of spread and intensity of the fire.

Where are fire weather days increasing?
To explore changes in weather conditions that increase risk of wildfire, Climate Central analyzed data from weather stations in 225 locations across 17 states going back to 1973. The data from individual weather stations was then aggregated by climate division (you can find your climate division here). 

  • Parts of New Mexico, Texas, and Southern California have experienced some of the largest increases in fire weather days each year. Areas of New Mexico are now seeing two more months of fire weather than was the case nearly a half century ago. 
  • Some of the climate divisions in Texas, California, Oregon, and Washington are experiencing fire weather more than twice as often now as in the early 1970s. 
  • Fire weather days increased more in interior regions than in coastal regions. Higher humidity levels along the coast mean these areas are less likely to reach the low relative humidity threshold used in the analysis. 
  • By contrast, some parts of North Dakota, South Dakota, Kansas, and Nebraska experienced a decline in the frequency of fire weather days. This is part of a region where springs and summers have been cooling slightly—most likely from local agricultural practices

Fire weather conditions are also causing problems even where fires don’t ignite.

  • On fire weather days, power companies are shutting off electricity to millions of people in an attempt to avoid equipment-related ignitions. These “public safety power shut offs” (PSPSs) reduce the risk of fire but create health risks, especially to those who depend on refrigeration or need air conditioning to stay cool during heat waves. Researchers found that the daily power needs for 12 million people were unavailable in Northern California in 2019 due to the PSPSs, causing estimated economic impacts of around $10 billion. 
  • Communities near wildfires and those far downwind are also being affected. Smoke is a dangerous pollutant that contributes to a variety of health problems, increasing susceptibility to asthma and asthma attacks. It can also make one more vulnerable to influenza and other viruses like COVID-19. Smoke poses especially high risks to those with other health problems, particularly among seniors and others with weakened lung health.


What are solutions to the increasing risk of wildfires? 
A number of solutions to adapting to the risk of wildfire include increased use of land management techniques that eliminate excessive fuels, such as prescribed burns; forest thinning to remove young trees and bushes; and allowing small fires to burn themselves out when it’s safe to do so. There are also toolkits to prepare homes and create evacuation plans. But fire weather conditions will increase around the world as the planet warms. Reducing carbon pollution to net zero by 2050 by aggressively switching away from fossil fuels would limit global warming and stabilize climate conditions. 

Is my area at risk of wildfires?
You can find daily reports of elevated fire weather conditions at NOAA’s Storm Prediction Center. The Incident Information System identifies where wildfires have been reported and provides detailed information on conditions. You can stay updated about risk of fire with the North American Seasonal Fire Assessment and Outlook, produced by the National Interagency Fire Center (NIFC) in Boise, Idaho at the beginning of each month. You can also search your locality on the Wildfire Risk to Communities website. 

Are wildfires affecting air quality in your area?
AirNow, a partnership of multiple government agencies, has a number of publications on wildfire smoke and air quality, and a wildfire and smoke tracking map. California Air Resources Board (CARB) maintains a series of interviews with experts on wildfire smoke and air quality, that are available for attribution, as well as air quality data. PurpleAir also maps air quality indexes across the country. 


The SciLine service500 Women Scientists or the press offices of local universities may be able to connect you with local scientists who have expertise on wildfires and climate change. The American Association of State Climatologists is a professional scientific organization composed of all 50 state climatologists



See detailed methodology in the appendix of the report.


Here is more climate and weather news from Wednesday:

(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article. The most noteworthy items will be listed first.)

Now here are some of today’s articles and notes on the horrid COVID-19 pandemic:

(If you like these posts and my work please contribute via the PayPal widget, which has recently been added to this site. Thanks in advance for any support.) 

Guy Walton “The Climate Guy”

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