Extreme Temperature Diary- Tuesday March 24th, 2020/ Main Topic: Pollution And The Pandemic… Let’s Clear The Air

Tuesday March 24th… Dear Diary. The main purpose of this ongoing blog will be to track United States 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: Pollution And The Pandemic… Let’s Clear The Air

Dear Diary. What if we could see up close a world in which pollution was shut off at the source? What if we could briefly experience an urban world, which is just as fresh and smells as sweet as the most remote mountain meadows or country vistas? Would we all wake up from such a dream world to commit to going towards renewables much faster as the current pace of progress? You bet.

As bad as the coronavirus crisis is, it does have a silver lining. We can see this pollution silver lining on satellite remote sensing imagery. Also, because of Democratic proposals of decoupling oil subsidies with financial aid made to wage earners during this unique period of history in the United States, we might be able to wean ourselves off of fossil fuels faster had there been no pandemic. Common people should get help, not the carbon polluting oil industry or the air lines from a treasury that will significantly be strained from this crisis. The fossil fuel industry deserves to die just as fast as the coronavirus.

Bob Henson’s writing and work often overlaps with my topics on carbon pollution, air pollution in general, and global warming. Today is one of those times. I’m taking the liberty of posting his fine article written yesterday on pollution and this pandemic:


Will the Global Response to the Coronavirus Give Climate a Nudge?

Bob Henson  ·  March 23, 2020, 5:25 PM EDT

Above: The A5 highway at Isle-Aumont, France, was deserted on Monday, March 23, 2019, the seventh day of a lockdown aimed at curbing the spread of the novel coronavirus in France. (Stephane de Sakutin/AFP via Getty Images)

In just a matter of weeks, the rapid spread of the novel coronavirus has pushed the world into a mammoth dual experiment in public health and economic policy. As the impacts of COVID-19 illness spike in country after country, governments are mandating business closures, quarantines, and “shelter in place” practices at a scale that few would have imagined.

Given that large parts of the world are shutting down large parts of their economies for weeks if not months, a new question emerges: what kinds of short- and long-term effects could this drastic slowdown have on the atmosphere—not only on air quality, but also on regional and global climate?

It’s obvious from satellite-based sensors that the sudden drop-off in industry and transport in some areas has literally cleared the air. The most vivid evidence is from measurements of nitrogen dioxide (NO2), a pollutant that can lead to harmful ground-level ozone. High-resolution NO2 data gathered in recent weeks by the Copernicus Sentinel-5P satellite is especially striking. NO2 concentrations plummeted in the Wuhan area of east-central China after the highly industrialized region was put under virtual lockdown. Similar drop-offs were detected over northern Italy after that hard-hit nation put in place severe restrictions on commerce and mobility. And some U.S. cities are seeing big reductions in NO2 this month, as measured by Sentinel-5P and reported by the New York Times on Sunday.

Sentinel-5P is also monitoring carbon monoxide (CO), which evolves over a longer time period. Potential reductions in CO may not be as dramatic as for NO2, in part because changes in emissions from power generation, transportation, industry, and residences are likely having different effects on different pollutants, according to Helen Worden (National Center for Atmospheric Research). Worden is the U.S. principal investigator for the U.S./Canadian MOPITT instrument on the NASA/Terra satellite.

Power plants and vehicles are key sources of NO2, Worden points out, which means factory shutdowns and stay-at-home orders would have a big impact on that pollutant. However, a large part of carbon monoxide (CO) in China is still from residential burning—which would presumably continue even if folks are staying home—so it is possible we won’t see as dramatic a drop in CO emissions.

Moreover, NO2’s short lifetime in the atmosphere (only a day or so) means that the impact of the coronavirus shutdown is immediately evident.

“When you see NO2, you’re basically seeing the sources of it,” Worden says. “With CO, the lifetime is a couple of months, and so you’re not only seeing the local sources—you’re seeing contributions from global transport of CO.”

Carbon monoxide (CO) emissions over Asia averaged across February 2018, 2019, and 2020 (left to right), as measured by the TROPOMI instrument aboard the Sentinel-5P satellite. The large variations over Southeast Asia may be related to wildfire, while the drop in 2020 near Beijing is likely a product of the coronavirus response. (Sara Martinez-Alonso, ACOM/NCAR)

Worden has been collaborating with Kevin Bowman (Jet Propulsion Laboratory) on a JPL study using “inverse modeling”—working backwards from the satellite measurements to figure out more precisely where pollutants have come from over the last several months. Bowman and colleagues are now writing up results from a study that quantifies changes in emissions during the coronavirus era.

“We’re also actively looking at the impact of Australian fires on the carbon balance. These were incredibly intense fires,” said Bowman. He believes there is great promise in analyzing short-fuse events like these using “chemical weather” inversion models that take into account the usual atmospheric conditions as well as pollutants and photochemistry (sunlight-driven effects, such as the formation of ground-level ozone).

“With the world changing at the speed we’re seeing, these inversion models are becoming critical to timely scientific and policy-relevant information,” he added.

Aerosols at work

If there’s an immediate effect on climate from the world’s response to COVID-19, it will be from changes in aerosols (or particulates)—the tiny airborne solids and liquids spewed out by factories, vehicles engines, and furnaces, including the pollutants above. Even though their atmospheric lifespan is only a matter of a few hours to a few weeks, these sun-blocking aerosols are continually replenished as we burn fossil fuels, and they can have a surprisingly strong cooling effect as a whole.

Computer models strongly suggest that the aerosols belched out from the multi-decade surge in industrial activity after World War II are a prime reason why air temperature held roughly steady worldwide—and actually dropped a bit in parts of the highly industrialized Northern Hemisphere—from the late 1940s to the 1970s.

A couple wearing smog masks in London in November 1953, just before a catastrophic smog episode in early December that killed at least 4000 people and led to thousands of other indirect deaths. (Monty Fresco/Topical Press Agency/Getty Images)

Environmental laws in North America and Europe (the world’s industrial powerhouses at that time) began to tighten in the Seventies, and aerosol pollution began to decrease. Greenhouse gases weren’t addressed, though. The decline in globally averaged aerosol pollution, combined with ever-increasing concentrations of carbon dioxide and other greenhouse gases, fostered a rise in global air temperature that gained traction in the 1980s and has continued into the 2020s, with only slight variations modulating the trend from decade to decade.

The 21st-century explosion of industry in eastern and southern Asia, especially China, led to a regional increase in aerosols, one that’s been suddenly crimped by the coronavirus shutdown. If factories and transportation are slow to ramp up this spring and summer, it’s possible that an otherwise hot summer in parts of this region might be slightly hotter in the absence of the usual sun-blocking aerosols. Likewise, North America and Europe could see a slightly warmer summer than one would otherwise expect, although the effects there would likely be more muted because of previous aerosol reductions over the past 40 years.

A longtime researcher in climate and air quality, Drew Shindell (Duke University), elaborated on these possibilities in an email:

“Aerosols have decreased over East Asia, and now over Europe and North America too (though there are fewer there to begin with), so most of the Northern Hemisphere mid-latitudes will see a drop. As the climate response is slow, I can’t see the slightly earlier drops in emissions in East Asia having an effect before the others. And climate response is also spread out in the zonal (east-west) direction. So my best guess would be a very minor warming in the Northern Hemisphere midlatitudes for the next few months, a warming that is likely to be within the seasonal noise and thus undetectable in observations.”

WU co-founder Jeff Masters, who worked on air quality matters for his doctoral degree, called out another regional angle in an email: “The nation-wide shut down in business just ordered in India, if sustained, has the potential to bring about a noticeable increase in the summer monsoon rains, since aerosol particles emitted by India have been shown to decrease the intensity of the monsoon.”

One other regional effect of the shutdown might be a reduction in the amount of pollution blowing toward the Arctic from northern midlatitudes. Aerosols deposited on ice and snow can darken its surface, increasing its ability to absorb sunlight and potentially leading to an enhanced melt-off once spring arrives. A multiyear research project, Dark Snow, is focused on quantifying the impact on Arctic melt from soot produced by industry and wildfires, along with mineral dust and microbes.

The project hasn’t yet detected any signals related to the coronavirus effects, according to Dark Snow PI Jason Box (Geological Survey of Denmark and Greenland). He expects that systems such as AERONET, a global network of photometers that measure sunlight blockage from aerosols, would eventually pick up on a signal of reduced pollution. “However, I expect the signal to be lower than the variability, so one would perhaps need to average many stations,” Box said in an email.

A factory worker was back on the job on March 2, 2020, in Weifang, China, after a shutdown triggered by the novel coronavirus. (TPG/Getty Images)

The long view

It remains to be seen how much the world’s output of greenhouse gases—carbon dioxide in particular—will be blunted by the massive global response to the novel coronavirus. We already know that economic downturns can trim emissions slightly from one year to the next. The carbon dioxide emitted globally from fossil fuels dropped by about 1% from 1991 to 1993 with the dissolution of the Soviet Union and the subsequent regional turmoil. Likewise, fossil-fuel-based CO2 emissions dropped by about 2% from 2008 to 2009 as the Great Recession took hold. In both cases, the drops were quickly swamped by subsequent increases.

Already, it’s been estimated by Carbon Brief that CO2 emissions from China have dropped by 25% since the coronavirus outbreak began early this year. If so, that would represent roughly a 6% drop in global emissions. If at least some of the world’s other major emitters experience a similar economic hit, then a global emissions drop on the order of 10% would be conceivable.

The bad news is that even a big reduction in emissions means that we’re still increasing the amount of carbon dioxide in the atmosphere, albeit at a slower rate. Think of it this way: if you trim the amount by which you overspend your household budget each year, your total debt is still adding up. Even a massive slowdown in global economic activity won’t be enough to produce a major effect on global CO2 concentrations, which have increased every year in the 60-plus years they’ve been measured atop Mauna Loa, Hawaii. NOAA reported in February that the CO2 concentration averaged 407.4 parts per million in 2018, an increase of 2.5 ppm from 2017.

Trends in daily and weekly averages of carbon dioxide concentrations measured at Mauna Loa Observatory, Hawaii, from late September 2019 to March 19, 2020. The daily and weekly numbers have been relatively flat since early February, at a time of year when CO2 is normally undergoing a seasonal increase (blue line). (Scripps Institution of Oceanography)

At the Scripps Institution of Oceanography, which has conducted Mauna Loa observations since they began, researcher Ralph Keeling recently estimated that a 10 percent decline in global emissions sustained for a full year—a drop far larger than anything observed on Mauna Loa to date—would shave a mere 0.5 ppm from atmospheric CO2 concentrations.

“A minor relative cooling [is possible] due to the drop in CO2,” said Shindell, “but that’s happened before with economic downturns and is likely temporary and therefore small. It’d be interesting, though, if we have a lasting effect on emissions, for example if teleworking becomes more accepted and widely practiced and so transportation emissions never return to their prior levels. Not sure if that’ll happen of course, but that could have a long-term effect big enough to see.”

Indeed, an economic slowdown might open a window of opportunity for activists and innovators to push for greener policies and technologies that can be picked up as the economy eventually recovers.

Demonstrators led by Fridays for Future stand in front of a coal-fired power plant in Datteln, Germany, on January 24, 2020. (Fabian Strauch/picture alliance via Getty Images)

“History has shown that carbon dioxide levels typically resume their climb quickly as normal economic activity rebounds,” noted Scripps media specialist Rob Monroe, who summarized Keeling’s take on the matter in a March 11 post at the Keeling Curve website.

“If there is any benefit of the coronavirus event in terms of slowing the pace of climate change, it could be the changing of people’s travel and work habits in ways that lead to sustained reductions in fossil fuel use. Only those kinds of long-term systemic reductions will change the trajectory of carbon dioxide levels in the atmosphere.”

It’s worth remembering that the mid-2010s saw global gross domestic product (GDP) increase by about 3% in each year from 2014 to 2016 while emissions held virtually flat. We now know that economies can grow without expanding their carbon footprint—and as many activists have pointed out, GDP is only one measure of people’s health, happiness, and well-being. Once we emerge from the immediate public health crisis posed by COVID-19, we may look at old economic assumptions—along with so many other things—in a new light.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

author image

Bob Henson

Bob Henson is a meteorologist and writer at weather.com, where he co-produces the Category 6 news site at Weather Underground. He spent many years at the National Center for Atmospheric Research and is the author of “The Thinking Person’s Guide to Climate Change” and “Weather on the Air: A History of Broadcast Meteorology.”


It has also been suggested that U.S. recovery from coronavirus can be linked to the Green New Deal. Of course, I support any approaches that would help tackle COVID-19 and the climate crisis simultaneously. Since it now appears that Joe Biden will be the Democratic nominee, I would encourage him as the next President to adhere to recommendations put forth from experts, linking the two crises together such that their solution can come about quicker, leading us into a brighter future after some very dark days to come. Look for future updates on solutions from this, the Extreme Temperature Diary.

Now, here are some of todays articles on the horrendous coronavirus pandemic:

Here is more climate and weather news from Tuesday:

(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.)

(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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