From the Harvard School of Engineering and Applied Sciences
“Warming hole” delayed climate change over eastern United States
April 26, 2012
50-year model suggests regional pollution obscured a global trend
CONTACT: Caroline Perry, (617) 496-1351
Cambridge, Mass. – April 26, 2012 – Climate scientists at the Harvard School of Engineering and Applied Sciences (SEAS) have discovered that particulate pollution in the late 20th century created a “warming hole” over the eastern United States—that is, a cold patch where the effects of global warming were temporarily obscured.
While greenhouse gases like carbon dioxide and methane warm the Earth’s surface, tiny particles in the air can have the reverse effect on regional scales.
“What we’ve shown is that particulate pollution over the eastern United States has delayed the warming that we would expect to see from increasing greenhouse gases,” says lead author Eric Leibensperger (Ph.D. ’11), who completed the work as a graduate student in applied physics at SEAS.
“For the sake of protecting human health and reducing acid rain, we’ve now cut the emissions that lead to particulate pollution,” he adds, “but these cuts have caused the greenhouse warming in this region to ramp up to match the global trend.”
At this point, most of the “catch-up” warming has already occurred.
The findings, published in the journal Atmospheric Chemistry and Physics, present a more complete picture of the processes that affect regional climate change. The work also carries significant implications for the future climate of industrial nations, like China, that have not yet implemented air quality regulations to the same extent as the United States.
Observed change in surface air temperature between 1930 and 1990. Observations are from the NASA GISS Surface Temperature Analysis. Image courtesy of Eric Leibensperger.
Until the United States passed the Clean Air Act in 1970 and strengthened it in 1990, particulate pollution hung thick over the central and eastern states. Most of these particles in the atmosphere were made of sulfate, originating as sulfur emissions from coal-fired power plants. Compared to greenhouse gases, particulate pollution has a very short lifetime (about 1 week), so its distribution over the Earth is uneven.
“The primary driver of the warming hole is the aerosol pollution—these small particles,” says Leibensperger. “What they do is reflect incoming sunlight, so we see a cooling effect at the surface.”
This effect has been known for some time, but the new analysis demonstrates the strong impact that decreases in particulate pollution can have on regional climate.
The researchers found that interactions between clouds and particles amplified the cooling. Particles of pollution can act as nucleation sites for cloud droplets, which can in turn reflect even more sunlight than the particles would individually, leading to greater cooling at the surface.
The researchers’ analysis is based on a combination of two complex models of Earth systems. The pollution data comes from the GEOS-Chem model, which was first developed at Harvard and, through a series of many updates, has since become an international standard for modeling pollution over time. The climate data comes from the general circulation model developed by NASA’s Goddard Institute for Space Studies. Both models are rooted in decades’ worth of observational data.
Since the early 20th century, global mean temperatures have risen—by approximately 0.8 degrees Celsius from 1906 to 2005—but in the U.S. “warming hole,” temperatures decreased by as much as 1 degree Celsius during the period 1930–1990. U.S. particulate pollution peaked in 1980 and has since been reduced by about half. By 2010 the average cooling effect over the East had fallen to just 0.3 degrees Celsius.
“Such a large fraction of the sulfate has already been removed that we don’t have much more warming coming along due to further controls on sulfur emissions in the future,” says principal investigator Daniel Jacob, the Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at SEAS.
Jacob is also a Professor of Earth and Planetary Sciences at Harvard and a faculty associate of the Harvard University Center for the Environment.
Besides confirming that particulate pollution plays a large role in affecting U.S. regional climate, the research emphasizes the importance of accounting for the climate impacts of particulates in future air quality policies.
“Something similar could happen in China, which is just beginning to tighten up its pollution standards,” says co-author Loretta J. Mickley, a Senior Research Fellow in atmospheric chemistry at SEAS. “China could see significant climate change due to declining levels of particulate pollutants.”
Sulfates are harmful to human health and can also cause acid rain, which damages ecosystems and erodes buildings.
“No one is suggesting that we should stop improving air quality, but it’s important to understand the consequences. Clearing the air could lead to regional warming,” Mickley says.
Leibensperger, Jacob, and Mickley were joined by co-authors Wei-Ting Chen and John H. Seinfeld (California Institute of Technology); Athanasios Nenes (Georgia Institute of Technology); Peter J. Adams (Carnegie Mellon University); David G. Streets (Argonne National Laboratory); Naresh Kumar (Electric Power Research Institute); and David Rind (NASA Goddard Institute for Space Studies).
The research was supported by the Electric Power Research Institute (EPRI) and the U.S. Environmental Protection Agency (EPA); neither EPRI nor the EPA has officially endorsed the results. The work also benefited from resources provided by Academic Computing Services at SEAS.
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Notice the evident effect of pollution in the heavily industrialized states of Mississippi and Arkansas compared to other areas like Southern California.
Guess the air was squeaky clean over the eastern half of the country last month, ay? Hope you were wearing a mask this last week, though.
http://www.hprcc.unl.edu/products/maps/acis/7dTDeptUS.png
Asia, Africa, and Europe should also have huge warming holes, since they all produce massive quantities of airborne particles. In particular, the burning of wood and other biofuels (think cow dung) in Asia and Africa should qualify, especially since the density of human activities is so much greater than in the relatively unpopulated US. It’s odd then that we see cooling in the Southern Hemisphere, with much less aerosols, and warming in Asia, where high levels of aerosols have been produced for decades.
Here in Northern California, our small to medium cities show flat to cooling trends since 1895, but San Francisco, and the populous Bay Area in general, is steadily warming. The Bay Area smog does not seem to be masking any warming, and those of us happily living by the Pacific, caressed by prevailing, clean ocean breezes and not protected by a warming hole, are still in a cooling trend when it should be warming.
Frankly, I feel cheated. I believed Al Gore when he said we would get hotter weather, and decided to stay on the coast and enjoy the warming. I could have voted for warming with my feet and move to Arizona, like the Canadian Snowbirds, but I stayed and trusted the warming would come to me.
Serves me right for trusting Al Gore. Now I know how Tipper felt.
The CAGW cult are getting really, rellay desperate to find a way to explain why they can’t find the warming.
A “warming hole”.
Seriously???
Would be a bit like one of those other-worldy rabbit holes that precocious Victorian girls tripping-out on LSD get go down…?
I think I might have heard it all now.
“Major models,” eh? As with the U.K. Met Office’s self-fulfilling prophecies of doom, enhanced computations merely make more serious mistakes much faster.
If these magical models have any validity whatever (har), let’s see some explicit non-linear projections over periods of (say) five, ten, and twenty years, replicable by independent third-party evaluators concerned solely with assessing their unadjusted accuracy.
What’s that you say– AGW’s famed Precautionary Principle demands “action now”? Terrific– let’s start vetting these high-grant coefficient studies (sic) with due diligence and integrity TODAY.
DesertYote says:
April 26, 2012 at 7:59 pm
> I love measuring things, don’t care to much about what the results prove or disprove, just how accurate they are.
I approve. While I don’t have an accurate pH meter or radiation meter, I have an oscilloscope, scanner radio, telescope, and microscope. It’s nice to have extended senses, I least, I think so.
> … Once the monsoon gets rolling, the PH will fall to 6.8 to 7.2 if it is not proceeded by dust storms. In such cases, I have measured PH up to 7.8!
Eek! (In the surprise sense, not the body parts are falling off sense.) Do you know what ions are involved with the OH-? The actual number of ions involved is pretty small given the priximity to 7.0, but I didn’t realized we had rain that alkaline in the USA.
In our field biology class in high school, I had the task of measure O2 concentrations in water. Interesting process, involving fixing the water in the field (surprising what little droplets of concentrated H2SO4 does to cotton pants) and titrating in the lab.
Something is horribly wrong in the kingdom of science. 🙁
I worked in the Government for 40+ years and believe me “Based on” is one big BIG red flag because it has no real meaning. I no longer trust it in any context.
Correction: 30+ years.
Did they look at other parts of the world that would have had similar air characteristics (N England, Germany, the USSR and its satellites etc) or at China nowadays? and find a similar anomalous cooling effect? If not, they will need also to explain exactly what is ‘special’ about NA before their theory can gain much credence.
So smog kept southern California cool? It must have! In the 50s and 60s I could smell the sulphur! In the San Fernando Valley, we had summer temps of 110+ back then. Wow! How hot might it have been without smog? Did it blow to the east and make Arizona cool, too? Nevada? New Mexico? Please explain. I’m facinated!
@M Hastings who said: “Today it rained again and because I read this article and was curious I took the PH of the rain puddles on my deck and walkways and in the garden, all three puddles had a PH of 7.8 or higher.”
What’s your deck made of?
davidmhoffer: “By extension, all the warming we’ve seen is clearly due to the reduction in the use of high particulate fuels such as wood and coal in the 1800′s … ”
To take it further …
Is it possible the dustbowl in the 1930s was caused by sudden temporary de-industrialization caused by he 1929 stock market crash? And that resulted in much cleaner air?
Pay no attention to the Mann behind the curtain….
Wait until the Kardassians find out about the warmhole — Benjamin Sisko will be the only one who can save us!
What anyone else would have thought would be that warming was caused locally and this area was not warmed so it needed to have the warmth spread from the areas that were already warmed. Much more probable but totally unproven because when it was suggested a decade ago the grants were removed from those that suggested it should be investigated. They joined as engineering computer modellers instead of climate ones or no one at all would have heard of the idea.
Consensus is not a convincing argument when you meet a dissident thrown out of the club.
davidmhoffer: “By extension, all the warming we’ve seen is clearly due to the reduction in the use of high particulate fuels such as wood and coal in the 1800′s …
Don’t mock it.
One of the acid rain activists I knew in the early sixties worked out that the removal of particles and sulphur would result in a one degree rise in temperatures based on some climate chamber and cloud formation work he was doing. It does not seem that out of line with the reality, the difference is that his projections flattened not escalated.
Seems mighty contrived. Model on top of model?
Aerosols acting as condensation nuclei for cloud formation? Not a giant leap from hypothesising galactic cosmic rays acting as condensation nuclei. One wonders whether this will backfire on their narrative?
As for them proudly declaring that their models are rooted in decades of observational data, that should hardly be taken as a vote of confidence. It would be as if a polling company boased “our survey on American voting behaviour is based on sample sizes of dozens and dozens of individuals.
It is so clearly a weakness that one wonders again, whether this will backfire. It should be obvious that centuries of observation data are needed.
So in 1941 when the Soviet Union moved all its heavy industry east of the Urals, European Russia warmed up and the German Army didn’t freeze to death then…who knew?
The researchers found that interactions between clouds and particles amplified the cooling. Particles of pollution can act as nucleation sites for cloud droplets, which can in turn reflect even more sunlight than the particles would individually, leading to greater cooling at the surface.
Wait, are they saying cloud feedback is negative?
Became the solar system and in him and the Earth and on Earth all for life, and only came after a human being-man.
The man invented the computer and it programs.
With programs performed a variety of models to check everything before its creation.
And guess what. Man who believed in their models in which he has inserted his desire and knowledge!
I now models “took power into their own hands” and command the man what will work and what to believe.
Get a grip!
For your general Reading Amusement, here’s the definition from the ever-reliable wikipedia, of an Ad hoc hypothesis …
“In science and philosophy, ad hoc means the addition of extraneous hypotheses* to a theory** to save it from being falsified …. Ad hoc hypotheses are often characteristic of pseudoscientific subjects***”
My added notations
*Aerosols
** CAGW
*** Well yes, exactly. 🙂
Jason says: April 26, 2012 at 4:36 pm
Nothing about this makes any sense.
What they are trying (not) to say is this:-
The world has been in a warming phase since the little iceage. However increasing pollution before 1970s was repressing this rise … this wasn’t noticed, as it occurred slowly, but in the 1970s quite suddenly a lot of clean air legislation was passed which removed this pollution which repressed US (i.e. global) temperatures, and caused them to rise rapidly from 1970s for a few decades.
In other words, much of the “worrying and rapid increase” in global temperatures was due to previous environmental policies which had been artifically repressing global temperatures”.
The thing to note, is that this a one off effect. It will not continue. Indeed, the real truth is that far from warming the planet, air pollution causes cooling.
And, let’s say it …. it was the environmentalists that saved us from this colder world!
Assuming the temperature map is accurate and the asserted cooling mechanism is true, the coolest areas (southern MO, AR, and NE Mexico) do not correspond with the locations of heavy industry and coal-fired power stations (upper Mid-West, North-Central, and NE US), and prevailing winds are from the W and NW.
Remind me never to hire consultants or graduates from Harvard’s SEAS to engineer stuff that must operate in the real world.
We should see dramatic cooling in China, German Ruhrland or whatever industrial area then. We do not see anything like that. One thing is clear, whether it warms or cools, all is man’s fault.