January 04, 2006
Reduced Aerosol Pollution May Accelerate Global Warming

Aerosols cause much greater cooling than previously estimated.

Writing in the journal Nature today, scientists at the Meteorological Office and the US government's National Oceanic and Atmospheric Administration report that climate models used to predict future global warming have badly underestimated the cooling effect of aerosols.

"We found that aerosols actually have twice the cooling effect we thought," said Nicolas Bellouin, a climate modeller at the Met Office. The consequence is that as air quality improves and aerosol levels drop, future warming may be greater than we currently think."

Pollutants are a source of aerosols that have been decreased by environmental regulations - at least in the more industrialized countries. A decline in pollutant aerosols might cause a much higher level of global warming.

The group has produced the most precise estimates yet of how tiny particles, known as aerosols, could affect the world's climate. Aerosols, which include pollutants, have a cooling effect on the atmosphere, and the team's work suggests that the cooling effect is strong - nearly as strong as the top estimates of the United Nation's Intergovernmental Panel on Climate Change (IPCC).

Thus, the dwindling presence of aerosols means that global average temperatures could rise faster than previously estimated and reach toward the high end of projections for the end of the century.

Those estimates currently range from 2.7 to 7.9 degrees F., depending on how emissions of greenhouse gases and other factors play out in coming years.

The second article says some of the effects of aerosols still haven't been puzzled out. So the story could change. But suppose the aerosol effect turns out to be as these researchers say. Would it be possible to come up with an artificial aerosol that would have no negative health impacts yet which could lower the Earth's temperature? If such an aerosol was discovered would environmentalists oppose its widespread release?

There's an interesting angle to this report that I haven't seen reported: Rapid economic growth in China is greatly boosting particulate emissions from coal burning. But when living standards in China rise far enough the population will start demanding cleaner air. At that point a decline in Chinese aerosol emissions would happen under much higher atmospheric CO2 conditions. This could cause a temperature spike at that point.

You can read the Nature abstract here.

Share |      Randall Parker, 2006 January 04 10:59 PM  Climate Trends

D. F. Linton said at January 5, 2006 5:31 AM:

An interesting question is: how much of the observed warming in the final quarter of the last century could reasonably be attributed to the reduction in air polution during that time?

Jake said at January 5, 2006 8:05 AM:

Not to worry. A volcano will erupt in the not too distant future and it will spew forth more emissions in a week than mankind has since we first got off our knees.

Fly said at January 5, 2006 1:35 PM:

Fleets of blimps circling above the cloud layer covered in solar cells and beaming microwave power back to earth. Blocks sunlight and supply power at the same time.

Engineer-Poet said at January 5, 2006 3:17 PM:

Jake, look at annual emissions from coal plants vs. an eruption like Pinatubo.

Randall, you just hit on something I've been musing about writing about - one of a set of engineering responses to energy and environmental problems.  I think we can find uses for some of our pollutants.

momochan said at January 6, 2006 1:19 PM:

It's interesting to note comments over on ParaPundit, regarding topics such as Iraq and immigration, versus comments here regarding global warming issues. Even though global warming's potential to undermine our civilization is orders of magnitude greater, it is the human-oriented threats that engage people the most (leading to more blog commenting!).

We humans have evolved to focus on security threats posed by animals and 'outsider' humans, whereas we have not evolved to respond to climate catastrophe. It's as though people just can't get their minds around the risk that we are running. Once the remaining ice and glaciers melt, the temp is going to shoot up like a cork from a bottle. Methane hydrate destabilization could cause a vicious upward spiral that our current technology cannot contain.

aa2 said at January 6, 2006 1:30 PM:

I highly recommend the book State of Fear by Michael Chricton. Even if global warming is true, we clearly don't have the knowledge to understand how our actions influence something as complex as global climate. In fact we don't even have a way to measure average global temperature.

Actions we take could just as easily undermine the system as help it.

momochan said at January 6, 2006 7:40 PM:

aa2, uncertainty is the best reason there is for extreme caution on changing greenhouse gas concentrations. We are conducting a big experiment with the atmosphere by emitting so much CO2 and CH4.
Saying that we should continue on the course we're on because we don't know what the climate effect will be is like saying that we should continue driving full speed ahead even if we can't see the road in front of us, because heck, we don't *know* that there might be a cliff. There is a fundamental problem with the logic.
I heartily agree with you that any actions we take might have unintended consequences. That's why prevention is better than cure. Deliberate injection of aerosols to cool the planet down might do some other kind of harm, and it would certainly be difficult to judge just the right amount.
There's so much inertia in our climate system that the warming we're seeing now reflects the emissions/pollution status of a few years, perhaps a few decades ago. Today's emissions might be tomorrow's tragedy.

Engineer-Poet said at January 6, 2006 9:40 PM:

Hear, hear, momochan.

Randall Parker said at January 6, 2006 10:36 PM:


I've said this before: I think it imprudent to sit back and just let the CO2 build up and hope for the best. Seems like a really large risk.

At the same time, I do not expect Kyoto-style agreements to accomplish much. I see only accelerated technological advances will provide solutions that have a chance of worldwide adoption.

But maybe Ray Kurzweil is right though. Maybe the advances will accelerate so much that we'll get huge solutions in the 2020s and 2030s. If so, fossil fuels will be obsolesced rather quickly.

Tdean said at January 7, 2006 2:51 PM:

Aerosol emissions from the burning of fossil fuel have to be cleaned up as a first priority because they directly and quickly cause huge health and environmental problems that increase illnesses, early death and lost productivity of the population. Unbeknownst to Parker, the Chinese government has long been aware of the dire effects of aerosol pollution (http://www.usembassy-china.org.cn/sandt/bjplca.htm) and is taking strong steps to reduce the problem, even as the economy grows at historic levels (http://www.worldbank.org/nipr/work_paper/survive/china-htmp5.htm). But relative to the US, they have gotten a late start in the cleanup, their energy sector is far more dependent on dirty coal and they still have a long way to go. The Chinese population continues to suffer from high pollution levels. But at least their government doesn't challenge the clear economic sense of protecting the populace from pollution.

Parker's lame suggestion of a magic aerosol that is harmless at levels that would cool the earth is non-sense. Any particle that is large enough to scatter sunlight is large enough to cause lung damage when inhaled. If it were water soluable so as to disappear when inhaled, it would rain out of the atmosphere too fast to be useful. And who is going to accept trillions of dollars in potential liability when nations damaged by cold spells or unforseen climate disruption come screaming to court? Parker uselessly dreams of finger snapping technological miracles, but forgets that technological advance is always the product of strong economic incentives. Truly global environmental agreements can supply a large part of those incentives, but ignorant and self-serving politicians can torpedo those agreements. If Kyoto is is ineffective it is because it was amBushed by a corrupt idiot.

aa2 said at January 8, 2006 12:18 PM:

The precautionary principle seems like a good idea at first, but I dont' believe it usually works. For example we don't know if there is a god, therefore you might as well join the church just incase they are right. As there you have eternity on the line, liek the end of the world some environmentalists are talking about. But you have to factor in the costs of joining their church, for example a ten percent tithe on your income and a change in your lifestyle.

And maybe the environmentalists in the 1960's were right and we were on the verge of a new ice age. But increased human carbon emissions staved it off. My own feeling is that the earth self-regulates, for example with more co2 in the air, more plants grow.

Engineer-Poet said at January 10, 2006 7:18 AM:
with more co2 in the air, more plants grow.
That's only true if CO2 is the limiting nutrient.  IIRC, in forestry tests tree growth rose for a few years but then levelled off as other nutrients were depleted.
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