• Sarychev Peak, in Russia, as seen from the International Space Station

    Sarychev Peak, in Russia, as seen from the International Space Station

    Image courtesy of NASA

    Full Screen

Small volcanoes make a dent in global warming

Sarychev Peak, in Russia, as seen from the International Space Station

Study shows that the effects of smaller eruptions have been underestimated in climate models.

Press Contact

Andrew Carleen
Email: expertrequests@mit.edu
Phone: 617-253-1682
MIT News Office

Media Resources

1 images for download

Access Media

Media can only be downloaded from the desktop version of this website.

New research shows that relatively small volcanic eruptions can increase aerosol particles in the atmosphere, temporarily mitigating the global warming caused by greenhouse gases. The impact of such smaller eruptions has been underestimated in climate models, the researchers say, and helps to account for a discrepancy between those models and the actual temperatures observed over the last 15 years.

The findings are reported in a paper in the journal Geophysical Review Letters, co-authored by MIT Professor Susan Solomon, postdoc David Ridley, and 15 others. They help to explain the apparent slowdown in the pace of global warming recorded over the last 10 to 15 years — possibly explaining as much as half of that slowdown, the researchers say.

“We’ve learned a lot of new things about how the Earth’s climate changes, not just from year to year but from decade to decade, as a result of recent research,” says Solomon, the Ellen Swallow Richards Professor of Atmospheric Chemistry and Climate Science at MIT. “Several independent sets of observations show that relatively modest volcanic eruptions are important.”

For the last several years, “It’s been quite clear that the observed trends are not following what the models say,” Ridley adds: While the overall warming trend continues, its rate is slower than projected. Previous research has suggested that some of that discrepancy can be accounted for by an increase in the amount of warm water being carried down to the deep ocean, but other processes can also contribute.

The cooling effect of large volcanic eruptions, such as that of Mount Pinatubo in the Philippines in 1991, was already widely recognized; the new work shows that smaller eruptions can have a significant cooling effect as well, and provides a better estimate of how much of the recent reduction in warming could be explained by such eruptions: about 30 to 50 percent of the discrepancy, the team found.

The team found that small eruptions produce a significant amount of aerosol particles, which reflect sunlight, in a region of the upper atmosphere that is relatively poorly monitored: Satellites can provide good data about the atmosphere down to around 15 kilometers above ground level, below which clouds interfere. The team filled in the missing region using multiple balloon, laser radar (lidar), and ground-based measurements.

Aerosols in that intermediate zone, from about a dozen modest eruptions around the world during the last 15 years, may double previous estimates of the cooling effect of eruptions, Ridley says.

 “It’s always exciting in science when you can find multiple measurements that lead to a common conclusion,” Solomon adds. “Several independent sets of observations now show that relatively modest volcanic eruptions are more important for global climate than previously thought.”

Overall, these smaller eruptions have lowered the increase of global temperature since 2000 by 0.05 to 0.12 degrees Celsius, counteracting some of the warming that would otherwise have occurred. Now, using this new information, groups that carry out climate modeling can update their models to more accurately project global climate change over the coming decades, Ridley says.

Alan Robock, a professor of environmental sciences at Rutgers University, says, “This work helps to better quantify the impacts of the most important natural cause of climate change, volcanic eruptions. We have an imperfect observational system for volcanic aerosols, and this work exploits some previously unused sources of information to better quantify the effects of small eruptions for the past decade.”

Robock, who was not involved in this research, adds that in light of these findings, “We need a more robust observing system for volcanic aerosols, to do a better job of measuring future small eruptions.”

Ridley and Solomon were the lead authors of this paper, joining authors from Wyoming, Russia, Germany, Japan, California, New York, Virginia, Colorado, and the U.K. The work was supported by the National Science Foundation, the Ministry of Science and Education of the Russian Federation, and the Russian Science Foundation.

Topics: Research, School of Science, School of Engineering, , Civil and environmental engineering, Climate change, National Science Foundation (NSF), EAPS


Just to enlighten those of you inmtelligent enough to read this, the war on climate change will determine the future survival of all life forms on the planet. While Gore and Limbaugh squared off and republicans take the Ostrich view of this crisis, they have all overlooked the drop dead factor that rising tempratures, melting ice sheets, and thus sea levels will produce. That of smaller land masses with far less foliage to recycle the CO2 into anything breathable. As the percentage of Oxygen is reduced we or our offspring,will suffocate in a slow deliberate suicide and all because we the people failed to push the politicians aside and do something about this issue while there still may be time. Food for thought!

This sounds like poor science to me. Weren't there volcano eruptions in the data used to develop the predictive model? I suggest enviros stop trying to justify incorrect predictions, build a model from scratch, then test it on a hold out. It's not that difficult and until I see that, everything is just propaganda.

Whatever the effect of volcanoes, the heart of the global warming controversy is what contribution humans make. Here are some crucial, verifiable facts - with citations - about human-generated carbon dioxide and its effect on global warming that people interested in this matter should be aware of.

The fact is, there has been global warming, but the contribution of human-generated carbon dioxide is necessarily so minuscule as to be nearly undetectable. Here's why:

Carbon dioxide, considered the main vector for human-caused global warming, is some 0.038% of the atmosphere[1]- a trace gas. Water vapor varies from 0% to 4%[2], and should easily average 1% or more[3] near the Earth’s surface, where the greenhouse effect would be most important, and is about three times more effective[4] a greenhouse gas than carbon dioxide. So water vapor is at least 25 times more prevalent and three times more effective; that makes it at least 75 times more important to the greenhouse effect than carbon dioxide[5]. The TOTAL contribution of carbon dioxide to the greenhouse effect is therefore 0.013 or less. The total human contribution to atmospheric carbon dioxide since the start of the industrial revolution has been estimated at about 25%[6]. So humans’ carbon dioxide greenhouse effect is a quarter of 0.013, works out to about 0.00325. Total warming of the Earth by the greenhouse effect is widely accepted as about 33 degrees Centigrade, raising average temperature to 59 degrees Fahrenheit. So the contribution of anthropogenic carbon dioxide is less than 0.2 degrees Fahrenheit, or under 0.1 degree Centigrade. Global warming over the last century is thought by many to be about 0.6 degrees Centigrade.

But that's only the beginning. We've had global warming for more than 10,000 years, since the end of the last Ice Age, and there is evidence temperatures were actually somewhat warmer 9,000 years ago and again 4,500 to 8,000 years ago than they are today[7]. Whatever caused that, it was not human activity. It was not all those power plants and factories and SUVs being operated by Stone Age cavemen while chipping arrowheads out of bits of flint. Whatever the cause was, it melted the glaciers that in North America once extended south to Long Island and parts of New York City[8] into virtually complete disappearance (except for a few mountain remnants). That's one big greenhouse effect! If we are still having global warming - and I suppose we could presume we are, given this 10,000 year history - it seems highly likely that it is still the overwhelmingly primary cause of continued warming, rather than our piddling 0.00325 contribution to the greenhouse effect.

Yet even that trend-continuation today needs to be proved. Evidence is that the Medieval Warm Period centered on the 1200s was somewhat warmer than we are now[9], and the climate was clearly colder in the Little Ice Age in the 1600s than it is now[10]. So we are within the range of normal up-and-down fluctuations without human greenhouse contributions that could be significant, or even measurable.

The principal scientists arguing for human-caused global warming have been demonstrably disingenuous[11], and now you can see why. They have proved they should not be trusted.

The idea that we should be spending hundreds of billions of dollars and hamstringing the economy of the entire world to reduce carbon dioxide emissions is beyond ludicrous in light of the facts above; it is insane. Furthermore, it sucks attention and resources from seeking the other sources of warming and from coping with climate change and its effects in realistic ways. The true motivation underlying the global warming movement is almost certainly ideological and political in nature, and I predict that anthropogenic Global Warming, as currently presented, will go down as the greatest fraud of all time. It makes Ponzi and Madoff look like pikers by comparison.

[1] Fundamentals of Physical Geography, 2nd Edition

by Michael Pidwirny Concentration varies slightly with the growing season in the northern hemisphere. HYPERLINK "http://www.physicalgeography.n..." http://www.physicalgeography.n...

[2] ibid.

[3] HALOE v2.0 Upper Tropospheric Water Vapor Climatology Claudette Ojo, Hampton University; et al.. HYPERLINK "http://vsgc.odu.edu/src/Conf09..." http://vsgc.odu.edu/src/Conf09.... See p. 4.The 0 - 4% range is widely accepted among most sources. This source is listed for its good discussion of the phenomena determining that range. An examination of a globe will show that tropical oceans (near high end of range) are far more extensive than the sum of the earth’s arctic and antarctic regions and tropical-zone deserts (all near the low end). Temperate zone oceans are far more extensive than temperate-zone desert. This author’s guess of an average of 2% or more seems plausible. I have used “1% or more” in an effort to err on the side of understatement.

[4 NIST Chemistry Webbook, Please compare the IR absorption spectra of water and carbon dioxide. ] HYPERLINK "http://webbook.nist.gov/" http://webbook.nist.gov/

[5] Three quarters of the atmosphere and virtually all water vapor are in the troposphere. Including all the atmosphere would change the ratios to about 20 times more prevalent and 60 times more effective. However, the greenhouse effect of high-altitude carbon dioxide on lower-altitude weather and the earth’s surface seems likely to be small if not nil.

[6] National Oceanographic and Atmospheric Administration. HYPERLINK "http://www.ncdc.noaa.gov/oa/cl..." http://www.ncdc.noaa.gov/oa/cl.... The estimated 90ppm increase in carbon dioxide, 30% above the base of 280 ppm, to a recent reading of 370 ppm, equates to just under 25% of present concentration, the relevant factor in estimating present contribution to the greenhouse effect.

[7] Oak Ridge National Laboratory http://www.esd.ornl.gov/projec...

[8] New York Nature - The nature and natural history of the New York City region. Betsy McCully http://www.newyorknature.net/I...

[9] Global Warming: A Geological Perspective John P. Bluemle HYPERLINK "https://www.dmr.nd.gov/ndgs/Ne..." http://www.azgs.az.gov/arizona... This article, published by the National Oceanographic and Atmospheric Agency, is drawn from a paper by the author in Environmental Geosciences, 1999, Volume 6, Number 2, pp. 63-75. Note particularly the chart on p.4.

[10] Ibid.

[11] Wikileaks: Climatic Research Unit emails, data, models, 1996-2009 HYPERLINK "http://wikileaks.org/wiki/Clim..." http://wikileaks.org/wiki/Clim....

See also HYPERLINK "http://www.dailymail.co.uk/new..." http://www.dailymail.co.uk/new... and

HYPERLINK "http://online.wsj.com/article/..." http://online.wsj.com/article/... and, more diplomatically: HYPERLINK "http://www.nytimes.com/2009/12..." http://www.nytimes.com/2009/12.... Et al.


What initially troubled me was the aberrant behavior of the climate research unit at East Anglia University, which has been the main data source for AGW arguments. They initially refused (!) to reveal their algorithms and data on the grounds that they were proprietary(!!). They responded to critics with ad hominem attacks and efforts to block their publication in scientific journals. Now, as I am sure you know, this is not how one does honest science, in which you PUBLISH your data and methodology and invite critical comment to ferret out error or oversights. It took the now-famous Wikileaks "Climategate" to pry loose the data and expose their machinations. Yet despite the devastating blow these revelations should have to their credibility, the AGW "cause" has taken on a life of its own.

Fundamentally, the argument seems to rest on a logical fallacy, post hoc ergo propter hoc - after this, therefore because of this. We see a rise in temperature and a rise in (principally) carbon dioxide, and therefore conclude one must have caused the other. It does not necessarily follow at all. There can be other causes entirely behind both phenomena, and as you see above, almost certainly there are. Beyond that, I have encountered numerous assertions of fact that cannot add up given the physical properties of water vapor and carbon dioxide that go unchallenged. One-sided arguments proliferate and people arguing the other side are frequently denounced as being employed by business interests rather than rebutted on the merits.

In sum, I have not come lightly to the conclusion that the AGW argument as it applies to carbon dioxide is largely untrue and certainly does not account for more than a very small, nearly negligible part of the phenomena we are seeing. The implications of widespread assertions of and belief in such an untruth are staggering, and potentially enormously destructive. It is unwise indeed to let oneself be stampeded in this matter, and stampede is clearly what many have been and are trying to induce.

I can understand politicians behaving this way; a carbon tax or carbon trading regime would allow enormous revenues to fall into their hands. I can understand "Progressive" ideologues; it logically leads to enormous expansion of government power over industry, the economy, and the daily life of individuals, which they regard as a good thing. I understand the environmentalists; they want to shrink the size and impact on the environment of modern civilization. But responsible citizens need to put aside such considerations.

I'm surprised this comment section isn't already a war zone.

EDIT: Never mind.

There have been many possible theories dreamed up to try to explain the lack of recent warming, and the fact that Planet Earth has failed to show any respect for the computer models.

However, there is one explanation that should at least be considered. I'm not claiming it's correct, but it should be regarded as a possibility, yet it doesn't seem to occur to the scientists - is it just possible that the reason there has been no recent warming is : "The bloody computer models are wrong?"

Here come the waves of people hoping to flame. Unfortunately, this is the MIT website, and we are all science geeks. This will come to nothing. Let's go cure cancer instead.

Just consider yourself lucky that we discover every day another explanation for the pause in global warming that gets worse every day!?!?'?

The reason we know CO2 levels have risen isn't because we have a meter to read the levels,it's because the information we give the models tell us that is what it should be if all our theories are correct. ( In a worst case scenario) This is true. All increases in CO2 are derived from models.ha ha ha??????

THE un-anwered elephant question in the room, is obvious: How has the frequency of occurrence of small volcanic outbursts varied over time, and how do the current times (last 100-150 years, or smaller time frames) measure up against that ?

It goes to reason that the frequency of outburst from small volcanoes is nearly constant and does not vary a whole lot. That is simply my guestimate, and scientific input on that is more than welcome. Now, assuming my hunch is at least nearly right (i.e. there is decadal variation but always less than ± 25 %), then the total decadal output from small volcanoes is hardly a variable, but more like a constant. On severity of volcanoes there is a link here: http://en.wikipedia.org/wiki/V...
That link however, does not provide any clue on outburst frequency versus volcano outburst class \ severity.

In summary, if my hunch is correct, then the 'alarm' raised in this article is more or less the equivalent of a storm in a glass of water.

Some will deny that 400ppm can cause the atmosphere to retain solar energy. I will marvel that every molecule of oxygen essential to life, every molecule of fossil fuel humans will burn, every calorie of nectar that will fuel the least butterfly began as a molecule of CO2 fixed by a microscopic green organ scavenged from that same 400ppm. A photon here, a CO2 there and soon all life as we know it sprang forth.

So what's the difference in volcanic activity/aerosol production over the last ten years compared with previous decades ?

And how do you distinguish aerosols of volcanic origin from other types of aerosols? Aerosols from a major eruption [Pinatubo for instance] are easy to identify initially but more difficult over the longer term.

Or are we clutching at straws ?

sulfur quantities elevate for which the atmosphere becomes hotter due tu the heat of the sun

Back to the top