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Volcanic Eruptions May be Masking ‘Lost’ Warming

By Alex Kirby, Climate News Network

LONDON — Climate scientists think they may have found at least part of the answer to a conundrum which has been puzzling them recently — why the atmosphere has not warmed as much as expected over the last decade or so.

A team led by the University of Colorado-Boulder (CU-Boulder) thinks the reason may be emissions of sulphur dioxide (SO2), a known inhibitor of atmospheric warming, from many of the world’s volcanoes.

The puzzle is why the global average temperature has not increased as expected in step with rising greenhouse gas emissions. This has led some to suggest that global warming itself is faltering, and with it the entire scientific justification for action to stabilize the climate.

Alaska’s Mount Redoubt.
Credit: R Clucas via Climate News Network

The chair of the Intergovernmental Panel on Climate Change, Dr R K Pachauri, was reported in The Australian on February 22 as having acknowledged “a 17-year pause in global temperature rises, confirmed recently by Britain’s Met Office”, but “said it would need to last ’30 to 40 years at least’ to break the long-term global warming trend”.

Most SO2 emissions are from fossil fuel burning at power plants and in industry, with smaller amounts coming from railways, large vessels, and some industrial processes.

Volcanoes Downplayed

Small quantities of the emissions eventually rise into the stratospheric aerosol layer of the atmosphere, where chemical reactions create sulphuric acid and water particles that reflect sunlight back into space, cooling the planet.

Scientists have known for years that this cooling mechanism from a range of aerosols is helping to prevent global average temperatures rising as much as they otherwise would under the influence of greenhouse gases, but it appears they have underestimated the effect of volcanic SO2.

India and China are estimated to have increased their industrial SO2 emissions by about 60 percent between 2000 and 2010 through coal burning.

But the study, published online in Geophysical Research Letters, suggests it is volcanic eruptions, not Asia’s emissions, that are largely responsible for the warming slowdown.

The study’s lead author, Ryan Neely, said previous observations had suggested that increases in stratospheric aerosols as a whole since 2000 had cancelled out as much as 25 percent of the warming from greenhouse gases.

“This new study indicates it is emissions from small to moderate volcanoes that have been slowing the warming of the planet”, said Neely, a researcher at the Cooperative Institute for Research in Environmental Sciences, a joint venture of CU-Boulder and the National Oceanic and Atmospheric Administration (NOAA).

Negligible Overall Effect

 The new study relies on long-term measurements of changes in the stratospheric aerosol layer’s “optical depth,” which is a measure of transparency, said Neely. Since 2000 the optical depth in the layer has increased by about 4 to 7 percent, meaning it is slightly more opaque now than it was.

“The biggest implication here is that scientists need to pay more attention to small and moderate volcanic eruptions when trying to understand changes in Earth’s climate”,  said Professor Brian Toon of CU-Boulder’s Department of Atmospheric and Oceanic Sciences.

“But overall these eruptions are not going to counter the greenhouse effect. Emissions of volcanic gases go up and down, helping to cool or heat the planet, while greenhouse gas emissions from human activity just continue to go up.”

“This paper addresses a question of immediate relevance to our understanding of the human impact on climate,” said Neely. “It should interest those examining the sources of decadal climate variability, the global impact of local pollution and the role of volcanoes.”

While small and moderate volcanoes mask some of the human-caused warming of the planet, larger volcanoes can have a much bigger effect, said Toon. When Mount Pinatubo in the Philippines erupted in 1991, it emitted millions of tonnes of SO2 that cooled the Earth slightly for the next few years.

Alex Kirby, a former BBC environment correspondent, is a founding journalist of Climate News Network. Climate News Network is a news service led by four veteran British environmental reporters and broadcasters. It delivers news and commentary about climate change for free to media outlets worldwide.


By dan_in_illinois
on March 11th, 2013

“Climate scientists think they may have found at least part of the answer to a conundrum which has been puzzling them recently — why the atmosphere has not warmed as much as expected over the last decade or so.”

Here’s a possibility - they were wrong.

Reply to this comment

By Anaxamander Q. Gormlay (Somewhere in the Great White North)
on March 11th, 2013

Egads!  The facts do not fit the foregone conclusions! Hide the decline! Blame the volcanoes!

Or—- gulp—- review the assumptions of the inaccurate model.

Easy for me to say.  I don’t have any government grants riding on the outcome!

BTW, if Al Gore is for it, then I’m against it.  Especially when it enriches him beyond the avarice of Croesus.

Good luck on those epicycles, guys. 

Paging Dr. Lysenko!  :Your order of phlogiston has arrived!!!

Reply to this comment

By Physics undergrad (Seattle)
on March 11th, 2013

Heyyyy Dan, show me your license. Your license. You know, your intellectual license to claim to know anything about the climate. Oh, what? You don’t have one? Did you study it in College? Oh it rarely was mentioned. Oh you didn’t study science? Oh ok.

Yo Dan,
Back in like 1896
There was some physicists
trying all of that and this
making some measurements of this s*it
known as the CO2 infrared scattering coefficient
and quantity that after being measured made them cognizant
that doubling CO2 concentrations should produce about 5 degrees of warming
What? That’s pretty close to what the IPCC stated in their 2007 warning?
Yeah man but that was in 2007, were talking about 1896,
No tricks, these guys were physicists.

So why do you think exactly that 98% of scientists have come to agreement with a collection of statements about the validity of the root cause of climate change that are considered controversial in the public eye? Its because the public have become completely moronic and inundated from their lack of knowledge in science, willing to believe almost anything.

Reply to this comment

By Dave (Basking Ridge, NJ 07920)
on March 11th, 2013

Obviously there are puzzles about atmospheric heat flux and the role and sources of aerosols and there is a great deal of ongoing research to do with just that. I find it interesting that according to the report here volcanic emissions may play a more important role than previously thought in this context. However there is also a deeper context in that global mean surface temperatures have indeed been relatively flat for a while and what should we seriously make of that. This is a topic in itself which is rightly or wrongly not addressed in the report.

So, to add my 2c worth here; it is misleading to view trends in the global mean surface temperature as the sole indicator of climate change because of the more recent observational disconnect between that and sea level rise, melting of the Arctic, the frequency of extreme weather events, and so on all around the world – which are instead hard to ignore and obvious top level indicators of continuing and rapid climate change.  At least for most of us…

Also, when one instead considers average land surface temperature data – where we live and experience climate - separately from sea surface temperature (SST) data the ‘temperature data’ picture changes.  See for instance the graph “Decadal land surface average temperature” here which shows a clear continuing rise. In other words, as if we needed that confirmation, it really has been getting warmer!

Furthermore, to go back to SST and reconsider that; if instead of SST one considers changes in heat content of a surface layer (in this case the top 700 meters) of the oceans (the acronym here is OHC) we see a continuing rise there too. This European Environment Agency web page states that “The warming of the World Ocean accounts for approximately 90 % of the warming of the Earth during the last 6 decades.”  According to the data shown there, OHC is clearly continuing to trend upwards quite steeply.


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By Physics Grad (La Jolla, Ca)
on March 11th, 2013

Hey, Physics undergrad! Have you not learned about logical fallacies and strawmen yet? No? Well, I did study physics- quite a lot at UCSD, and I do have a “license”, and I nee no consensus. A faulty simulation model is just that. They will continue to try to alter the model to maintain CO2 as the damning factor, regardless. They have already made their conclusion and have now resulted to altering the simulation to maintain the same conclusion. That is, by definition, not science.

Reply to this comment

By Jayme
on March 11th, 2013

Aside from a couple cooler years, why did higher volcanic SO2 emissions before 2000 not likewise cool the planet more than the relatively lower emissions that occurred after 2000?  I don’t believe the claim.

Reply to this comment

By Tanya Stone
on March 11th, 2013

As a representative of people who do not have PhDs in climate science, but who follow the discussion, my reaction to the assertion that climate change is an emergency threatening the future of humanity was based upon what our global fearless leaders planned to do about it: carbon credit trading. A little investigtion determined that carbon credit trading will have NO impact on carbon in the atmosphere, but will make a whole bunch of people who are already very rich, even richer.

On the other hand, I look at Holland, who before Industrialization was able to figure out how to live on land that is below sea level. Building infrastructure to protect our cities from rising oceans will create jobs. Figuring out how to survive in a different climate will make humans more innovative. The human race has lived through ice ages and warming periods before. Are we really to believe that the civilized version of mankind cannot cope with what our less-sophisticated ancestors took in their stride?

Reply to this comment

By Robert (Amsterdam Netherlands)
on March 11th, 2013

Yo Mr.Physics undergrad

Regarding your reply to Dan fron Illinois

All through history the ‘consensus’scientists have thought they were right , even when the evidence against
their theories were piling up and new discoveries were labeled by them as amazing , baffling ,
unexpected by their theory (which had to be right , because there was consensus after all , and their theory
was based on science ,was it not?)
And all those times the consensus scientists tried to adjust their theories after every new contradicting fact.
Not to gain more knowledge ,but for the sake of not daring to admit to themselves and the people that they
were wrong , not to lose face, to lose funds etc, or because to lose (political) power.

All those times ,a few scientist who were not from the ‘consensus’ , and had come up with an alternative theory
(although also not perfect and complete like every theory) were, in the end ,proven right.
But not before , by the consensus ‘scientists’ and their bosses and followers ,they were ridiculed ,vilified,
marginalised and attacked , by word and/or sword.

I think this AGW is (just) another of those cases.

Btw , you don’t have to have a diploma or whatever ‘official’ degree ,as long as you use your brain and try to
advance your knowledge by every means ,in an honest and .open way.
Maybe it’s even better not to have studied at an ‘official’ institution , because you will be (more) free of
the dogma’s and feeling ‘better’ ( because ,after all,  i have studied at an official institution and thus
in essence , i have to be right ,like my teachers before me).
In the light of the last sentence , a lot of science looks a bit like (fanatic) religion does it not ?


Reply to this comment

By dan_in_illinois
on March 12th, 2013

Mr. Physics undergrad,

Just for the record, I graduated in Computer Engineering and have a Masters and have another 20+ semesters hours of additional graduate work in engineering.  I don’t know if that qualifies as a “license”.  I also don’t think it’s relevant to this discussion.

Reply to this comment

By geohydro2011 (Portland, OR 97236)
on March 12th, 2013

I am a modeler. My models are never completed as new data or new understanding of processes affects the conceptual and thus numerical models. Too, after a simulation is completed, I check to see how well it agrees with empirical evidence such as historical and proxy records. Indeed, I much prefer the empirical or real world data. For example, Hansen et al recent work based on real world data vis-a-vis model simulations shows that, in some places, today we are experiencing hotter summers over larger expanses of land much more so than can be explained by chance alone. Marcott et al shows a new temperature record that shows that the mean global air temperature in the near future is about to exceed the upper range of variability in the air temperature record that was present over the Holocene when humans developed into societies. The rapid change in air temperature seem unprecedented in the Holocene. That is the crux of the problem. Rapid loss of Arctic Sea ice is affecting polar and subtropical jet thus leading to prolonged drought or storms. A warmer atmosphere too hold more water leading to more rain and potentially more floods. We can’t throw away the IPCC model—we continue to work with it as it has a strong theoretical basis.

Reply to this comment

By Patrick AUCOIN (MISSION/BC/v2v1m9)
on March 19th, 2013

The polarizing impact of science literacy and numeracy on perceived climate change risks…. is an article presented in Nature Climate Change states:
public divisions over climate change stem not from the public’s incomprehension of science but from a distinctive conflict of interest: between the personal interest individuals have in forming beliefs in line with those held by others with whom they share close ties and the collective one they all share in making use of the best available science to promote common welfare.
Ice core data has shown a 5 degree Celsius planet temp change in as little as 3 years in the past, to err on the side of caution, seems to be the only logical course. I’ll ride my bike for now and do what I can to encourage a much less carbon intensive lifestyle for everyone…. at least till the solid data is in….
  a curious jack of trades

Reply to this comment

By robert (Amsterdam Netherlands)
on March 20th, 2013

Icecore data also shows that the CO2-levels lag BEHIND the temperature-increase

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