Small volcanic eruptions could be slowing global warming
From the AGU: WASHINGTON, DC— Small volcanic eruptions might eject more of an atmosphere-cooling gas into Earth’s upper atmosphere than previously thought, potentially contributing to the recent slowdown in global warming, according to a new study.
Scientists have long known that volcanoes can cool the atmosphere, mainly by means of sulfur dioxide gas that eruptions expel. Droplets of sulfuric acid that form when the gas combines with oxygen in the upper atmosphere can remain for many months, reflecting sunlight away from Earth and lowering temperatures. However, previous research had suggested that relatively minor eruptions—those in the lower half of a scale used to rate volcano “explosivity”—do not contribute much to this cooling phenomenon.
Now, new ground-, air- and satellite measurements show that small volcanic eruptions that occurred between 2000 and 2013 have deflected almost double the amount of solar radiation previously estimated. By knocking incoming solar energy back out into space, sulfuric acid particles from these recent eruptions could be responsible for decreasing global temperatures by 0.05 to 0.12 degrees Celsius (0.09 to 0.22 degrees Fahrenheit) since 2000, according to the new study accepted to Geophysical Research Letters, a journal of the American Geophysical Union.
These new data could help to explain why increases in global temperatures have slowed over the past 15 years, a period dubbed the ‘global warming hiatus,’ according to the study’s authors.
The warmest year on record is 1998. After that, the steep climb in global temperatures observed over the 20th century appeared to level off. Scientists previously suggested that weak solar activity or heat uptake by the oceans could be responsible for this lull in temperature increases, but only recently have they thought minor volcanic eruptions might be a factor.
Climate projections typically don’t include the effect of volcanic eruptions, as these events are nearly impossible to predict, according to Alan Robock, a climatologist at Rutgers University in New Brunswick, N.J., who was not involved in the study. Only large eruptions on the scale of the cataclysmic 1991 Mount Pinatubo eruption in the Philippines, which ejected an estimated 20 million metric tons (44 billion pounds) of sulfur, were thought to impact global climate. But according to David Ridley, an atmospheric scientist at the Massachusetts Institute of Technology in Cambridge and lead author of the new study, classic climate models weren’t adding up.
“The prediction of global temperature from the [latest] models indicated continuing strong warming post-2000, when in reality the rate of warming has slowed,” said Ridley. That meant to him that a piece of the puzzle was missing, and he found it at the intersection of two atmospheric layers, the stratosphere and the troposphere– the lowest layer of the atmosphere, where all weather takes place. Those layers meet between 10 and 15 kilometers (six to nine miles) above the Earth.
Traditionally, scientists have used satellites to measure sulfuric acid droplets and other fine, suspended particles, or aerosols, that erupting volcanoes spew into the stratosphere. But ordinary water-vapor clouds in the troposphere can foil data collection below 15 km, Ridley said. “The satellite data does a great job of monitoring the particles above 15 km, which is fine in the tropics. However, towards the poles we are missing more and more of the particles residing in the lower stratosphere that can reach down to 10 km.”
To get around this, the new study combined observations from ground-, air- and space-based instruments to better observe aerosols in the lower portion of the stratosphere.
Four lidar systems measured laser light bouncing off aerosols to estimate the particles’ stratospheric concentrations, while a balloon-borne particle counter and satellite datasets provided cross-checks on the lidar measurements. A global network of ground-based sun-photometers, called AERONET, also detected aerosols by measuring the intensity of sunlight reaching the instruments. Together, these observing systems provided a more complete picture of the total amount of aerosols in the stratosphere, according to the study authors.
Including these new observations in a simple climate model, the researchers found that volcanic eruptions reduced the incoming solar power by -0.19 ± 0.09 watts of sunlight per square meter of the Earth’s surface during the ‘global warming hiatus’, enough to lower global surface temperatures by 0.05 to 0.12 degrees Celsius (0.09 to 0.22 degrees Fahrenheit). By contrast, other studies have shown that the 1991 Mount Pinatubo eruption warded off about three to five watts per square meter at its peak, but tapered off to background levels in the years following the eruption. The shading from Pinatubo corresponded to a global temperature drop of 0.5 degrees Celsius (0.9 degrees Fahrenheit).
Robock said the new research provides evidence that there may be more aerosols in the atmosphere than previously thought. “This is part of the story about what has been driving climate change for the past 15 years,” he said. “It’s the best analysis we’ve had of the effects of a lot of small volcanic eruptions on climate.”
Ridley said he hopes the new data will make their way into climate models and help explain some of the inconsistencies that climate scientists have noted between the models and what is being observed.
Robock cautioned, however, that the ground-based AERONET instruments that the researchers used were developed to measure aerosols in the troposphere, not the stratosphere. To build the best climate models, he said, a more robust monitoring system for stratospheric aerosols will need to be developed.
###
The paper:
Total volcanic stratospheric aerosol optical depths and implications for global climate change
Abstract
Understanding the cooling effect of recent volcanoes is of particular interest in the context of the post-2000 slowing of the rate of global warming. Satellite observations of aerosol optical depth (AOD) above 15 km have demonstrated that small-magnitude volcanic eruptions substantially perturb incoming solar radiation. Here we use lidar, AERONET and balloon-borne observations to provide evidence that currently available satellite databases neglect substantial amounts of volcanic aerosol between the tropopause and 15 km at mid to high latitudes, and therefore underestimate total radiative forcing resulting from the recent eruptions. Incorporating these estimates into a simple climate model, we determine the global volcanic aerosol forcing since 2000 to be −0.19 ± 0.09 Wm−2. This translates into an estimated global cooling of 0.05 to 0.12 °C. We conclude that recent volcanic events are responsible for more post-2000 cooling than is implied by satellite databases that neglect volcanic aerosol effects below 15 km.
http://onlinelibrary.wiley.com/doi/10.1002/2014GL061541/abstract?campaign=wlytk-41855.5282060185
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I do not quite understand how volcanoes behaved in the past. Did they remain stock-still until some 18 years ago they decided to blow their acids into the atmosphere to influence it and to fool mankind? How about the influence of volcanoes in these many billions of years B.C.?
You can look up plots of known volcanic activity over various spans. The best records realistically only go back a few years in a remotely trustworthy manner. We know about major eruptions earlier, but, they were major and easily observed. So, prior to satellite based observation there are numerous eruptions on dry land that were never recorded and at sea … no way to really know. Undersea eruptions would probably not affect the albedo much, though warm plumes of water could potentially affect the formation of low level clouds locally. If you read Willis Eschenbach’s analyses of volcanic events vs temperature data, there really is not much, if any, evidence for global effects.
Even major eruptions become problematic when you deal with records from the deeper past (say around the time of the fall of the Roman Empire). There are mentions in Chinese of historical texts of something big that happened, probably in Indonesia around 400 – 500 CE, but the Chinese were too far away to know what actually happened, and closer to the event either no records survived later historical events, like wars and fires and mildew, or no one literate survived to write a record. The best guess is that Krakatoa erupted on roughly the same scale as the known 19th C event, but that’s is just an educated guess at best.
When you come down to it, we know some about how the planet works, but really only just “some.” There is a huge reserve of historical documentation for rare events for which we have no direct empirical explanation, just guesses.
Is The Pause caused by an increase in small volcanos? Or was the warming period caused by a temporary decrease in small volcanos?
As far as I can tell from the abstract & press release, I can’t see any “control” case – ie the same data set prior to “the pause” showing substantially less aerosols to come to the conclusion they did. As far as I can tell, they assumed that was the case & used a “climate model” to get the answer. But of course it is all just to get funding : ” To build the best climate models, he said, a more robust monitoring system for stratospheric aerosols will need to be developed “.
This doesn’t appear to prove anything. It is either a shameless ploy for funding or they are doing really poor science.
The science is “settled”, but it seems every year there are dozens of stories like this about “underestimating” this or that feature of the climate. It implies they may need to rethink the basic theory, but they never do. Yet each time some minor little natural thing turns out to have a bigger affect on climate than they thought it only goes to show to skeptics how much more effect natural variation has than AGW proponents allow for.
So add this to the study
If 97% of Scientists Say Global Warming is Real, 100% Say It Has Nearly Stopped
Does that make it 101% saying there is a pause….(sarc)
James Bull
If AGW is a serious problem and if vulcanologists concur with this new theory for the “hiatus,” then a solution has been identified. Hallelujah! Now all we need to do is get working on producing aerosol producing machines that pump pollution into the atmosphere. I hope environmentalists will welcome this planet saving pollution.
These mad ideas have been around for some time.
http://news.bbcimg.co.uk/media/images/69962000/jpg/_69962679_624_e1000287-atmosphere_engineering-spl.jpg
http://assets.inhabitat.com/wp-content/blogs.dir/1/files/2012/07/Sulfate-Infusions-Dispensers.jpg
From a June 14 WUWT posting – Study: Climate engineering can’t erase climate change
Other climate engineering strategies are less appealing, such as fertilizing the ocean with iron to absorb carbon dioxide or reducing global warming by injecting particles into the atmosphere to block sunlight.
“Take the example of solar radiation management, which is the idea of putting aerosols into the stratosphere, kind of like what happens when a large volcano erupts,” Axsen explains.
“This is asurprisingly cheap way to reduce global temperatures, and we have the technology to do it. But our study asked other important questions. What are the environmental risks? Will global citizens accept this? What country would manage this? Is that fair? Suddenly, this strategy does not look so attractive.”
Mount Pinatubo Facts
• 15-20 million tons of sulfur dioxide were discharged in the atmosphere following the eruption which caused a global cooling among others.
• Mount Pinatubo’s eruption caused the ejection of 10 cubic kilometers of magma
The Pinatubo eruption delayed temperatures for about 3 years, so this would require 5 to 7 millions tons of SO2 per year and 3 KM^3 of dust per year. All injected up around 50,000 ft.
In what world besides an ‘Ivory Tower’ is this cheap and easy?
Maybe. This is certainly the oft-quoted assertion. But if so, why didn’t the double-whammy of Mt. St. Helens and El Chichon in 1980 and 1982, respectively, which very definitely affected the stratosphere (El Chichon dumped 7 million tons) have no discernible effect on global temperatures? See the graphics I included or linked in another reply, or Willis’ other thread on this general subject.
variation of solar intensity for a nearly constant power output by the sun. Yet we see the annual peak in global average temperature in the northern hemisphere summer when the Earth is farthest from the sun and the minimum in its winter when it is closest to the sun.
It is by no means clear that even large volcanic explosions like Mt. Pinatubo have an effect on the climate that is distinguishable from natural variation. Note well I’m not saying no effect, I’m saying that that effect is within the range of natural noise and is rapidly erased because the climate is almost completely insensitive to even 1 to 10% variations in the amount of sunlight being received at the top of the troposphere.
But we know that already! The top of atmosphere insolation varies by 7% maximum to minimum every year (by over 90 watts/meter^2) as the Earth undergoes its elliptical orbit. I’m assuming that the Mauna Loa apparent transmission is relative to this much larger baseline, although I’ll have to read the referenced papers to see if in fact they cancel it out (and if so, how). If they don’t, I have a pretty serious problem with what they are publishing, as I’m a pretty firm believer in
Insolation per se is not the determining factor in global average temperature! It is much more complex than that.
Given this, why in the world would we expect some immediate, significant, year spanning response even to large volcanic perturbations that are only transiently larger than the annual fluctuation and are not similarly sustained? They are lost in the noise. Not as an assertion, as a simple matter of observational fact. Nobody, and I do mean nobody, can look at the temperature data and guess where volcanoes happened. One can barely look at where volcanoes happened and interpret some variation in the temperature as the response.
rgb
RGB, you noted that:
“we see the annual peak in global average temperature in the northern hemisphere summer when the Earth is farthest from the sun and the minimum in its winter when it is closest to the sun.” despite top of atmosphere insolation varying by 7%, with max at time of NH winter.
Perhaps the Earth warms the most during NH summer because the NH has 68% of the total land area, while the the SH has only 32%. Thus 7% weaker sunlight is falling on approximately twice the land area during peak of NH summer compared to peak of NH winter when 7% stronger sunlight is falling on approximately half the land area. The change in land area exposed to the sun is far greater than the change in strength of sunlight due to the change in Earth-Sun distance.
Since land is warmed by sunlight (temperature rises) more readily than ocean, the peak warming would be during the time of year when the most land is receiving sunlight.
SR
NH winter receives less radiation despite being closer to the sun because the angle of incidence reduces and the days are shorter.
RGB ” Nobody, and I do mean nobody, can look at the temperature data and guess where volcanoes happened.”
You’ll stand a better chance of finding them by looking at temperature deviations before the events.
Didn’t these guys spend over a decade telling us how little affect any amount volcanic activity had?
Yes. And, they’re the same ones who’ve been saying that changes in solar activity have no effect on climate.
Offhand I would observe that the aerosol rich eruptions of Agung 1963, El Chichón 1982 and Pinatubo 1991 caused clearly visible warming of the upper atmosphere due to the particles heating up in the sun.
http://www.climate.gov/sites/default/files/Stratospherictemp_1958-2012_radiosondes.png
So where is the stratospheric warming now from those aerosols? Instead it appears that the stratospheric temperatures are having the same pause as the surface records.
This is empirical evidence disproving their hypothesis. Next.
OK – can someone remind me about the claim that efforts to reduce pollution in the 60’s and 70’s were successful and changed the radiation balance? So SO2 from volcanoes caused the pause. What about the SO2 we used to throw into the atmosphere. Did humans cause some warming by cleaning up our emissions? If not A then not B?
Excuse no. 53
Chris,
Do you have the list compiled? I’d love a copy if you don’t mind sharing.
See on WUWT (at the top) Climate Fail Files
Thank you. I’d gone there but only saw the 3, but after clicking on the list of excuses there it is.
Appreciated.
“To build the best climate models, he said, a more robust monitoring system for stratospheric aerosols will need to be developed.”
OH, Goodie! More Grant money!
It’s pretty clear that the warmists have staked out some ideological turf and are going to defend it no matter what. This isn’t science.
Certainly it could be possible possible that scientists have miscalculated the impact of volcanoes on global temperatures. But if using that to even partially explain the pause wouldn’t you have to also make a claim that there has been an increase in eruptive output since some time before the pause started? Have they made that claim? Without that then the miscalculation cannot explain the pause, although if they’re correct then it’s another source of error in the models.
Oh I get it, when they crank up aerosols the models don’t run as hot. The modeling community can say my bad and use this to justify changing their aerosol numbers to to generate numbers closer to what’s actually happened and then claiming the models are much improved while still making sure the algorithms show dangerous warming in the longer term future.
@Non Nomen
…When will we shut off these volcanoes???
I propose that we should institute Carbon Trading to suppress them. Basically, if you are a country with a volcano in it and it erupts, you should pay $1 per estimated tonne of CO2 released to the Volcanic Emissions Climate Foundation. Just let me set it up…
When will we shut off post-modern science???
This is one of many cases where new measurement technologies have been used, and the papers assume that the effect they are claiming only began when they could measure it. As noted above, there doesn’t seem to be a trend in volcanic activity, just new measurements.
The negative forcing they are quoting is tiny, not much different from TSI that has been derided as too small to account for climate change. If their conjecture is right then the divergence currently occurring between observation and models couldn’t possibly grow any larger.
But if the divergence continues to increase . ..
Hi Vince, the number they use for blocked TSI is .05 too .120 C are they trying to steal the TSI change from there being a lower solar cycle? Off the top of my head the numbers look disconcerting. Also the time frame. The pause has only been openly admitted to for two or so years, has there been time to think up a study, submit grants obtain equipment take measurements etc. Or did they just grab existing sat data and wing it.
Sorry something seems off with all this.
Michael
The phrase “grasping at straws” springs to mind.
First the Alarmists tell us that volcanic eruptions cause global warming because of the CO2 they emit–now they are telling us that volcanic eruptions cause global cooling! These are the same people that claim the global cooling of 1945-1977 (when CO2 emissions were soaring) was caused by burning higher-sulfur coal (which somehow must have mysteriously ended abruptly in 1978 despite the fact that much more coal is being burned now than in the 1960’s and 70’s).
Volcanic eruptions have been going on for many hundreds of millions of years. To blame recent cooling on eruptions, you would need to prove abrupt changes in eruptive activity (that’s how climate changes have typically occurred throughout geologic history) and explain why climate shows no correlation with volcanic eruptions. As Willis and I have both argued, the influence of volcanic eruptions on climate is insignificant. Read Willis’s post of a few days ago about the Icelandic eruption of 1783, which didn’t have any unusual effect on Europe’s climate.
I suppose the pause might be caused by the Cold Fairy waving her magic wand. This is a about as likely as most of the other excuses given so far.
I also conclude that these small volcanic eruptions are having NO cooling effect as evidenced by looking at the stratospheric temperature profile which shows no warming in response to all these small volcanic eruptions.
Look at the chart Leftturnandre sent a few post back.
Nevertheless I would like to know what is the residence time in the atmosphere for all the SO2 BARDARBUNGA volcano in Iceland is putting out? It is putting out vast amounts of SO2 but at very low altitudes.
I think a great indicator of what effect volcanic activity is having on the climate is the Volcanic Aerosol Optical Thickness Chart which shows very low levels since the turn of the century.
“The prediction of global temperature from the [latest] models indicated continuing strong warming post-2000, when in reality the rate of warming has slowed,” said Ridley. That meant to him that a piece of the puzzle was missing
Yeah, but when you correct it for time of observation it fits perfectly.
In other news…b.b.b.b.but Pinatubo!
https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcTQxfWH7AVCU0WcftRFyy2Hxwy_1R5r2RK1fNA3ydtZpSkZzqsP
As one can see volcanic aerosol optical thickness has been low this century.
https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcRLttNBRV01duMr5BJm3pEL5yenzcg0pnrxT9on6cQEpYGJkYzHfQ
One more chart .
I don’t know which causes the alarm bells to go off first, the AGU or the words “small” and “excuse.”
There have been no more small eruptions since 2000 than were from 1985 to 1999.
Total garbage and lame excuse making.
Also, it’s not a slow down in warming, but in unadjusted data, a cooling since the late 1990s.
“Slowing” is not the same as “hiatus”.
The reviewer shows his warmist position by using “slowing” while the authors use”hiatus”.
I suspect glaciers would have to be bearing down on Toronto before the global warming enthusiasts will admit that maybe, just maybe, they don’t know all the factors that cause climate change.
Nah, they would just claim that unseasonably high temperatures had caused the glacier to slip its moorings.
For evidence that they can’t be dissuaded, see the comments on the Guardian reporting of the snow in the USA.
‘Hiatus’ from google:- a pause or break in continuity in a sequence or activity.
“there was a brief hiatus in the war with France”
synonyms: pause, break, interval, interruption, suspension, intermission, interlude, gap, lacuna, lull, rest, respite, breathing space, time out
I think youre being harsh Doug – slowing down of a rate could still just about be called Hiatus. And as an admission from a warmist I’ll take that any day. Still splitting hairs really