“MOST people are under the impression global warming has risen by about 0.8 degrees C since the dawn of the industrial age. Unfortunately, mean temperatures have risen much further when account is taken of the short-term masking effect of aerosols emitted from coal and oil, mainly sulphur dioxide and its oxidized products…
“Thus, according to the IPCC AR4-2007 report (figure SPM.2), the total anthropogenic greenhouse effect since 1750 AD, which is equivalent to about +2.3 degrees C, is masked by a compensating aerosol albedo effect equivalent to about -1.1 degrees C. However, given the short-lived residence time of sulphur aerosols in the atmosphere, this masking effect dissipates within periods up to a few years.
“Currently continuing emission of SO2 maintains the aerosol albedo effect, preventing further sharp temperature rises. But in a situation akin to methadone addiction, proposed reduction of sulphur emissions would lift this barrier, enhancing global warming.
“A dissipation of aerosols and the melting of polar ice would raise polar temperature anomalies to levels exceeding even the current 4 to 5 degrees C warming in parts of the Arctic circle, Siberia and west Antarctica.”
That’s according to Andrew Glikson, a visiting fellow at the Australian National University, writing for www.crikey.com.au last week.
I’m wondering whether Dr Glikson has a point when it comes to aerosols – they are so prevalent in the skies of south-east Asia. Is the -1.1 degrees C a reasonable guestimate for their impact globally?
*******************
Notes and Links
Global warming toward the EU’s upper limit, MONDAY 1 JUN 2009, by
paleoclimate scientist Andrew Glikson, http://www.crikey.com.au/2009/06/01/global-warming-toward-the-eus-upper-limit/
Dr Glikson’s home page: http://ems.anu.edu.au/people/glikson/
Hong Kong harbour in a mist of smog; the photograph was taken in September 2006 by Jennifer Marohasy.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
This is typical of Glikson who is both a catastrophist par excellance and misanthrope; there are any number of inconsistencies with the masking theory of aerosols; the sop to the masses version is that the great burst of industrialisation during the 40s kicked off the masking effect and this explains the 30 year dip in world temperature up to 1976, the year of the GPCS and transition to El Nino conditions; the problems with this idea is that aerosol forcing continued to at least the 80s in Europe;
http://www.agu.org/pubs/crossref/2007/2006JD008037.shtml
And thereafter Asia took up the cudgels to increase aerosol production despite reduction in the West. Another problem with the aerosol theory is that since industrialisation took place entirely in the Northern Hemisphere the masking effect should have featured a hemispheric demarcation; it didn’t, the 40-76 drop in temperatures occurred globally without any hemispheric lag.
The main dilemma for the aerosol theory however is noone knows whether aerosols have a heating or cooling effect;
http://www.geotimes.org/aug07/article.html?id=WebExtra080307.html
Andrew Glikson doesn’t seem to be able to work out whether aerosols cool or warm.
According to Dr V Ramanathan, this Asian Brown Cloud was melting the third largest ice mass on the planet, namely those 46,000 glaciers on the Tibetan Plateau.
So, if anything, it’s having the opposite effect.
More about Glickson here.
http://webdiary.com.au/cms/?q=node/2843
“This is typical of Glikson who is both a catastrophist par excellance and misanthrope; ”
I’m going to have to call you the misanthrope, you value property more than people.
“According to Dr V Ramanathan, this Asian Brown Cloud was melting the third largest ice mass on the planet, namely those 46,000 glaciers on the Tibetan Plateau.
So, if anything, it’s having the opposite effect.”
It can have both effects, since he says the black carbon component can warm, but we already know that other components that don’t absorb radiation like the black carbon can cool, like the sulphides. Once again, the claim is made that since we don’t perfectly understand everything, and we never will, we understand nothing, which is clearly false.
And if the sun was not out there masking things, the atmosphere would freeze out.
All Gilkson accomplishes is to show that humans bring many sorts of forcings to the climate.
The AGW promoters ahve obsessed on one, which happens to be where they see the money$.
SJT,
You might want to check those Tibetan glaciers. They are not all cooperating with AGW:
http://global-warming.accuweather.com/2009/05/glaciers_that_are_actually_gro.html#comments
I have a problem with the concept than SO2 GAS is an aerosol ( liquid or solid particle by definition) SO2 is extremely soluble in water thus it dissolves in the water drops in the atmosphere i.e. clouds very quickly but it does not increase them. I have seen residence times of 8 days quoted and it is definitely not in the region of 3 years. Now the reaction of a drop of water or a drop of water with SO2 dissolved in it with respect to capturing and reemiting outgoing long wave radiation is the same and gasses do not nucleate clouds so I am puzzled about this long standing fiction that SO2 is affecting the atmosphere. I can see that if there was a colour change in the droplet it woud absorb more incoming short wave and reflect less this would INCREASE the temperature of the lower troposphere.
Smog is actually produced by carbon and flyash particulate which does nucleate drops of water and discolours it to produce the brown haze and increses the low level cloud thus obscuring sunlight but as previously stated because of the colour it absorbs the incoming and does not reflect it so I question the hypothesis that it has an overall cooling effect. I think this is an area which requires considerably more research.
I grew up in London in the 40’s and 50’s so I am very familiar with smog, once the area became smokeless the smogs cleared up thus it is the particulate which creates smog not gasses and CO2 is an odorless, colourless gas and can not produce smog or airborn aerosols of any descrition.
I agree that the particulate is discolouring the snow and could be increasing the heat absorbtion especially in the arctic so by all means let us clear up the particulate emissions I believe this to be a positive antipollution program but this has absolutely nothing to do with CO2.
Clearly the climate alarmists who are promoting and stand to gain by this CO2 tax swindle like to play the guilt by association game and throw a large blanket over the entire subject but each element has to be treated on an individual basis and judged accordingly.
Barry Moore wrote:
“Smog is actually produced by carbon and flyash particulate which does nucleate drops of water and discolours it to produce the brown haze and increses the low level cloud thus obscuring sunlight but as previously stated because of the colour it absorbs the incoming and does not reflect it so I question the hypothesis that it has an overall cooling effect. I think this is an area which requires considerably more research.
I grew up in London in the 40’s and 50’s so I am very familiar with smog, once the area became smokeless the smogs cleared up thus it is the particulate which creates smog not gasses and CO2 is an odorless, colourless gas and can not produce smog or airborn aerosols of any descrition.”
You’re talking about London smog. I grew up in Los Angeles County. And there, the rustic charm of the purplish-brown cloud comes mostly NOx, courtesy of the friendly, indigenous automobiles.
Several years ago, I was talking about this with an engineer who used to work for the state. Mario told me that back in the late 1960s, the state encouraged automakers to design car engines for stoichiometric fuel-air mixtures, rather than the formerly rich mixtures. An interesting side-effect was that the newer engines were hotter, and generated more NOx. But in those days, CO and other products of incomplete combustion were considered to be the ‘bad guys’, just as CO2 is the current villain of choice.
“Unfortunately, mean temperatures have risen much further when account is taken of the short-term masking effect of aerosols emitted from coal and oil”
Typical of these charlatans. “Unfortunately”: for catastrophists? Or farmers? “mean temperatures”: the Hansen-adjusted mean temperatures, or the satellite record? “have risen”: no, all records show a fall over the past 10 years, even Hansen’s. “much further”: than what? More decrease in temperature than we have seen for the past decade? “short-term masking effect”: so if the nonexistent problem actually became real, it would be easily solved? “emitted from coal and oil”: so that’s the means of solving the nonexistent problem if it actually became a real problem?
Or, to paraphrase: I have a theory that you will give me a lot of money. This theory is a fact.
He’s wrong – The global sea ice extent has been increasing, not decreasing. I can’t understand how these guys can be wrong so blatantly.
Glikson has goofed up.
“mean temperatures have risen much further… ”
Is he saying that the mean temperatures have risen much further than our thermometers are showing ?
That there is a huge hidden rise, hidden from surface stations and satellite measurements ? Maybe it’s something that only he knows about ?
I think that he really means that temperatures WOULD HAVE risen much further than they have, except the global warming is masked by something smaller. Wonder why he did not write it like this ?
janama,
We denier scum are not worthy to point out pesky little facts that show AGW promoters are wrong.
In fact, we should not even have the right to discuss such enlightened, lofty intellectuals such as Glikson.
“Once again, the claim is made that since we don’t perfectly understand everything, and we never will, we understand nothing, which is clearly false.”
Only SJT could dredge up a statement like that.
What sceptics claim is that when someone like Dr Glikson gets his facts up to 180 degrees from where they should be, what chance is there of getting truth and accuracy in current and predicted climate.
The usual stupidity from the boofhead deniers – the change from solar dimming to solar brightening has been well investigated. Well except for you lot who only read blog trash and get angry at talk back radio.
Andrew Glikson isn’t automatically wrong about everything, just because he’s Andrew Glikson. The dimming effect from sulfur oxides pollution is real. SO2 and especially SO3 molecules serve as nucleation sites for nascent water droplets. When the concentration of sulfur oxide pollution is high, too many small water droplets form. They exhaust the available local supply of gas-phase H2O. These tiny droplets take a very long time to reach the critical mass necessary for rain. The net result: A given airborne H2O formula unit will spend a greater proportion of its time in the liquid phase, rather than the gas phase, and will contribute a tad more to the Earth’s albedo.
In the past, this effect did partially offset global warming (which peaked in 1998). What was the magnitude of the offset? Hell if I know. I trust quantitative claims from the IPCC as much as I trusted the claims of WMDs in Iraq from the Smirking Chimp.
A bigger question that came up a few years ago: Did sulfur oxide pollution contribute to some of the big African droughts of the past? A related question that I did NOT see in the MSM: Has Asian sulfur oxide pollution affected rainfall patterns in Australia?
Well, I have had this discussion several times in the past, including on RealClimate. The aerosol argument is quite dubious. Even the (global) sign of effects is not known for sure.
The main problem is that climate models can’t explain the 1945-1975 cooling period (neither the 2000-current period) without something that offsets the effect of an increasing amount of CO2 in the atmosphere. That was found in the aerosols, without knowing anything real about their properties, amounts and ratio between human made and natural aerosols (sea salt spray, terpentines, sand dust,…). The problem now is that the amount of cooling aerosols didn’t increase in the past decade (far less in Europe and North America, far more in SE Asia), but we now see a similar flat temperature trend. The correlation of the PDO with the temperature trend is striking…
Back to aerosols:
First have a look at the first graph of http://www.realclimate.org/index.php?p=168 : There is a direct coupling between the cooling effect of aerosols and the warming effect of CO2. If aerosols have a strong cooling effect, then CO2 must have a strong warming effect and reverse. Now the strong cooling effect is rather discutable, as the effect of the huge reduction in SO2 emissions in Europe has no measurable effect at the places downwind the highest emissions (according to the models):
http://www.ferdinand-engelbeen.be/klimaat/aerosols.html
Thus what happens if one substitutes a much lower effect of aerosols in a (simple) climate model? One need to reduce the effect of 2xCO2 in order to match the 1945-1975 trend and the “projection” for the year 2100 is reduced to +1.2°C instead of +2.5°C (as far as any such projection is real):
http://www.ferdinand-engelbeen.be/klimaat/klim_img/oxford_2100.jpg
A detailed comment on aerosols can be found here:
http://www.realclimate.org/index.php?p=245#comment-8526
Some important items:
The Pinatubo eruption caused a drop of about -0.6°C due to aerosol load in the stratosphere, lasting a few years. The human aerosol load only lasts average 4 days before raining out, which means that the average impact is about -0.1°C, way lower than the -1.1°C mentioned by Andrew Glikson.
Aerosols found over land in the free troposphere are mainly of natural origin. See the 2005 GRL paper of Heald ea. at
http://www-as.harvard.edu/chemistry/trop/publications/heald_2005.pdf
The main points:
– natural SOA (secondary organic aerosols) in the free troposphere are some factor 7 higher than anthropogenic.
– the mass ratio SOA/SOx (SO2+sulfate) aerosol is app. 2:1 to >10:1, between 0.5 and 5.5 km altitude.
– chemical transport models underestimate SOA’s with a factor 2 at the boundary layer and up to 10-100 times in the free troposphere.
That means that aerosols are not the ideal scapegoat that the models needed to fit the temperature trend of the past century (a necessary, but insufficent condition for the validity of any climate model)…
Comment from: Luke June 8th, 2009 at 2:40 pm
The usual stupidity from the boofhead deniers – the change from solar dimming to solar brightening has been well investigated. Well except for you lot who only read blog trash and get angry at talk back radio.
I don’t think that global dimming and brightening have much to do with aerosols, as even in Antarctica dimming and brightening was measured, while aerosols there are very rare. Moreover India sees a continuous dimming (and aerosol increase), but China sees a brightening after an initial dip. I don’t think that China’s factories got that much cleaner in the past decade(s)… See Wild e.a. at:
http://www.sciencemag.org/cgi/content/abstract/308/5723/847
and the supporting material at:
http://www.sciencemag.org/cgi/data/308/5723/847/DC1/1
“Well except for you lot who only read blog trash”
We might have to read it but we don’t have to write it.
Our picture of the relationship between sulfate aerosols and climate is complicated by microscopic beasties is the world’s oceans. They are sources of dimethyl sulfide (DMS) gas, which enters the atmosphere, where it is oxidized to form SO2 and SO3. Here’s a tidbit from Wikipedia:
“DMS originates from S-methylmethionine(SMM).[1] DMS is the most abundant biological sulfur compound emitted to the atmosphere.[2] Emission occurs over the oceans by phytoplankton. DMS is also produced naturally by bacterial transformation of dimethyl sulfoxide (DMSO) waste that is disposed of into sewers, where it can cause environmental odor problems.[3].
DMS is oxidized in the marine atmosphere to various sulfur-containing compounds, such as sulfur dioxide, dimethyl sulfoxide (DMSO), dimethyl sulfone, methane sulfonic acid and sulfuric acid. [4] Among these compounds, sulfuric acid has the potential to create new aerosols which act as cloud condensation nuclei. Through this interaction with cloud formation, the massive production of atmospheric DMS over the oceans may have a significant impact on the Earth’s climate.”
Of course, pollution can affect oceanic DMS production. There have also been informed speculations that naturally produced DMS can participate in either negative or positive feedback loops, in the face of a changing world climate. In light of the oceanic biochemistry, which is more abundant: anthropogenic atmospheric sulfur compounds or the naturally-produced ones from microorganisms (and volcanoes)? Hell if I know.
Larry,
The IPCC has a good overview of the emissions (natural and human) at:
http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/167.htm
For natural, the margins are very wide, as can be expected, because measurements are sparse and emissions are rapidely changing with temperature, sunlight,…
DMS is about 25 GtS/year (counted as sulfur)
Anthro is about 80 GtS/year