Pollution controls have contributed to a more transparent atmosphere, thus allowing for “…a staggering increase in surface solar radiation of the order of ∼20% over the last decade.”
A new paper (O’Dowd et al.) from the National University of Ireland presented this summer at the 19th International Conference on Nucleation and Atmospheric Aerosols suggests that clean air laws put in place in the 1970’s and 80’s have resulted in an increase in sunlight impacting the surface of the Earth, and thus have increased surface temperatures as a result. In one fell swoop, this can explain why surface temperature dipped in the 1970’s, prompting fears of an ice age, followed by concerns of global warming as the air got cleaner after pollution laws and controls were put in place.
WUWT covered a similar effort (Wild 2009) here and paper here (PDF 1.4 mb) which showed the issue but fell short of showing a provable causation for temperature.
Now with this new effort by O’Dowd et al., it seems quite likely that cleaner air is in fact allowing in more solar radiation to the surface, and thus increasing surface temperatures by that increase of insolation.
Wild 2012, was a follow up, and figure 1 above is from that paper.
Martin Wild, 2012, Institute for Atmospheric and Climate Science, Zurich, Switzerland. Published in BAMS: Enlightening Global Dimming and Brightening
http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-11-00074.1 (open PDF)
Now with O’Dowd et al. and their findings, this “global brightening” as a climate driver is looking much more plausible.
The authors write in the new O’Dowd paper:
This study has demonstrated for the first time, using in-situ PM measurements, that reducing aerosol pollution is driving the Insolation Brightening phenomenon and that the trends in aerosol pollution, particularly for sulphate aerosol, is directly linked to anthropogenic emissions. Ultimately, the analysis demonstrates that clean air policies in developed regions such as Europe are driving brightening of the atmosphere and increasing the amount of global radiation reaching the Earth’s surface. The actual impact of cleaner air and insolation brightening on temperature remains to be elucidated.
And offer this graph:
This is inline with Hatzianastassiou et al., 2012, Features and causes of recent surface solar radiation dimming and brightening patterns:
Surface incident solar radiation has been widely observed since the late 1950s. Such observations have suggested a widespread decrease between the 1950s and 1980s (“global dimming”) and a reverse brightening afterward.
http://adsabs.harvard.edu/abs/2012EGUGA..1413344H
The new O’Dowd paper:
Cleaner air: Brightening the pollution perspective?
AIP Conf. Proc. 1527, pp. 579-582; doi:http://dx.doi.org/10.1063/1.4803337 (4 pages)
Abstract:
Clean-air policies in developing countries have resulted in reduced levels of anthropogenic atmospheric aerosol pollution. Reductions in aerosol pollution is thought to result in a reduction in haze and cloud layers, leading to an increase in the amount of solar radiation reaching the surface, and ultimately, an increase in surface temperatures. There have been many studies illustrating coherent relationships between surface solar radiation and temperature however, a direct link between aerosol emissions, concentrations, and surface radiation has not been demonstrated to date. Here, we illustrate a coherence between the trends of reducing anthropogenic aerosol emissions and concentrations, at the interface between the North-East Atlantic and western-Europe, leading to a staggering increase in surface solar radiation of the order of ∼20% over the last decade.
h/t to Sunshine Hours
It seems like a possible case of Occam’s Razor in action – the simplest explanation is the most likely.
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1) Does anyone believe that China’s air got cleaner between 1980 and 2000? I don’t.
2) If ∼20% increasing surface radiance over the last decade is ballpark correct globally and if increasing surface radiance is an important driver of temps, how is it that global temps have stagnated in the last decade?
3) Won’t these materials also absorb IR? IOW, isn’t it possible that increasing tropospheric concentrations might trap heat making temps higher?
Let’s keep the Sun out of this eh.
smoky vs clean air is a factor, but not the whole story.
Why the ” shocker ” superlative ? It’s old news.
michael hammer says:
August 19, 2013 at 4:00 pm
NO!
Well, not to be dramatic or anything, but NO!
Your point is close, but I think misses few things, most important that first-and-most-important “average” watts/sq mtr. Break that whole problem up by latitude 10 degree latitude bands and then try again. See where that logic leads to.
See, the “Clear Air Act”ONLY affected the USA from a narrow band of 40 north to 48 north. The south (say between the absolute furthest south point of Key West at 24.5 latitude up to 40 north latitude) had very little industry, and most of its “air pollution” if it could be counted at all was dust and dirt and tree pollen and emissions (Ozone is still high even today from the billions of pine trees …) LA was dirty, but that was one valley in one state. Where was the rest of this “pollution” that everybody claims?
Overseas? Europe was also in the high 40-50 latitude. Sahara (etc) are down low in the northern hemisphere. Nothing below the Equator to speak of that would be “turned off” to “stop” pollution.
Yet each of these latitude bands can be shown to absorb energy and reflect solar energy. Their emitted energy to space will depend on that emitted energy per latitude band three ways:
A. More is absorbed on the surface the closer you get to the Equator as a function of the cosine of latitude: At low equatorial latitudes, MUCH, MUCH more gets through the shallow air masses between the earth and the sun than reached the surface at higher latitudes.
B. .
C. ALL that solar energy that was absorbed at ANY latitude will be readily emitted back into space directly away from earth with a air mass of 1.0 by definition: The earth and sea will radiated “straight” into space, but will always be able to absorb less and less energy as you go away from the Equator to the pole.
D. In addition to the ever higher and higher attenuation of the solar energy through the atmosphere as it is absorbed trying to reach earth surface, less and less hits the earth’s surface per sq meter as you get closer to the poles because the earth’s surface slopes away from teh sun’s rays .
SO, for example, a 1.5 degree increase in the equatorial belts will matter far more than the
1850 to 1950 warming, blame man. 1910 to 1940 warming, blame man. Recent warming, blame Michael Mann and his Hockey Stick Trickery.
Quick, Mr. Obama, tweet it.
So, now we have 2 candidates for inadvertent anthropogenic effects? Fix the smog, warm the earth. Fix the ozone hole, warm the earth. Count me out of any theory attributing global variation to anthropogenic climate change of any stripe. To quote Rumsfeld, “we don’t know what we don’t know.” Enough already. We need to figure out the natural cycle first, and put the loons in the box with the cat.
(I didn’t have a chance to read the paper yet, nor all the comments.)
Can this technique illustrate differences between Northern and Southern hemisphere measurement trends and or model outputs? Would that be a further proof of the technique?
Zeke Hausfather says:
August 19, 2013 at 3:43 pm
[…]
Also, its worth pointing out that GCMs have long failed to match reality
—————————————————————————————————-
fixed that for you 😉
The world has warmed by 0.8C since ~1850 / 1880. Most of the rise between that time and 1950 was mostly natural. What is the present problem? At most 0.4C? How much of that was caused by man?
As 1st world Clean Air Laws were becoming effective, 3rd world air pollution skyrocketed. Mace Head is hardly representative of the global atmosphere.
I would disagree with one point. The air didn’t get cleaner because of laws, but because technology and wealth enabled us not to pollute.
China would love to clear the air over their cities. But this won’t happen until they reach a certain stage of development, and no law will change that.
I’m not being pedantic here. The fallacy that regulations improve our lives – rather than technological progress – is a belief driving many of the policies in the west today.
Regressive policies.
We know the effect of vulcanos..1000 coalplants in China would have the same effect wouldent it ? Sounds reasonable…
Ie, we pay taxes for a situation that’s created by taxes …
… for what purpose …?
Disgusting …!
Nope, nothing more than a small factor.
Do any of you remember Bob Tisdale’s analysis? If it were aerosols we wouldn’t see the stepwise warming. It’s no more likely that aerosols created this warming than GHGs. For aerosols to have a cooling effect they need to get into the stratosphere. Man-made pollution just doesn’t get that high in any quantity. When lower in the Troposphere they have both a warming and cooling effect. Yes, they block sunlight but they also act like GHGs. The net result is they don’t have much effect at all.
Also, why did the recent warming stop right when the ENSO/PDO went into its cool mode? Why has the temperature trend matched the Pacific ENSO variability for almost 100 years? As Zeke noted, why don’t local patterns show more cooling where aerosols are the highest?
I’m afraid this is just another example of climate science failing to look at the bigger picture.
@Schrodinger’s Cat :
” I realise that many people are not old enough to have experienced smog.”
Major problem …
@Latitude says:
” … but doesn’t fit this one at all
http://tamino.files.wordpress.com/2010/08/emission.jpg”
Why not?
NH – lots of smog
SH – not so much. South America? South Africa? Australia/New Zealand? Pitcairn Island?
Since there is about 10% annual interchange across the ITCZ, and much of the muck has a short residence time in the atmosphere, there should be a significant difference.
Occam’s razor might suggest simply natural variability combined with
a 60 year climate cycle. Hurricanes also have a 30 year cycle, don’t they?
Occam’s razor would say that you take the difference in slope (or the difference in
the magnitude of the change) between the warming from 1910 to 1940 and the warming
between ~1980 and 2005 and assign that to CO2 (possibly combined with other human effects
on climate such as soot and albedo changes).
If this hypothesis is proven correct, this looks like the “law of unintended consequences ” in full effect.
Hmmm …. what’s a good environmentalist to do ????
This is an example of why” The science is settled” claims of Big Al and other Mann made global warming promoters are such utter garbage. Ignoring the affects of the sun ,oceans and even improvements to air quality (with note worthy exceptions vary apparent) it is contrary to basic principles of science that a trace gas (CO2) drives temperature as these promoters say.
Yes humans have an affect and the long term trend has been warming fortunately. Can you imagine if the world had actually bought their BS and the cooling over the last 16 years was attributed to reduced CO2 ? Instead CO2 is up and temperature is flat. We need to use less and what we do use more wisely… no doubt..but this scam is over.
Mike Jonas says:
August 19, 2013 at 1:42 pm
Count me out. This smells just like the claims that the ~1940-70 cooling was caused by (man-made, unmeasured) aerosols. This hypothesis only runs marginally OK from ~1940 onwards. It has no explanation for the ~1910-40 warming, or for the cooling before that. To me, it’s a non-starter.
The 1910 -1940 warming was caused by electricity (and to a lesser extent gas) replacing wood and coal fires for cooking.
In the USA and UK most new homes had electricity after 1910.
Owen in GA says:
August 19, 2013 at 2:36 pm
This is fine to a point, but what would explain the decline between ~1878-~1910?
In the UK between 1830 and 1900 coal production increased from 30 to 230 million tons. Air pollution would have increased in line with production, as consumption of coal in power stations, which pollute far less, was still fairly limited in 1900.
Pamela Gray, Stephen Wilde, and Ed (and others with like arguments) win the day, here.
The latest attempt to blame humans for “climate disruption” has provided NO EVIDENCE that the alleged human emissions’ effect is not obliterated-to-the-point-of-insignificance by nature’s emissions.
Humans cannot warm,
cool,
change,
disrupt,
or even significantly affect
GLOBAL climate.
Until this is PROVEN, no economy-devastating policies should be formed based on such conjecture.
Richard M says:
August 19, 2013 at 4:38 pm
Nope, nothing more than a small factor.
Do any of you remember Bob Tisdale’s analysis? If it were aerosols we wouldn’t see the stepwise warming. It’s no more likely that aerosols created this warming than GHGs. For aerosols to have a cooling effect they need to get into the stratosphere. Man-made pollution just doesn’t get that high in any quantity. When lower in the Troposphere they have both a warming and cooling effect. Yes, they block sunlight but they also act like GHGs. The net result is they don’t have much effect at all.
Did Bob Tisdale’s analysis separate the aerosols distributed primarily below the boundary layer from those above it, or did he analyze the troposphere as a whole?
Hmmm….not convinced. It’s an interesting hypotheses but now you need to find a way to test it. Just making a series of statements that sound reasonable is not enough. The other side has abandoned the scientific method. We can’t do the same.
Fascinating. This is a reverse Fallen Angels scenario, where government action against global warming makes it worse..
Fallen Angels was a Larry Niven – Jerry Pournelle – Michael Flynn SciFi novel written in 1991 that had the greens and religious Luddites take over the US government and pass a series of anti-technology laws to curb global warming. Unfortunately the clean up worked too well, ushering in the next ice age, complete with glaciers marching out of Canada. Fun book if you like Niven & Pournelle. Cheers –
http://en.wikipedia.org/wiki/Fallen_Angels_%28science_fiction_novel%29