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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A similar paper using Netherlands data:
——
“Besides leading to a better visibility (a direct
aerosol effect), a decrease in aerosol concentration
might also lead to a reduction in
cloudiness (indirect aerosol effect). The sunshine
duration measurements1, which are
considered to be more accurate than cloud
cover estimates, can be used as a good
proxy of (daytime) cloudiness. The trends of
yearly average daily sunshine duration
(Figure 4), presented as a percentage of the
day length, in both De Bilt and Schiphol
show a similar pattern to the trends in high
visibility days, and are consistent with what
is expected from both the aerosol direct and
indirect effect. Since the early 1980s, the
sunshine frequency has increased by as
much as 25%.
This trend is, however, occurring almost
exclusively in summer: between 1985 and 2010,
the average value of the surface
global short-wave radiation in De Bilt in
summer has increased by more than
15Wm−2 (i.e. 0.6Wm−2yr−1). The average level
of the surface global short-wave radiation
in summer for this period is 194.7Wm−2,
compared with 188.7Wm−2 for the dimming
period between 1958 and 1983. The increase
during the brightening period is strongest
in the morning, between 0700 and 1000 UTC,
at more than 1.5Wm−2yr−1.”
http://sunshinehours.wordpress.com/2012/05/15/more-sunshine-in-the-netherlands/
So, in other words, the EPA is responsible for global warming. People are stupid.
Lance Wallace says:
August 19, 2013 at 1:41 pm
“One wonders whether the increase in sulfur dioxide that will occur in Germany and China and India due to coal will be sufficient to roll back the general decrease that occurred in the 43 years since EPA was created. Perhaps not if good scrubbing techniques are employed.”
Since about 1995 all German power plants burning brown coal have been fitted with flue gas scrubbers; with federal tax incentives; China still builds new coal power plants without. In the 90ies there was still the Waldsterben / Acid Rain hysteria raging in Germany so desulfurization was a top political theme.
So the warming actually is manmade? Or rather man-cleaning-after-himself-made? That would be too much fun.
Cleaner air however also causes cleaner and more persistent snow in the winter (and in polar regions).
M Courtney says:
August 19, 2013 at 2:05 pm
“They fail to report lots of things.
The number of unreal things the BBC fails to report is not greater than the number of real things.”
But they never fail to lie about the things they report. (They are an EU medium and bound by EU law.)
Mikeyj says:
August 19, 2013 at 1:31 pm
Base on this theory Washington D.C. should be friggin freezing with all the crap being thrown into the air there.
>>>>>>>>>>>>>>>>
Well DC is certainly a bit on the cool side at 73.8 °F Normal is 86 °F and the MAX was 98 °F in 2002.
Mid North Carolina is even cooler at 72F (Summer what summer?)
Also wondering, as many stations are in or near cities\ airports, how this will affect UHI for weather stations.
Schrodinger’s Cat says onAugust 19, 2013 at 1:24 pm :
“Joe makes a good point. In the seventies, climate scientists (including some of the same culprits), were warning of an imminent ice age. Then it started warming. It does fit.”
Do you suppose 17 year temperature plateau can be credited to China’s increasingly dirty air?
thought for over 20 years now that this is the case .. that IF man has caused observable changes in the earth’s temperature .. it is these changes in aerosols .. also note we reduced black soot in North America and Europe .. yet China .. mostly .. and Russia have increased coal burning and black soot emissions since the 1990s .. and at a much faster rate since 2000 .. black soot may explain Northern Hemisphere ice melt trends better than temperature changes .. per Hansen, J., and L. Nazarenko (2004) Soot climate forcing via snow and ice albedos .. “The calculated global warming from soot in snow and ice, by itself in an 1880-2000 simulation, accounted for 25 percent of observed global warming” .. not that I totally buy the “25%” figure .. but that in itself is a larger effect that Gavin’s claimed 20% CO2 effect within the greenhouse gas category of effects on global temperature .. and changes in greenhouse gasses .. in my informed opinion .. do not have nearly the effect land use changes have had ..
Lance Wallace….
A friend in Alaska several years ago was complaining about the smog rolling in from China that was mucking up Alaska’s pristine clean air.
Peter Miller says:
August 19, 2013 at 1:23 pm
Seems to make a lot of sense, so the Global Warming Industry will do their very best to ensure this theory is stillborn.
C’mon trolls, do your best..
====================================
…….. unless they can figure a way to tax it …….. then they will be solidly behind it.
I think its interesting. We should not categorically rule out anything until its proven to be false. Especially in climate science, something we truly know little about.
20% Would indeed be staggering. Like MattN, I’m not staggered yet.
I realise that many people are not old enough to have experienced smog. This is an attempt to explain what the smogs were like. Visibility would drop to a few feet and the best way I can think of it is very dirty fog.
Fog is normally a dispersion of water droplets in air and smoke is a dispersion of particulate solids in air. Smog is a combination of both, so it has a much lower transmission to light and so the sky appears much darker and the air more opaque.
The smogs in Glasgow and London and other major cities were pretty real and very spectacular. I expect US industrialised cities were even worse. Many people had serious breathing problems and lung conditions. Traffic would grind to a halt. Ships would be unable to navigate in rivers, ports or close to the coast. The pollution was not evident all of the time, but from time to time particular weather conditions would make the smog descend like an opaque curtain, reducing visibility to a few feet. Areas prone to mist, such as near rivers, would get badly affected.
Basically, the solid pollutants in the atmosphere would nucleate on dispersed water droplets and the result would be very dirty fog. Smokeless zones were introduced in the sixties and in time, this solved the problem.
it fits this one…..mostly
http://www.skepticalscience.com/pics/1_so2emissionssmallpic-Smith2011.jpg
but doesn’t fit this one at all
http://tamino.files.wordpress.com/2010/08/emission.jpg
Been saying this for years. Like this in 2011 … “Like most UK sceptics I’ve written my fair share of complaints regarding BBC bias. But one person really does take the biscuit for their response. Richard Black wrote an article about Chinese pollution causing warming … he must also we aware that the wholesale cleaning of the air due to clean air acts in the the 1970s must have led to much larger warming.” Scottish Sceptic
Logical enough but only as a modulating factor superimposed on natural variability.
Given the scale of the changes from MWP to LIA to date I don’t see the aerosol proposition as being significant.
It does, however seek to maintain the ‘our fault’ meme by replacing the CO2 scare with something else that was human generated.
Anyhow the improvements in developed nations would have been largely offset by deterioration in developing nations would they not?
And then again how to explain the global cloudiness changes between regimes of zonal jets and meridional jets which seem to correlate with changes in solar activity.
Gail correctly points out that natural variations in atmospheric opacity from wind borne sea spray and dust would be a far larger effect than our puny efforts.
DirkH says:
August 19, 2013 at 2:04 pm
………….
And all the youngsters now studying climate science to become do nothing rent seekers will have to find a way to earn their bread.
====================================
The phrase, “Would you like some fries with that ?”, pops into my mind for most of these jokers.
TomR,Worc,MA says:
August 19, 2013 at 2:21 pm
…….. unless they can figure a way to tax it …….. then they will be solidly behind it.
————————————————————————————————
“Well done all you voters, between us we’ve really cleaned up the air throughout the Western World. Give yourselves a pat on the back and a tax increase”
Honestly, if the electorate let them get away with that one without glorious Revolution then they deserve to freeze in winter!
So, would one expect LH going from -3 to +3 to increase the relative humidity? Perhaps not. Considering there would also be isobaric heating which increases the saturation pressure thereby reducing the relative humidity. Hmmm. I’ll have to mull this over a bit more.
What is certain is that air pollution was pretty significant back to the 19thC. This may have slowed down the LIA rebound, but does not explain the 1930-1950 warming.
REPLY: Remember the Great Depression of the 1930’s? Less GDP output, less energy used, less coal, etc. Wouldn’t it be wild if 1934, the hottest year in USA, was result of 1929 stock market crash and subsequent downsized GDP in the years following? – Anthony
Sorry. Pamela not Gail.
This is fine to a point, but what would explain the decline between ~1878-~1910? Did we have a sudden increase in world-wide smog events during that period as well? It doesn’t seem to really explain things very well. Simplicity says it is likely a small warming recovery from the little ice age with ocean oscillation cycles thrown in on top of it. (What causes the ocean cycles or the periodic ice-age/recovery cycles for that matter – I haven’t seen a completely satisfying explanation of “why”, just the “what”)
Schrodinger’s Cat – I remember it well from LA and Denver, as the Smog got better it turned into haze if my memory serves.
Sunshinehours
That Netherlands data ties up with what l noticed about three years ago here in the UK.
That here in the UK since 1930, there has been a much stronger link to changes in the annal mean temps and changes to the annal sunshine hours. Then they has been to changes in CO2 levels. As the amounts of sunshine hours go up so the the temps seem to follow.