From the abstract of the lead paper by Martin Wild: Recent evidence suggests that solar radiation reaching the Earth’s surface has not been constant over time but has undergone substantial variations on decadal timescales. The available observations suggest a widespread decrease in surface solar radiation between the 1950s and 1980s (popularly referred to as “global dimming”), with some more recent evidence for a partial recovery (“brightening”).
From ETH Zurich News
“Global dimming and brightening” – The role of solar radiation in climate change
A special volume of the “Journal of Geophysical Research” reviews the growing research field of “global dimming” and “global brightening” in over 20 articles. These phenomena, supposedly human-induced, control solar radiation incident at the Earth’s surface and thus influence climate.
Special instruments have been recording the solar radiation that reaches the Earth’s surface since 1923. However, it wasn’t until the International Geophysical Year in 1957/58 that a global measurement network began to take shape. The data thus obtained reveal that the energy provided by the sun at the Earth’s surface has undergone considerable variations over the past decades, with associated impacts on climate.
Research focus at ETH Zurich
Investigating which factors reduce or intensify solar radiation and thus cause “global dimming” or “global brightening” is still very much a nascent field of research in which especially scientists from ETH Zurich became renowned. The American Geophysical Union (AGU) has now published a special volume on the subject which presents the current state of knowledge in detail and makes a considerable contribution to climate science. “Only now, especially with the help of this volume, is research in this field really taking off”, stresses Martin Wild, senior scientist at the Institute for Atmospheric and Climate Science of ETH Zurich, who is a specialist on the subject.
Decrease in solar radiation discovered
The initial findings, which revealed that solar radiation at the Earth’s surface is not constant over time but rather varies considerably over decades, were published in the late 1980s and early 1990s for specific regions of the Earth. Atsumu Ohmura, emeritus professor at ETH Zurich, for example, discovered at the time that the amount of solar radiation over Europe decreased considerably between the 1950s and the 1980s. It wasn’t until 1998 that the first global study was conducted for larger areas, like the continents Africa, Asia, North America and Europe for instance. The results showed that on average the surface solar radiation decreased by two percent per decade between the 1950s and 1990.
In analyzing more recently compiled data, however, Wild and his team discovered that solar radiation has gradually been increasing again since 1985. In a paper published in “Science” in 2005, they coined the phrase “global brightening” to describe this new trend and to oppose to the term “global dimming” used since 2001 for the previously established decrease in solar radiation.
Only recently, an article in the journal “Nature”, which Wild was also involved in, brought additional attention to the topic of global dimming/brightening.
Air pollution favors photosynthesis
In this study, for the first time, the scientists examined the connection between global dimming/brightening and the carbon cycle. They demonstrated that more scattered light is present during periods of global dimming due to the increased aerosol- and cloud-amounts, enabling plants to absorb CO2 more efficiently than when the air is cleaner and thus clearer. According to the scientists, this is because scattered light penetrates deeper into the vegetation canopy than direct sunlight, which means the plants can use the light more effectively for photosynthesis. Consequently, there was around 10 percent more carbon stored in the terrestrial biosphere between 1960 and 1999.
The special volume, which appears in the AGU’s renowned “Journal of Geophysical Research”, provides an overview of the current state of knowledge. Almost half of the publications in the volume were either completely or partially written by ETH Zurich scientists. Wild is the guest editor, and author or co-author of ten of these articles.
The articles provide the first indication of the magnitude of these effects, how they vary in terms of time and space and what the possible consequences might be for climate change. They also discuss in detail the underlying causes and mechanisms, which are still under debate.
Many questions left open
It is particularly unclear as to whether it is the clouds or the aerosols that trigger global dimming/brightening, or even interactions between clouds and aerosols, as aerosols can influence the “brightness” and lifetime of the clouds. The investigation of these relations is complicated by the fact that insufficient – if any – observational data are available on how clouds and aerosol loadings have been changing over the past decades. The recently launched satellite measurement programs should help to close this gap for the future from space, however.
“There is still an enormous amount of research to be done as many questions are still open”, explains Wild. This includes the magnitude of the dimming and brightening effects on a global level and how greatly the effects differ between urban and rural areas, where fewer aerosols are released into the atmosphere. Another unresolved question is what happens over the oceans, as barely any measurement data are available from these areas.
A further challenge for the researchers is to incorporate the effects of global dimming/brightening more effectively in climate models, to understand their impact on climate change better. After all, studies indicate that global dimming masked the actual temperature rise – and therefore climate change – until well into the 1980s. Moreover, the studies published also show that the models used in the Intergovernmental Panel on Climate Change’s (IPCC) fourth Assessment Report do not reproduce global dimming/brightening adequately: neither the dimming nor the subsequent brightening is simulated realistically by the models. According to the scientists, this is probably due to the fact that the processes causing global dimming/brightening were not taken into account adequately and that the historical anthropogenic emissions used as model input are afflicted with considerable uncertainties.
“This is why at ETH Zurich we are working with a research version of a global climate model, which contains much more detailed aerosol and cloud microphysics and can reproduce global dimming/brightening more effectively”, says Wild. For him, the studies so far constitute “initial” estimates that need to be followed up with further research.
Link to these papers in JGR here
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
“Another unresolved question is what happens over the oceans, as barely any measurement data are available from these areas.”
So, 70% of the data is missing and yet …
Another publish or perish bit of incomplete science. I wouldn’t believe any conclusions from this paper.
Stephen Wilde (02:29:44) :
Normal everyday people report a ‘lemony-white’ Sun. Certain species of trees are badly wilted this year, even though plenty of water and cooler temps. There is a marked change in what species flourish in the shade vs direct sunlight.
Richard111 (03:53:44) :
“”The results showed that on average the surface solar radiation decreased by two percent per decade between the 1950s and 1990.””
But the IPCC say solar variation was only 0.1% !! Somebody is wrong
You are probably confusing solar radiation (output from the sun) and insolation (received by the earth). I’m guessing the “surface solar radiation” refers to insolation. Even if the sun’s output remains constant, the amount of sunlight received by the earth can still vary.
Albedo is either the thimble or the mattresses under which the pea of anthropogenic climate change will be hidden.
=========================================
Richard111 (03:53:44) :
“”The results showed that on average the surface solar radiation decreased by two percent per decade between the 1950s and 1990.””
But the IPCC say solar variation was only 0.1% !! Somebody is wrong
It´s too big a business that of carbon credits/carbon shares:
Carbon Credit offered to SA natives per 01 hectare of amazon forest/year: 1.30 Euros
Price carbon share per ton of CO2:15.50 Euros
Tons of CO2 capture per hectare:5500
Carbon share per hectare, to be paid by the 1st. world polluter/buyer:5500 x 15.50=85250 Euros.
Gross Profit=85250-1.3=85248.7 Euros. per forest hectare/year
That´s why we see that O.1% so often..
Anthony, you may have had something to do with this new impetus:
“and how greatly the effects differ between urban and rural areas, where fewer aerosols are released into the atmosphere”
This likely how they will explain that the UHI doesn’t increase average temperatures and the data is therefore indicative of real global temperatures. Of course, they will also have to explain how we will all be frying in the cities under 10-15 deg higher temps.
pyromancer76 (06:42:47):
Final question: Is the AGU a “real” scientific organization, or do they practice pseudo-science, too? I guess this must be another grumpy morning.
Judge yourself:
http://www.agu.org/about/leadership/committees_boards/
Whenever I see a photo of a tall chimney belching smoke such as the one that appears at the top of the article, I wonder how deep into the archives they had to go to find one like that. Or is it maybe current emissions from a stack somewhere in Europe where there is so much concern about AGW that, after they pay the carbon cap and tax fees, there aren’t enough funds left to fix the dirty emissions?
Bob
Reflected shortwave can bounce back to Earth, like a pingpong game played on a table in the kitchen. Clear sky reflection means that any warming/photosynthesis advantage gained by keeping more shortwave radiation, is lost. It also means that the warming affects of longwave radiation is lost as well. Meacham, Oregon regularly breaks temperature records of all sorts and is generally the coldest place in Oregon year round. It sits in a clearsky pocket at the summit of the Blue Mountains. Dry clear air, and witch tit cold. If CO2 ever becomes labeled a pollutant and some agency is in charge of pawning off captured CO2 waste, Meacham would be first in line to gladly accept the nasty stuff.
I think Christopher Booker will make mince-meat of the Mann letter in next week’s Sunday Telegraph. I’m sure Christopher will produce numerous lines of evidence to show that the significant climate changes taking place are very likely due to natural phenomena.
Denis Hopkins (01:31:39) :
Mann writes that;
‘However, the focus on the “Hockey Stick” is a distraction.’
I thought the whole point was that the ‘”Hockey Stick” proved global warming?
Now its a mere “distraction”
End game approaching.
The new strategy from AGWers camp is to qualify anything which is opposed to their idea like pseudoscience, even when the knowledge is founded in clean science. This is called solipsism. Solipsism, as someone pointed here, is a very damaging philosophy against science which brings to disbelief every bit of the scientific knowledge accrued until the present time.
I have experienced in my flesh this kind of attacks when my argument, based on clean science, show that something from the AGW idea is wrong. I have endeavored to prove my arguments with scientific literature, and anyway, the AGWers argue that what I am managing is pseudoscience.
I have shown references like books, articles and essays written by serious scientists; however, these references have been marked like pseudoscience by AGWers. An example on this ridiculous tactic from AGWers is when someone assured that a particle that is doing work does not emit radiative energy. Another person’s argumentum was that my definition of thermodynamic system was pseudoscience, yet when I had taken the description from books on thermodynamics written by well known authors like Van Ness, Engels, Modest, Glasser, etc.
We have to be extremely careful with this innovation in the tactics of AGWers because most people don’t enjoy corroborating references written on paper and prefer to resort to links provided by those AGWers to antiscientific solipsist online articles that, ordinarily, were written by AGWers who doesn’t know the basics of physics and are creating a bogus science which fits with their beliefs.
🙂
BTW Danny storm´s track still lingering after several days, so not getting enough heating from the sun:
http://www.osdpd.noaa.gov/data/sst/anomaly/2009/anomw.8.27.2009.gif
CO2 it is not a pollutant:
Is the Ongoing Rise in the Air’s CO2 Content Enhancing the Health-Promoting Properties of the Food We Eat
http://www.co2science.org/articles/V6/N34/EDIT.php
Perhaps this is why Mathusalem and other bible guys lived longer!!
Michael Mann, in his letter to the Sunday Telegraph, does not mention that the US Congress House Committee on Energy and Commerce (Wegman Report) made many negative comments and concluded that the Mann et al paper showed, ‘a lack of robustness and statistical flaws’. Among its findings was that, ‘it misused statistical methods which inappropriately produced hockey stick shapes in the temperature history’. The committee also said, “Dr Mann’s assessments that the decade of the 1990’s was the hottest decade of the millennium and that 1998 was the hottest year of the millennium cannot be supported by his analysis…” I also think I am right in saying that the NAS supported the Wegman Report.
His comments in the Telegraph sheds no light on anything of substance.
I’m a bit puzzled by the temperature sensitivity coefficient of 0.05C-m^2/W, mentioned in Ohmura’s abstract, versus 0.19 which one would determine from Stefan law, to estimates over 0.5 which the IPCC uses. Units are the same in all cases, and I suppose the various estimates are valid over different time spans. However, the factor of twenty seems quite surprising to me.
Anyone offer any explanation or commentary?
“His comments in the Telegraph sheds no light on anything of substance.”
No surprise there then.
It’s probably right to say that the dispute over exactly which was the warmest year of the last century is a bit of a sideshow. I’m open to correction but is it not the case that 1998 was not the warmest year in the US but might well have been globally?
Though I still cannot understand how they could tell! Or even whether it matters all that much (except, I suppose, that truth is always important.)
paul maynard (05:19:35) : Re Mann Letter
Does anybody know where to find the NAS paper?
I collected the cutting-edge of the evidence – the story timeline, what the NAS North report said, what it was reported as saying, and what Wegman said – here. I was determined to get to the bottom of all those conflicting statements and leave a manageable checkpoint for others to check out.
Alexander Feht (01:26:32) : I have an ability to see a little more into the UV part of the spectrum than most people… and I routinely noticed that the sunlight in the end of 1990s was much harsher, and much more suffused with the UV radiation than the sunlight of my childhood years (1960s)… But who would pay attention to the observations of an obscure Russian poet? “Experts” know it all, don’t they.
Nogw (08:19:50) : Thanks [Alexander Feht] for saying that. I just felt it like a more “aggresive” sunlight; in the 90’s going to the beach was really a burning experience, quite different than in the 50´s or 60´s, now it has turned to be “normal”.
Stephen Wilde (02:29:44) : I have noticed the changes in quality of light referred to but have always regarded it as a trick of my own perceptions. Currently, in August, I am certainly aware of less power to the light than for many years past and oddly the leaves on plants and trees are deteriorating early this year. I’m not yet prepared to draw a scientific conclusion from it though.
rbateman (08:24:48) : [in reply to Stephen Wilde] Normal everyday people report a ‘lemony-white’ Sun. Certain species of trees are badly wilted this year, even though plenty of water and cooler temps.
Glad to hear these reports. I reported similar here a little while back, when I noticed the current Sun a weeny bit livelier around the time it had a few sunspots, and remembered my own perceptions from the nineties. Nobody had said anything like this, and I reckoned that many here would regard such observations as highly suspect, but I wanted to put it out anyway for the record, in case others could bear me out. It’s good to see others reporting similar perceptions.
Oh, rats, I meant factor of ten not twenty.
At any rate, from the abstract for the paper of Long, et al,…
We show that widespread brightening has occurred over the continental United States as represented by these measurements over the 12 years of the study, averaging about 8 W m−2/decade for the all‐sky shortwave and 5 W m−2/decade for the clear‐sky shortwave. This all‐sky increase is substantially greater than the 2 W m−2/decade previously reported over much more of the globe as represented by data from the Global Energy Balance Archive spanning 1986–2000 and is more than twice the magnitude of the corresponding 1986–2000 2–3 W m−2/decade increase in downwelling longwave. Our results show that changes in dry aerosols and/or direct aerosol effects alone cannot explain the observed changes in surface shortwave (SW) radiation, but it is likely that changes in cloudiness play a significant role. These SW increases are accompanied by decreasing tendencies in cloudiness, and an increasing tendency in the clear‐sky SW diffuse/direct ratio that is often associated with atmospheric turbidity.
So, variations from 1960 to the present for SW and LW are bound by +12 and -4 W/m^2; and, then comparing this to variations in temperature over the same period leads one to the conclusion that the sensitivity coefficient really is around 0.05 C-m^2/W. If provedtrue, this would make fears of runaway warming from CO2 a bit hard to gin up, yes?
Lucy Skywalker (11:56:35) “Glad to hear these reports. […]”
When sea-kayaking at a dusk (regularly) I’ve noticed a switch from deep colors to pastels and an increase in ‘streaky’ & ‘fragmented’ high-altitude features of various forms.
About early leaf deterioration I have noticed a tiny trickle of leaves starting to fall off the trees, some trees are already seeing a decent number fall off.
Also when you look at the conditions of the bands on the right side of this site this is the first time they all said ‘poor’ at once indicating the sun’s output may still be decreasing.
This could have implications for Earth’s climate indeed, Intellicast seems to be predicting an early onset of fall-like weather here in Wichita when looking at the current forecast, the sea ice really looks like it could stay above the 2008 minimum, Intellicast showing below freezing temperatures set to return to pars of Siberia (who knows how cold it’ll get there this Winter especially if the sharp drop in temps. seen in the arctic according to one of the site links starts a trend) ect…
Lucy Skywalker (11:56:35) :Those reports are real, they worth much more credibility than adjusted satellites or next to barbacues surface stations (which are “corrected” again afterwards to avoid contradicting their “masters”).
This is why “new progressive science” says the sun has nothing to do with climate or it rains from ground to sky, and so on…
It is likely some combination of longer term solar cycles and volcanic aerosol clustering leads to periods of brightening and dimming. The 1960s after Agung had measured solar radiation declines as much as 7%.
See the following paper.
http://www.newscientist.com/article/dn13376-lunar-eclipse-may-shed-light-on-climate-change.html
and this image with data during lunar eclipses
http://icecap.us/images/uploads/AOT_LUNAR.jpg
and longer term using VEi and other inputs as compiled by Sato at GISS http://icecap.us/images/uploads/AOT.jpg
See also this story that shows how low aerosols leads to warming just as high aerosols cooling – an intuitive result but not necessarily considered. Average conditions are somewhere in between high and low.
http://icecap.us/docs/change/HOWVOLCANISMAFFECTSCLIMATE.pdf
Pamela Gray (08:11:30) “Just to clarify for those readers who may be confused, global dimming/brightening is an endogenous (Earth) source of variation”
This reads like a suggested “consensus” Pamela. What is the benefit in pretending we know everything about solar-terrestrial relations?
I’ve noticed in recent WUWT threads that a lot of contributors are finally managing to get the social-conformity distortion-wool off their eyes — Bravo to those who do not automatically misinterpret frequent repetition as brain-numbing truth.