Global dimming and brightening: A review
Martin Wild
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
There is increasing evidence that the amount of solar radiation incident at the Earth’s surface is not stable over the years but undergoes significant decadal variations. Here I review the evidence for these changes, their magnitude, their possible causes, their representation in climate models, and their potential implications for climate change. The various studies analyzing long-term records of surface radiation measurements suggest a widespread decrease in surface solar radiation between the 1950s and 1980s (“global dimming”), with a partial recovery more recently at many locations (“brightening”). There are also some indications for an “early brightening” in the first part of the 20th century. These variations are in line with independent long-term observations of sunshine duration, diurnal temperature range, pan evaporation, and, more recently, satellite-derived estimates, which add credibility to the existence of these changes and their larger-scale significance.
Current climate models, in general, tend to simulate these decadal variations to a much lesser degree. The origins of these variations are internal to the Earth’s atmosphere and not externally forced by the Sun. Variations are not only found under cloudy but also under cloud-free atmospheres, indicative of an anthropogenic contribution through changes in aerosol emissions governed by economic developments and air pollution regulations. The relative importance of aerosols, clouds, and aerosol-cloud interactions may differ depending on region and pollution level. Highlighted are further potential implications of dimming and brightening for climate change, which may affect global warming, the components and intensity of the hydrological cycle, the carbon cycle, and the cryosphere among other climate elements.
Received 14 November 2008; accepted 10 March 2009; published 27 June 2009.
Citation: Wild, M. (2009), Global dimming and brightening: A review,
J. Geophys. Res., 114, D00D16, doi:10.1029/2008JD011470.
I found this passage that parallels a lot of what I’ve been saying about data quality:
The assessment of the magnitude of these SSR (surface solar radiation) variations faces a number of challenges. One is related to data quality. Surface radiation networks with well-calibrated instrumentation and quality standards as those defined in BSRN [Ohmura et al., 1998] need to be maintained on a long-term basis and if possible expanded into underrepresented regions (see Figure 1b).
However in this figure, citing CRU surface temperature, he likely doesn’t understand what data quality issue might have contributed to the trend from 1960-2000
One of the effects of urbanization is the compression of the diurnal temperature variation. I recently was able to demonstrate this between two stations in Honolulu. One is in the middle of the Airport and had a sensor problem, the other was in a more “rural” setting about 4 miles away. Note how the ASOS station at the airport has an elevated temperature overall, but that the biggest difference occurs in the overnight lows, even when the ASOS sensor giving new record highs was “fixed”:
Urbanization affects Tmin more than Tmax. For example, here’s the nighttime UHI signature of Reno, NV that I drove as a measurement transect using a temperature datalogger:
Click for larger image
Even several hours after sunset, at 11:15PM, the UHI signature remained. The net result of urbanization is that it increases Tmin more than Tmax, and thus minimizes the diurnal range, which we see in Wild’s diurnal range graph.
Even the IPCC misses it:
Wild probably has no idea of this type of issue in the CRU data, but again it speaks to data quality which he seems to be keen on. He’s looking for a global solar signature in temperature data, something Basil Copeland and I have done, to the tune of much criticism. The signature is there, but small. But, when diurnal temperature variation is looked at, any solar signature is likely swamped by the urbanization signal. I’m not saying there is no solar component to what Wild is looking at, but it seems fairly clear that UHI/urbanization/land use change plays a significant role also.
Even rural stations can be affected by our modern society, as Dr. John Christy demonstrated in California’s central valley:
A two-year study of San Joaquin Valley nights found that summer nighttime low temperatures in six counties of California’s Central Valley climbed about 5.5 degrees Fahrenheit (approximately 3.0 C) between 1910 and 2003. The study’s results will be published in the “Journal of Climate.”
The study area included six California counties: Kings, Tulare, Fresno, Madera, Merced and Mariposa.
While nighttime temperatures have risen, there has been no change in summer nighttime temperatures in the adjacent Sierra Nevada mountains. Summer daytime temperatures in the six county area have actually cooled slightly since 1910. Those discrepancies, says Christy, might best be explained by looking at the effects of widespread irrigation.
Wild’s study is a very interesting and informative paper, I highly recommend reading the entire paper here (PDF 1.4 mb)
h/t and sincere thanks to Leif Svalgaard for bringing this paper to my attention.
“A two-year study of San Joaquin Valley nights found that summer nighttime low temperatures in six counties of California’s Central Valley climbed about 5.5 degrees Fahrenheit (approximately 3.0 C) between 1910 and 2003.”
I believe there will be correlation with the amount of irrigation going on. The Central Valley is probably much more humid in 2003 at dawn that it was in 1910 due to more overnight irrigation. More humidity means less radiation into space and more warming of the lower layers of air.
Sort of like the difference in temperature between Winnamucca and Miami at 5am on a May morning.
Leif Svalgaard (13:21:18) :
Allan M R MacRae (12:54:27) :
“There are actual measurements by Hoyt and others that show NO trends in atmospheric aerosols, but volcanic events are clearly evident.”
But increased atmospheric CO2 is NOT a significant driver of global warming – that much is obvious by now.
Leif: But what has that to do with aerosols?
**************************
Leif, I did say:
The sensitivity of global temperature to increased atmospheric CO2 is so small as to be inconsequential – much less than 1 degree C for a doubling of atmospheric CO2. CO2 feedbacks are negative, not positive. Climate model hindcasting fails unless false aerosol data is used to “cook” the model.
Connecting the dots, to answer your question:
The fabricated aerosol data allows climate model hindcasting to appear credible while assuming a false high sensitivity of global temperature to atmospheric CO2.
The false high sensitivity is then used to forecast catastrophic humanmade global warming (the results of the “cooked” climate models).
What happens if the fabricated (phony) aerosol data is not used?
No phony aerosol data > no credible model hindcasting > no artificially high climate sensitivity to CO2 > no model forecasting of catastrophic humanmade global warming.
Regards, Allan
Supporting P.S.:
Earth is cooling, not warming. Pass it on…
Leif Svalgaard (13:21:18) :
There is no good evidence for that. Solanki’s ‘result’ is partly based on a now [generally accepted] refuted doubling
It is the refutation that is generally accepted by now, even by Lockwood and by me [we were the ones culpable of advocating that notion in the past].
**************************
I can’t argue with you on this point. I am much more conversant on the other eight points in the SPPI document, and generally find them acceptable.
Willie Soon is the Chief Science Advisor of SPPI
http://scienceandpublicpolicy.org/personnel.html
Presume you know Willie since you are in a similar line of work – you may want to take this up with him.
BTW, some time ago I sent you a paper by Jan Veizer (GAC 2005) that in Figure 2 showed an apparently strong correlation between Cosmic Ray Flux and Low Cloud cover, (after Marsh and Svensmark 2003 and Marsh et al 2005). Did you get this paper? Do you accept or reject this correlation?
Regards, Allan
Allan M R MacRae (16:39:22) :
The fabricated aerosol data allows climate model
As I read Wild’s paper, I don’t see any fabricated aerosol data, unless you invoke a global conspiracy going back almost a century. It that the message?
Allan M R MacRae (16:39:22) :
Supporting P.S.:
Earth is cooling, not warming.
Supporting P.P.S.:
Human-made CO2 emissions have increased almost 800% since 1940, but the best data shows no significant net warming since ~1940. This lack of significant warming is evident in UAH Lower Troposphere temperature data from ~1980 to end April 2008, and Hadcrut3 Surface Temperature data from ~1940 to ~1980.
See the first graph at:
http://www.iberica2000.org/Es/Articulo.asp?Id=3774
Climate sensitivity to increased atmospheric CO2 and humanmade CO2 emissions is insignificant.
Figure 2 shows a huge change in annual mean surface solar radiation. It’s about 95 watts/sq meter in the early 20’s to 135 in the early 40’s. If that data is correct it must be highly localized. If that kind of a change occurred over a large portion of the earth it would cause a very large jump in temperature, far more than the .7 C the IPCC claims.
Allan M R MacRae (16:58:30) :
BTW, some time ago I sent you a paper by Jan Veizer (GAC 2005) that in Figure 2 showed an apparently strong correlation between Cosmic Ray Flux and Low Cloud cover, (after Marsh and Svensmark 2003 and Marsh et al 2005). Did you get this paper? Do you accept or reject this correlation?
It doesn’t look too good, and employs a standard technique of persuasion, namely plotting some other quantities as well that are well correlated to ‘guide’ the eye. Svensmark notes that perhaps a better calibration of the spacecraft data would improve the correlation. The recent albedo data of Palle also do not support the correlation, as there is no clear solar signal.
Leif Svalgaard (17:03:08) :
Allan M R MacRae (16:39:22) :
The fabricated aerosol data allows climate model
As I read Wild’s paper, I don’t see any fabricated aerosol data, unless you invoke a global conspiracy going back almost a century. It that the message?
__________________
Leif, thanks for clearing this up with your question.
I am not addressing Wild’s model – I am addressing the 1992 paper in Science by Charlson, Hansen et al, that has been used as a basis for so many climate models that falsely predict catastrophic global warming.
The Charlson et al paper fabricates aerosol data based on industrial activity, when actual measurements were available that refute Charson’s conclusions.
I have no opinion on Wild’s paper. Normally I read a paper several times, check the raw data and calculations, read many related papers, and then form an opinion. As you can appreciate, this takes some time.
Allan M R MacRae (20:03:32) :
I am not addressing Wild’s model
Which is the topic of this thread.
Isn’ t this review a proxy for albedo?
Leif,
do you have an ‘adjusted’ sunspot number series file I can test my cumulative method on? Is the sunspot area series available from NASA still valid in your view?
Leif Svalgaard (13:21:18) :
“There is no good evidence for that. Solanki’s ‘result’ is partly based on a now [generally accepted] refuted doubling of the Sun’s open magnetic flux, and partly on wrongly calibrated group sunspot number.”
You may like to comment on this paper as you are heavily cited.
On the long term change in the geomagnetic activity during the 20th century
F. Ouattara1, C. Amory-Mazaudier2, M. Menvielle3,4, P. Simon*,†, and J.-P. Legrand*
Abstract. The analysis of the aa index series presented in this paper clearly shows that during the last century (1900 to 2000) the number of quiet days (Aa<20 nT) drastically diminished from a mean annual value greater than 270 days per year at the end of the nineteenth century to a mean value of 160 quiet days per year one hundred years later. This decrease is mainly due to the decrease of the number of very quiet days (Aa<13 nT). We show that the so-evidenced decrease in the number of quiet days cannot be accounted for by drift in the aa baseline resulting in a systematic underestimation of aa during the first quarter of the century: a 2–3 nT overestimation in the aa increase during the 20th century would lead to a 20–40% overestimation in the decrease of the number of quiet days during the same period.
The quiet days and very quiet days correspond to periods during which the Earth encounters slow solar wind streams flowing in the heliosheet during the period where the solar magnetic field has a dipolar geometry. Therefore, the observed change in the number of quiet days is the signature of a long term evolution of the solar coronal field topology. It may be interpreted in terms of an increase in the magnitude of the solar dipole, the associated decrease of the heliosheet thickness accounting for the observed decrease in the number of quiet days.
http://www.ann-geophys.net/27/2045/2009/angeo-27-2045-2009.html
anna v (22:37:14) :
Isn’ t this review a proxy for albedo?
Close, but not quite. Albedo is seen from the outside, the solar radiance from the inside of the atmosphere.
tallbloke (22:43:11) :
do you have an ‘adjusted’ sunspot number series file I can test my cumulative method on? Is the sunspot area series available from NASA still valid in your view?
The ‘corrected sunspot number’ is still a work in progress. You can find what I have at http://www.leif.org/research/files.htm
Look for:
Corrected SSN and TSI.prn
Corrected SSN and TSI.txt
Corrected SSN and TSI.xls
Corrected Sunspot Series 1841-Present.xls
The sunspot areas between 1874 and 1976 are good. Hathaway has a continuation until the present at http://solarscience.msfc.nasa.gov/greenwch.shtml
There are some issues with splicing together the newer and older data.
maksimovich (22:54:40) :
You may like to comment on this paper as you are heavily cited.:
On the long term change in the geomagnetic activity during the 20th century
F. Ouattara1, C. Amory-Mazaudier2, M. Menvielle3,4, P. Simon*,†, and J.-P. Legrand*
This is a poor paper, and their interpretation of their ‘result’ is a rehash of thirty-year old ideas of Simon and Legrand [which I do not subscribe to]. The story about aa has two aspects:
1) an error in calibration before 1957
2) inhomogeneity in the index caused by Mayaud providing all values before 1937, but using existing scalings afterwards.
(1) is addressed in section 5.3 of http://www.leif.org/research/2007JA012437.pdf
and (2) is touched upon here:
http://www.leif.org/research/Analysis%20of%20K=0%20and%201%20for%20aa%20and%20NGK.pdf
Leif Svalgaard (21:30:47) “[…] i.e. not the climate models that pretend to forecast a hundred years ahead the effect of a butterfly beating its wings.”
priceless
Re: tallbloke (08:35:17)
Something you might want to try sometime when you do your integrations: Use variable-bandwidth. (Excel is friendly to this sort of calculation if you are adept at using the “offset” function. If you run into problems with ragged vector-lengths as bandwidth varies (which results in triangular arrays), use the “count” & “counta” functions [in concert] to guide Excel around missing/error values.
Leif Svalgaard (23:20:46) “[…]
1) an error in calibration before 1957
2) inhomogeneity in the index caused by Mayaud providing all values before 1937, but using existing scalings afterwards.”
Aside:
I hope you will write an authoritative (but concise) overview of the aa index & its history one day (for a non-specialist general-science audience).
– –
Question for anyone who can answer:
Recently I estimated the historical Chandler wobble period using wavelet methods. I contrasted the curve I got with a precipitation curve. When studying the residuals I noticed a *consistent phase agreement with aa index up until (but not beyond) the 1930s – so the first question that popped into my mind was about instruments & measurement methods – and since I know little of instruments & measurements I have to ask:
Is there anything [obvious] that would affect
BOTH
a) aa index measurements
AND
b) precipitation measurements &/OR polar motion measurements
BEFORE the 1930s
but NOT afterward?
To WUWT: Thank you for running a story paying attention to DTR (which is on the radar of the “top” climate modelers).
General Note:
When considering DTR, it is important to differentiate between coastal & continental sites.
anna v, I had a look at the tree-ring paper you mentioned. After looking at the wavelet plots and reading the accompanying text: I’d want to run my own analyses (if I had access to the tree-ring data) and ask the authors some questions before drawing conclusions. Note: I am thankful that a liberal publication system allows us to see what others are doing.
Paul Vaughan (01:08:50) :
Is there anything [obvious] that would affect
BOTH a) aa index measurements
AND b) precipitation measurements &/OR polar motion measurements
No
Paul Vaughan (01:08:50) :
I hope you will write an authoritative (but concise) overview of the aa index & its history one day (for a non-specialist general-science audience).
This may not be possible as the issues are complex.
I’m giving an invited talk on this at the IAGA 2009 conference http://www.iaga2009sopron.hu/ in August:
H02. History of geomagnetic observations, observatories, & indices
This session of invited talks will trace the history of the study of earth’s magnetism including: Gilbert’s De Magnete, early studies of geomagnetic activity by Graham and Celsius, Gauss and Weber’s Magnetic Union, Sabine’s British Colonial Observatories, establishment of the solar-terrestrial connection, Bartels’ development of geomagnetic indices, and the modern Intermagnet and space borne observation programs.
—–
Perhaps my write-up of the talk might serve.
P.S. You still have not told me her ‘central thesis’ was.
Please do.
Paul Vaughan (01:08:50) :
Leif Svalgaard (06:47:49) :
“I’m giving an invited talk on this at the IAGA 2009 conference http://www.iaga2009sopron.hu/ in August:”
I forgot to include the abstract:
Geomagnetic variation is an extremely complicated phenomenon with multiple causes operating on many time scales. 250 years ago, Hjorter noticed its ‘regular irregularity, and irregular regularity’. The immense complexity of geomagnetic variations becomes tractable by the introduction of suitable geomagnetic indices on a variety of time scales, some specifically targeting particular mechanisms and physical causes. We review the historical evolution of the ‘art of devising indices’. Different indices [by design] respond to different combinations of solar wind and solar activity parameters and in Bartels’ [1932] words “yield supplemental independent information about solar conditions” and , in fact, have allowed us to derive quantitative determination of solar wind parameters over the past 170 years. Geomagnetic indices are even more important today as they are used as input to forecasting of space weather and terrestrial responses.
Is it from Gauss that we get our term de-gauss, a step in computer screen maintenance to right a skewed monitor view? I had a problem with that once when I placed a tower speaker next to the screen and the view appeared to be magnetically attracted to the speaker. When I looked into it, the problem was a magnetic one? Or was it related to static electricity? These two sometimes confuse me as static electricity sometimes appears magnetic as in the balloon on hair trick.
Leif and Paul,
Thank you both for your input. FWIW the cumulative running totals I get for sunspot numbers and sunspot areas agree very closely, except for very recent data where the large number of ‘tiny tims’ of negligible area upsets the correlation.
Pamela Gray (07:44:49) :
Is it from Gauss that we get our term de-gauss, a step in computer screen maintenance to right a skewed monitor view?
Yes.
I had a problem with that once when I placed a tower speaker next to the screen and the view appeared to be magnetically attracted to the speaker. When I looked into it, the problem was a magnetic one?
Magnetic. You can distort the TV image [if you still have a tube] with a powerful magnetic held [or better yet, moved around] next to the tube.
Leif, I was wondering about your thoughts of my two criticisms of the article.
One, I wonder if trade wind and jet stream patterns can be linked to the presence or absence of aerosols over time. The presence of aerosols at any one place cannot be assumed to be its source. They were probably driven there.
And two, natural dust is a powerful aerosol. It kicks up here in the northeast corner of Oregon. A case in point, palouse soil is soil brought by the wind. We have plenty of it here but it came from somewhere else. Palouse soil is easily kicked up into the wind. We have had cloudless rain on many occasions. When farmers lay a circle of soil to rest instead of plant and water it, the soil takes to the wind. We don’t grow nearly the acres of wheat we used to grow since crop land was put into conservation programs. But this dry shrubby desert soil then gets kicked up by the wind during high wind seasons because there is little cover crop land to anchor it. In the old days, before high plains soil was planted, dust storms were as bad as ever. Then when Columbia River water was used to drive circle irrigation systems, that soil was anchored. We are now beginning to experience dust storms again because the high plains are not as intensively farmed. I think natural dust, like you get off of the deserts of Africa, is a very significant source of aerosols and may overwhelm what the authors seem to infer as major anthropogenic sources. His conclusions seem to place more emphasis one anthropogenic sources than the study merits.