From the FECYT – Spanish Foundation for Science and Technology via Eurekalert comes this interesting note about solar forcing. It seems there’s a 2.3% per decade increase in solar radiation observed in Spain. Surely this is more than enough to account for the warming there? Cloud cover is said to be the issue, as Dr. Roy Spencer has previously pointed out, it only takes a small amount of cloud cover change to make a warming trend. – Anthony
Spain receives ever more solar radiation
Solar radiation in Spain has increased by 2.3% every decade since the 1980s, according to a study by researchers from the University of Girona and the Federal Institute of Technology (ETH) in Zurich. This increase is linked to the decreased presence of clouds, which has increased the amount of direct radiation reaching us from the Sun.
“The mean annual G series over Spain shows a tendency to increase during the 1985-2010 period, with a significant linear trend of + 3.9 W m-2 [2.3% more] per decade.” This is the main conclusion of a study published in the magazine ‘Global and Planetary Change‘ by researchers from the University of Girona and the Federal Institute of Technology in Zurich (ETH, Switzerland).
The season-by-season data show the same “significant” increase in solar radiation impacting the nation: + 6.5 W/m2 per decade during the summer, + 4.1 W/m2 in autumn, + 3.2 W/m2 in spring and + 1.7 W/m2 in winter.
“These data relate to global solar radiation, in other words the increase in direct radiation reaching us from the Sun plus diffuse radiation which is scattered previously by clouds, atmospheric gases and aerosols,” explains one of the authors, Arturo Sánchez-Lorenzo, currently a postdoctoral researcher at the University of Girona.
What is intriguing is that the scientists found a decrease in the diffuse component, because of which direct radiation has increased to a proportionately higher degree. Only in 1991 and 1992 did diffuse radiation rise, and this was due to the ashes from Mount Pinatubo. In general, however, we can observe a downward trend of – 2.1 W/m2 per decade between 1985 and 2010.
VIDEO: Solar radiation in Spain has increased by 2.3 percent every decade since the 1980s.Click here for more information.
“The explanation lies in the fact that in Spain the amount of cloud has decreased markedly since the 1980s – as we have ascertained through other studies – and the tropospheric aerosol load may also have decreased,” states Sánchez Lorenzo. “It seems to be very simple: fewer clouds result in higher solar radiation on the surface,” he continues.
According to the scientists, this increase may also go hand in hand with more ultraviolet rays, an excess of which presents a health risk, potentially leading to skin cancer.
More global brightening
The increase in global solar radiation is a phenomenon that has been observed in other parts of the world for almost 30 years, especially in developed countries, and it has been named “global brightening”. The fall in the diffuse component has also been observed in Central European and Eastern countries.
The team behind the study has not yet analysed the solar radiation data for 2011-2013 provided by the Spanish State Meteorological Agency, but the data from other European weather stations suggests that this brightening is still on the rise.
“Studies such as these may be of interest to the solar energy industry, especially in countries like Spain, where not only do we already have a lot of direct solar radiation but now we are getting even more,” affirms one of the other authors, Josep Calbó, who is a professor at the University of Girona.
References:
A. Sanchez-Lorenzo, J. Calbó, M. Wild. “Global and diffuse solar radiation in Spain: Building a homogeneous dataset and assessing their trends”. Global and Planetary Change 100: 343–352, 2013.
h/t to Dr. Leif Svalgaard
Ulric Lyons says:
June 14, 2013 at 6:30 pm
the numbers of coronal holes were well down from late 2008 to early 2010.
There were not anomalously few coronal holes during that time, see Figure 3 of http://www.leif.org/research/ApJ88587.pdf
There are most coronal holes near minimum and fewest near maximum as you can also see. In any case the dominant effect is from EUV/X-rays, so your fundamental thesis that solar wind speed/temperature are dominant drivers is simply not supported by the data over many solar cycles.
so it doesn’t really add up
Experts [including myself] find that things add up fine. As Solomon notes: “NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model are compared to thermospheric density measurements, yielding evidence that the primary cause of the low thermospheric density was the unusually low level of solar extremeultraviolet irradiance” and “The purpose of this paper is to demonstrate through model simulations that the solar and terrestrial observations are compatible, and mutually supporting”. and “The model densities are in good agreement with global average densities shown in figure 3 for 1996 and 2008, and the density decrease is very close to the 29% inter-minima difference derived from satellite drag measurements.”
So, the situation is well under control and our understanding seems robust.
Leif Svalgaard says:
“There were not anomalously few coronal holes during that time, see Figure 3 of http://www.leif.org/research/ApJ88587.pdf”
I don’t see the figures there, but here’s the head count, and there were many months where they thin right out during that time, mostly small and weak too if you look at the Max speed:
http://www.solen.info/solar/coronal_holes.html
“Experts [including myself] find that things add up fine.”
I’m not arguing that the EUV was low, I just don’t buy their coronal idea, it doesn’t add up, there were less holes and they were often very small. And what about Emmert’s missing 60%?
Ulric Lyons says:
June 14, 2013 at 7:42 pm
I don’t see the figures there
Scroll to page 12.
but here’s the head count, and there were many months where they thin right out during that time, mostly small and weak too if you look at the Max speed:
Doesn’t go back to the previous minimum. My Figure 3 shows the fraction of the Sun covered by coronal holes.
I’m not arguing that the EUV was low, I just don’t buy their coronal idea, it doesn’t add up, there were less holes and they were often very small.
You don’t buy it because you are fixated on your misconception. The Solomon paper is a careful analysis of the numbers and the theory.
And what about Emmert’s missing 60%?
Due to obsolete model. Solomon’s work is with the latest and greatest and finds no stuff missing.
There is no doubt about what the dominant driver of thermospheric heating is.
Ulric Lyons says:
June 14, 2013 at 7:42 pm
mostly small and weak too if you look at the Max speed
It is not the speed that is important, but the area of the holes: a large area means less EUV and less heating of the thermosphere.
Ulric Lyons says:
June 14, 2013 at 7:42 pm
mostly small and weak too if you look at the Max speed
The whole discussion about coronal holes and solar wind speed is just about a straw man. The principal agent is the EUV/X-ray flux. That was very low in 2009, hence an expanded thermosphere. The modeling performed by Solomon reproduces the observations, so we have to go by that.
Ulric Lyons says:
June 14, 2013 at 2:25 pm
“That leaves as much as 60% unaccounted for.”
That would be the dearth of coronal holes and slow plasma from late 2008.
Note that there were more coronal holes at the 2008/9 minimum than at the 1996/7 minimum. This is one of the reasons for the colder thermosphere as more coronal holes means less EUV:
http://arxiv.org/ftp/arxiv/papers/1003/1003.4524.pdf
Leif Svalgaard says:
“Scroll to page 12.”
That’s polar hole decline.
“It is not the speed that is important, but the area of the holes: a large area means less EUV and less heating of the thermosphere.”
There may have been some larger low latitude ones earlier in 2008, but the strong decline was from much later in 2008 and they became smaller from there on, though to 2010. Mean meanwhile Woods says:
“But the total coronal hole area might not be the most appropriate component for the solar EUV irradiance”
“Note that there were more coronal holes at the 2008/9 minimum than at the 1996/7 minimum. This is one of the reasons for the colder thermosphere as more coronal holes means less EUV:
http://arxiv.org/ftp/arxiv/papers/1003/1003.4524.pdf”
One would expect to see more high speed streams with an increase in number and size of trans-equatorial CH’s, http://snag.gy/7OSW2.jpg http://snag.gy/YGoNK.jpg
Ulric Lyons says:
June 15, 2013 at 3:31 am
That’s polar hole decline.
There may have been some larger low latitude ones earlier in 2008
Again the decrease in EUV is not confined to low-latitude holes. Although holes near disk center may have a larger effect.
“But the total coronal hole area might not be the most appropriate component for the solar EUV irradiance”
Another example of your selective quoting. Just before that he also says: “there are several large coronal holes at low-latitudes in 2008; whereas, there were few, if any, low-latitude coronal holes during the 1996 minimum”.
One would expect to see more high speed streams with an increase in number and size of trans-equatorial CH’s
Is irrelevant as it is the EUV that is important, not the speed.
Leif Svalgaard says:
“Is irrelevant as it is the EUV that is important, not the speed.”
No it’s the number of CH’s that is important (reduced), and that the speeds were lower during the recent minimum is some confirmation that they were often smaller too. Or look here:
http://www.solen.info/solar/old_reports/
http://www.solen.info/solar/coronal_holes.html
“Another example of your selective quoting. Just before that he also says: “there are several large coronal holes at low-latitudes in 2008”
I already dealt with that, they were earlier in 2008 before the sharp decline in activity.
Ulric Lyons says:
June 15, 2013 at 9:20 am
No it’s the number of CH’s that is important (reduced), and that the speeds were lower during the recent minimum is some confirmation that they were often smaller too.
I already dealt with that, they were earlier in 2008 before the sharp decline in activity.
I’m not sure what you are claiming. The facts are that thermospheric density is controlled mainly by EUV; coronal holes emit less EUV; active regions emit more EUV; so a combination of more coronal holes and fewer active regions explain quantitatively the lower thermospheric density observed in 2008-2009. This has nothing to do with solar wind speed or temperature. This is the fundamental fact you have to embrace.
Leif Svalgaard says:
“so a combination of more coronal holes and fewer active regions explain quantitatively the lower thermospheric density observed in 2008-2009”
I can see from the solen list that there were fewer coronal holes then, I also remember this clearly as I monitor them all the time, and I clearly remember you saying how few coronal holes there were back then.
Ulric Lyons says:
June 15, 2013 at 9:48 am
“so a combination of more coronal holes and fewer active regions explain quantitatively the lower thermospheric density observed in 2008-2009″
I can see from the solen list that there were fewer coronal holes then, I also remember this clearly as I monitor them all the time, and I clearly remember you saying how few coronal holes there were back then.
The solen list does not go back to the previous minimum in 1996/1997 and the whole issue with the thermosphere was why its density 2008/9 was lower than in 1996/7. The reason is that there were more coronal holes in 2008/9 than in 1996/7 [regardless of how many coronal holes there are now] hence less EUV plus that there were fewer sunspots hence also less EUV, net result: lower thermospheric density. The more accurate model used by Solomon quantitatively confirms just that. So no mystery, and no issue with solar wind temperature [or speed].
Ulric Lyons says:
June 15, 2013 at 9:48 am
I can see from the solen list that there were fewer coronal holes then…
As per Solomon [with the usual caution]: “The only reasonable result is that the solar 26 to 34 nm irradiance from SOHO SEM appears 15% lower in 2008 than in 1996. This EUV decrease could possibly be explained by the abundance of low-latitude coronal holes during this current cycle minimum, unlike in 1996”. The thermospheric density was low not just in 2009 but “During 2007–2009 thermospheric densities at a fiducial altitude of 400 km were the lowest observed in the 43-year database” [Emmert].
Ulric Lyons says:
June 15, 2013 at 9:48 am
I can see from the solen list that there were fewer coronal holes then…
To continue the Emmert quote [ http://onlinelibrary.wiley.com/doi/10.1029/2010GL043671/abstract ] “The density anomalies appear to have commenced before 2006, well before the cycle 23/24 minimum, and are larger than expected from enhanced thermospheric cooling by increasing concentrations of CO2. The height dependence of the mass density anomalies suggests that they are attributable to a combination of lower-than-expected exospheric temperature (−14 K) [due to lower EUV] and reductions in the number density of atomic oxygen (−12%) and other species (−3%) near the base of the diffusive portion of the thermosphere [anthropological ?]”.
Leif Svalgaard says:
“The reason is that there were more coronal holes in 2008/9 than in 1996/7..”
More low latitude holes than 1996/7, but highly infrequent for a minimum, down to one or two per month at times, and often very small too.
Ulric Lyons says:
June 15, 2013 at 10:07 am
“The reason is that there were more coronal holes in 2008/9 than in 1996/7..”
More low latitude holes than 1996/7, but highly infrequent for a minimum, down to one or two per month at times, and often very small too.
To say that you must have extensive statistics for that number for several minima. No such statistic exists, but we don’t really need that for discussing the difference between 1997/7 and 2008/9. Perhaps this link http://inspirehep.net/record/844965/plots will set you straight: “During the current solar minimum (2006-2009) low-latitude CHs occur more frequently and they occupy an area larger when compared to the previous solar minimum(1995-1997)”.
The Sargent Recurrence Index http://sss.leif.org/research/Sargent-Recurrence-Index.png is often used as a proxy for the extent of low-latitude coronal holes. It is a quantitative measure of the tendency of solar activity to recur after one rotation [as coronal holes often do]. As you can see 2008/9 ranks highest of all minima since 1868.
UV comes from the corona as the plasma picks up energy (somehow) on the way outward, correct?
Leif Svalgaard says:
June 15, 2013 at 10:20 am
The Sargent Recurrence Index http://www.leif.org/research/Sargent-Recurrence-Index.png is often used as a proxy for the extent of low-latitude coronal holes.
Was fat-fingered. Moving the keyboard a few millimeters closer helped turning sss into the coreect www 🙂
pochas says:
June 15, 2013 at 10:22 am
UV comes from the corona as the plasma picks up energy (somehow) on the way outward, correct?
UV [actually EUV and x-rays] comes because the corona is HOT [millions of degrees]. The corona expands also because it is hot.
Leif Svalgaard says:
“The Sargent Recurrence Index http://www.leif.org/research/Sargent-Recurrence-Index.png is often used as a proxy for the extent of low-latitude coronal holes. It is a quantitative measure of the tendency of solar activity to recur after one rotation [as coronal holes often do]. As you can see 2008/9 ranks highest of all minima since 1868.”
OK I’m looking, and I’m seeing one of the fastest drop off’s in the whole series.
Ulric Lyons says:
June 15, 2013 at 10:44 am
OK I’m looking, and I’m seeing one of the fastest drop off’s in the whole series.
At the time where the thermospheric density is recovering, so very consistent with the role of EUV in controlling the thermosphere. We are perhaps making progress in your understanding of this fundamental fact.
Leif Svalgaard says:
“At the time where the thermospheric density is recovering, so very consistent with the role of EUV in controlling the thermosphere.”
No the drop is at the end of 2008 when the thermosphere collapsed, I thought the recovery didn’t get under way till early 2010?
Ulric Lyons says:
June 15, 2013 at 10:53 am
No the drop is at the end of 2008 when the thermosphere collapsed, I thought the recovery didn’t get under way till early 2010?
The thermosphere collapsed starting in 2006. Emmert:
http://onlinelibrary.wiley.com/doi/10.1029/2010GL043671/abstract ] “The density anomalies appear to have commenced before 2006, well before the cycle 23/24 minimum”
so you have not made any progress in your understanding yet.
Leif Svalgaard says:
“The thermosphere collapsed starting in 2006. Emmert:
http://onlinelibrary.wiley.com/doi/10.1029/2010GL043671/abstract ] “The density anomalies appear to have commenced before 2006, well before the cycle 23/24 minimum”
so you have not made any progress in your understanding yet.”
“This is the biggest contraction of the thermosphere in at least 43 years,” says John Emmert of the Naval Research Lab, lead author of a paper announcing the finding in the June 19th issue of the Geophysical Research Letters (GRL). “It’s a Space Age record.”
The collapse happened during the deep solar minimum of 2008-2009—a fact which comes as little surprise to researchers. The thermosphere always cools and contracts when solar activity is low. In this case, however, the magnitude of the collapse was two to three times greater than low solar activity could explain.
http://science.nasa.gov/science-news/science-at-nasa/2010/15jul_thermosphere/
Ulric Lyons says:
June 15, 2013 at 11:03 am
The collapse happened during the deep solar minimum of 2008-2009—a fact which comes as little surprise to researchers. The thermosphere always cools and contracts when solar activity is low. In this case, however, the magnitude of the collapse was two to three times greater than low solar activity could explain.
so? The ‘explanation’ is based on the old [1970s] Jachia model. The superior model used by Solomon explains the magnitude well as the result of more coronal holes [less EUV] and much lower solar activity [even less EUV]. No mystery, no dependence on solar wind.
Leif Svalgaard says:
“The superior model used by Solomon explains the magnitude well as the result of more coronal holes”
I still don’t accept that, there were fewer holes even if there were relatively more low latitude ones. The amount of EUV decline is not totally certain either.