Climate Change: Don't Blame the Sun

[donsutherland1]

One of the common counterarguments to anthropogenic global warming (AGW) is that fluctuations in solar activity explain much of the observed warming. Fluctuations in total solar irradiance (TSI) are typically very small. As a result, the overall radiative forcing attributable to changes in solar activity is also small, both in absolute and relative terms.

Source: Intergovernmental Panel on Climate Change

Given those constraints, the expected climatic impact from solar cycle variability and longer-term solar cycle trends is modest. By itself, solar activity cannot account for a large, much less largest, portion of the observed warming since the start of the 20th century. From an objective standpoint, that should be the end of the debate: the largest radiative forcings have the largest impact.

It isn't. The solar proponents counter that solar activity is greatly magnified. The 'super amplification' argument assumes that most of the temperature trend that cannot be accounted for by direct solar activity is an indirect response to that activity. Hence, the total response to solar activity is magnitudes of order larger. In other words, amplification or an indirect response is a sort of fudge factor to account for the large gap between the temperature response and radiative impact of changes in solar activity.

Careful research that accounts for the major natural and anthropogenic forcings and leading oceanic cycles reaches a different conclusion. Natural forcings include volcanic activity and solar radiance. Anthropogenic forcings include atmospheric increases in CO2 from human activities. Natural oceanic cycles include ENSO. Perhaps the definitive work on this matter is Judith Lean's and David Rind's "How natural and anthropogenic influences alter global and regional surface temperatures: 1889-2006."

Lean and Rind found:

Natural changes cannot account for the significant long-term warming in the historical global surface temperature anomalies... Only by associating the surface warming with anthropogenic forcing is it possible to reconstruct the observed temperature anomalies... Solar-induced warming...contributes 10%...of surface warming in the past 100 years and, if anything, a very slight overall cooling in the past 25 years...

The paper also provides a table listing the trends in temperature anomalies attributable to four factors: ENSO, volcanic activity, solar activity, and anthropogenic forcing. The following are the data for the 1905-2005 period:

ENSO: +0028°C/decade contribution

Volcanic Activity: -0.0029°C/decade contribution

Solar Activity: +0.0070°C/decade contribution

Anthropogenic Forcing: +0.0590°C/decade contribution

Global Temperature Change: +0.0740°C/decade

If one wants to treat all those factors as making an independent contribution, one is left with an unaccounted for difference between the net contribution of all those factors and the overall temperature change of +0.0081°C/decade. If one assigns that entire difference to solar activity (not likely), the total solar impact would be 2.2 times the direct contribution of +0.0070°C/decade. If one assigns responsibility to all those factors based on the weight of their individual contributions, the total solar impact would wind up being just over 1.1 times the direct solar contribution.

However, ENSO is not a forcing. It is a natural oceanic cycle. It represents a transfer of energy and not an addition of energy to the climate system. Hence, if one focuses strictly on the forcings and treats ENSO as a function of those forcings (alternating cycles where the ocean retains heat and then releases it), the respective total solar impacts after adding ENSO to the sum of unaccounted for temperature change would come to 2.6 times and 1.2 times the direct contribution of +0.0070°C/decade.

In other words, one can approximate a total solar impact of somewhere between 1.1 and 2.6 times the direct solar impact. The lower figure is perhaps the closer one.

The oceans, which account for the majority of energy reaching the earth on account of the external forcings (natural and anthropogenic), do not discriminate in absorbing/releasing only the solar-related heat or only the added heat from anthropogenic forcing. Therefore, one cannot assign all of the unaccounted for temperature impact to any single forcing. However, it should be noted that some amplification mechanisms e.g., cosmic rays, are specific to fluctuations in solar activity. Therefore, the true figure lies somewhere between 1.1 and 2.6 times direct forcing based on Lean's and Rind's paper and perhaps closer to the lower bound due to the weighting of the various forcings. In terms of the possible upper limit implied by that paper, research by Tung et al. (2008) found an amplification factor between 2 and 3.

Putting aside the literature, the recent solar minimum offered a laboratory setting of sorts to test the super amplification idea. If super amplfication were present, one could have expected an abrupt short-term reversal of the earth's positive energy imbalance to a negative one. Instead, the earth maintained a sizable positive energy imbalance. Oceanic heat content continued to increase and surface warming continued. In addition, that imbalance was consistent with expectations related to anthropogenic forcings.

In sum, attempts to explain 20th century and later warming as largely or mainly solar-related are not supported by the research. The super amplification hypothesis that is at the heart of that solar-based counterargument falls apart when the data are examined more closely. Once anthropogenic forcings are considered, a much smaller solar impact (direct and indirect) is found. That finding was bolstered by the recent solar minimum during which the earth maintained a large positive energy imbalance and during which global land and sea surface temperatures remained well above their climatic reference points (20th century average for the NCDC dataset and 1951-1980 for GISS).

[Vandy]

Putting aside the literature, the recent solar minimum offered a laboratory setting of sorts to test the super amplification idea. If super amplfication were present, one could have expected an abrupt short-term reversal of the earth's positive energy imbalance to a negative one. Instead, the earth maintained a sizable positive energy imbalance. Oceanic heat content continued to increase and surface warming continued. In addition, that imbalance was consistent with expectations related to anthropogenic forcings.

Great post Don. I think the quoted paragraph really hammers it home. The Sun has provided us a perfect test of the solar forcing hypothesis at the perfect time, and it just hasn't held water.

[WxMidwest]

It hasn't so far, I agree preliminarily, but wouldn't we have to wait for a grand solar minimum, like the Dalton minimum, or minimum in the Late 1800's to prove that? I don't think half of SC #24 or the relative lull between SC#23/#24 is quite deterministic of that yet , when there could be three to four 11 year solar cycles within this grand minimum to affect outcomes. I don't think 4-6 years within this 33 to 44 year period is enough "statistically" to say otherwise. Don't get me wrong, Climate change is happening, but we finally do have this likely grand minimum anomaly and we must wait till the majority of it is over to actually access. Just some words of caution from the middle ground....

[bluewave]

It hasn't so far, I agree preliminarily, but wouldn't we have to wait for a grand solar minimum, like the Dalton minimum, or minimum in the Late 1800's to prove that? I don't think half of SC #24 or the relative lull between SC#23/#24 is quite deterministic of that yet , when there could be three to four 11 year solar cycles within this grand minimum to affect outcomes. I don't think 4-6 years within this 33 to 44 year period is enough "statistically" to say otherwise. Don't get me wrong, Climate change is happening, but we finally do have this likely grand minimum anomaly and we must wait till the majority of it is over to actually access. Just some words of caution from the middle ground....

At least according to a recent paper, they calculate that it wouldn't have a significant impact.

http://www.pik-potsd...mstorf_2010.pdf

http://www.pik-potsdam.de/news/press-releases/archive/2010/weakening-sun-would-hardly-slow-global-warming

[donsutherland1]

It hasn't so far, I agree preliminarily, but wouldn't we have to wait for a grand solar minimum, like the Dalton minimum, or minimum in the Late 1800's to prove that? I don't think half of SC #24 or the relative lull between SC#23/#24 is quite deterministic of that yet , when there could be three to four 11 year solar cycles within this grand minimum to affect outcomes. I don't think 4-6 years within this 33 to 44 year period is enough "statistically" to say otherwise. Don't get me wrong, Climate change is happening, but we finally do have this likely grand minimum anomaly and we must wait till the majority of it is over to actually access. Just some words of caution from the middle ground....

The following are excerpts from a paper on the Maunder Minimum:

We examine the climate response to solar irradiance changes between the late 17th-century Maunder Minimum and the late 18th century. Global average temperature changes are small (about 0.3° to 0.4°C) in both a climate model and empirical reconstructions. However, regional temperature changes are quite large. In the model, these occur primarily through a forced shift toward the low index state of the Arctic Oscillation/North Atlantic Oscillation as solar irradiance decreases. This leads to colder temperatures over the Northern Hemisphere continents, especially in winter (1° to 2°C), in agreement with historical records and proxy data for surface temperatures.

On a global scale, that magitude cooling effect would not be sufficient to produce negative anomalies (GISS and NCDC) from today's readings on a global scale. Larger regional differences could be possible. Also, there would be additional anthropogenic forcing between now and such a future event.

[WxMidwest]

Don, I'm not saying it's right/wrong, but wouldn't we actually have to go through it 1st for Hypothesis testing, especially now that a grand minimum is showing up in the modern era of meteorological sensors and remote sensing. It would be nice to actually see this event fold without needing to use proxy data in a scientific sense. I just caution putting the cart before the horse...

[donsutherland1]

Don, I'm not saying it's right/wrong, but wouldn't we actually have to go through it 1st for Hypothesis testing, especially now that a grand minimum is showing up in the modern era of meteorological sensors and remote sensing. It would be nice to actually see this event fold without needing to use proxy data in a scientific sense. I just caution putting the cart before the horse...

I agree. should such an event occur, it would be interesting to test the scientific explanations against what actually occurs. No matter the outcome, I'm sure some new things would be learned.

[WeatherRusty]

It hasn't so far, I agree preliminarily, but wouldn't we have to wait for a grand solar minimum, like the Dalton minimum, or minimum in the Late 1800's to prove that? I don't think half of SC #24 or the relative lull between SC#23/#24 is quite deterministic of that yet , when there could be three to four 11 year solar cycles within this grand minimum to affect outcomes. I don't think 4-6 years within this 33 to 44 year period is enough "statistically" to say otherwise. Don't get me wrong, Climate change is happening, but we finally do have this likely grand minimum anomaly and we must wait till the majority of it is over to actually access. Just some words of caution from the middle ground....

The amplified change in external radiative forcing would be detected immediately. It was not. The forcing is analogous to lowering the flame on the burner, the change in energy is flow is instantaneous. The full temperature response is what takes time, but a transient response depends on the net forcing from all contributors.

The Sun was recently about as low as it can go, yet we did not detect an amplified negative radiative forcing response. The forcing would not be any less if the Sun remained in a similar state for a century.

[WxMidwest]

Again, the event needs to ACTUALLY happen wxrusty. Your dismissing the lag, see: http://www.sciencedirect.com/science/article/pii/S1364682612000417

Highlights

► A longer solar cycle predicts lower temperatures during the next cycle. ► A 1 °C or more temperature drop is predicted 2009–2020 for certain locations. ► Solar activity may have contributed 40% or more to the last century temperature increase. ► A lag of 11 years gives maximum correlation between solar cycle length and temperature.

It will not be hypothesis tested until this grand minimum in reality occurs, and not using prognosticated "proof".

[WeatherRusty]

Again, the event needs to ACTUALLY happen wxrusty. Your dismissing the lag, see: http://www.sciencedi...364682612000417

Highlights

► A longer solar cycle predicts lower temperatures during the next cycle. ► A 1 °C or more temperature drop is predicted 2009–2020 for certain locations. ► Solar activity may have contributed 40% or more to the last century temperature increase. ► A lag of 11 years gives maximum correlation between solar cycle length and temperature.

It will not be hypothesis tested until this grand minimum in reality occurs, and not using prognosticated "proof".

Two points to make:

1) The study you cite is speaking to regional response rather than global response. The TOA energy flux is a temporal/spatially averaged value which applies to the entire Earth. The recent extended solar min did not strongly influence the energy balance.

2) I am not dismissing any lag on a global basis. A lag from what physical mechanism? The radiative forcing is very small, understood to produce a radiative forcing likely no greater than 0.30W/m^2. That's enough to give a Planck temperature response ( before feedback) of 0.1C AT EQUILIBRIUM.

[WxMidwest]

You make good points rusty, I'm just waiting to see what will actually happesn in the next 30 years.

[WeatherRusty]

You make good points rusty, I'm just waiting to see what will actually happesn in the next 30 years.

Same here, I just hope to live another 30 years. I do place a great deal of faith in fundamental physics, since our understanding of the underlying rules which govern reality is what makes doing science possible.

For the Earth to warm or cool, the exchange of radiative energy at the TOA necessarily must change. Variation in TSI is not known to be sufficient to alter the TOA energy balance to the degree many anticipate. Lacking a physical reality capable of doing what you are looking for leaves me extremely skeptical that a prolonged solar minimum could affect global temperature more than a tenth or two degrees Kelvin. (before feedback)

Unless some new physics which we are not accounting for is at play, there is no way for what you are looking for to occur. The energy or lack thereof must come from somewhere.

[gracetoyou]

Humility!! Dogmatic conclusions are ridiculous with our limited knowledge. Time will tell.

[WeatherRusty]

Humility!! Dogmatic conclusions are ridiculous with our limited knowledge. Time will tell.

The closest thing to certainty in science is represented by natural law. Unlike social, legal law, natural law can not be broken.

The most fundamental of all natural law is represented by the Laws of Thermodynamics.

When a claim such as what is being made here runs up against the test of the first law of thermodynamics, it meets with trouble. Energy must be accounted for. Intrinsic variations in solar output do not add up sufficiently to bring about significant global change.

Find the energy to be lost. Otherwise there should be no scientifically based reason to expect solar variation, extended solar minimum, or anything else related to the Sun to cause significant cooling in the next two or three decades. The anthropogenic forcing is sufficient to wipe out any solar change in as little as 7 years.

[GaWx]

You make good points rusty, I'm just waiting to see what will actually happesn in the next 30 years.

I agree with you and have posted as such about wanting to see what happens in the near future with regard to the upcoming apparent grand min., which could quite possibly end up making much of the 1st third or so of the 21st century the quietest at least since the Dalton min. of ~200 years ago. However, I don't think we'll need to wait a full 30 years to determine whether or not there will ever be a sig. global temp. response from this grand min. I feel we'll know a lot more by ~2017-8 based on the past. Looking at old global temp. charts, it appears quite possible that there was about a 5 year lag from the start of the last longterm min. in ~1875 to the start of a downturn in global temp.'s in ~1880. I must admit that there not having yet been the establishment of a new downward global temp. trend is decreasing the chances in my mind of this possibility since we're now almost four years from the min. of cycle 23. However, I still remain open to that finally occurring. If, say, 2017 and 2018 are still near a top global tempwise, then that should be enough for me to just about give up on the idea that there may be a sig. cooling upcoming due to the grand solar min. What happens over the next five years or so will tell me a lot with regard to the solar factor, both direct and, perhaps more significantly, indirect.

Edit: One thing that is puzzling is the much different behavior of the southern hem. vs. the northern in recent years. Don has mentioned that it could be related to some kind of balancing since it has been so warm in the Arctic. Regardless, I do have to wonder if recent southern hem. temp.'s could be indicative of what's to come globally due to the sun.

[Isotherm]

I agree with you and have posted as such about wanting to see what happens in the near future with regard to the upcoming apparent grand min., which could quite possibly end up making much of the 1st third or so of the 21st century the quietest at least since the Dalton min. of ~200 years ago. However, I don't think we'll need to wait a full 30 years to determine whether or not there will ever be a sig. global temp. response from this grand min. I feel we'll know a lot more by ~2017-8 based on the past. Looking at old global temp. charts, it appears quite possible that there was about a 5 year lag from the start of the last longterm min. in ~1875 to the start of a downturn in global temp.'s in ~1880. I must admit that there not having yet been the establishment of a new downward global temp. trend is decreasing the chances in my mind of this possibility since we're now almost four years from the min. of cycle 23. However, I still remain open to that finally occurring. If, say, 2017 and 2018 are still near a top global tempwise, then that should be enough for me to just about give up on the idea that there may be a sig. cooling upcoming due to the grand solar min. What happens over the next five years or so will tell me a lot with regard to the solar factor, both direct and, perhaps more significantly, indirect.

Edit: One thing that is puzzling is the much different behavior of the southern hem. vs. the northern in recent years. Don has mentioned that it could be related to some kind of balancing since it has been so warm in the Arctic. Regardless, I do have to wonder if recent southern hem. temp.'s could be indicative of what's to come globally due to the sun.

Regarding the northern vs southern hemisphere, the oceanic cycles south of the Equator oscillate between cold and warm phases in a similar way to the PDO/AMO. However, when the AMO/Atlantic is warm, the southern waters tend to be cold, and vice versa.

Prior to 1995, in the time of the -AMO (cold north atlantic), the southern waters were warmer, and thus sea ice was below normal in the sern hemisphere. Since 1995, notice the positive change / increase in sea ice in the sern hemisphere, as the AMO turned warm. As the north atlantic warms, the southern ocean cools:

Since there is a much higher percentage of land mass in the northern hemisphere, the warmer oceans will create a positive feedback of warming continents, and thereby warmer oceans, etc. The Arctic Ocean is essentially a puddle of water surrounded by asphalt. When the land masses continue to warm w/ the accumulation of +AMO years post 1995, the arctic sea ice will also continue to decline. Hence this summer and recent summers are fairly close to record low ice minima in the arctic, and this particular pattern is probable to continue for at least the next few years.

The Southern Hemisphere has far less land, thus when the southern oceans are in their warm phase it doesn't have as significant an impact on the ice. Therefore when the AMO is warm, global sea ice is skewed below normal due to the far greater percentage of land mass N of the equator.

Global temp lag from solar output is about 5 years from what I've researched, so I'm not too surprised with the lack of cooling thus far. However, as you noted, I would like to see some sign of gradual cooling in the next several years to bolster the notion that the increased solar cycle length and decreased output leads to globe's thermostat turned down a tick.

[Isotherm]

The problem I have w/ the chart in the original post is it simplifies the climate system too much. There's more to it than radiative forcing.

[Snow_Miser]

The problem I have w/ the chart in the original post is it simplifies the climate system too much. There's more to it than radiative forcing.

The chart that Don Sutherland posted does not adequately capture the indirect solar forcing that has been observed, and has been observed to be much larger than the TSI Forcing alone.

Therefore it is not capturing reality.

[Snow_Miser]

Again, the event needs to ACTUALLY happen wxrusty. Your dismissing the lag, see: http://www.sciencedi...364682612000417

Highlights

► A longer solar cycle predicts lower temperatures during the next cycle. ► A 1 °C or more temperature drop is predicted 2009–2020 for certain locations. ► Solar activity may have contributed 40% or more to the last century temperature increase. ► A lag of 11 years gives maximum correlation between solar cycle length and temperature.

It will not be hypothesis tested until this grand minimum in reality occurs, and not using prognosticated "proof".

I think that 1 Degree C is extreme, but we should see cooling over the next couple of decades on the order of a couple tenths of a degree C from the quiet sun.

[donsutherland1]

The chart that Don Sutherland posted does not adequately capture the indirect solar forcing that has been observed, and has been observed to be much larger than the TSI Forcing alone.

Therefore it is not capturing reality.

The chart shows direct forcings. At the high end, solar forcing could be amplified by a factor of 2 or 3. That would still result in a small contribution relative to net anthropogenic forcings.

[Snow_Miser]

The chart shows direct forcings. At the high end, solar forcing could be amplified by a factor of 2 or 3. That would still result in a small contribution relative to net anthropogenic forcings.

The direct solar forcing does not directly amplify the direct solar forcing. That doesn't make llogical sense. What the chart shows is the possible range for the direct solar forcing, not any possible amplification mechanism. The direct solar forcing may be higher than the upper end of the IPCC range, as is shown in many TSI reconstructions. The indirect forcing is very likely higher than the anthropogenic forcing as it amplifies the direct solar forcing by a factor of 7 to 8.

[Mallow]

The direct solar forcing does not directly amplify the direct solar forcing. That doesn't make llogical sense. What the chart shows is the error range for the direct solar forcing. The direct solar forcing may be higher than the upper end of the IPCC range. The indirect forcing is very likely higher than the anthropogenic forcing as it amplifies the direct solar forcing by a factor of 7 to 8.

What?

[Snow_Miser]

What?

To explain, here is a previous post of mine on the 2012 Global Temps Thread:

Observationally, the total radiative forcing from the sun has been estimated to be 7-8 times as large as the TSI Forcing over the course of a solar cycle. We can also expect that this amplification mechanism also applies to long term trends, and thus a significant portion of the warming is likely solar induced, depending on which TSI reconstruction is used.

Shaviv 2008, Marsden and Lingenfelter 2003, Kirkby and Laaksonen 2000, Svensmark and Friis-Christensen 1996, and Reis and Serrano 2009 find that (or cite papers that show) that an amplifying mechanism is needed to explain the total forcing during a solar cycle. It should be noted that the last paper claims that a decrease in Cloud Cover during a solar cycle leads to a 0.8-1.7 w/m^2 radiative forcing may be underestimating the Cloud Cover effects during a Solar Cycle, since the Cosmic Ray impact is with the Low Clouds, and Low Clouds cool the climate more than just Clouds overall (Usoskin et. al 2004).

It is well accepted that solar irradiance changes range by about 1 w/m^2 over the course of a solar cycle, so in order to translate this value, we need to account for the Earth's albedo and geometry. We first need to divide this value by 4 to account for the geometry of the Earth, (The Earth is a sphere) and multiply this value by 0.7 to account for the Earth's albedo.

This means that the irradiance forcing during the course of a Solar Cycle is around 0.18 w/m^2. Kirkby and Laaksonen and Reis and Serrano agree that the forcing from GCRs over the course of a solar cycle is approximately 1.2-1.3 w/m^2. This is a value that is much higher than just irradiance changes alone. To get the total forcing over the course of a solar cycle, we need to add the irradiance forcing onto the GCR forcing to get a mean value of around 1.43 w/m^2. It should be noted that the total forcing during the solar cycle, (~11 years) once this amplification mechanism is accounted for, is highly comparable to the Total Anthropogenic Forcing since 1750 (~1.6 w/m^2). To find out how much bigger the total solar forcing is compared to the irradiance forcing, we can divide the total solar forcing by the irradiance forcing to get the multiplying factor. This is nearly a factor of 8 larger than the TSI forcing alone, and the IPCC may be underestimating the total solar forcing by a factor of 8. In addition, we have various TSI proxies since the Maunder Minimum that are not in agreement with each other, so the TSI forcing from the IPCC may not be correct either.

Take Haigh 2003 which finds a 3-4 w/m^2 increase in TSI since the Maunder Minimum. TSI insolation changes need to be divided by 4 and multiplied by 0.7 for the reasons stated above. When you do so, you get a TSI forcing of 0.61 w/m^2 since the Little Ice Age. The Maunder Minimum roughly ended during the same time that the IPCC's total radiative forcings started, so comparing the direct and indirect Solar Forcing to the anthropogenic forcing is reasonable. If TSI alone were the solar forcing, we would have a problem, since the net anthropogenic forcing is larger than the TSI forcing by a factor of 2.6. However, when we include the amplification from the indirect solar forcing, we can find that the Anthropogenic Forcing is dwarfed by a much larger solar forcing. When we multiply the TSI forcing by a factor of 8 to account for an amplification mechanism, we get a total solar forcing of nearly 5 w/m^2 (4.88 w/m^2). This is significantly larger than the anthropogenic forcing during the same timeframe by over a factor of 3. We get a solar contribution of around 75% to the warming observed since the Little Ice Age. This is highly significant.

The temperature has increased by roughly a Degree C since the LIA, so we can also roughly calculate the sensitivity of the Climate based off of this rough analysis. Since a combined forcing of 6.5 w/m^2 from solar and anthropogenic causes created a 1 Degree C increase in temperatures, we can use the 6.5 w/m^2 as a constant. The 3.7 w/m^2 forcing for a doubling of CO2 gives you about a 0.57 Degree C response, which is significantly smaller than the IPCC climate sensitivity.

The role of natural internal climatic variability also needs to be considered as another significant contributing factor to the recent warming episode, and if it is, the sensitivity to CO2 may go down even further.

[Mallow]

1. I was under the impression that the "cosmic ray theory" as it pertains to modern climate change has been effectively debunked.

2. The LIA was likely a somewhat localilzed phenomenon, rather than a global phenomenon. No need to introduce an arbitrary solar multiplying factor to explain a non-global temperature trend.

[donsutherland1]

The direct solar forcing does not directly amplify the direct solar forcing. That doesn't make llogical sense. What the chart shows is the possible range for the direct solar forcing, not any possible amplification mechanism. The direct solar forcing may be higher than the upper end of the IPCC range, as is shown in many TSI reconstructions. The indirect forcing is very likely higher than the anthropogenic forcing as it amplifies the direct solar forcing by a factor of 7 to 8.

The chart shows direct forcing only. If the papers on the high-end of indirect amplification are correct, the impact could be increased by a factor of 2-3.

[donsutherland1]

1. I was under the impression that the "cosmic ray theory" as it pertains to modern climate change has been effectively debunked.

2. The LIA was likely a somewhat localilzed phenomenon, rather than a global phenomenon. No need to introduce an arbitrary solar multiplying factor to explain a non-global temperature trend.

It has been. The recent solar minimum provided a good example where the hypothesized cosmic ray impact on climate failed to materialize.

[Snow_Miser]

The chart shows direct forcing only. If the papers on the high-end of indirect amplification are correct, the impact could be increased by a factor of 2-3.

Right, the chart only shows direct solar forcing only. The values for the direct solar forcing could be higher, as multiple TSI proxies show TSI increasing by the order of a few w/m^2 since the Maunder Minimum, giving you a direct solar forcing of closer to 0.6 w/m^2 than 0.12 w/m^2. While this is not an amazingly large difference in the direct solar forcing, it makes an enormous difference with regard to how large the multiplying factor from Cloud Cover changes over the solar cycle. It could be as low as 0.84 w/m^2, if one assumes the IPCC TSI Forcing to be correct, or as high as 4.8 w/m^2 if one assumes that the TSI proxies showing a larger increase in TSI are correct.

[Snow_Miser]

1. I was under the impression that the "cosmic ray theory" as it pertains to modern climate change has been effectively debunked.

2. The LIA was likely a somewhat localilzed phenomenon, rather than a global phenomenon. No need to introduce an arbitrary solar multiplying factor to explain a non-global temperature trend.

According to Yu 2002, the Cosmic Ray Flux has decreased on the order of 2-4% during the late-20th Century, according to previous studies' estimates. However, Yu 2002 estimates this decrease in GCR to be on the order of 5-8%, represebting a significant increase in solar actiity, and a significant solar contribution to the late-20th century global warming.

The Cosmic Ray Theory has not been debunked by any means. In fact, there is a growing body of evidence that suggests that Cosmic Rays have a substantial impact on Global Cloud Cover.

Where is your evidence that the "LIA was a localized phemomenon?" The LIA can be observed in many historical documents, and multiple proxy series over the last 1000 years.

[Snow_Miser]

It has been. The recent solar minimum provided a good example where the hypothesized cosmic ray impact on climate failed to materialize.

One should be very skeptical of the Hansen Energy Imbalance paper that you like to post a lot on this forum. There are substantial regions of the ocean that the ARGO floats are not covering, and the timeframe is way too small to make any reasonable conclusions from the data.

Especially when the people at ARGO themselves say that a 6 year period for evaluating trends as Hansen has done is,

“not yet long enough to observe global change signals.”

[donsutherland1]

Where is your evidence that the "LIA was a localized phemomenon?" The LIA can be observed in many historical documents, and multiple proxy series over the last 1000 years.

LIA during the Maunder Minimum saw a global cooling of around 0.3° to 0.4°. However, some areas, particularly in the Northern Hemipshere saw a decline in temperatures on the order of around 1°C - 2°C during the winter. The mechanism was the increased incidence of blocking that led to that outcome.

http://pubs.giss.nas...dell_etal_1.pdf