Johhny Electriglide wrote:
From http://www.skepticalscience.com/solar-a ... ediate.htm
Solar activity & climate: is the sun causing global warming?
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The skeptic argument...
It's the sun
"Over the past few hundred years, there has been a steady increase in the numbers of sunspots, at the time when the Earth has been getting warmer. The data suggests solar activity is influencing the global climate causing the world to get warmer." (BBC)
What the science says...
Select a level... Basic Intermediate Advanced
In the last 35 years of global warming, the sun has shown a slight cooling trend. Sun and climate have been going in opposite directions.
As supplier of almost all the energy in Earth's climate, the sun has a strong influence on climate. A comparison of sun and climate over the past 1150 years found temperatures closely match solar activity (Usoskin 2005). However, after 1975, temperatures rose while solar activity showed little to no long-term trend. This led the study to conclude, "...during these last 30 years the solar total irradiance, solar UV irradiance and cosmic ray flux has not shown any significant secular trend, so that at least this most recent warming episode must have another source."
In fact, a number of independent measurements of solar activity indicate the sun has shown a slight cooling trend since 1960, over the same period that global temperatures have been warming. Over the last 35 years of global warming, sun and climate have been moving in opposite directions. An analysis of solar trends concluded that the sun has actually contributed a slight cooling influence in recent decades (Lockwood 2008).
Figure 1: Annual global temperature change (thin light red) with 11 year moving average of temperature (thick dark red). Temperature from NASA GISS. Annual Total Solar Irradiance (thin light blue) with 11 year moving average of TSI (thick dark blue). TSI from 1880 to 1978 from Krivova et al 2007 (data). TSI from 1979 to 2009 from PMOD.
Foster and Rahmstorf (2011) used multiple linear regression to quantify and remove the effects of the El Niño Southern Oscillation (ENSO) and solar and volcanic activity from the surface and lower troposphere temperature data. They found that from 1979 to 2010, solar activity had a very slight cooling effect of between -0.014 and -0.023°C per decade, depending on the data set (Table 1, Figure 2).
Table 1: Trends in °C/decade of the signal components due to MEI, AOD and TSI in the regression of global temperature, for each of the five temperature records from 1979 to 2010.
Figure 2: Influence of exogenous factors on global temperature for GISS (blue) and RSS data (red). (a) MEI; (b) AOD; (c) TSI.
Like Foster and Rahmstorf, Lean and Rind (2008) performed a multiple linear regression on the temperature data, and found that while solar activity can account for about 11% of the global warming from 1889 to 2006, it can only account for 1.6% of the warming from 1955 to 2005, and had a slight cooling effect (-0.004°C per decade) from 1979 to 2005.
A number of studies have used a variety of statistical and physical approaches to determine the contribution of greenhouse gases and other effects to the observed global warming, like Lean & Rind and Foster & Rahmstorf. And like those studies, they find a relatively small solar contribution to global warming, particularly in recent decades (Figure 3).
Figure 3: Solar contribution to global warming according to various peer-reviewed attribution studies
Other studies on solar influence on climate
This conclusion is confirmed by many studies finding that while the sun contributed to warming in the early 20th Century, it has had little contribution (most likely negative) in the last few decades:
Huber and Knutti (2011): "Even for a reconstruction with high variability in total irradiance, solar forcing contributed only about 0.07°C (0.03-0.13°C) to the warming since 1950."
Erlykin 2009: "We deduce that the maximum recent increase in the mean surface temperature of the Earth which can be ascribed to solar activity is 14% of the observed global warming."
Benestad 2009: "Our analysis shows that the most likely contribution from solar forcing a global warming is 7 ± 1% for the 20th century and is negligible for warming since 1980."
Lockwood 2008: "It is shown that the contribution of solar variability to the temperature trend since 1987 is small and downward; the best estimate is -1.3% and the 2? confidence level sets the uncertainty range of -0.7 to -1.9%."
Lean 2008: "According to this analysis, solar forcing contributed negligible long-term warming in the past 25 years and 10% of the warming in the past 100 years..."
Lockwood 2008: "The conclusions of our previous paper, that solar forcing has declined over the past 20 years while surface air temperatures have continued to rise, are shown to apply for the full range of potential time constants for the climate response to the variations in the solar forcings."
Ammann 2007: "Although solar and volcanic effects appear to dominate most of the slow climate variations within the past thousand years, the impacts of greenhouse gases have dominated since the second half of the last century."
Lockwood 2007: "The observed rapid rise in global mean temperatures seen after 1985 cannot be ascribed to solar variability, whichever of the mechanism is invoked and no matter how much the solar variation is amplified."
Foukal 2006 concludes "The variations measured from spacecraft since 1978 are too small to have contributed appreciably to accelerated global warming over the past 30 years."
Nice copy and paste job from Skeptical Science.
The image they use in their "Basic" portion of their rebuttal has this caption: Figure 1: Global temperature (red, NASA GISS) and Total solar irradiance (blue, 1880 to 1978 from Solanki, 1979 to 2009 from PMOD).
I hope you are aware that there are three datasets that measure TSI and not just PMOD.
In addition to PMOD, there are also the IRMB and the ACRIM TSI datasets, both which show an increase in TSI over the late-20th Century. The IRMB dataset shows a mean increase of 0.15 w/m^2 from 1986-1996
. This is not very much at all, but with large amplifying mechanisms from GCRs, this could represent a significant contribution from the sun to the recent warming. The ACRIM dataset shows a statistically significant trend upward
in TSI from 1986-1996, and therefore could represent a possibly dominant climate forcing over the last 30 years. In fact, with ACRIM, 65% of the warming over the last 30 years can be explained by solar activity variations.
I will give you the benefit of the doubt that you did not know that other TSI datasets existed other than PMOD, but your copy and paste post is definitely misleading.
Let me post quotations to studies I will select:Palamara and Bryant 2004Our findings represent a solar-climate relationship that has
practical, as well as statistical significance, evidenced by the
importance of the NAM to Northern Hemisphere climate.The crucial question now relates to how solar/geomagnetic
activity is coupled to the lower atmosphere. For part of
this mechanism it is likely that geomagnetic activity influences
the meridional temperature gradient, and subsequently
the stratosphere zonal wind structure of the stratosphere,
which, in turn, impacts upon tropospheric circulation
through a number of possible processes outlined in Shindell
et al. (2001) and Baldwin and Dunkerton (2001). The
seasonality of the relationship is a function of stratospheretroposphere
coupling, which only occurs during winter
Further research must consider how these stratospheric
changes originate. Crucial to this endeavour is the elucidation
of which physical processes in the atmosphere can be
associated with geomagnetic activity. It is also important to
explain the temporal pattern, as well as the role of the QBO
in modulating the relationship.Therefore, we conclude that
geomagnetic activity plays an important role in recent climate
change Mayewski et. al 2005We present highly resolved, annually dated, calibrated proxies for atmospheric circulation from several Antarctic ice cores (ITASE (International Trans-Antarctic Scientific Expedition), Siple Dome, Law Dome) that reveal decadal-scale associations with a South Pole ice-core 10Be proxy for solar variability over the last 600 years and annual-scale associations with solar variability since AD 1720. We show that increased (decreased) solar irradiance is associated with increased (decreased) zonal wind strength near the edge of the Antarctic polar vortex. The association is particularly strong in the Indian and Pacific Oceans and as such may contribute to understanding climate forcing that controls drought in Australia and other Southern Hemisphere climate events. We also include evidence suggestive of solar forcing of atmospheric circulation near the edge of the Arctic polar vortex based on ice-core records from Mount Logan, Yukon Territory, Canada, and both central and south Greenland as enticement for future investigations. Our identification of solar forcing of the polar atmosphere and its impact on lower latitudes offers a mechanism for better understanding modern climate variability and potentially the initiation of abrupt climate-change events that operate on decadal and faster scales. Belov et. al 2005,
and Borie and Thoyaib 2006
found that using solar parameters, you can predict climate changes with a degree of accuracy. Cliver et. al 1998
Cliver et. al 1998 also used the Geomagnetic AA Index to estimate the solar contribution to climate change.
Above figure: From Cliver et. al 1998. The AA Index is the dotted line, and the solid line are the temperature anomalies.
They found that 50-100% of the warming could be due to the sun, but it should be noted that this analysis does not include other factors like volcanic activity and anthropogenic greenhouse gas emissions when estimating the total contribution. Nonetheless, this study also shows that other studies which do include these factors are only at the lower end of the 50-100% range for the solar contribution over the last 100-150 years. It also supports other studies with a larger solar contribution to climate change because of the remarkable correlation with the AA Index and temperatures.Scafetta and West 2008
Scafetta and West 2008 adresses the uncertainty raised in the first paper. If a TSI curve that shows an upward trend from Solar Cycle 21 to 22 is used from the ACRIM TSI composite rather than the flat PMOD TSI composite, then a higher contribution from the sun would be needed. The authors find that up to 69% of the variances in temperatures can be explained by solar activity.
The image above from Scafetta and West 2008 shows the divergence between the PMOD and ACRIM TSI datasets, which makes attribution to past climate change even harder. The red curve is the ACRIM TSI composite, the blue curve is the PMOD TSI Composite, and the black curve and green line are the Global Temperature anomalies. Kilcik et. al 2010 By applying multitaper methods and Pearson test on the surface air temperature and flare index used as a proxy data for possible solar sources of climate-forcing, we investigated the signature of these variables on middle and high latitudes of the Atlantic–Eurasian region (Turkey, Finland, Romania, Ukraine, Cyprus, Israel, Lithuania, and European part of Russia). We considered the temperature and flare index data for the period ranging from January 1975 to the end of December 2005, which covers almost three solar cycles, 21st, 22nd, and 23rd.
We found significant correlations between solar activity and surface air temperature over the 50–60° and 60–70° zones for cycle 22, and for cycle 23, over the 30–40°, 40–50°, and 50–60° zones.
The most pronounced power peaks for surface air temperature found by multitaper method are around 1.2, 1.7, and 2.5 years which were reported earlier for some solar activity indicators. These results support the suggestion that there is signature of solar activity effect on surface air temperature of mid-latitudes.Mufti and Shah 2011
The abstract and key points read: A long uninterrupted homogeneous data set on the annual mean Sea Surface Temperature (SST) anomaly records as a representative of the Earth's climatic parameter has been analyzed in conjunction with 158 year long time series on the annual sunspot indices, Rz and geomagnetic activity indices, aa for the period 1850–2007. The 11-year and 23-year overlapping means of global (δtg) as well as northern (δtn) and southern (δts) hemispheric SST anomalies reveal significant positive correlation with both Rz and aa indices. Rz, aa and δtg depict a similar trend in their long-term variation and both seem to be on increase after attaining a minimum in the early 20th century (∼1905). Whereas the results on the power spectrum analysis by the Multi-Taper Method (MTM) on δtg, Rz and aa reveal periodicities of ∼79–80 years (Gleissberg's cycle) and ∼9–11 years (Schwabe solar cycle) consistent with earlier findings, MTM spectrum analysis also reveals fast cycles of 3–5 years. A period of ∼4.2 years in aa at 99% confidence level appears recorded in δtg at ∼4.3 years at 90% confidence level. A period of ∼3.6–3.7 years at 99% confidence level found in δtg is correlating with a similar periodic variation in sector structure of Interplanetary Magnetic Field (IMF). This fast cycle parallelism is new and is supportive of a possible link between the solar-modulated geomagnetic activity and Earth's climatic parameter i.e. SST.Raspopov et. al 2007
Found that long term trends in solar activity can create SIGNIFICANT temperature changes. A substantial lag can also occur with the sun and the temperature on the Earth, which would refute your earlier logic that just because the sun's irradiance according to PMOD has flatlined, does not bmean that it has not contributed to the recent warming. They also find that recent warming from 1945-2003 matches with expected predictions from a long term increase in solar activity.
From the abstract: The influence of ∼200-year solar activity variations (de Vries cyclicity) on climatic parameters has been analyzed. Analysis of palaeoclimatic data from different regions of the Earth for the last millennium has shown that ∼200-year variations in solar activity give rise to a pronounced climatic response. Owing to a nonlinear character of the processes in the atmosphere–ocean system and the inertia of this system, the climatic response to the global influence of solar activity variations has been found to have a regional character. The regions where the climatic response to long-term solar activity variations is stable and the regions where the climatic response is unstable, both in time and space, have been revealed. It has also been found that a considerable lag of the climatic response and reversal of its sign with respect to the solar signal can occur. Comparison of the obtained results with the simulation predictions of the atmosphere–ocean system response to long-term solar irradiance variations (T > 40 years) has shown that there is a good agreement between experimental and simulation results.