When Lockwood and Froehlich go on to say that the intensification of solar activity seen in the past hundred years has now ended, we don't disagree with that. We part company only when they say that temperatures have gone on shooting up, so that the recent rise can't have anything to do with the Sun, or with cosmic rays modulated by the Sun.

- Nigel Caulder, PhD

Summary for Policy Makers 

The authors of a newly published paper on the role of the sun’s variability on global temperatures overstate their case that there has been no impact of solar variations on the earth’s temperature history during the past several decades. Antithetically, changes to the sun are generally known to influence the earth’s climate on all time scales, from eons to hours. However, the difficulty comes in trying to fully measure the magnitude of the sun’s variability and then to understand how such changes result in changes to the earth’s climate. 

In a new paper, authors Lockwood and Fröhlich seem to ignore these difficulties and uncertainties, dismissing any work on this complex subject that doesn’t agree with their pre-conclusions.

For instance, in a series of papers published within the past two years, researchers Scafetta and West have concluded that the solar variations may have been responsible for 10 to 30 percent of the observed global surface temperature increase from 1980-2002. Lockwood and Fröhlich fail even acknowledgment of these widely-publicized findings. This is but one example of the inadequacies of the research of Lockwood and Fröhlich.

The following discussion reviews the analysis and conclusions of Lockwood and Fröhlich and then asks other notable scientists in the field of solar/terrestrial relations to comment on the findings.  In doing so, it is found that the conclusions being forwarded by Lockwood and Fröhlich—that the sun has had no impact on the earth’s surface temperature history during the past several decades—is not consistent with the thinking of many other researchers, and instead, indicates more a personal dogma rather than scientific truth.

- Robert Ferguson

Shining More Light on the Solar Factor

 Since the release of the IPCC report a number of peer review papers and analyses found the sun was not given enough credit for the changes in climate in the Fourth Assessment. In chapter 2, the AR4 discussed at length the varied research on the direct solar irradiance variance and the uncertainties related to indirect solar influences through variance through the solar cycles of ultraviolet and solar wind/geomagnetic activity. They admit that ultraviolet radiation by warming through ozone chemistry and geomagnetic activity through the reduction of cosmic rays and through that low clouds could have an effect on climate but in the end chose to ignore the indirect effect. They stated:

Since TAR, new studies have confirmed and advanced the plausibility of indirect effects involving the modification of the stratosphere by solar UV irradiance variations (and possibly by solar-induced variations in the overlying mesosphere and lower thermosphere), with subsequent dynamical and radiative coupling to the troposphere. Whether solar wind fluctuations (Boberg and Lundstedt, 2002) or solar-induced heliospheric modulation of galactic cosmic rays (Marsh and Svensmark, 2000b) also contribute indirect forcings remains ambiguous. (AR4 2.7.1.3)  

For the total solar forcing, in the end the AR4 chose to ignore the considerable recent peer review in favor of Wang et al. (2005) who used an untested flux transport model with variable meridional flow hypothesis and reduced the net long term variance of direct solar irradiance since the mini-ice age around 1750 by up to a factor of 7. This may ultimately prove to be AR4’s version of the AR3’s “hockey stick” debacle.

NEW PAPER CLAIMED TO BE THE NAIL IN THE COFFIN

The effort to debunk the sun did not end with the IPCC. Just recently, with the release in the Proceedings of the Royal Society of the paper “Recent Oppositely Directed Trends In Solar Climate Forcings And The Global Mean Surface Air Temperature” by Mike Lockwood and Claus Frohlich[1], the global warmers declared victory and went home.

In their abstract, the authors noted “There is considerable evidence for solar influence on the Earth’s pre-industrial climate and the Sun may well have been a factor in post-industrial climate change in the first half of the last century. Here we show that over the past 20 years, all the trends in the Sun that could have had an influence on the Earth’s climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures.”

Hansen chimed in "These half-baked notions are usually supported by empirical correlations of climate with some solar index in the past. Thus, by showing that these correlations are not consistent with recent climate change, the half-baked notions can be dispensed with.

Dr. Lockwood said the study was "another nail" in the coffin of the notion that solar activity is responsible for global warming.

Lockwood’s involvement and statement was a surprise as he was one of those whose previous work is frequently cited as evidence for a solar role in climate during the industrial era. Lockwood and colleagues at the Rutherford Appleton Laboratory reported in 1999 that the Sun's magnetic field has doubled over the century, and that this natural "solar forcing" will have affected the earth's climate (Nature 399 437).  Lockwood and Stamper (GRL 1999) in “Long-Term Drift Of The Coronal Source Magnetic Flux And The Total Solar Irradiance” tested the method of Lockwood et al. [1999] and found a linear relationship between this magnetic flux and the total solar irradiance. From this correlation, they showed that the 131 percent rise in the mean coronal source field over the interval 1901-1995.

Claus Frohlich, meanwhile, constructed a composite time series from satellite observations of total solar irradiance (TSI) made since the late 1970’s. His composite, the so-called ‘PMOD’ model, modifies the published results of the Nimbus7/ERB and ACRIM1 science teams to provide better agreement with the predictions of a statistical model by Judith Lean based on linear regressions against solar emission and absorption line proxies for TSI.

To learn more about this I went to Dr. Richard Willson of Columbia University, the Principal Investigator for the series of NASA ACRIM projects, designed to provide high precision monitoring of TSI and detect variations of significance for climate change and solar physics..

RICHARD WILLSON ON LOCKWOOD/FROLICH

Construction of a TSI composite time series stretching over the past, nearly three decades of satellite observations, requires connecting the results of the ACRIM1 and ACRIM2 TSI monitoring experiments across the two year ‘ACRIM gap’ between them. Two, relatively low precision satellite experiments measured TSI during the gap: the Nimbus7/ERB and the ERBS/ERBE. Unfortunately connecting ACRIM1 and ACRIM2 results using these two experiments gives dramatically different results for multi-decadal TSI composites. The Nimbus7/ERB ‘gap’ connection produces a significant upward solar trend during solar cycles 21 – 23, and a return to cycle 21 levels in cycle 24 as shown by the ACRIM TSI composite (Willson & Mordvinov, 2003). The ERBS/ERBE connection produces a multidecadal TSI composite without a significant trend. ERBS/ERBE results are by far the least reliable of the two ‘gap’ experiments and their difference from the Nimbus7/ERB results during the ‘gap’ is readily shown to be uncorrected sensor degradation. Nevertheless, Lean and

“The selective use of data and models and the rush to judgment by Lockwood and Frohlich do not lend credibility to their investigation.”

Frohlich chose to use the ERBS/ERBE connection for their (PMOD) composite. It agreed better with the predictions of Lean’s proxy model and demonstrated no significant long term trend, supporting the anthropogenic global warming scenario of the United Nations’ IPCC reportsThe recent Lockwood/Frohlich publication’s assessment depends on the absence of a significant trend in the Lean/Frohlich (PMOD) TSI composite. A more objective use of the TSI satellite observational database does not support the PMOD model or their conclusions. Just as it would be premature to claim we understand TSI variability on climate time scales with extant satellite data, it is equally premature to use the existing TSI database to relegate TSI's role in climate change to negligible levels. The selective use of data and models and the rush to judgment by Lockwood and Frohlich do not lend credibility to their investigation.  [End]

Willson believes the most convincing and recent work on the significance of TSI variability in climate change has come from Scafetta and West, experts in systems analysis who have used a phenomenological approach to study the solar impact on 400 years of a global surface temperature record since 1600. This period includes the pre-industrial era (roughly 1600–1900), when a negligible amount of anthropogenic-added climate forcing was present and the sun realistically was the only climate force affecting climate on a secular scale, and the industrial era (roughly since 1800–1900), when anthropogenic-added climate forcing has been present in some degree. In their abstract, they noted, the use a recent secular Northern Hemisphere temperature reconstruction (Moberg et al., 2005), three alternative total solar irradiance (TSI) proxy reconstructions (Lean et al., 1995; Lean, 2000; Wang et al., 2005) and a scale-by-scale transfer climate sensitivity model to solar changes (Scafetta and West, 2005, 2006).

The phenomenological approach they propose is an alternative to the more traditional computer-based climate model approach, and yields results proven to be almost independent of the secular TSI proxy reconstruction used. They found good correspondence between global temperature and solar induced temperature curves during the pre-industrial period such as the cooling periods occurring during the Maunder Minimum (1645–1715) and the Dalton Minimum (1795–1825). And importantly, the sun might have contributed approximately 50% of the observed global warming since 1900 (Scafetta and West, 2006).

As Dr. Willson noted, Scafetta and West use much more sophisticated analytical techniques than Lean, Frohlich or Lockwood and their approach doesn't rely on complex and uncertain modeling of climate phenomena. The simple statistics used by Lean, Frohlich, Lockwood et. al. and the large uncertainties associated with TSI forcing models in GCM's cannot compete with Scafetta's phenomenological approach in deriving new understanding of complex systems from observational data.

SCAFETTA’S RESPONSE TO LOCKWOOD AND FROLICH

Lockwood and Frolich are using the PMOD TSI composite (prepared by Frolich himself) to deduce their conclusions. By using ACRIM TSI composite (prepared by Willson) the result would be quite different. Lockwood and Frolich just "assume" that ACRIM is wrong and PMOD is right, and do not care to repeat their calculation with the ACRIM TSI composite. In our own works, we always try to repeat the calculations with both data sets to be fair to both groups.

But, what is the difference between ACRIM and PMOD TSI composites?

This is an important question because many scientists do not seem to know the real difference. ACRIM is just a composite of the published TSI satellite data, everybody with basic mathematical knowledge can obtain such a result by downloading the published satellite data and following the instruction found in the Willson and Mordinov's paper. So, ACRIM faithfully reproduces the observations as the experimental groups have really seen.