‘Two-Thirds Of Climate Warming’
Since 1750 Due To ‘Solar Causes’
– Dr. Alan D. Smith, Geoscientist
Though advocates of the dangerous anthropogenic global warming (AGW) narrative may not welcome the news, evidence that modern day global warming has largely been driven by natural factors – especially solar activity – continues to pile up.
Much of the debate about the Sun’s role in climate change is centered around reconstructions of solar activity that span the last 400 years, which now include satellite data from the late 1970s to present.
To buttress the claim that solar forcing has effectively played almost no role in surface temperature changes since the mid-20th century, the IPCC has shown preference for modeled reconstructions of solar activity (i.e., the PMOD) that show a stable or decreasing trend since the 1970s. Why? Because if the modeled results can depict steady or decreasing solar activity since the last few decades of the 20th century – just as surface temperatures were rising – then attributing the post-1970s warming trend to human activity becomes that much easier.
The trouble is, satellite observations using ACRIM data (which have been affirmed to be accurate by other satellite data sets and are rooted in observation, not modeled expectations) indicate that solar activity did not decline after the 1970s, but actually rose quite substantially. It wasn’t until the early 2000s that solar activity began to decline, corresponding with the denouement of the Modern Grand Maximum.
ACRIM Composite Is ‘Data Driven’, While The PMOD Composite Is ‘Model Driven’
• Comparison of the results from the ACRIM3, SORCE/TIM and SOHO/VIRGO satellite experiments demonstrate the near identical detection of TSI variability on all sub-annual temporal and amplitude scales during the TIM mission. A solar magnetic activity area proxy [developed in 2013] for TSI has been used to demonstrate that the ACRIM TSI composite and its +0.037 %/decade TSI trend during solar cycles 21–23 [1980s-2000s] is the most likely correct representation of the extant satellite TSI database.
• The occurrence of this trend during the last decades of the 20th century supports a more robust contribution of TSI variation to detected global temperature increase during this period than predicted by current climate models.
• One of the most perplexing issues in the 35 year satellite TSI database is the disagreement among TSI composite time series in decadal trending. The ACRIM and PMOD TSI compostite time series use the ERB and ERBE results, respectively, to bridge the Gap. Decadal trending during solar cycles 21–23 is significant for the ACRIM composite but not for the PMOD. A new  TSI-specific TSI proxy database has been compiled that appears to resolve the issue in favor of the ACRIM composite and trend. The resolution of this issue is important for application of the TSI database in research of climate change and solar physics.
• The ACRIM TSI composite is data driven. It uses ACRIM1, ACRIM2, ACRIM3 and Nimbus7/ERB satellite results published by the experiments’ science teams and the highest cadence and quality ACRIM Gap database, the Nimbus7/ERB, to bridge the ACRIM Gap.
• The PMOD TSI composite, using results from the Nimbus7ERB, SMM/ACRIM1, UARS/ACRIM 2 and SOHO/ VIRGO experiments, is model driven. It conforms TSI results to a solar-proxy model by modifying published ERB and ACRIM results and choosing the sparse, less precise ERBS/ERBE results as the basis for bridging the ACRIM Gap (Frohlich and Lean 1998).
• The Earth’s climate regime is determined by the total solar irradiance (TSI) and its interactions with the Earth’s atmosphere, oceans and landmasses. Evidence from 35 years of satellite TSI monitoring and solar activity data has established a paradigm of direct relationship between TSI and solar magnetic activity. (Willson et al. 1981; Willson and Hudson 1991; Willson 1997, 1984; Frohlich and Lean 1998; Scafetta and Willson 2009; Kopp and Lean 2011a, 2011b) This paradigm, together with the satellite record of TSI and proxies of historical climate and solar variability, support the connection between variations of TSI and the Earth’s climate. The upward trend during solar cycles 21–23 coincides with the sustained rise in the global mean temperature anomaly during the last two decades of the 20th century.
Assessment Of The Sun’s Climate Role Largely Depends On The TSI Model Adopted
• [T]he IPCC neglects strong paleo-climatologic evidence for the high sensitivity of the climate system to changes in solar activity. This high climate sensitivity is not alone due to variations in total solar irradiance-related direct solar forcing, but also due to additional, so-called indirect solar forcings. These include solar-related chemical-based UV irradiance-related variations in stratospheric temperatures and galactic cosmic ray-related changes in cloud cover and surface temperatures, as well as ocean oscillations, such as the Pacific Decadal Oscillation and the North Atlantic Oscillation that significant affect the climate.
• [T]he cyclical temperature increase of the 20th century coincided with the buildup and culmination of the Grand Solar Maximum that commenced in 1924 and ended in 2008.
• Since TSI estimates based on proxies are relatively poorly constrained, they vary considerably between authors, such as Wang et al. (2005) and Hoyt and Schatten (1997). There is also considerable disagreement in the interpretation of satellite-derived TSI data between the ACRIM and PMOD groups (Willson and Mordvinov, 2003; Fröhlich, 2009). Assessment of the Sun’s role in climate change depends largely on which model is adopted for the evolution of TSI during the last 100 years (Scafetta and West, 2007; Scafetta, 2009; Scafetta, 2013).
• The ACRIM TSI satellite composite shows that during the last 30 years TSI averaged at 1361 Wm-2, varied during solar cycles 21 to 23 by about 0.9 Wm-2, had increased by 0.45 Wm-2 during cycle 21 to 22 [1980s to 2000s] to decline again during cycle 23 and the current cycle 24 (Scafetta and Willson, 2009).
• By contrast, the PMOD TSI satellite composite suggests for the last 30 years an average TSI of 1366, varying between 1365.2 and 1367.0 Wm-2 that declined steadily since 1980 by 0.3 Wm-2.
Total Solar Irradiance Increased By 3 W m-2 Between 1900 And 2000
Van Geel and Ziegler, 2013 (continued)
• On centennial and longer time scales, differences between TSI estimates become increasingly larger. Wang et al. (2005) and Kopp and Lean (2011) estimate that between 1900 and 1960 TSI increased by about 0.5 Wm-2 and thereafter remained essentially stable, whilst Hoyt and Schatten (1997) combined with the ACRIM data and suggest that TSI increased between 1900 and 2000 by about 3 Wm-2 and was subject to major fluctuations in 1950-1980 (Scafetta, 2013; Scafetta, 2007).
• Similarly, it is variably estimated that during the Maunder Solar Minimum (1645- 1715) of the Little Ice Age TSI may have been only 1.25 Wm-2 lower than at present Wang et al., 2005; Haig, 2003; Gray et al., 2010; Krivova et al., 2010) or by as much as 6 ± 3 Wm-2 lower than at present (Shapiro et al., 2010; Hoyt and Schatten, 1997), reflecting a TSI increase ranging between 0.09% and 0.5%, respectively.
Graph Source: Soon et al., 2015
After Removing Instrumental ‘Adjustments’, Urban Bias, Temperatures Follow Solar Activity
The combined Hadley Centre and Climatic Research Unit (HadCRUT) data set — which is featured in the Intergovernmental Panel on Climate Change (IPCC) reports — underwent a revision from version 3 to version 4 in March of 2012. This was about a year before the latest IPCC report was to be released (2013). At the time (early 2012), it was quite inconvenient to the paradigm that HadCRUT3 was highlighting a slight global cooling trend between 1998 and 2012, as shown in the graph below (using HadCRUT3 and HadCRUT4 raw data from WoodForTrees). So, by changing versions, and by adjusting the data, the slight cooling was changed to a slight warming trend.
This 0.5°C rise in global temperatures between 1880-1950 (and 0.6°C between 1880 and 1940) can clearly be seen in the NASA GISS graph from 1987:
Schneider, S. H. 1989. The greenhouse effect: Science and policy. Science 243: 771-81.
Today, it is no longer acceptable for the NASA global temperature data set to graphically depict a strong warming trend during the first half of the 20th century. This is because anthropogenic CO2 emissions were flat and negligible relative to today during this abrupt warming period.
So as to eliminate the inconvenience of a non-anthropogenic warming trend in modern times, NASA has now removed all or nearly all the 0.5°C of warming between 1880 and 1950.
• [B]etween 65-80% of the apparent warming trend over the 1961-2000 period for the Beijing and Wuhan station records was probably due to increasing urban heat islands. [T]he temperature trends increase from +0.025°C/decade (fully rural) to … +0.119°C/decade (fully urban). … If we assume that the fully rural stations are unaffected by urbanization bias, while the other subsets are, then we can estimate the extent of urbanization bias in the “all stations” trends by subtracting the fully rural trends. This gives us an estimate of +0.094°C/decade urbanization bias over the 1951-1990 period [+0.38°C of additional non-climatic warmth]– similar to Wang & Ge (2012)’s +0.09°C/decade estimate.
•We have constructed a new estimate of Northern Hemisphere surface air temperature trends derived from mostly rural stations – thereby minimizing the problems introduced to previous estimates by urbanization bias.
• Similar to previous estimates, our composite implies warming trends during the periods 1880s-1940s and 1980s-2000s. However, this new estimate implies a more pronounced cooling trend during the 1950s-1970s. As a result, the relative warmth of the mid-20th century warm period [1930s-1950s] is comparable to the recent [1980s-2000s] warm period – a different conclusion to previous estimates. Although our new composite implies different trends from previous estimates, we note that it is compatible with Northern Hemisphere temperature trends derived from (a) sea surface temperatures; (b) glacier length records; (c) tree ring widths.
• However, the recent multi model means of the CMIP5 Global Climate Model hindcasts failed to adequately reproduce the temperature trends implied by our composite, even when they included both “anthropogenic and natural forcings”. One reason why the hindcasts might have failed to accurately reproduce the temperature trends is that the solar forcings they used all implied relatively little solar variability. However, in this paper, we carried out a detailed review of the debate over solar variability, and revealed that considerable uncertainty remains over exactly how the Total Solar Irradiance has varied since the 19th century.
• When we compared our new composite to one of the high solar variability reconstructions of Total Solar Irradiance which was not considered by the CMIP5 hindcasts (i.e., the Hoyt & Schatten reconstruction), we found a remarkably close fit. If the Hoyt & Schatten reconstruction and our new Northern Hemisphere temperature trend estimates are accurate, then it seems that most of the temperature trends since at least 1881 can be explained in terms of solar variability, with atmospheric greenhouse gas concentrations providing at most a minor contribution.
• This contradicts the claim by the latest Intergovernmental Panel on Climate Change (IPCC) reports that most of the temperature trends since the 1950s are due to changes in atmospheric greenhouse gas concentrations (Bindoff et al., 2013).
New Paper: Since 1750, About 0.8°C – 0.9°C Of CET Increase Is Due To Solar Forcing
Yearly mean temperatures in the CET [Central England Temperature] record show an increase in temperature of approximately 1.3°C degrees from the end of the 17th Century to the end of the 20th Century/beginning of 21st Century. … Subtle difference in timing between the warming/cooling phases between the Central England record and the other localities may reflect local climate variation, but the similarity in events between continents suggests the CET [Central England Temperature] record is recording global temperature patterns.
Records of sunspot numbers began in 1610 such that detailed estimates of solar variation for the years covered by the CET record can be made without resort to the use of proxy data. Reconstructions of TSI [e.g. 16-18] differ in magnitude (Table 1), but there is agreement in form with 4 peaks and 4 to 6 troughs occurring over the time-scale of the CET record (Fig. 4). These are: a minimum in TSI associated with the Maunder Sunspot Minimum in the latter half of the 17th Century; a peak, possibly bi-modal approaching modern TSI values during the 18th Century; a well-defined trough corresponding with the Dalton Sunspot Minimum between 1800- 1820; a poorly defined TSI peak in the mid 19th Century; a reduction in TSI during the late 19th Century; increasing TSI during the early 20th Century; a decrease in TSI from around 1950- 1975; and a second phase of TSI increase in the late 20th Century [1980s-2000s]. There is good correspondence with TSI throughout the CET record, with warm events correlating with high TSI and cool phases correlating with plateaus or decreases in TSI .
However, for temperature increases from the beginning of the Industrial Revolution (Maunder Minimum and Dalton Minimum to end of 20th Century), high TSI models can account for only 63-67% of the temperature increase. This would suggest that one third of Global Warming/Climate Change can be attributed to AGW. … Approximately two-thirds [0.8°C to 0.9°C] of climate warming since the mid-late 18th Century [1.3°C] can be attributed to solar causes, suggesting warming due to anthropogenic causes over the last two centuries is 0.4 to 0.5°C.
All Over The Globe, Trends In Solar Forcing Correlate With Temperature Changes
“[T]he period just before AD 1950 was substantially warmer than more recent decades.”
“[I]n the framework of empiric [observable] models, the estimate of the solar activity contribution in the variation in the air global temperature in the 20th century is about 70%.” – Kovalenko and Zherebtsov, 2014