Readers may recall when Dr. Gavin Schmidt appeared on a television program with Dr. Roy Spencer, but by Gavin’s cowardly choice, not at the same time.
After listing the known causes for climate change aka global warming, Gavin Schmidt said:
“We’ve looked at the sun; it’s not the sun. We’ve looked at volcanoes; it’s not volcanoes. We’ve looked at the orbit; it’s not the orbit.”
Interestingly, Gavin lists solar forcing as primary cause of colder temperatures during the Maunder Minimum and “little ice age” in this 2001 paper co-authored with Mike Mann:
Science 7 December 2001: Vol. 294 no. 5549 pp. 2149-2152 DOI: 10.1126/science.1064363
Solar Forcing of Regional Climate Change During the Maunder Minimum
+ Author Affiliations
NASA Goddard Institute for Space Studies and Center for Climate Systems Research, Columbia University, New York, NY 10025, USA.
Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22902, USA
Department of Geosciences, University of Massachusetts, Amherst, MA 01003, USA
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.
The full paper is here at PSU: http://www.meteo.psu.edu/holocene/public_html/shared/articles/Shindelletal01.pdf
The conclusion reads (bold mine):
The GISS model results and empirical reconstructions both suggest that solar-forced regional climate changes during the Maunder Minimum appeared predominantly as a shift toward the low AO/NAO index. Although global average temperature changes were small, modeled regional cooling over the continents during winter was up to five times greater. Changes in ocean circulation were not considered in this model. However, given the sensitivity of the North Atlantic to AO/NAO forcing (37), oceanic changes may well have been triggered as a response to the atmospheric changes (38). Such oceanic
changes would themselves further modify the pattern of SST in the North Atlantic (39) and, to a lesser extent, the downstream air temperature anomalies in Europe.
These results provide evidence that relatively small solar forcing may play a significant role in century-scale NH winter climate change. This suggests that colder winter temperatures over the NH continents during portions of the 15th through the 17th centuries (sometimes called the Little Ice Age) and warmer temperatures during the 12th through 14th centuries (the putative Medieval Warm Period) may have been influenced by long-term solar variations.
In the paper: A History of Solar Activity over Millennia (PDF) it is demonstrated:
The modern level of solar activity (after the 1940s) is very high, corresponding to a grand maximum. Grand maxima are also rare and irregularly occurring events, though the exact rate of their occurrence is still a subject of debates. These observational features of the long-term behavior of solar activity have important implications, especially for the development of theoretical solar-dynamo models and for solar-terrestrial studies.
Another paper recently published predicts the sun is headed for a Dalton-like solar minimum around 2050
The author notes solar activity has been at a higher level in the 20th century saying”
“the Sun has emerged from a Grand Maximum, which includes solar cycle 19, the most active solar cycle in the last 400 years. Earth was cooler in Grand Minima. The trend line indicates we have entered a period of low solar activity.”
Note the red horizontal line on the graph below shows 50-year mean solar activity was at the highest levels of the past 300 years during the latter half of the 20th century.
From the WUWT Solar reference page, Dr Leif Svalgaard has this plot comparing the current cycle 24 with recent solar cycles. The prediction is that solar max via sunspot count will peak in late 2013/early 2014 (now):
Predictions are that cycle 25 will be even lower: First Estimate of Solar Cycle 25 Amplitude – may be the smallest in over 300 years
Based on the slowing of the Sun’s “Great Conveyor Belt”, NASA solar scientist David Hathaway predicted that
“The slowdown we see now means that Solar Cycle 25, peaking around the year 2022, could be one of the weakest in centuries.” He is very likely to have got the year wrong in that Solar Cycle 25 is unlikely to start until 2025.
In this paper: http://www.probeinternational.org/Livingston-penn-2010.pdf,
Livingston and Penn provided the first hard estimate of Solar Cycle 25 amplitude based on a physical model. That estimate is 7, which would make it the smallest solar cycle for over 300 years.
Yet according to Gavin in his recent television interview,
“We’ve looked at the sun; it’s not the sun.”
Right, apparently the sun can only force climate one-way.
So in the upcoming two decades, as solar activity wanes, if it becomes globally cooler, will Gavin and Mike blame the sun, or will the disavow their previous work, pointing to studies like this one?
- Claim: Solar activity not a key cause of climate change, study shows (wattsupwiththat.com)