Two years ago, this December, I wrote an essay titled “Sun and Climate Change”. The essay opened with this summary statement:
Climate change has always been underway on Earth. Periods of cooling, then warming, then cooling, etc. are historical facts. These changes, over millions of years, have had natural causes that do not include burning of fossil fuels.
Correlation might mean causation. But no correlation clearly means no causation. The ice core and ocean bottom core data that provide a look back into time, show that atmospheric carbon dioxide (CO2) lags global temperature change. It says that CO2 begins to increase after the global temperature begins to increase and it decreases after the temperature decreases. So CO2 does not cause temperature to change. Yes, I am aware that CO2 plays a small role as a greenhouse gas. But it is water, in the form of vapor and clouds, which does 90% of the greenhouse work.
The Sun, however, has correlation with climate change. After many years of low solar activity (known as the Sporer, Maunder and Dalton Minimums), a comparatively cool climatic period followed that lasted from 1450 to 1820. This cool period is known as The Little Ice Age. Then came many years of increasingly greater solar activity that stretched into the 20th century. Some solar scientists say that this period has been the most active in the last 11,000 years. Global warming has been a consequence of these more active, recent solar cycles.
So where are we now? At the moment, the global temperature is falling. The global temperature is cooler now than it was at the end of the last century. Figure 1, shows how the global temperature has been declining. The solar activity is down; in fact, August 2008 was the first calendar month in 100 years that no sunspots were recorded. Sunspots appear to be a reliable proxy for solar activity. Will this period of cooling last? I don’t know. I hope that we do not descend into another Ice Age, Little or Big. I would rather have warming. What I am reasonably confident of is that fossil fuel use restrictions (in order to reduce atmospheric CO2) will make little difference relative to global warming. I am reasonably confident that the Sun is the critical player here and there is little we can do to change whatever the Sun decides to do. Even though the exact mechanism linking the Sun and global climate change has not yet been definitively established, it is kind of like gravity–it is obvious even if we cannot fully define it.
Two years later some tweaking could be done to the preceding but for the most part it is accurate and further, the intervening time has provided even more compelling evidence.
Solar Activity, Solar magnetism, Solar cycles, and Sunspots will be discussed in this and future postings.
A new peer-reviewed paper was recently published in the Journal of Geophysical Research: (the source is the Blog IceCap. To read more click here)
...that reconstructions of total solar irradiance (TSI) show a significant increase since the Maunder minimum in the 1600’s during the Little Ice Age and shows further increases over the 19th and 20th centuries. The TSI is estimated to have increased 1.25 W/m2 since the Maunder minimum ………..
It remarkable that the authors say that most of the warming since 1850 can be accounted for by the increase in solar activity:
Use of the Stefan-Boltzmann equation indicates that a 1.25 W/m2 increase in solar activity could account for an approximate .44C global temperature increase [the HADCRU global warming from 1850 to 2000 is .55C].
The paper is Reconstruction of solar spectral irradiance since the Maunder Minimum, by N.A. Krivova, L.E. A. Vieira, S. K. Solanki
Journal of Geophysical Research
For more on this topic see Sun and Climate Change Part 2 Sun Spots