There is a good article at Climate Progress about the role of solar cycles in climate warming. The intensity of the sun has been relatively low, which mutes the effects of greenhouse gases on global warming. There was speculation earlier last year that we could be heading toward an even lower phase, but more recent evidence and models suggest otherwise. As Joe Romm says on this new post: “2009 ends with a “sunspot surge” as solar cycle 24 revs up”.
From ClimateProgress: The 2000s were the hottest decade in recorded history by far — even though we’re at “the deepest solar minimum in nearly a century.” The 2000s were a full 0.2°C warmer than the 1990s, which of course had been the hottest decade on record, 0.14°C warmer than 1980s (according to the dataset that best tracks planetary warming). Hmm. It’s almost like the warming is accelerating.
The sun is in the pits of the deepest solar minimum in nearly a century. Weeks and sometimes whole months go by without even a single tiny sunspot. The quiet has dragged out for more than two years, prompting some observers to wonder, are sunspots disappearing
If sunspots do go away, it wouldn’t be the first time. In the 17th century, the sun plunged into a 70-year period of spotlessness known as the Maunder Minimum that still baffles scientists. The sunspot drought began in 1645 and lasted until 1715; during that time, some of the best astronomers in history (e.g., Cassini) monitored the sun and failed to count more than a few dozen sunspots per year, compared to the usual thousands.
“Whether [the current downturn] is an omen of long-term sunspot decline, analogous to the Maunder Minimum, remains to be seen,” Livingston and Penn caution in a recent issue of EOS. “Other indications of solar activity suggest that sunspots must return in earnest within the next year.”
From Climate Progress: When we last looked at the sun [please, don’t try that at home], NASA was reporting that the sunspot cycle was about to come out of its depression, if a newly discovered mechanism for predicting solar cycles — a migrating jet stream deep inside the sun — proved accurate (see National Solar Observatory, NASA say no “Maunder Minimum”). It now appears TSI is well on its way to recovering, as NASA and others had predicted
Even as Solar Cycle 24 picks up, it won’t affect global temperatures quickly. Again, as NASA explained in January:
Because of the large thermal inertia of the ocean, the surface temperature response to the 10-12 year solar cycle lags the irradiance variation by 1-2 years. Thus, relative to the mean, i.e, the hypothetical case in which the sun had a constant average irradiance, actual solar irradiance will continue to provide a negative anomaly for the next 2-3 years.