In a previous Climate Change Dispatch article, I noted that solar output remained at extremely high levels throughout the twentieth century. And this heightened output, which has correlated quite well with previous warm periods (e.g., Medieval Warm Period, Roman Warm Period), offers a valid explanation for the current warm period.
Climate alarmists, though, are quick to dismiss any possibility of solar impact on climate. In fact, the U.N.’s Intergovernmental Panel on Climate Change (IPCC) simply disregards solar activity as a factor in global warming. Their argument is that changes in solar irradiance (i.e., “brightness”) vary by only a few tenths of a percent. Therefore, solar variability can impose only a minor forcing on climate.
However, this completely ignores the larger, associated impacts of changes in solar activity that can indeed affect global climate.
Researchers have demonstrated that, when the sun is active, it produces a stronger solar wind. This flow of ionized particles helps to deflect some of the cosmic rays that perpetually bombard the Earth. And it is these cosmic rays that affect ionization in the troposphere, and thus the formation of clouds.
The overall mechanism essentially works like this: An active sun produces a stronger solar wind. That strengthened solar wind reduces the incoming level of cosmic rays, which in turn reduces cloud formation in the troposphere. Consequently, more solar radiation reaches the Earth’s surface, yielding a progressive rise in surface temperatures.
Conversely, a weak sun—like the one experienced during the “Little Ice Age”—means an overall increase in low altitude cloud cover, which reduces surface temperatures.
As geologic proxies have shown, changes in solar activity track very closely with the climate swings seen over the past few thousand years. Research into solar variability is now demonstrating this clear cause and effect. It would be helpful if the wider climate community gave the matter more attention.