I just finished reading The Sun Kings by Stuart Clark. It’s one of best science books I’ve read in a long time. I heard an interview with the author on The Naked Scientist podcast back in April. The discussion was mainly about this largest solar magnetic storm ever to hit the Earth back in 1859. Auroras were seen as far south as Cuba. Telegraphs were disrupted. Operators were electrocuted. If a storm of equal power were to hit the Earth today the effects would be devastating. There’s a transcript of the podcast and you can just read the discussion with Clark.
The last chapter dealt with Global Warming. The suspected causes of global warming are becoming more and more like the murder suspects in Murder On The Orient Express. Everyone did it. Humans are pumping out an unprecedented amount of carbon into the atmosphere. The Sun is also having an impact. It is well established that periods of reduced sunspots corresponded to periods of global cooling and increased sunspots just the opposite. Here’s the kicker. It’s not because of solar variance.
It seems that with increased sunspots there is increased magnetic activity which blocks the amount of cosmic rays the Earth receives. There is a theory that cosmic rays may help to form clouds or rather create the nucleations necessary for droplets to condense. So if the Earth is not being bombarded by cosmic rays less clouds form and more sunlight gets through thus warming the Earth. Here is an article about a proposed experiment to test that theory. Finding a heavenly key to climate change.
Some people think that man-made causes of increased global temperature is mutually exclusive with natural causes of increased temperature. If increased solar magnetic activity is reducing cloud cover and humans reducing the amount of particulates in the atmosphere are happening at the same time that’s a double whammy. But we are also pumping out carbon dioxide and with increased numbers of factory farms our livestock are pumping out record amounts of methane and nitrous oxide. That makes it a quadruple whammy.
However it is possible there could still yet be some other unknown factor responsible for increased cloud cover when sunspots are at a minimum.
Update – It seems there is no link between cosmic rays and cloud formation. So it is still a mystery as to why fewer sunspots increase cloud cover.