There is the claim that sunspot numbers correlate with climate change. The pattern of sunspot numbers indeed correlates with changes in climate. But its not the whole story. While some patterns are clear, the big problem is we simply dont have enough data to work out whats going on.
The hypothesis is that …
- the high frequency energy released from sunspots causes changes in the earths ionosphere,
- that then block more of the cosmic rays that are constantly bombarding earth from outside the solar system.
- In turn, this means that cosmic rays can cause the formation of less clouds,
- and therefore more of the heat from the sun is able to warm the earths surface, because the “albedo” of the earth is reduced. Lower altitude clouds are considered to keep more heat out than they keep in.
This graph clearly shows that sunspots correlate very well with reduced cosmic rays. The correlation is highly significant. Theres enough data to settle this part of the effect. Also it suggests a simple relationship with few variables.
The next step is cloud formation. The classic school science cloud chamber experiment shows that cosmic rays seed clouds. Its settled. Yet its not so certain how much of atmospheric cloud is formed by cosmic rays. Investigations are ongoing and also available data is recent. The following graph shows some correlation, but it doesnt cover a long time period. it only really shows about 2 solar cycles. thats not enough. one cycle correlates well, one doesnt so well. which one is a typical cycle? – maybe neither is. We dont have the data. Also, as you can see, the data can be presented very differently. Heres 2 different graphs about the same thing.
Then there is also uncertainty how much albedo affects climate. We know it does, but we havent yet measured how much. Earths climate is obviously a complex system. A lot of things affect it.
This graph of sunspot numbers shows enough correlation to say it makes a difference. but it also clearly shows that sunspot numbers arent the only thing making a difference. As the sunspot cycle turns down, global temperatures dont follow it, but we can see the signature of the sunspot numbers in the shape of the graph.
Clearly sunspot numbers correlate with an affect on the climate, yet the above graph covers a short period and doesnt show how influential the sun cycles can be. The following graph covers all of the data we have about sunspot numbers. Note that the temperature line is arbitrarily placed and therefore there is no significance about where the 2 graphs overlap. Just look at the overall shape.
The above graph shows that sunspot number, and solar activity, have quite an effect on climate in the long term. However, other factors can influence the global temperature. The big dip in solar irradiance on the left is called the Maunder Minimum, and happened at the same time as the “little ice age” Yet in recent times, the global temperature has stayed higher than it would if solar activity was the only thing controlling climate.
Sunspot numbers and the solar irradiance they represent have a very significant effect on climate, but other factors are also significant. Solar activity alone cannot explain changes in Earths complex climate.