Global warming is not caused by changes in the sun’s activity – cosmic ray theory no longer viable

I have written about various theories of global warming; the most widely accepted is that it is due to green house gas emissions mainly from fossil fuel, but as we cannot verify the cause of the climate warming by experimentation, there are plenty of alternative theories, where you can pay your money and take your choice. 

One theory is that climate change has nothing to do with carbon emissions but is caused by the sun’s cosmic rays which vary in intensity. The chief proponent of this theory is Henrik Svensmark of the Danish National Space Centre. It is also supported by scientists at the Armagh Observatory in Northern Ireland and builds on a discovery relating to water droplet cloud formation by C T R Wilson who won the Nobel Prize for Physics in 1927, so there is scientific provenance for this idea. 

Last year Channel 4 TV showed a documentary “The Great Global Warming Swindle” which explained the cosmic ray theory, but the title of the documentary did not do justice to the fact that the documentary was reasonably balanced; I suppose that they have got to sell advertising somehow. 

I shall try to explain the cosmic ray theory. Cosmic rays fall on the earth from the sun. Many of them are deflected by the earth’s magnetic field and by solar wind. Solar wind consists of streams of electrically charged particles emitted by the sun.

The theory goes that when solar wind is weak (when the sun emits fewer electrically charged particles) more cosmic rays penetrate the earth; this causes more clouds to form, making the planet cooler.

When the solar wind is strong more cosmic rays penetrate causing less clouds and making the planet hotter. It was established by C TR Wilson that cosmic ray particles produce ionizing radiation (particles that can detach one atom from a molecule) and under certain conditions water droplets condense on the ions detached, forming (eventually) clouds.

There was not enough data to establish the relationship between the rises and falls in cosmic rays hitting the earth and cloud formation and the global temperature changes until recently; it was assumed that more clouds were formed and these prevented as much radiation hitting the earth than before, thereby cooling the planet, with the reverse happening to explain global warming. 

Recently Professors Sloan (of the University of Lancaster) and Wolfendale (of the University of Durham) have examined whether there is a correlation between cosmic ray intensity and cloud cover. They found only a very weak correlation. At best they found during one eleven year cycle of sun activity only a quarter of the changes in cloud variation could be explained and nothing at all in the following 11 year cycle.

They also found that massive bursts of cosmic rays from sun spot activity had no effect on cloud formation. They also examined the deflection of cosmic rays by the earth’s magnetic field; they would have expected to see a decrease in cloud cover the further away you move from the magnetic equator, as the deflection becomes greater and the quantity of cosmic rays falling on the planet becomes less. They found that the dip in cloud cover did not lessen cloud formation by more than 23%.

It is an important finding as there is a small influence, but one that the climate scientists can build into their simulation models. This research adds to the work at the Rutherford-Appleton Laboratory which shows that although solar activity has declined over the past 20 years the climate had warmed, whereas under the Svensmark theory the earth should have cooled.  

I do not suppose that Channel 4 will now commission a program called “the Great Cosmic Ray Swindle”.

The truth is that scientific hypotheses are not swindles but genuine attempts by rational learned people who have devoted lifetimes to studying a discipline in order to advance human knowledge. Sometimes they are wrong, but right now it looks as though Svante Arrhenius got it right in 1895 when he postulated that large amounts of carbon dioxide makes the atmosphere warmer.