The Mystery in the Debate on Climate Change
During the past few months the effect of cosmic rays on global warming has been debated in the Danish newspaper Jyllands-Posten. Dorthe Dahl-Jensen and Bo Møllesøe Vinther have entered into the debate pointing out that measurements of cosmic radiation show that cosmic rays cannot have contributed significantly to the global warming observed during the past 55 years:
Translated opinion piece printed in Jyllands-Posten the 27th of February (originally in Danish):
The Mystery in the Debate on Climate Change
By Bo Møllesøe Vinther, post.doc. and Dorthe Dahl-Jensen, professor
MEASUREMENNTS SHOW, that the rise of approximately 0.6°C in mean temperature that happened during the past 55 years cannot be explained by changes in cosmic radiation. With that knowledge it is a mystery how the debate on cosmic ray influence on global warming can be so heated.
In the documentary "The Climate Mystery" (shown on TV2 the 30th of January) the theory is presented that cosmic rays plays a decisive role in shaping the global climate. This is based on the idea that at lower cosmic radiation gives fewer clouds in the atmosphere leading to higher temperatures here on Earth.
Subsequently the debate has been ongoing: Can global warming be explained by changes in cosmic radiation instead of greenhouse gas emissions? Or is the warming caused by a bit of both?
Luckily we need neither guess nor debate to get the answers to these questions, if we limit ourselves to look into the causes of the global warming during the past 55 years.
Because from 1953 an onwards systematic observations of both cosmic radiation and global temperature conditions have been carried out. Hence the figure above shows changes in the global average temperature and changes in cosmic radiation from 1953 and onwards. It can be seen that the temperature has been rising by 0.6 degrees C during the past 55 years, while no clear trend can be seen in cosmic radiation during the same period.
It is important to stress that this does not mean that the theory on cosmic ray influence on global climatic conditions is without significance.
Changes in cosmic radiation can very well have had an influence on climate, and the 11-year cycle visible in cosmic radiation can be discerned in the temperature curve in the figure.
But the measurements also do show that the about 0.6 degrees C that the average temperature has risen during the past 55 years cannot be due to changes in cosmic radiation.
Average global temperature (blue curve) and cosmic radiation (red curve).