personal research

Cosmic Rays and Climate

Solar Activity and Climate

It is already more than 200 years since Sir William Herschel claimed that variations in solar activity affect climate on Earth. Since he did not have any reliable temperature measurements, Herschel looked for indirect proxies. He compared the price of wheat in the London wheat exchange to the solar activity as mirrored in the sunspot number, and found a correlation between them.

With the exception of those who have been living in a dark cave, it is well known that Earth has warmed over the 20^th century. Anyone who reads papers or watches TV knows that it is humans who are those responsible for this warming. According to most media sources, and unfortunately according to many academics, there is no room anymore for any discussion of questions concerning the nature of the warming and its causes.

What is climate sensitivity?

The equilibrium climate sensitivity refers to the equilibrium change in average global surface air temperature following a unit change in the radiative forcing. This sensitivity (often denoted as λ) therefore has units of °C/(W/m²).

Often, instead &\lambda;, the sensitivity is expressed through the temperature change &Delta T_x2, in response to a doubled atmospheric CO₂ content, which is equivalent to a radiative forcing of 3.8 W/m². Thus, &Delta T_x2 = 3.8 W/m² λ

General Remarks

The manuscript submitted by Jahnke is an attempt to repeat analyses previously carried by myself (Shaviv PRL, 2002, New Astronomy, 2003). Although Jahnke raises a few interesting aspects, his analysis excludes several critical problems, because of which he obtains his negative result, that is, that there is no statistically significant periodicity in the data. By far, the most notable problem is that Jahnke's analysis does not consider the measurement errors. In his analysis, poorly dated meteorites were given the same weight as those with better exposure age determinations. As I show below, this has a grave effect on the signal to noise ratio (S/N) and consequently, on the statistical significance of any result.

A quick review of the cosmic ray / climate link.

Is 20th century global warming due to anthropogenic sources (i.e., greenhouse gasses) or natural variability? Find out here.