12 Mar 2008
03 Dec 2007
On Sunday last week, a global warming debate was held at the Hebrew University, in front of a large public audience. The speakers included myself, and Prof. Nathan Paldor from the HU, on the so called sceptic side, and Prof. Dan Yakir (Weizmann) and Prof. Colin Price (Tel-Aviv Univ.) on the anthropogenic greenhouse gas (AGHG) side.
You can watch the debate, in Hebrew at the Authority for Community and Youth of the Hebrew University. Since most of the readers are not from Israel (98% of the visitors to sciencebits.com), here is a short synopsis. It is followed by a detailed response to the claims raised against the cosmic ray climate link.
27 May 2007
05 Feb 2007
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 Tx2, in response to a doubled atmospheric CO2 content, which is equivalent to a radiative forcing of 3.8 W/m2. Thus, &Delta Tx2 = 3.8 W/m2 λ
17 Sep 2006
appeared in nature. In it, Kanipe explains the solar → cosmic-ray → climate connection, and the planned CLOUD experiment in CERN, expected to finally resolve the issue. Given that my work is mentioned in the review, I through I should mention a few relevant points.
General RemarksThe 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.
On long time scales, it appears that our journey through the Milky Way is responsible for large climate variations. Each time we pass through spiral arms of the galaxy, we witness a higher flux of cosmic rays, which in turn reduce the global temperature. Read more about the effect and the evidence in this article.