My colleague and friend, Prof. Jan Veizer of the University of Ottawa, has written a review on the climatic role of carbon dioxide, cosmic rays and solar variability over different time scale. Unlike other material you will find on this web site, which was written with my subjective physicist's point of view, this review was written by one of the world's leading geochemists. Originally, Prof. Veizer set out to collect the most comprehensive geochemical data set, to reconstruct the paleoclimate variations over Phanerozoic (the past 550 Million years over which there are multicellular fossils to work with). His goal was to find the climatic signature of carbon dioxide in the data. To his disappointment, there was no clear correlation between his paleoclimatic reconstruction and the CO2 reconstruction (e.g.,
25 Aug 2006
13 Jun 2006
Many physical systems have a tendency to equilibrate the energy between different subcomponents. Sometimes it is exact, and sometimes not. For example, in an acoustic wave, the wave's energy is on average half kinetic (motion of the gas) and half internal (pressure). In the interstellar medium, there is roughly the same energy in the different components, such as internal energy, turbulent energy, magnetic field and energy of the cosmic rays. Stars are no different. In the sun, there is roughly the same binding energy (which is negative) as there is thermal energy. This can also be shown using the virial theorem. In white dwarfs, the thermal energy is unimportant, instead, there the degenergy energy of the electrons is comparable to the binding energy. We can use this tendency for equipartition to estimate different stellar parameters.
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.
Twice every 117 years or so, Venus transits the disk of the sun. Here is some info on the events (and a photograph I took of it).
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.