"Using historic variations in climate and the cosmic ray flux, one can actually quantify empirically the relation between cosmic ray flux variations and global temperature change, and estimate the solar contribution to the 20th century warming. This contribution comes out to be 0.5±0.2°C out of the observed 0.6±0.2°C global warming (Shaviv, 2005).
Fig. 5: Solar activity over the past several centuries can be reconstructed using different proxies. These reconstructions demonstrate that 20th century activity is unparalleled over the past 600 years (previously high solar activity took place around 1000 years ago, and 8000 yrs ago). Specifically, we see sunspots and 10Be. The latter is formed in the atmosphere by ~1GeV cosmic rays, which are modulated by the solar wind (stronger solar wind → less galactic cosmic rays → less 10Be production). Note that both proxies do not capture the decrease in the high energy cosmic rays that took place since the 1970's, but which the ion chamber data does (see fig. 6). (image source: Wikipedia)
Fig. 6: The flux of cosmic rays reaching Earth, as measured by ion chambers. Red line - annual averages, Blue line - 11 yr moving average. Note that ion chambers are sensitive to particles at relatively high energy (several 10's of GeV, which is higher than the energies responsible for the atmospheric ionization [~10 GeV], and much higher than the energies responsible for the 10Be production [~1 GeV]). Plot redrawn using data from Ahluwalia (1997). Moreover, the decrease in high energy cosmic rays since the 1970's is less pronounced in low energy proxies of solar activity, implying that cosmogenic isotopes (such as 10Be) or direct solar activity proxies (e.g., sun spots, aa index, etc) are less accurate in quantifying the solar → cosmic ray → climate link and its contribution to 20th century global warming.
Summary
As explained above, there is no real direct evidence which can be used to incriminate anthropogenic greenhouse gases as the being the main factor responsible for the observed global warming. The reason these gases were blamed are primarily because (1) we expect them to warm and indeed the global temperature increased, and (2) there is no other mechanism which can explain the warming."
The short version for all you drama queens is......
ITS THE SUN STUPID
Lots of nice charts there for all you guys who think nothing is proven till someone makes a chart too.
lazs
