Wanting to look at solar irradiance against global temperature anomalies in more detail (than in my last article on climate) and over a longer time period, I prepared a chart comparing global temperatures to solar irradiance over the period of 843 to present times.

Solar radiance and temperature data going back hundreds of years is obviously reconstructed information, interpreted and extrapolated based on other factors ranging from tree-rings to sun spot observations to particle measurements in ice cores and so on. As you can see, there is a significant difference in the data sets (Bard vs Lean); the chart I prepared in a prior article contains only solar irradiance from direct observation which, while more accurate, spans only 30 some odd years. Sunspot records have been kept for much longer, and date back hundreds of years.

Click on image for full-size chart

NASA (source of the balance of these images; check link for data and discussion) analysis meets up with that from the IPCC: while there is a solar impact on temperature change, solar activity is but one of many causative factors which can not on its own explain the temperature anomalies we are experiencing.

NASA pegs the influence of the sun as approximately 1/5th that of CO₂, which is more or less in line with conclusions made by both the U.S. NOAA NCDC and the U.N. Intergovernmental Panel on Climate Change (IPCC).

If you've not already done so, I recommend reading the IPCC Summary for Policymakers (PDF), a readable piece published as part of its latest report, released 17 November 2007, which helps put context around the science they are relying upon to drive their policymaking agenda.

In an installment coming soon, I'll try to outline where I am going with all of this.