The United Nations Intergovernmental Panel on Climate Change (IPCC) boldly declared in its Fourth Assessment Report (AR4) in 2007, “Most of the observed increase in global average temperatures [GAT] since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas [GHG] concentrations.” That conclusion rested in no small measure on another conclusion: variations in the Sun’s activity had little impact on global average temperature. On the basis of those two … [Read more...]