Global warming: a review of this mostly settled issue

Global warming and attendant climate change have been controversial for at least a decade. This is largely because of its societal implications since the science is largely straightforward. With the recent publication of the Fourth Assessment Report of the United Nations' Intergovernmental Panel on Climate Change (Working Group 1) there has been renewed interest and controversy about how certain the scientific community is of its conclusions: that humans are influencing the climate and that global temperatures will continue to rise rapidly in this century. This review attempts to update what is known and in particular what advances have been made in the past 5 years or so. It does not attempt to be comprehensive. Rather it focuses on the most controversial issues, which are actually few in number. Is the surface temperature record accurate or is it biased by heat from cities, etc.? Is that record significantly different from past warmings such as the Medieval Warming Period? Are human greenhouse gases changing the climate more than the sun? Can we model climate and predict its future, or is it just too complex and chaotic? Are there any other changes in climate other than warming, and can they be attributed to the warming?.