Explorations: The Sun and Climate
News reports and Web sites regularly claim “proof” that changes in solar radiation are the cause of the average warming of the earth during the last quarter of the twentieth century and into this century. These claims are usually based on a single study or the opinion of a single scientist, or sometimes even the opinion of a politician or writer.
While much remains to be learned, one paper or hypothesis is not enough to outweigh the evidence that added greenhouse gases, not changes in solar output, are responsible for the earth’s average warming since the last quarter of the twentieth century. The evidence is strong that the total output of the sun has not changed significantly since the 1970s, when satellite measurements began. As explained in Chapter 2 of The AMS Weather Book, the relation between the sun and climate is complex and involves more than changes in total solar output.
Almost all scientists who specialize in studies of links between the sun and earth are convinced that these often complex links cannot account for most of the average warming of the earth in recent decades.
Following is a list of sources of information about the scientific study of links between the sun and earth’s climate and evidence that the sun is not responsible for recent warming.
- Spencer Weart, “Changing Sun, Changing Climate?” in The Discovery of Global Warming, Second Edition (Cambridge, MA: Harvard University Press, 2008). This is the best Web site to begin an exploration of both the history of scientific concern about connections between the sun and climate and the current scientific thinking about the question. The site has numerous links to sources of information and also to discussions of related topics.
- How the Sun Affects Climate: Solar and Milankovitch Cycles Web page on University Corporation for Atmospheric Research's Windows to the Universe Web site.
- The 2007 IPCC report includes extensive discussions of the role of solar changes and other natural factors on climate change since the 1970s. These are found in: S. Solomon, et al., Climate Change 2007: The Physical Science Basis, contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge and New York: Cambridge University Press, 2007). Chapters 2 and 9 have extensive discussions of the evidence for the roles of the sun, greenhouse gases, and other factors on global climate.