Lab co-director Robert Kopp helped write the “Climate Science Special Report: Fourth National Climate Assessment, Volume I,” released by the United States Global Change Research Program. This comprehensive report provides the most up-to-date climate science assessment in the world. It was compiled by 51 authors, the majority of whom were drawn from federal agencies.
Abstract
This assessment concludes, based on extensive evidence, that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century. For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.
In addition to warming, many other aspects of global climate are changing, primarily in response to human activities. Thousands of studies conducted by researchers around the world have documented changes in surface, atmospheric, and oceanic temperatures; melting glaciers; diminishing snow cover; shrinking sea ice; rising sea levels; ocean acidification; and increasing atmospheric water vapor.