Last week, the government released the Climate Science Special Report, the first
volume of the Fourth National Climate Assessment. It makes grim
reading – or perhaps more accurately, grim reaper –
reading. Here's what we might call the executive summary of the
Executive Summary. First, the bottom line:
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;
