evidence: What evidence exists that Earth is warming and that humans are the main cause? [...] In addition to our surface station data, we have many different lines of evidence that Earth is warming (learn more). Birds are migrating earlier, and their migration patterns are changing. Lobsters and other marine species are moving north. Plants are blooming earlier in the spring. Mountain glaciers are melting worldwide, and snow cover is declining in the Northern Hemisphere (Learn more here and here). Greenland’s ice sheet—which holds about 8 percent of Earth’s fresh water—is melting at an accelerating rate (learn more). Mean global sea level is rising (learn more). Arctic sea ice is declining rapidly in both thickness and extent (learn more). [...] Finally, no other known climate influences have changed enough to account for the observed warming trend. Taken together, these and other lines of evidence point squarely to human activities as the cause of recent global warming.