What is the evidence linking observed temperature changes and climate change to the anthropogenic increase in greenhouse gases?
• How are public health and welfare threatened by these changes to climate and the environment, now and in the future? Each element of the causal chain is discussed below. Evidence related to each element is based on the underlying scientific assessments (e.g., IPCC and USGCRP) that EPA relied on to develop the TSD to support the Administrator’s Endangerment Finding, and, where noted, is also based on the most recent scientific assessment, published in May 2010, of the NRC. 10 1. What effects do greenhouse gases have on the environment and on climate in particular? The physical effect of greenhouse gases on climate and the environment remains a basic scientific fact – greenhouse gases slow the loss of Earth’s heat, which would otherwise escape to space. Much like a blanket keeps a person warm by preventing heat loss, greenhouse gases blanket the planet and warm the Earth by trapping in heat that would otherwise escape to space. This is the Earth’s natural greenhouse effect. An increase