In a blunt letter to Congress, 31 leading scientific societies reaffirmed the reality that humans are causing climate change and only we can stop it. “To reduce the risk of the most severe impacts of climate change, greenhouse gas emissions must be substantially reduced,” they write. This is the umpteenth report from scientists — see, for instance, “Climate Scientists: We’re Alarmed. Here’s Why You Should Be, Too” and “IPCC Scientists Emphasize Immorality Of Inaction By Focusing On ‘Irreversible Impacts’.” It’s not even the first letter to Congress from most of these groups — 18 of them wrote a similar letter back in 2009. “Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research concludes that the greenhouse gases emitted by human activities are the primary driver,” explain the 31 scientific groups.