The document summarizes evidence of climate change from increasing greenhouse gas concentrations to rising global temperatures. It notes that carbon dioxide, methane and nitrous oxide levels in the atmosphere are unprecedented over the last 800,000 years. Multiple lines of evidence show a clear warming trend, including rising temperatures in the atmosphere and oceans, melting ice and snow, and sea level rise. Human influence on the climate system through greenhouse gas emissions is evident. Limiting climate change will require substantial reductions in emissions.