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Climate Change 2013: The Physical Science Basis – Summary for Policymakers

This Summary for Policymakers (SPM) follows the structure of the Working Group I report. The degree of certainty in key findings in this assessment is based on the author teams’ evaluations of underlying scientific understanding and is expressed as a qualitative level of confidence (from very low to very high) and, when possible, probabilistically with a quantified likelihood (from  exceptionally unlikely to virtually certain).