The main lines of evidence for climate change are outlined. Alternative explanations to increased greenhouse gas concentrations are described. After discussing some statistical issues, attribution approaches are briefly described. Policy issues dealing with mitigation and adaptation are mentioned.

Based on observations <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$$X_1,\dots ,X_n$$</EquationSource> <EquationSource Format="MATHML"> <math xmlns:xlink="http://www.w3.org/1999/xlink"> <mrow> <msub> <mrow> <mi>X</mi> </mrow> <mrow> <mn>1</mn> </mrow> </msub> <mo>,</mo> <mo stretchy="false">…</mo> <mo>,</mo> <msub> <mrow> <mi>X</mi> </mrow> <mrow> <mi>n</mi> </mrow> </msub> </mrow> </math> </EquationSource> </InlineEquation> of successive generations of a discrete-parameter Galton–Watson branching process, one wishes to predict whether extinction or explosion will ultimately occur. This problem can be formulated as a simple...</equationsource></equationsource></inlineequation>