This technical summary provides a detailed overview of the scientific basis for the key findings of the IPCC Working Group I assessment and provides a road map to the chapters of the report. It focuses on key findings, highlighting what is new since the TAR. The structure of the Technical Summary is as follows:
Section 2: an overview of current scientific understanding of the natural and anthropogenic drivers of changes in climate;
Section 3: an overview of observed changes in the climate system (including the atmosphere, oceans and cryosphere) and their relationships to physical processes;
Section 4: an overview of explanations of observed climate changes based on climate models and physical understanding, the extent to which climate change can be attributed to specific causes and a new evaluation of climate sensitivity to greenhouse gas increases;
Section 5: an overview of projections for both near and far-term climate changes including the time scales of responses to changes in forcing, and probabilistic information about future climate change; and
Section 6: a summary of the most robust findings and the key uncertainties in current understanding of physical climate change science.

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By: Working Group I of the IPCC Fourth Assessment