Natural climate variability is sufficiently large that even the record warmth of the 1980s does not allow us to proclaim beyond a reasonable doubt detection of the greenhouse effect signal from human pollution. Another decade or two of continued warming will be required for a high degree of certainty, but waiting for this added assurance is at the risk of a larger dose of climate change than if actions to slow down greenhouse gas buildups were pursued today. It is doubtful that more research will produce a consensus on the projection of regional climatic changes in less than one to two decades. -from Author