Predictions of Warming Continue to Drop

The extent of human impact on climate remains a highly complex scientific matter, as witness the by the latest report from the U.N. Intergovernmental Panel on Climate Change (IPCC). “Our ability to quantify the human influence on global climate,” said the IPCC, “is limited because ? there are uncertainties in key factors.”

Indeed, global warming predictions by the IPCC for the next century have decreased by nearly 40% in the last seven years. In 1990 the first IPCC report predicted that without CO2 emission controls the average global temperature would increase 3.3 degrees C between 1990 and the year 2100 as a result of human activities such as the burning of coal and oil. Two years later and on the basis of better computer models of the global climate system, the IPCC reduced the predicted warming to 2.8 degrees C by 2100. The latest IPCC report, Climate Change 1995, reduced the predicted warming to 2 degrees C by 2100. With the cooling effect of aerosols included, the predicted warming drops to 1 degree C.

Our understanding of long-term climate change is as variable as the climate itself. V. Ramanathan of the Scripps Institution of Oceanography, a prominent member of the climate research community, said recently about current efforts to devise reliable predictions of climate change 100 years in the future, “I used to think of clouds as the Gordian knot of the problem. Now I think it is aerosols. We are arguing about everything.”

Our ability to model the future climate and predict the human impact on global temperatures cannot provide much guidance to policymakers interested in global warming.

The Fading Crisis

  • In 1990 the IPCC predicted 3.3 degrees C of global warming by 2100
  • In 1992 the IPCC predicted 2.8 degrees C of global warming by 2100
  • In 1995 the IPCC predicted 1-2 degrees C of global warming by 2100

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