Evidence that global warming is caused by humans gains strength

The UN Intergovernmental Panel on Climate Change (IPCC), consisting of over 150 delegates from 100 governments, met in Shanghai, China, from 17 to 20 January. The panel reported that although there are still many gaps in the understanding of the process of global warming, reconstructions of climate data for the past 1,000 years, combined with model estimates of natural climate variations, suggest that the global warming of the past 100 years is unusual, and likely to be at least partly due to human activity. On top of this, the IPCC has also increased its prediction for the global average surface temperature rise between 1990 and 2100 from a previously predicted maximum of 3.5°C, to 1.4 – 5.8°C.

Using analysis of data from tree rings, corals, ice cores and historical records for the Northern Hemisphere, the IPCC reports that over the last 1,000 years, the 1990’s was the warmest decade, with 1998 being the warmest year. There has been a 40% decrease in the summer thickness of arctic ice in recent decades, and a 10% decrease in mid and high latitude snow-cover since the 1960’s.

The rise in temperature has coincided with a 31% increase in the atmospheric concentration of carbon dioxide since 1750 – prior to the Industrial Revolution, and is probably now at the highest level that it has been in the last 20 million years, says the IPPC.

“Intensive climate research and monitoring over the past few years has given scientists greater confidence in their understanding of the causes and effects of global warming,” said UNEP Executive Director Klaus Töpfer. “The scientific consensus presented in this comprehensive report about human-induced climate change should sound alarm bells in every national capital and in every local community. We must move ahead boldly with clean energy technologies, and we should start preparing ourselves now for the rising sea levels, changing rain patterns, and other impacts of global warming.”

In the future, the IPCC predicts that many of the northern hemisphere’s mid- to high-latitude land areas will experience an increase in rainfall, though the observed intensities and frequencies of tropical and extra-tropical cyclones currently show no clear long-term trends. Sea-levels are now projected to rise by 0.09 to 0.88 metres from 1990 to 2100, slightly lower than previously predicted.

“This report makes grim reading. Man-made climate change is likely to be worse even than we previously feared,” said Roger Higman, climate campaigner at Friends of the Earth. “Everyone on the planet is at risk. The time for debating the science of climate change is over. The truth is now clear. But we have been desperately slow in moving from discussion to action.”

“Climate change should now be at the top of the world political agenda.

In particular, the United States must end its long history of denial

about the truth of climate change and resistance to effective action,” added Higman. “President Bush must find a way to free himself from the fossil fuel lobby that paid so much money to get him elected. And European politicians must stop squabbling among themselves and put the pressure on the US to agree tough cuts in the burning of coal, oil and gas.”

In November 2000, delegates at a UN conference in The Hague on climate change failed to reach an agreement on how to cut greenhouse gas emissions (see related story).