BY JIM GREEN
Government delegates from 99 countries met in Shanghai, China, from January 17-20 to finalise and unanimously approve a report on climate change science, which presents new and deeper evidence of the human impact on the world's weather patterns.
The report was prepared by a working group of the Intergovernmental Panel on Climate Change (IPCC), which is jointly sponsored by the United Nations Environment Program and the World Meteorological Organisation.
The report runs to over 1000 pages and is the work of hundreds of authors, editors and reviewers. It updates the IPCC's Second Assessment Report, released in 1995, and includes observations on the current changes and trends in the climate system, a reconstruction of past changes and trends, analysis of the processes involved in climate change, and predictions of future scenarios.
The IPCC is nearing completion of further reports on the impacts of climate change and on response strategies. All three reports will be accepted by the full IPCC plenary when it meets in Nairobi from April 4-6.
The IPCC's findings include:
- the global average surface temperature has increased over the 20th century by about 0.6 degrees Celsius (a slight increase on earlier assessments);
- it is "very likely" (90-99% probability) that the 1990s was the warmest decade, and 1998 the warmest year, since instrumental records were first taken in 1861;
- there has been a decline in sea-ice cover in recent decades;
- the global average sea level rose between 0.1 and 0.2 metres during the 20th century;
- it is likely that there has been a 2-4% increase in the frequency of heavy precipitation events in the mid- and high-latitudes of the northern hemisphere over the latter half of the 20th century;
- since 1950 it is very likely that there has been a reduction in the frequency of extreme low temperatures, with a smaller increase in the frequency of extreme high temperatures;
- warm episodes of the El Nino-Southern Oscillation phenomenon, which consistently affects regional variations of precipitation and temperature over much of the tropics, sub-tropics and some mid-latitude areas, have been more frequent, persistent and intense since the mid-1970s;
- in some regions, such as parts of Asia and Africa, the frequency and intensity of droughts have been observed to increase in recent decades; and
- since 1750, the atmospheric concentration of carbon dioxide has increased by 31%, methane by 151%, and nitrous oxide by 17%.
Based on historical trends, the IPCC working group also puts forward a wide range of predictions:
- the global average surface temperature is projected to increase by 1.4-5.8 degrees Celsius over the period 1990 to 2100, higher than an assessment by the same panel five years ago of a 1.0-3.5 degrees Celsius warming;
- global average water vapour concentration and precipitation (rain and snow) are projected to increase; and
- sea levels are projected to rise by 0.09 to 0.88 meters from 1990 to 2100, slightly lower than the range projected five years ago.
The report says, "Global mean surface temperature increases and rising sea level from thermal expansion of the ocean are projected to continue for hundreds of years after stabilisation of greenhouse gas concentrations (even at present levels), owing to the long time scales on which the deep ocean adjusts to climate change. Ice sheets will continue to react to climate warming and contribute to sea level rise for thousands of years after climate has been stabilised."
Research over the past five years has confirmed the impact of human activities on climate change. The report says there is "new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities".
It says that about three-quarters of the human-caused emissions of carbon dioxide to the atmosphere during the past 20 years are due to fossil fuel burning and the rest are predominantly due to land-use change, especially deforestation.
Klaus Toepfer, executive director of the United Nations Environment Program, said, "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", Toepfer said.