Steady rise in global greenhouse gases continues
The amount of greenhouse gases in the earth's atmosphere continued to rise last year, reaching a level 21.5% above the 1990 baseline, the US National Oceanic and Atmospheric Administration reported this week.The US meteorological agency issued its Annual Greenhouse Gas Index (AGGI), a measure of total heat-trapping gases in the atmosphere, on Monday. It showed a 1.25% rise in total greenhouse gas levels during 2005.
"Overall, the AGGI shows a continuing, steady rise in the amount of heat-trapping gases in the atmosphere," the agency said in a statement. But it described the increase as "relatively low" compared to previous years, with the record standing at 2.8% for 1987-88.
The index takes into account the climate warming potential as well as concentrations of all major greenhouse gases. As such, it reflects the degree to which total greenhouse gas emissions affect the climate.
Carbon dioxide and nitrous oxide (N2O), a byproduct of farming and industry, rose in 2005, and methane remained constant. Levels of two hydro-fluorocarbons (CFCs), extremely potent climate-warming gases used in refrigeration and air conditioning which also destroy the ozone layer, decreased.
But it is carbon dioxide that accounts for most - 62% - of greenhouse warming produced since 1990. During 2005, CO2 rose from 376.8 to 378.9 parts per million in 2005, compared to its pre-industrial level of around 278.9 ppm.
Scientists from NOAA, which is part of the US Department of Commerce, calculate the AGGI each year using measurements from air samples from across the globe.
These are taken at the agency's five observatories, about 100 sampling sites and along shipping routes, and sent back to the US for analysis.
NOAA administrator Conrad C. Lautenbacher said: "NOAA adds operational value to climate research by observing and quantifying the changes that are occurring around us, and reporting their effects."
The agency is working with 61 countries and the EU to develop a "global earth observation network." Its AGGI index will be included in the World Meteorological Organisation's annual Greenhouse Gas Bulletin in November.
For more information on the AGGI see here.