Human Farts cause GW (Global Warming)

Global-Warming Study Weighs
Impact of Human Action
By GAUTAM NAIK
May 15, 2008; Page A10

A new study says humans have changed the world's environment more by warming the climate than by directly encroaching on habitats.

The research, published Wednesday in the journal Nature, also establishes a link between climate change and narrower, continental changes such as the earlier spring flight of butterflies in California, the earlier release of pollen in the Netherlands and the increased growth of pine trees in Mongolia.

Also, the research could guide policy makers as they tussle with different approaches to fighting global warming. In an article accompanying the study, two scientists not involved with the paper say more such studies are needed "to allow decisions about adaptive measures to be based on a firmer footing."

The localized focus provides more evidence of global warming's impact on the planet's ecology and terrain.

"It's not necessarily a surprise, but the studies had not previously been done on a continental scale," said Cynthia Rosenzweig of the NASA Goddard Institute for Space Studies and the Center for Climate Systems Research at Columbia University in New York, who is lead author of the Nature paper. "Our research shows that the signals are strong." Her co-authors included an international team of more than a dozen scientists.

It is hard to draw clear-cut links between human activity -- which increases the atmospheric presence of global-warming gases such as carbon dioxide -- and its role in raising planetary temperatures, and thereby affecting physical and biological systems. The scales are vast and the time horizon stretches for decades.

Last year, the Intergovernmental Panel on Climate Change could conclude only that human-induced climate change was "likely" behind the shifts seen in biological and physical systems since 1970. The group estimated there was a 66%-to-90% probability of such a link.

The latest effort uses data from scores of on-site measurements noted in previous research papers. Dr. Rosenzweig and her colleagues used nearly 30,000 data sets to statistically establish that higher recorded temperatures -- on a global and continental basis -- are the result of human activity rather than any natural variation. They then statistically linked the warming trend to observed physical and biological changes, such as the faster melting of glaciers and the earlier flowering of 89 plant species in Washington, D.C.

The conclusion: In about 90% of the cases, such trends were consistent with the predicted effects of warmer climes.

The paper has limitations. Because of a lack of available data, it didn't explore the continental impact of climate change in Africa and South America.

The Nature study also mainly relied on site data from 1970 to 2004. Many scientists ideally prefer data sets over a longer period -- say, 50 or even 100 years -- when drawing conclusions about climate change.

Write to Gautam Naik at gautam.naik@wsj.com