Scientific group: Cut carbon dioxide emissions in half

To curb global warming, we're going to have to crack down on greenhouse gases in a big way, says the American Geophysical Union.

The AGU, an organization that publishes and promotes geophysical research, issued a statement Thursday stating that, to avoid a 2-degree Celsius rise in average temperatures, carbon dioxide emissions will have to be cut in half during the century.

"In the next 50 years, even the lower limit of impending climate change--an additional global mean warming of 1 degree C above the last decade--is far beyond the range of climate variability experienced during the past thousand years and poses global problems in planning for and adapting to it. Warming greater than 2 degrees C above 19th century levels is projected to be disruptive, reducing global agricultural productivity, causing widespread loss of biodiversity, and--if sustained over centuries--melting much of the Greenland ice sheet with ensuing rise in sea level of several meters. If this 2 degree C warming is to be avoided, then our net annual emissions of CO2 must be reduced by more than 50 percent within this century," the organization stated.

Warming, the AGU further emphasized, is both real and attributable to humans. Global average surface temperatures rose on average by around 0.6 degrees Celsius from 1956 to 2006. Eleven of the years between 1995 and 2006 inclusive were warmer on average than any year since 1850.

"Evidence from most oceans and all continents except Antarctica shows warming attributable to human activities," the group said.

The looming question, of course, is how to cut emissions. Many believe that energy efficiency technologies and strategies--such as replacing conventional light bulbs with LEDs or fluorescents, or designing buildings to take advantage of passive cooling--could put a dent in emissions in the near term without breaking much of a sweat. Beyond that it's going to take a lot of money, subsidies, and time. Many have proposed replacing cars powered by gasoline with electrics or ethanol cars, but the alt-car business is in its infancy. Solar power provides an alternative to coal, but it will likely take years to build up an infrastructure.

Several politicians and scientists have begun to advocate nuclear power, but it remains controversial.