Tiempo Climate Newswatch

As it is looking increasingly unlikely that the United States Senate will pass a climate bill this year, environmentalists are gearing up to defend the plans by the Environmental Protection Agency (EPA) to limit greenhouse gas emissions from major polluters. "Obviously, the chances are slim that we'll see a comprehensive bill this year - but regardless, the regulations that EPA will be considering next year can achieve some pretty substantial global warming pollution reductions on their own," said Nathan Willcox of Environment America.

According to Sara Chieffo from the League of Conservation Voters, the fight will be two-fold: "One is fighting off legislative attacks to hamstring, weaken or delay EPA's ability to move forward with reductions from our nations' largest emitters" and the second is "pushing EPA to be ambitious on the direct greenhouse gas rules." Democrat senator Jay Rockefeller from West Virginia intends to seek a vote on a bill that would stop the agency from regulating stationary source emissions for two years. Others are expected to try to block climate rules through riders to appropriations bills or other legislation.

Researchers from the United Kingdom, China and Denmark have concluded that, even if all but the most far-reaching emissions control measures, such as geo-engineering, are implemented, global sea level will rise by 30-70cm this century. The team used 300 years of tide gauge measurements to reconstruct how sea level responded in the past to changes in the amount of heat reaching the Earth from the Sun, the cooling effects of volcanic eruptions and past human activities. This information was then used to model sea level under geo-engineering schemes and other emissions control scenarios over the present century.

"Natural sea-level variations caused by extreme events such as severe volcanic eruptions... were generally much smaller than those caused by anthropogenic carbon dioxide emissions or predicted under effective geo-engineering schemes," said Svetlana Jevrejeva of the National Oceanography Centre in the United Kingdom. Injections of sulfur dioxide particles into the upper atmosphere on the scale of a major volcanic eruption every 18 months would delay sea-level rise by 40 to 80 years. The researchers caution that such an approach would be costly and also risky. "We simply do not know how the Earth system would deal with such large-scale geo-engineering action," commented Jevrejeva.

A new analysis of observational data for the Antarctic coupled with climate modelling suggests that the recent trend towards increasing Antarctic sea ice could be the result of regional warming. "We just want to understand this paradox," said Jiping Liu of Georgia Institute of Technology in the United States. "For the past 30 years, the Arctic sea ice has been decreasing while Antarctic sea ice has been increasing. We've been trying to explain this."

The proposed explanation is that higher sea surface temperatures have strengthened the hydrological cycle above the Southern Ocean, with increased evaporation towards the equator resulting in greater precipitation, mostly snow, close to Antarctica. Snow stabilizes the upper ocean, insulating it from the heat stored below, as well as reflecting heat away from the ice surface. The additional precipitation also lowers the salinity of the surface water, slowing ice melt. There may come a point, though, the researchers warn, when the temperature rise is such that rainfall rather than snowfall dominates, leading to decreasing Antarctic sea ice.