Extreme weather and climate change present a potential threat to U.S. national security for which "we are not prepared," a study says.

The study, prepared by Harvard University, was conducted to explore the forces driving extreme weather events, their impacts over the next decade and their implications for national security planning.

Such events will affect water and food availability, energy decisions, the design of critical infrastructure and critical ecosystem resources, the report's authors said.

"Lessons from the past are no longer of great value as a guide to the future," environment studies Professor Michael McElroy said. "Unexpected changes in regional weather are likely to define the new climate normal, and we are not prepared."

That holds for both underdeveloped and industrialized countries with large costs in terms of economic and human security, the study found, and specific regional climate impacts -- droughts and desertification in Mexico, Southwest Asia, and the Eastern Mediterranean, and increased flooding in South Asia -- were singled out as being of particular strategic importance to the United States.

Extreme weather require the U.S. to improve its scientific and technical capacity to observe key indicators, monitor unfolding events, and forewarn of impending security threats as nations around the world adapt to a changing climate, the report authors said.

Activists press Obama to move on climate
Washington (AFP) Feb 11, 2013 - Activists are stepping up pressure on US President Barack Obama to issue concrete plans to battle climate change, with a major rally planned in Washington following his annual address to Congress.

More than 100 groups are planning what they hope will be the largest rally in the United States on climate change, with organizers saying that tens of thousands will descend on the National Mall Sunday with buses from 28 states.

The demonstration comes after the United States last year experienced record high temperatures, extensive drought and the devastation of superstorm Sandy which some have linked to changing climate patterns.

Advocacy groups urged Obama to lay out specific proposals Tuesday in his annual State of the Union speech. Obama spoke forcefully, albeit in general terms, on fighting climate change during his inaugural speech last month.

"We can no longer afford to wait to respond to the threat of climate change," said David Foster, executive director of the BlueGreen Alliance, a partnership of organized labor and environmental organizations.

"We can no longer wait to fix our nation's crumbling infrastructure. The systems we rely on every day are not prepared to deal with the impacts of these events," Foster told reporters on a conference call.

The BlueGreen Alliance and like-minded groups called for Obama to focus on measures including reducing carbon pollution from power plants, rebuilding the US water system and investing in alternative forms of transit.

Separately, the Center for Biological Diversity called for more ambitious steps, such as having the US Environmental Protection Agency (EPA) setting a national cap on pollution of greenhouse gases which are blamed for rising temperatures.

Obama has relied increasingly on executive authority in fighting climate change due to stiff resistance from the rival Republican Party, many of whose members question conclusions of mainstream scientists on greenhouse gases.

A proposal to set up a "cap-and-trade" system that restricts carbon emissions across the United States died in the Senate in 2010.