WASHINGTON: An island in the Indian Ocean, vital to the US military, disappears as the sea level rises. Rivers critical to India and Pakistan shrink, increasing military tensions in South Asia. Drought, famine and disease forces population shifts and political turmoil in the Middle East.

US defense and intelligence agencies, viewing these and other potential impacts of global warming, have concluded if they materialize it would become ever more likely global alliances will shift, the need to respond to massive relief efforts will increase and US forces will become entangled in more regional military conflicts.

It is a bleak picture of national security that backers of a climate bill in Congress hope will draw in reluctant Republicans who have denounced the bill as an energy tax and jobs killer because it would shift the country away from fossil fuels by limiting carbon dioxide emissions from power plants and industrial facilities.