350.org and many scientists say ever rising amounts of greenhouse gases — mostly carbon dioxide— are contributing to global warming. Carbon dioxide is emitted by the burning of fossil fuels like coal, oil and gas, but other gases such as methane come from natural sources, too.
A poll last December found that a growing majority of Americans think global warming is occurring and that it will become a serious problem, an Associated Press-GfK poll found.
The poll found 4 out of every 5 Americans said climate change will be a serious problem for the U.S. if nothing is done about it. That's up from 73 percent when the same question was asked in 2009.
The 350.org statement said that on Tuesday the San Francisco Board of Supervisors voted unanimously to urge the city's $16 billion pension fund to divest over $583 million from the fossil fuel industry. 350.org said divestment petitions are being considered in 100 other cities and states across the country.
The other mayors who have endorsed divesting from fossil fuel companies are from Madison, Wis., Bayfield, Wis., Ithaca, N.Y., Boulder, Colo., Eugene, Ore., Richmond, Calif., Berkeley, Calif., San Francisco, Calif., and Seattle, Wash.