By Bill McKibbenIts not just Sandy. Sandy was off-the-charts terrible, a storm that broke every record in the books: for storm surge, for barometric pressure, for sheer size. But it also blew in toward the end of what will be the warmest year in North American history. It was a year that already had seen a summer-in-March heat wave described by meteorologists as the most statistically freakish weather event in the continents history, an epic drought that raised grain prices 40 per cent around the world and a record-setting melt of Arctic ice.It was a year in which scientists at NASAs Goddard Institute for Space Studies, who couldnt take the subway to their Manhattan offices in the days following Sandy, calculated that the one-degree rise in global temperature weve already seen has raised the chance of extreme heat events by an order of magnitude.In other words, this year has been a wake-up call. Theres no longer any room for doubt or for wishful thinking about the future. We know the damage that global warming has done so far, and we can predict with ugly certainty what will happen if we dont change course.The worlds governments the Group of Eight, the Group of 20, Brazil, Indonesia, Russia, China, the U.S. have all agreed to try to prevent the planets temperature from rising by more than two degrees. Thats too high a threshold weve already seen that a one-degree rise is melting the Arctic but its the red line the world has drawn, and its better than nothing.The worlds scientists have agreed, roughly, about how much more carbon we can emit and have a reasonable chance of staying below that two-degree line: about 500 billion tonnes by 2050. At current rates of emissions, well blow past that mark in less than 15 years.Well have our work cut out for us to meet that target in the best of circumstances. But heres a really scary complication: a number recently supplied by the Carbon Tracker Initiative in Britain. The worlds fossil-fuel companies, and the countries that operate like fossil-fuel companies (think Venezuela or Kuwait), already have about 2.8 billion tonnes of carbon in their reserves, five times more than the most conservative governments on Earth think is safe to burn. That coal and oil and gas hasnt yet been taken from the ground, but the companies and governments that own it clearly plan to extract it. Theyve declared it to the U.S. Securities and Exchange Commission, borrowed money against it, sold shares based on it. And they are searching for more. Exxon alone already has in its reserves six per cent of the carbon necessary to take us past two degrees, and they boast of spending $100 million a day looking for more.This math has a clear pragmatic meaning: We have to figure out how to keep that coal and oil and gas in the ground so it never gets burned, and the only way to do that is by speeding up the transition to renewable energy. That will require spending on research, and it will require a stiff price on carbon to spur conservation. That will be hard, but its not impossible. Germany is the one big country thats taken this crisis seriously, and there were days this summer when it generated more than half its power from solar panels within its borders. Germanys program isnt perfect, but then, Germany doesnt have Florida and Arizona and New Mexico and the California desert.The math has a clear moral meaning too: Companies that are determined to continue searching for and encouraging the use of fossil fuel are, in the age of global warming, rogue forces. They could choose instead to be part of finding solutions by spending more of their massive research budgets on developing clean energy instead of finding and marketing more fossil fuels. Instead, they make massive political contributions to ensure their continued input on the laws that affect them. (Just weeks before Sandy, Chevron gave $2.5 million to a conservative super PAC with close ties to House Speaker John A. Boehner.)Reining in the fossil-fuel purveyors will probably require revoking their social license, as we did in the past with tobacco companies and with firms that did business in apartheid South Africa. Until oil companies decide to stop blocking change in Washington and other world capitals and start turning themselves from fossil-fuel companies into energy companies, their favored status with its tax breaks and other perks should be revoked.All of us, clearly, help fuel global warming. But we dont always have the choice not to because we live in a world with highways instead of trains and subsidized oil instead of subsidized solar power. We can make changes in our personal lives, but until we can break the power of the fossil-fuel industry, its useless to expect our leaders to act. The 20-year bipartisan resistance in Washington to making real progress on climate is the ultimate proof of the industrys power.This year should have opened our eyes. And now that theyre open, maybe well finally read the math thats written on the wall. Bill McKibben is the founder of the global climate action campaign 350.org. He wrote this for the Los Angeles Times.