Johann Hari: The storm clouds that hang over John McCain

Will Hurricane Gustav blow over the presidential election, or have the levees of Republicanism creaked a little more? The start of the Republican National Convention has been displaced by a 150mph live-action replay of the early stages of the party's foulest domestic failure: the needless drowning of 1,836 of the poorest, blackest Americans while the President strummed his guitar on stage. The worst has been averted this time – but the hurricane should blow back into the debate the dangers of a McCain presidency.

It's no coincidence that the US – along with the rest of us – is now facing fiercer hurricanes, more often. Professor Kerry Emmanuel has shown that, since the mid-1970s, hurricanes across the world have doubled in intensity as a direct result of greenhouse gas emissions. Warm evaporating water provides fuel for hurricanes, making it possible for them to run further and destroy more.

Katrina was a small hurricane until it passed over the warmed-up Gulf of Mexico – when it picked up fuel and smashed into New Orleans. The city's mayor, Ray Nagin, warned that Gustav was particularly dangerous because it was passing over a Gulf that is an artificially warmed 90 degrees.

It's hard to pin any specific weather event on global warming, but this is undeniably part of a provable pattern predicted by climatologists. Hurricanes are spreading further too: in 2004, the first hurricane in human history to form in the south Atlantic hit Brazil. It could be coincidence that Katrina and Gustav came as the amount of heat-trapping gases in the atmosphere reached dangerous levels – but only a fool would bet on it.

So what is McCain's response to this national security threat? He claims to be worried about global warming – but he is taking huge sums from Big Oil and in return opposes extra funds for renewable energy. His commitment to the issue was best demonstrated this week in his pick of a Vice-President: Sarah Palin says global warming is "not man-made".

She's a denier married to an oilman, who even wants to take polar bears off the endangered species list because she believes there is no risk to them. (This is part of a wider lack of scientific understanding: she thinks creationism is "a credible scientific theory" too.) If McCain – a 72-year-old cancer survivor – dies in office, we get Dick Cheney with breasts as President.

Indeed, McCain's policies would make America more vulnerable to hurricanes twice over. Not only would he increase warming gases; to get to the fossil fuels that belch them out, he wants to drill for oil on wetlands. But these lush patches provide a protective buffer for hurricanes: every mile of wetlands trims three to nine inches off a storm surge. Suddenly "drill here, drill now" doesn't sound so populist.

And when the disasters come, McCain will not adequately protect the victims. He is no doubt glad to have an excuse to cancel George Bush's address to the Minneapolis convention, but he is implicated at every stage in the President's failure to make New Orleans safe – then, and now. While McCain claims he was "immediately" appalled by Bush's response, at the time he was literally chuckling with Bush. We have it on camera. Bush touched down in Phoenix as Katrina struck to present McCain with a giant cake to celebrate the Senator's 69th birthday. McCain hugged him and they told lots of gags. The cake was left on the airstrip to melt in the rain.

McCain voted repeatedly against a Senate investigation into what went wrong during Katrina. Evidently, he didn't think it was worth looking into the fact that for years before Katrina, Louisiana howled at the slashing of levee funding by 44 per cent to pay for tax cuts for the rich. Even the money they were given was being handed on to incompetent Bush cronies rather than the best people for the job.

The Army Corps of Engineers now admits, for example, that they knowingly installed broken pumps manufactured by a company headed by Jeb Bush's ex-business partner and campaign donor. The same people have been given a lackadaisical contract to rebuild the levees by 2011. McCain then voted against extending unemployment benefits and medical care to Katrina refugees, or even giving extra cash for new radio systems for the emergency services.

Of course, if Obama makes any of these points he will be accused of "politicising the tragedy". But what is more political than recklessly altering the world's weather-systems and failing to protect the victims? Hurricane Gustav could yet be a change in the wind – in every sense.

j.hari@independent.co.uk