The hostile reaction to George Osborne's refusal last week to let environmental issues play a part in restoring Britain's ailing economy is unsurprising. As a swath of enraged ecologists, academics and NGOs has claimed, his party – put in power on a promise to be the greenest ever elected – is now set to acquire the mantle of being the most environmentally destructive in recent history.

You can see their point. Threatening to weaken planning regulations, reducing subsidies for solar panels, scrapping plans to increase fuel duty and providing tax subsidies for our most polluting industries – on the grounds that "endless social and environmental goals" will cause businesses to fail – are not the actions of a chancellor sympathetic to green causes.

For his part, Osborne has made it clear that short-term expediency motivates his actions: we cannot save the planet until we have saved our economy, he argues. This view is straightforward but mistaken in many ways. Consider the political issues. Exposing parts of our finest countryside, such as Chesil Beach or the Norfolk Broads, to the threat of industrial development risks alienating the strong Tory vote of these areas. David Cameron, who made much of his championship of green causes at the last election, has also been made to look foolish.

Then there are the economic concerns. Slashing support for renewable energies and providing tax relief for heavy, energy-intensive industries will only increase Britain's reliance on fossil fuels. By contrast, committing the country to the development of wave, tide and solar energy projects would have helped Britain wean itself from oil and gas, which we are importing at ever-increasing costs. This investment could also have helped create technologies, including tide and wave power plants, whose sales round the world could have made billions for Britain in future decades. A golden opportunity has been lost.

The fact that Osborne has chosen this moment to reveal his climate-sceptic colours is also intriguing. In Durban, delegates from across the globe have gathered in a bid to revitalise international agreements to curb carbon emissions and global warming. Those who looked to Britain for a lead will have noted the signals sent out by our chancellor: there is no rush and we have other priorities. Like Canada, the US and several other developed nations, Britain appears to be happy to sit back and watch as hopes of reaching a binding international deal to cut carbon emissions fade away.

Two years ago, the Copenhagen climate summit was alive with the belief that an agreement would be reached. No such expectations have been voiced in Durban, where climate negotiations seem beset by political complacency and the prospect of failure. Yet scientists' warnings have never been clearer. Organisations such as the Royal Society, Nasa, the Met Office, the national science academies of virtually every country on the planet – as well as several dozen Nobel laureates – have made it clear they think greenhouse gases are having a major impact on the planet. A US poll of 1,380 climate scientists found that 97% backed the belief that carbon emissions are raising global temperatures. The science is straightforward. Yet politicians appear less and less inclined to listen or act.

In the US, this attitude has reached extraordinary levels. Most Republican candidates for the presidency openly doubt that climate change is real and have even accused scientists of fiddling facts in a bid to garner research grants. As New Scientist put it: "When candidates for the highest office in the land appear to spurn reason, embrace anecdote over scientific evidence, and even portray scientists as the perpetrators of a massive hoax, there is reason to worry."

Britain, until recently, has escaped the worst of these anti-intellectual excesses. There are signs that this state of affairs may not last, however. Climate sceptic groups, in particular Lord Lawson's Global Warming Policy Foundation, are increasingly influencing the media. Last week, a welter of stories that openly doubted any link between climate change and humanity's industrial actions appeared in the British press. A plurality of views about global warming is healthy, but the accusation that scientists are fiddling facts simply to attract grants is extraordinary. Nevertheless, most deniers' arguments rest on this assumption. It is a distressing trend which reveals that the desire to avoid uncomfortable truths is spreading.

It is therefore worth emphasising the dire consequences of our continued failure to address climate change. If humanity cannot get its emissions to peak by 2020, there is little chance of holding down temperature rises to under 2C by 2100. Major changes to our planet will then occur. Deserts will spread, ice caps melt, sea levels rise, coastal zones will be inundated and hundreds of millions of people will be left homeless. Rising temperatures will melt the world's regions of permafrost, releasing more carbon dioxide and methane, which will raise temperatures even further.

Humanity will be left with one last line of defence – geoengineering – a business involving schemes such as the seeding of seas with iron filings to boost the growth of plankton (which absorb carbon dioxide) and the spraying of the atmosphere with sulphur aerosol particles to reflect solar radiation back into space. All are untested and highly controversial because of their potential to trigger further ecological mayhem. The fact that these ideas, for all their inherent dangers, still have scientific support reveals an uncomfortable truth: many senior researchers realise that at our present rate of inaction we will soon find ourselves living on a cruelly scorched planet. Only high-risk strategies will be left to save us.

From this perspective, our obsession with our current economic headaches looks woefully misplaced. We should note that we are in our present financial mess because we let bankers and economists take irresponsible risks. Yet that fiscal gambling is dwarfed by the risks we are how taking with our entire planet.

Britain, creator of the industrial revolution, has the longest legacy of any nation for pumping carbon dioxide into the atmosphere. We have a duty to acknowledge what we have done and to recognise what our scientists are saying about the dangers we face. More importantly, we have a moral obligation to act on those warnings. If Britain will not act, most other developed countries will not bother either. The government's refusal to address environmental issues is therefore deeply worrying. An admission of failure and a pledge to restore past promises is urgently needed. We should be under no illusions about the impact of climate change. A true global meltdown awaits us.