Nothing namby-pamby about Margaret Thatcher, whatever you may think of her in the round.

Nothing wishy-washy, nothing bunny-hugging, nothing lefty about the Iron Lady. And this is what she told the assembled fellows of the Royal Society on 27 September 1988: "For generations, we have assumed that the efforts of mankind would leave the fundamental equilibrium of the world's systems and atmosphere stable. But it is possible that with all these enormous changes (population, agricultural, use of fossil fuels) concentrated into such a short period of time, we have unwittingly begun a massive experiment with the system of this planet itself."

Funny old world, innit? These days, if you're a right-wing Conservative, or a right-wing commentator or blogger, it is virtually a badge of honour to proclaim that all this global warming stuff, and action taken to counter it, is a load of cobblers, nay, more: it is a fraud, perpetrated upon a deceived public by free-spending liberal or left-wing politicians who don't have Britain's own best interests at heart, and who are backed up by scientists exaggerating the problem so that they can ensure the continuation of their research funding.

Yet the woman regarded by right-wingers as their icon thought just the opposite. She was at the forefront of those who first perceived, in the late 1980s, that our increasing production of greenhouse gases was posing a real and mortal threat to the stability of the atmosphere and thus to the welfare of human society itself. Her Royal Society speech, passionate in its rhetoric, set off the second wave of environmentalism in this country (after the first one in the late 1960s). In the two years remaining of her premiership, she treated the Tory cabinet to a global-warming seminar, instigated the process of the UK cutting its carbon dioxide emissions and oversaw the establishment of the Hadley Centre at the Met Office, Britain's world-renowned institute for climate prediction and research.

Why, then, as negotiators from nearly 200 countries gather this weekend in Durban for the latest UN climate conference, is there such a rejection of Mrs Thatcher's substantial climate change legacy among those who might be termed her political successors, not only here but in America? And why should there appear to be such a growing indifference among the general public to what many good judges esteem the greatest threat our world has ever faced?

The answer to the first question is a sad, not to say a tragic one: the issue has become politicised. I think it is fair to say the politicisation began on the left, especially among young radicals who saw climate change as a consequence of capitalism, and proceeded to campaign for action in traditional radical terms, with protests, and occupations, and name-calling ("climate change deniers"); and to this there was an instinctive reaction from the right, which took the view that if long-haired sub-Marxist youths want to close power stations and cover the countryside in wind turbines, then we are most definitely against it. At all events, the issue is now polarised, right and the left, and in America has even become poisonous, with many leading Republicans equating action on global warming with abortion, as the work of the devil.

At the real heart of the right-wing reaction, though, has been the matter of cost. Tackling carbon emissions means changing energy systems, which is very expensive. The initial emissions-cutting treaty, the 1997 Kyoto protocol, was drawn up in such a way that only the rich industrialised nations had to bear this cost, with China, India and other developing countries not required to take action. This was for reasons of historical equity: the rich countries put most of the excess CO2 into the atmosphere in the first place. But in terms of contemporary equity, it is increasingly seen as completely unfair, not least as China and India have gone from being "developing" countries to industrial giants, with no restrictions on their carbon emissions; indeed, China has overtaken the US to become the world's leading CO2 emitter, with India now in third place.

The issue of cost is also part of the answer to the second question: why such apparently diminishing public involvement with global warming? The expense of Britain decarbonising its power sector with renewable energy – wind and solar power – is beginning to appear on household energy bills, and will increase, and will be increasingly resented by people who cannot immediately see the reason for it. For that's the other point. To most ordinary people in Britain, climate change does not obviously seem to be happening.

Although in recent years there has been a long series of extreme events which appear clearly linked to a warming world, from the mind-boggling melt-back of the Arctic sea ice in September 2007 to the smashing of the British air temperature record on 10 August 2003 – it jumped from 98.8F (37.1C) to 101.3F, (38.5C), a staggering leap – the progressive warming of the whole globe which appeared to be observable in the 1990s appears, since the millennium, to have plateaued.

No one really knows why. (A good guess is the Chinese sulphur aerosol: China's vast, exploding carbon emissions are accompanied by huge emissions of sulphur dioxide, which have the effect of cooling, rather than warming the atmosphere.) Yet that's not what matters. What matters is that we know beyond peradventure that carbon dioxide is a greenhouse gas, and an increase in its atmospheric concentration will warm the atmosphere, and this increase is now proceeding at a frenzied rate.

It is proceeding even as right-wing commentators pooh-pooh the whole matter, even as members of the public pass it over completely and worry about other things, and unless the laws of physics are suspended, it will have the gravest consequences.

So although the forthcoming meeting at Durban may be on few people's lips, it is vital, not least in trying to bring the Chinese into a new global-warming treaty. One wonders what Baroness Thatcher might have to say about it, and it may seem unfortunate that her health no longer permits her to comment on the mortal threat which, with her training as a research scientist, she so presciently identified 23 years ago.