You could be forgiven for thinking it's not happening – and there, in fact, is the heart of the problem. Climate change, according to one view the greatest threat that human civilisation has ever faced, may seem a particularly nebulous danger to many people who look around them and see no evidence whatsoever of it taking place.
If you gazed out of your window last July – or in July 2008, or July 2007, for that matter – what did you see? Rain, most of the time. People in raincoats. Chilly grey skies. You saw no signs of the swelteringly hot super-summers we have been told to expect these past 20 years, since UN scientists began making their predictions of the future course of global warming.
Same with the winters. Supposed to be getting warmer, aren't they? But last winter was the coldest for more than a decade, and the snow in early February in London the heaviest for an even longer period, and clumping your frozen feet through it and blowing on your icy fingers, you could hardly be blamed for thinking: global warming, schwarming. These guys who are saying it's all a gigantic con are probably right.
How are we to relate the evidence of our own senses to what we are told is happening, when the one in no way supports the other? Here we have the central difficulty that our society faces in dealing with the potentially catastrophic threat of the warming climate: it takes place in the future.
Unique is a much overused word, but climate change is unique in the long history of grave human vicissitudes – war, disease, starvation, societal collapse – for a simple reason: in this case only, the future is known. Nobody knew the Thirty Years' War was coming, or the Irish potato famine. Nobody in Europe foresaw the Black Death before 1348. But we know what will happen with the global climate in the course of the 21st century if we carry on as we are – at least, it is known in so far as it is predicted through supercomputer programs of the world's climate, and the effect on that of pouring out an inexorably increasing amount of the trace gases that retain the sun's heat in the atmosphere, principally carbon dioxide (CO2) from industry, transport and the cutting down of forests.
Let it be said at once: every government in the world – from the US to China, from Norway to Brazil, from Ireland to Indonesia – accepts those predictions, in so far as they assert that an unremitting increase of CO2 in the atmosphere will cause an inexorable rise in global temperatures.
You may think commentator X or blogger Y has a point when they opine that this global warming business is all hugely exaggerated, all so much hot air, driven by scientists seeking research funding, but it's worth remembering that no government now thinks that, anywhere. By the end of 2007, not even the US administration of President George W Bush, for so long the climate sceptic supreme, thought that. Are the governments the ones out of step?
The problem is that although the senior politicians and officials in government have listened to the scientists and are now convinced of the terrifying reality of the prospect of a 4°C or even 6°C rise in average global temperatures during the course of this century – the latter would make the Earth largely uninhabitable for humans – in large measure, their citizens are not convinced. It is too far away for them to contemplate. We care about concerns that are immediate – our income, our health, the education of our children. Climate change seems to be a matter for posterity. And as Groucho Marx unforgettably put it: "Why should I care about posterity? What has posterity ever done for me?"
The consequence is that there is no groundswell of public opinion demanding the truly radical action that meteorological scientists increasingly say is necessary for the warming to be brought under control; and, since politicians seeking re-election on the whole respond to public opinion as dogs to bones, the possibility of such action retreats from view.
Some time ago I spoke to a very senior British figure who had just visited China, now the world's largest carbon emitter, and spoken to the Chinese leadership about climate change, "Of course they understand the problem and the danger," he said. "They understand it completely.
"Their difficulty is, they have 1.3 billion people underneath them who just want to make money." And by and large the same unconcern goes for the US, and for Britain... and, of course, for the rest of the world.
This disconnect, this chasm between what the scientists see coming and what ordinary people are bothered about on a day-to-day basis, is the central impediment to dealing with the climate threat. The core issue is not the technology, but the politics. We have the technology; we know how to produce energy without producing CO2. We just do not have the political will, stemming from ordinary people's feelings, to deploy that technology rapidly enough. By the time that political will exists – when ordinary people see that their immediate interests are threatened by rising temperatures – it will be too late.
An ancillary reason for the present lack of public concern, and a fascinating one, is that for the past decade, the warming itself has plateaued. The issue of climate change burst upon the world in the summer of 1988, with the testimony to US Congress of the leading American scientist James Hansen, in the middle of a record US heatwave, and then with the Toronto Conference on the Changing Atmosphere; that year the United Nations set up its Intergovernmental Panel on Climate Change (IPCC), the body of scientists taxed with assessing the global warming threat.
This activity coincided with a leap forward in world temperatures – the winter of 1988-9 was the warmest ever recorded in Britain, in a record dating back to 1659 – which continued to a climax in 1998, by some margin the hottest year ever recorded for the world. But since then, although global temperatures have not fallen back, they have not risen further. There have been remarkable episodes, such as the European heatwave of August 2003 that killed 35,000 people in continental Europe and saw the UK air temperature record exceed 100°F (37.8°C) for the first time. On 10 August 2003, it shot up from the previous record of 98.8°F (37.1°C), set in 1990, to 101.3°F (38.5°C), an enormous leap. But the steady upward progression of global temperatures, which was hitherto the general prediction, has halted.
In September, this issue was addressed directly by a group of scientists from the Hadley Centre, the UK Met Office's institute for climate prediction and research. Their paper, published in the Bulletin of the American Meteorological Society, was entitled "Do Global Temperature Trends Over the Last Decade Falsify Climate Predictions?" Their conclusion was simple: No. Investigating how often decades with a neutral warming trend occurred in computer-modelled simulations of climate change, they found that despite continued increases in greenhouse gas concentrations, a single-decade hiatus in warming occurred relatively often.
The paper's lead author, Dr Jeff Knight, said his team found: "About one in every eight decades has near-zero or negative global temperature trends in simulations that would otherwise warm at expected present-day rates. Given that we have seen fairly consistent global warming since the Seventies, these odds suggest the observed slowdown was due to occur."
Historical climate records indicate that global warming does not follow a linear pattern – it proceeds in leaps and bounds. And it is due to make another leap, according to the Hadley Centre's decadal forecast for the years 2004 to 2014, which shows temperatures surging upwards after next year. It predicts that "at least half the years between 2010 and 2019 will be hotter than the hottest year".
If you want to see the full details of what scientists believe global warming has in store for us over the coming century, simply turn to the IPCC's most recent report on the subject, which was published in 2007. (Google "4AR WG1" and you will get it instantly.) It predicts that, depending on the amount of CO2 emitted, global temperatures will rise by between 1.8°C and 4°C, with a worst-case scenario of 6.4°C, by 2100. Last month, a report from the Global Carbon Project, a group of 31 leading scientists from seven countries, reported that emissions are now rising so fast that we are firmly on course for the worst case. And, in that scenario, human society would be destroyed.
This is the situation facing the international community as it gathers in Copenhagen to try to broker a deal to bring carbon emissions under control. If ever there was a case for leadership from the top, it is now; the politicians must act on what the scientists are telling them, even if many of the voters cannot yet see the urgency. But perhaps that generalised insight is coming. It is true that July this year was wet, as were July 2008 and July 2007; but although we may have forgotten, July 2006 was the hottest month ever recorded in Britain in our 350-year-old temperature record, and to bet against a coming July being equally hot or hotter, perhaps even July 2010, is a bet that might well be lost. Yes, global warming happens in the future. But that future is a lot closer than you think.
The Copenhagen summit at a glance
The United Nations climate summit at Copenhagen lasts from 7 to 18 December. It is officially called COP15 (the 15th conference of the parties of the UN's Framework Convention on Climate Change, signed in 1992). It is likely that most world leaders will attend for the final two days.
* The summit will attempt to construct a new international climate treaty to follow on from the 1997 Kyoto Protocol, whose remit runs out on 31 December 2012.
* Such a treaty's main object will be to hold the rise in global temperatures to 2°C above the pre-industrial level, which is regarded as the threshold of dangerous climate change for the world. At present the global average temperature is about 0.7°C above the pre-industrial level.
* The summit will attempt to do this by securing agreement from all countries to reduce their carbon emissions – or, at least, to slow down their rate of increase. The overall goal is to cut global CO2 emissions to 50 per cent of what they were in 1990, by 2050. (Developed countries will need to reduce their emissions by 80 per cent.)
* For a successful agreement at the Copenhagen summit, the rich industrialised countries will be required to pledge medium-term cuts by 2020, which according to the UN's Intergovernmental Panel on Climate Change (IPCC), need to be within the range of 25–40 per cent (relative to 1990 levels). The European Union has already pledged a cut of 20 per cent, which will rise to 30 per cent if there is a successful deal at Copenhagen. The United Kingdom's own pledge is to cut CO2 by 34 per cent by 2020.
* The poorer developing countries will not yet be required to make absolute cuts in their emissions, as they need to continue growing to bring their people out of poverty. But they will need – if a deal is to be done – to pledge actions showing they are decisively moving away from "business as usual" in their rate of CO2 emissions growth.
* It is hoped that there will be a new agreement about providing substantial help for the developing countries to cut their carbon emissions and also to adapt to climate change that is now inevitable. The European Union has suggested such a new climate fund might be worth about €100m annually, with half of that figure coming from public funds in the rich countries.
* A new agreement is also expected about halting deforestation, which is responsible for about 20 per cent of carbon emissions – as much as global transport.
* A legally binding treaty will not be signed at Copenhagen but it is hoped there will be a firm political commitment to such an agreement, with a timetable for the detail to be worked out over the next year.
* Best-case outcome: agreements and commitments are made, as outlined above, that pave the way to a legally binding (and rapid) treaty requiring cuts in line with the IPCC recommendations.
* Worst-case outcome: failure to agree on substantive issues results either in indefinite postponement of a legally binding treaty or, alternatively, a treaty requiring inadequate cuts.