Every year for at least the past two decades, a ‘hole’ in the ozone layer in the stratosphere has formed over the Antarctic during the spring months. The destruction of the ozone layer allows more of the sun’s ultraviolet light to reach the earth’s surface, damaging people, animals and plants. It is caused by a reaction between ozone, a form of molecular oxygen, and man-made chemicals known as CFCs.

CFCs can quite easily be replaced with less harmful chemicals, and an international agreement that limited their production and use – the Montreal Protocol – was reached in 1987, within just a few years of the discovery of the phenomenon.

Under the Protocol, it will take decades for CFC emissions to come to an end; technically they could have been eliminated more quickly, politically the challenge has proved more intractable. The ozone hole over the Antarctic is still with us and is only just showing signs of moderating. It will remain for many decades, but a much more serious challenge has been averted.

There are two elements of the ozone depletion story that are relevant to much wider global issues, including some potentially massive problems of international security. One, as noted, is that it proved difficult to get a comprehensive agreement on CFC control, even though it was a relatively easy factor to isolate. The other is much more significant in that the damage to the ozone layer was the first evidence that human activity can actually have an impact on the whole global environment.

Recent centuries have seen several cases of human activity with dangerous environmental impacts, ranging from land degradation, the poisoning of rivers and air pollution episodes killing hundreds of people, through to the destruction of marine fisheries, deforestation and the salting up of previously rich croplands. But there was one significant difference between all of these and the case of ozone depletion: they were local or regional, while ozone depletion has global significance.

That ozone depletion is slowly being brought under control is good news, but it is likely to prove a minor environmental problem compared to human induced climate change. This is due not just to a single set of pollutants, such as CFCs, but to the worldwide burning of fossil fuels – coal, oil and gas. Combustion produces excess carbon dioxide and traps additional solar energy within the world’s atmosphere. The consequences for the climate are likely to be highly significant.

The climate is already changing in many parts of the world. The change seen so far is still within the bounds of natural variation. But the entire international community (including academe and government in the United States) accept – on the basis of the best and most rigorous science – that there is an overwhelming probability of future significant effects as a result of human emissions of greenhouse gases.

Winters are getting warmer in many parts of the northern hemisphere. Glaciers are in retreat from the Alps to Alaska. On a personal note, for the past thirty years we have run a smallholding on a few acres of land on the fringes of the Pennine Hills in the North of England and three years ago the climate had changed sufficiently for me to plant a small vineyard. It is doing well and I should be able to produce the first wine in a year or so – something that would have been unthinkable two decades ago.

For people in the north of Britain, climate change may be generally welcomed – at least in the near term – for making life a bit less wintry. This is a more general reflection in many of the more northern countries in the world. In any case, these are the countries that can most easily cope with climate change as they have the wealth and resources to adapt their agriculture and lifestyles. Until fairly recently, there has been a widespread view among climatologists that human-induced climate change would mainly affect temperate regions with less effect on the tropics. In the past, this was a reasonable assessment, given that studies of the effects of naturally-induced climate change stretching over many thousands of years have tended to indicate that the tropical regions were far less affected than the rest of the world.

This view is now changing, and it is becoming accepted that the tropics will not be immune from climate change. One effect will be that countries, which simply do not have the resources to cope, will experience tremendous difficulties. They are likely to be affected by two kinds of problem. The first is an increasing severity of weather episodes such as storms, which already have a far greater human impact in tropical regions. In 1992, for example, Hurricane Andrew hit parts of the United States, killing 52 people and causing around $22 billion of damage, 70 per cent of it covered by insurance. Six years later, Hurricane Mitch hit Honduras and Nicaragua. The death toll was 11,000 and only 3 per cent of the $7 billion damages were insured.

The second problem is a trend towards a general change in the distribution of rainfall as a direct consequence of climate change. More rain will fall over the oceans and the polar regions with substantially less likely to fall over the tropics, including the whole of southern and south-east Asia, the Middle East, and most of Latin America and Africa.

This is likely to prove a huge problem because these are the regions where most of the world’s people live, and where most of the world’s food is grown, the great majority of it for local consumption, often produced by subsistence farmers. If, as seems increasingly likely, these rich croplands start to dry out, the very carrying capacity of the land will decline sharply, and agriculture will be unable to support current populations, let alone any probable increases.

The implications of this trend are immense. As people become more desperate, the pressures on migration are likely to increase substantially, and states will have great difficulty in coping with accelerating humanitarian needs. Moreover, it will be abundantly clear that those countries that have contributed most to carbon emissions which are at the root of the problem, primarily the wealthy industrialised countries of the north, will be those most anxious to protect their own wealth and security.

This is likely to further exacerbate the north–south fracturing of international relations that is already in evidence. From a southern perspective, northern states and their associated corporate interests already control the world economy. They are seen to manipulate trade and financial processes in their own interests, dominating the World Trade Organisation (WTO) and the International Monetary Fund (IMF). Increasingly, they will be seen as further protecting their own narrow interests by ignoring the problems of climate change while erecting ever more substantial barriers to economic and environmental migration.

On the positive side, there is some evidence that a few northern states are beginning to recognise the political and security implications of climate change. The Kyoto Protocol, which requires a fractional reduction in emissions by some rich industrialised countries, is no more than a first tentative step in an urgent process. Some governments acknowledge – without making commitments – the need to go much further. The British government, for example, now accepts that emissions should ultimately be cut by at least 60% – a much more ambitious target than the 10% and 20% targets it envisages for the near term (and which Britain is still unlikely to achieve). More generally, there is a wider recognition in Europe that emissions need to be substantially reduced. This is in marked contrast to the view from Washington, but it is a view shared by some US state governments and others.

In the months or weeks leading up to a probable war with Iraq that will be fought partly to control the immense oil reserves of the Gulf region, oil resources are influential in current security thinking. They are also enormously significant for longer-term global trends.

At some time in the next few years the western powers – and others – will have to face up to the need to move away from oil as a fundamental energy resource and look to environmentally friendly ways of generating, storing and using energy. Such a view will cut little ice with the current regime in Washington, but it has to come.

Because of this blindness, we face yet another resource war in the Middle East in the short term. The medium- to longer-term prospect is of an even more bitterly divided world, made far more insecure as the impact of human induced climate change begins to bite.