Climate change - the hazards

On 2 February the Intergovernmental Panel on Climate Change published an eagerly awaited report from its Working Group on the scientific aspects of climate change. It will form part of the Panel's eventual Fourth Assessment. Reports from other Working Groups on the various impacts of change and on recommendation for action will be published later this year, together with a synthesis to bring the whole Fourth Assessment together.

I do not have to tell you that the report on the science, in particular its "Summary For Policy Makers", has made headlines all over the world. It has changed - indeed enlarged - thinking on this enormous and infinitely complex subject, and given new edge to the recommendations of Sir Nicholas Stern in his review on the economic implications of 30 October 2006. I think the most useful thing for me to do is to ask you to stand back and look first at the place of climate within the global environment, then go briefly through the science, and finally consider what might - and should - now be done.

Perhaps the point that still escapes many people is the limited, ephemeral and precarious character of the global environment. Our whole being is within a wafer-thin atmosphere surrounding the surface of a planet as it turns in space at exactly the right distance from the Sun for life. We are tiny parts of a system of life whose complexity passes, and always will pass, human understanding.

That system is highly vulnerable. It is just that the shortness of our lives and the narrowness of our perspective on the past mean that we are mostly unaware of change, and until now have scarcely noticed the pressures on the environment. But the last couple of centuries have seen an extraordinary stretching of our understanding of space and time. We can now look beyond the solar system, beyond our galaxy, beyond billions of other galaxies, back to the big bang which initiated the universe we know. As for time, we can now look beyond the last thousand years, beyond the beginnings of civilization, beyond the patch of varying warmth in the last 11,000 years, beyond the many spasms of the ice ages, and further back to the origins of the Earth itself.

During these almost unimaginable stretches of time, there have been huge changes both from outside the Earth and from within it. From outside there have been big hits from space, and the changing relationship between the Earth and the Sun (wobble, tilt and orbit); and from within it there have been the slow movement of tectonic plates on the Earth's surface, vulcanism and earthquakes, drastic changes in climate, the rise and fall of sea levels, and not least the influence of life itself.

The objects from space that hit the Earth almost continuously range from the very small to the very big. The smallest are the daily hail of tiny objects. Perhaps most famous was the Chicxulub event some 65 million years ago which caused, or at least contributed to, the extinction of the dinosaur family. Extinctions of this magnitude are a disaster for some, but an opportunity for others. Indeed the rise of the mammals, with humans a last-minute arrival among them, would not have happened without Chicxulub.

More recent was the Tunguska event of 1908 which destroyed some 2000 square kilometres of forest in Siberia. Had it struck London, there would have been little left. Only last year an asteroid sailed past the Earth at a distance slightly further away than the Moon. The next big one coming in our direction is timed for the 2030s.

Next I come to events within the Earth system. Tectonic plate movements can sometimes have dramatic effects. One example is the joining of North and South America some four million years ago, which led to big changes in the direction of ocean currents and in climate world wide. More recent was the eruption of Mount Toba in Indonesia over 70,000 years ago, which put enormous quantities of volcanic dust into the atmosphere, helped trigger a renewal of glacial conditions, and may even have affected human evolution. By comparison the eruptions of Mount Tambora in 1815, which led to the famous 'year without a summer', that of Krakatoa in 1883, that of El Chichon in 1982/3 and Mount Pinatubo in 1991, each with its specific global effects, were relatively minor.

Earthquakes are part of the same pattern. Mostly their effects, however destructive, are local. Most loss of life is associated with the tsunamis which, as we have seen in the last couple of years, can surge across the oceans doing enormous damage.

Then there are the over turnings in the living world. Extinctions for whatever reason are an essential element in evolution. Few ecosystems or species last more than a few million years. The Earth system behaves as a single, self-regulating system, comprised of physical, chemical, biological and even human components, operating within fairly wide limits. In a phrase this is Gaia theory, or Earth System Science.

Over the last 40,000 years, the human impact on the Earth has slowly, and then rapidly, increased. The association between humans and their environment, including the micro-world in and around them, has changed at every stage of human evolution: from hunter gatherers to farmers, from country to city dwellers, and from tribal groups to complex societies. Before the industrial revolution began some 250 years ago, the effects of human activity were local, or at most regional, rather than global. Now the impact is indeed global.

The idea may be hard to accept, but in its long history the Earth has not been in this situation before. In the words of the title of a recent book on environmental history, we confront Something New Under The Sun. This point was well brought out in a declaration published by some 1,500 scientists from the four great global research programmes at Amsterdam in July 2001. They stated squarely that:

"The nature of changes now occurring simultaneously in the Earth's system, their magnitudes and rates of change, are unprecedented. The Earth is currently operating in a no-analogue state ... The accelerating human transformation of the Earth's environment is not sustainable. Therefore the business-as-usual way of dealing with the Earth's system is not an option.

There are six main factors which have driven this transformation. Briefly they arise from human population increase; degradation of land, consumption of resources and accumulation of wastes; water pollution and supply; energy production and use; destruction of biodiversity; and climate change in its many aspects and impacts. These factors have to be seen and understood together.

In the last few years climate change has acquired pride of place among them, and been seen as a major potential disaster. In 2006 the British Government's Chief Scientific Adviser said that climate change was the biggest threat we faced, bigger than terrorism; and the Prime Minister has said more than once that "in terms of the long term future there is no issue that is more important ... "

Exactly how important has been well illustrated in the latest report form the Intergovernmental Panel on Climate Change. There it is stated that

"warming of the climate system is unequivocal ... Most of the observed increase in globally average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations."

In other words we face the challenge of global climate destabilization.

Until now the central difficulty for scientists has been how to distinguish natural change from human-driven change. This has been the battlefield between those who wish to deny human-driven change, and those who observe it on every side.

We now know far more about natural change however it may be caused. But there are still uncertainties, mostly deriving from the wider factors I mentioned at the beginning, in particular the Earth's relationship with the Sun. A new field of study has become tipping points, when one set of climatic circumstances can - sometimes rapidly - switch into another. Here are some things to watch:

• the state of the Amazonian rainforest:
• the direction of North Atlantic currents, including the Gulf Stream.
• the release of methane clathrates from beneath the tundra and ocean bed, and release of methane from living organisms
• changes in the pattern of the Indian monsoon.
• the frequency and intensity of El Niño and La Niña in the Pacific with its worldwide effects.
• the state of the Greenland and West Antarctic ice sheets: sometimes growing, sometimes diminishing.

There are two jokers in the pack for which we still have no complete explanation.

• a sudden cooling effect (the Younger Dryas event some 12,500 years ago): recent evidence suggests that the Gulf Stream is weakening
• a runaway greenhouse effect (Palaeocene / Eocene 55 million years ago)

I now come to the main points of human-driven change, admirably brought out in the report of the Intergovernmental Panel.

• Carbon dioxide emissions are now at their highest level in 650,000 years. We could indeed be heading back to conditions of 125,000 years ago when the configuration of land and sea was very different (and sea levels were between 4 and 6 meters higher)
• the rise in carbon dioxide emissions is well illustrated by figures relating to the quantities in the atmosphere: from roughly 190 ppm (parts per million) in glacial times, to 285 ppm in warm interludes, to 381 ppm today, and at present rising by around 2 ppm a year
• the global atmospheric concentration of methane, a 20 times more potent greenhouse gas than carbon dioxide, has risen from a pre-industrial level of 715 ppb (parts per billion) to 1774 ppb in 2005
• nitrous oxide has likewise increased from a pre-industrial value of around 270 ppb to 319 ppb in 2005
• warming of the oceans has also increased since 1961. Such warming now reaches down to depths of at least 3000 metres. Its effects on the atmosphere have a roughly 30 year time lag. Sea levels have risen by an average rate of 1.8 mm per year between 1961 and 2003, and are now accelerating
• increases in atmospheric pollution may have mitigated the effects of warming with the implication that the more we reduce pollution, the greater the degree of warming

What have been the effects so far? They can be seen in:

• changes in weather everywhere, and becoming more so, with most warming expected over land and high northern latitudes, and least over the Southern Ocean and parts of the North Atlantic
• melting of the Arctic and Antarctic icecaps, and on Himalayan and Andean glaciers with their effects on river systems
• availability of fresh water, and more extreme events, whether storm or drought
• increasing competition for natural resources, including food supplies
• changes in ecosystems, including insects and micro organisms of all kinds, with their multiple effects on human health and welfare
• undermining of current social, and in particular urban, infrastructure: sewage, reservoirs, buildings, public services, industry etc
• movement of people within and between countries, in particular environmental refugees

In the Intergovernmental Panel report, the likelihood of future trends based on projections for the 21st century, is assessed, all with a human driven cause of greater or lesser importance. Thus the Panel concluded that it was virtually certain that there would be more warmer and fewer colder days and nights over most land areas; more warm spells and heat waves, particularly in inland areas; more heavy precipitation and droughts; more intense tropical cyclones; and more extreme rises in sea level.

The social and economic impacts of these projected changes will be examined in future Panel reports. In the meantime it is obvious that such factors as human population increase, land degradation and resource depletion, loss of biodiversity and other hazards will affect our ability to cope effectively with climate change. The prime difficulty is that we will need new global as well as national policies, and that such policies will impinge on almost everything, requiring coordination of a kind rarely found in governments or international institutions.

We should not surrender to gloom, although no one who has seen Al Gore's film An Inconvenient Truth is likely to be cheerful. Already a change of mind is beginning, more so in some countries than in others, as governments realize how much their national interests are involved.

• internationally: there is already an institutional apparatus available. We have the Framework Convention on Climate Change of 1992; we have the Kyoto Protocol and work in progress on it post 2012; we have the work of the G8 in the so called Gleneagles process; and we have the successive Assessments of the Intergovernmental Panel, with the prospect of the synthesis recommendations later this year. Next time we need to bring in the world as a whole to curb emissions. In all this the industrial countries have to accept their primary responsibility for what has happened. This means not only advising and helping other countries, but giving the example in their domestic as well as international policies.
• nationally: governments need new energy policies, and a fundamental switch away from dependence on fossil fuels.

Here the process has at least begun, albeit at different speeds in different places. So far the talk greatly exceeds the action.

In Britain since the days of Margaret Thatcher, climate change has been on the political as well as the scientific agenda. She promoted discussion of the subject at the G7 meeting in London in 1984, gave a famous speech on it at the Royal Society in 1988, addressed the General Assembly of the United Nations on this alone in 1989, and was one of the handful of heads of government who attended the World Climate Conference in Geneva in 1990.

The tradition she established was carried forward by her two successors. Tony Blair made it one of the two main themes of his G8 Presidency in 2005, and he has energetically pursued the subject ever since. With the agreement of the other two main political parties, a Climate Change Bill will shortly be put before Parliament. Current arguments are mostly about tactics rather than strategy.

For his part the Chancellor of the Exchequer invited Sir Nicholas Stern to cross the long bridge between science and economics, and report on the implications for economics of climate change. His most quoted conclusion was:

" ... if we don't act, the overall costs and risks of climate change will be equivalent to losing at least 5 percent of global GDP each year, now and for ever. If a wider range of risks and impacts is taken into account, the estimates of damage could rise to 20 percent of GDP or more. In contrast the costs of action - reducing greenhouse gas emissions to avoid the worst impacts of climate change - can be limited to around 1 percent of global GDP each year."

Whatever the subsequent arguments among the economists, some more serious than others, his view that dealing with climate change is the biggest market failure ever seems to have been generally accepted. In some respects British business and industry are ahead of the government in taking action to protect what they see as their interests.

In Europe generally climate change has been taken very seriously. Progress has been made under the Emissions Trading Scheme (EU-ETS) with its many complexities, and more realistic arrangements will be made in the future. Last month the European Commission produced a paper, largely on future energy policy, which tried to predict the likely effects of climate change on Europe, and the implications for movement of peoples from south to north.

In the United States the Administration of President Bush Jr. has been the villain of the piece. Although the previous Administration signed the Kyoto Protocol at the behest of the then Vice President Al Gore, the current Administration decided not to put it to the Senate for ratification, and adopted a position of sceptical hostility. Things began to change last year. President Bush accepted the Gleneagles Declaration which recognized climate change as a serious long term challenge.

"We know enough to act now to put ourselves on a path to slow, and, as the science justifies, stop and then reverse the growth of greenhouse gases."

His previous doubts were not shared by many American cities, states and corporations. At the last count almost 300 city mayors (accounting for over 40 million Americans) were taking steps to reduce emissions. Work is in hand by the North Eastern and some Western states to take further action. Arnold Schwarzenegger of California has even made a separate agreement with Britain, and the British Environment Secretary will shortly be going to the United States to look into the possibility of other agreements with individual states.

As for US corporations, General Electric led last year with the slogan of Eco-Imagination and others have followed. Companies as beginning to sell themselves under 'green tags' or certificates of environmental virtue. Under popular as well as political pressure, President Bush sketched out some action to cope with climate change in his State of the Union address, but he clearly indicated that technical solutions in the form of biofuels might cope with the problem. Techno-enthusiasm, if not techno-delusion is a well-known and endearing US characteristic.

In China new efforts have been made to reduce dependence on native coal, to switch to nuclear power, and to search for other energy alternatives. The Chinese government is well aware of the vulnerability of China to climate change over the centuries, and is particularly concerned with the prospect of growing shortages of water. Such other countries as India, subject to the vagaries of the monsoon, are equally aware of the threat, but like others resent curbs to their own chosen path of economic development

Even if climate change is now at the top of the political and economic as well as the scientific and environmental agenda, most governments cannot get far without the support, or at least the understanding of public opinion. That has been changing fast. Event those who like to "deny, deride and do nothing" seem to be changing their tune. Already in some countries public opinion is becoming the driver, even if the implications go further than is generally realized. Pressure for action is coming from individuals, communities, regions and the many interested parties, particularly in business and industry. In fact we need a deep change of mind covering:

• conventional economics, and the need to bring in externalities with a wider assessment of costs
• attitudes towards the use of energy, with again a better assessment of costs
• replacement of consumerism as a goal. The Chinese already have a word for the new goal of a well-rounded sustainable society: xiaokung
• conservation of the natural world and appreciation of the diversity of other living organisms on which we wholly depend

We also need practical, identifiable, equitable, global action within existing or new institutions. In short we have to move from a high carbon to a low carbon society. That means setting a price on carbon. An example of what might be done has been sketched out by Aubrey Meyer in his programme of Contraction and Convergence for reduction of carbon emissions.

Cap-and-trade ideas are widely under consideration. There are a number of possible mechanisms, including a country-based approach, or global auctions in which those who produce and process fossil fuels would have to compete for quotas in a global market, such as the Kyoto 2 proposals.

Our descendants may regard the present as a disastrous epoch in the history of the Earth when everything went wrong. Or they may see it as a time when humans pulled themselves together, changed direction, and took advantage of the immense opportunities now open to us.

Those opportunities are partly technical, relating to use of information technology, and partly personal, relating to the thousands of miniscule ways in which we run our daily lives. Here are some obvious examples:

• how we feed ourselves, and decide where the food comes from
• how we warm and cool ourselves , in short how we receive and use energy, whether from the grid or from wind or solar power
• how we use and look after water
• where we live and work
• how we transport ourselves
• how we use, save and recycle materials
• how we work with others across the world, including those who are immeasurably poorer than ourselves
• how we treat the other animals and plants with which we share the planet

I conclude with a quotation from the Financial Times of 3 February:

"This is a huge, long term and global challenge that involves difficult questions of justice both within and across generations. Humanity's ability to address it is a test of its capacity to manage the consequences of its own actions. So far it has failed. It can afford to do so no longer."