On 10 December 1997, after a session lasting two days and nights virtually without a break, politicians at the climate summit in Kyoto, Japan, agreed a protocol limiting the emissions of greenhouse gases from developed countries. The agreement is not as strong as many countries and environmental groups would have liked – and participants have yet to sign and ratify the protocol – but to have achieved any agreement on an issue with such large global implications was an enormous step forward.

The agreement at Kyoto (Physics World January p14) is strongly rooted in accurate and honest science, and balanced technology, as was the UN Framework Convention on Climate Change, which was signed at the “Earth Summit” in Rio de Janeiro in 1992 and under whose auspices the Kyoto summit was held. The Kyoto agreement is also based on the belief that the science of climate change – as expounded by the UN’s Intergovernmental Panel on Climate Change – is basically sound, and that adequate and appropriate technology is available to enable the emissions of greenhouse gases to be reduced to the necessary levels. So what science and technology will be needed over the next decade if the objectives of the climate convention are to be realized?

The science of climate change

So far, scientists have been able to make useful projections of the likely climate change over the next century in terms of global averages. For example, in the absence of any mitigating action, the global average temperature is likely to rise over the next 100 years by about 2.5 ^oC (with a range of 1-3.5 ^oC), while the sea level will rise by about 0.6 m (with a range of 0.2-1 m) over the same period. The hydrological cycle is likely to be more intense, leading, in some places, to more frequent and more intense floods and droughts. (For full details, see Climate Change 1995: the Second Assessment Report 1996 Cambridge University Press).

Progress now needs to be made in reducing the uncertainties in such estimates and in providing more credible regional detail. So what are the greatest uncertainties in projecting the likely climate change over the next century? The increase in the atmospheric concentration of carbon dioxide – the main greenhouse gas – and its link with fossil-fuel burning is well understood. Less well known are the climate effects of particles in the atmosphere. These particles, also known as aerosols, arise from a variety of sources – for example, from the burning of forests or from sulphates generated by power stations and other industrial activity (see ” Air pollution: the role of particles” by Christopher Noble and Kimberly Prater Physics World January).

Uncertainties in quantifying the likely climate changes also come from our lack of knowledge of some of the major feedbacks that occur in the climate system, in particular: those arising from the effects of changes in cloudiness, which can lead to both positive and negative feedback; those due to interactions of the climate with the ocean circulation, which can have a large regional effect; and those due to changes in the biosphere. In addition to improvements in the accuracy of projections on a global scale, we also need much more accurate and more detailed information on local and regional scales.

Scientific progress will come from carefully planned and painstaking analyses of observations, and by incorporating better physics and dynamics into computer models of the climate. And as more computer power becomes available, progress will also be made from models that have higher spatial and temporal resolution. Increased understanding of major questions, such as those to do with cloud, ocean and biosphere feedback, will only come by combining more accurate observations possessing better coverage with careful model simulations.

One particular concern in recent years has been the tendency to cut back on some important climate observations, which have been discontinued to save money in the short term, with no thought to the long-term consequences for our understanding of the climate. A major challenge is therefore to improve the accuracy and coverage of global observations and to ensure that the data become more easily available to researchers – concerns that are being addressed by the international Global Climate Observing System. Well designed programmes of space observations that also manage, disseminate and analyse the data properly will be central to an effective observational network.

Impacts, adaptation and mitigation

In addition to the science of climate change itself, there is a lot of research to be done in understanding the impacts of climate change. Since some climate change will inevitably occur – whatever action is taken to reduce emissions – we urgently need to carry out scientific and technical work that will help us to adapt to climate change, for instance to changes in sea level and the availability of water. This work will need to take into account other causes of environmental degradation, such as those arising from deforestation or the overuse of ground water.

However, as the UN Framework Convention on Climate Change (UNFCCC) clearly recognizes, we cannot just prepare ourselves to adapt to climate change. We also need to put a lot of effort into mitigating against climate change. Indeed, the objective of the UNFCCC is to stabilize the concentration of greenhouse gases in the atmosphere at a level and on a timescale that is consistent with the needs both of the environment and of sustainable development. Stabilizing concentrations in this way will eventually demand severe cuts in global emissions. Emissions of carbon dioxide, for example, would have to fall to well below today’s levels by the second half of the 21st century. The Kyoto protocol, which agreed that the emissions of the main greenhouse gases from developed countries should be reduced by 5-8%, can therefore be seen as a rather modest first step towards what will be required later.

Since emissions of carbon dioxide, which arise from the burning of fossil fuels such as coal, oil and gas, contribute about two thirds of the total effect, most attention must be given to reducing our consumption of these sources. But emissions of methane, the second most important greenhouse gas, could also be lowered by stemming leaks from pipelines, by reducing deforestation (which is good for other reasons too) and by reducing the methane arising from agricultural sources. They could also be lowered by cutting the amount of waste going to landfill sites and by collecting the gas that such sites emit.

However, the availability of cheap energy is seen as the engine for industrial and economic growth, and these reductions are not going to be easily made. So what can be done to reduce our use of fossil fuels in the energy and transport industries?

Developing energy-supply technologies

The average efficiency of energy supplies has substantially increased in recent years, but there is still plenty of room for further improvement. For instance, technologies are available that could improve the efficiency of coal-fired power stations, which is typically no more than about 35%. I will mention just two possibilities. First, the materials used in the advanced aerospace industry could be transferred to steam-power plants, which would, according to Colin Humphreys of Cambridge University, raise the operating temperatures of such plants from 550 ^oC to 750 ^oC, and increase their efficiency by about 50%. Second, “combined heat and power” plants, which have a typical overall efficiency of about 80%, have a large potential for growth in countries like the UK, where their use has so far been comparatively limited.

There are also a number of possibilities for removing the carbon dioxide from fossil-fuel emissions so that the gas does not enter the atmosphere. The most promising idea is to pump the carbon dioxide down into spent (or partially spent) gas or oil wells, where it can then be used to increase the gas or oil yield. For example, a company in Norway, where there is a carbon tax, has found it makes economic sense to sequester unwanted carbon dioxide in a gas well, rather than pay the tax that would be required if it were released to the atmosphere.

However, the key to future sustainable energy provision lies in the rapid development and growth of renewable energy sources. Indeed, a number of such sources are poised for growth. In appropriate locations, wind energy can be supplied at a price that is becoming competitive with fossil-fuel sources. Power stations that use waste materials or renewable biomass as fuel are also being developed. And solar energy is likely to become one of the major sources of world energy, particularly through the use of photovoltaic cells to generate electricity, with hydrogen produced electrolytically as a storage medium. Wave and tidal energy sources could also be developed.

In 1993 the World Energy Council developed a detailed scenario for energy provision in the next century, in which “new” renewable energy sources would make up 12% of the total energy provision by 2020. However, the council pointed out that real commitment and substantial investment would be needed to achieve this goal, and it emphasized the need for urgent action. “The real challenge, ” said the council, “is to communicate the reality that the switch to alternative forms of supply will take many decades, and thus the realisation of the need and commencement of the appropriate action must be now [their italics].”

Developments in energy-use technologies

Most energy is used inefficiently, and only a few per cent of primary energy is turned into effective use; the rest is simply wasted. There is therefore enormous potential to increase energy efficiency in buildings, industry, domestic appliances and transport (see, for example, Factor Four: Doubling Wealth, Halving Resource Use by Ernst von Weizsacker, Amory Lovins and Hunter Lovins 1997 Earthscan Publications). We could, for example:

• improve the design of buildings by imposing higher building standards (for example, in insulation) and by integrating different areas of design and construction, through changes in engineering practice, to minimize energy use. About 35% of energy is used in buildings, over half of which could be saved in this way;
• improve electrical appliances – for example, by designing better insulated fridges that minimize their use of energy;
• develop and use more efficient lighting. Promising developments in light-emitting diode technology could provide bright, compact, cheap, long-life light sources that are ten times more efficient than incandescent sources (according to Colin Humphreys at Cambridge University);
• develop and market more efficient vehicles, for example hybrid vehicles, which combine small petrol or diesel engines with electric propulsion, and also vehicles that are powered by fuel cells.

Research and development

Another major concern is the current level of research and development into the science and technology of climate change and how to mitigate against any further decline. Particularly worrying has been the trend over the last ten years to reduce R&D investment in energy-supply and energy-use technologies. As the markets have increasingly taken over energy supply, neither governments nor the energy industry are investing as much in long-term R&D as they previously had done.

For example, government spending on energy R&D has fallen by a factor of ten in the UK since 1983, while the global average has fallen by a factor of three to about 0.04% of the world’s gross national product. This is a tiny sum compared with the capital investment in the energy industry, which is nearly 4% of the world’s gross national product. If greater energy efficiency and the necessary growth in renewable energy sources are to be achieved, we need much greater support for R&D by both industry and governments.

The way forward

The UK government has put forward its own target of a 20% reduction in carbon dioxide emissions by 2010. Although this target is not legally binding, it is nevertheless one that the government intends to take seriously. Such a demanding target can only be achieved through an effective partnership, in which all sectors of society play their part. The challenge for the UK government is to set up this framework – including appropriate economic and other incentives – in which change can occur. Industry, with the support of scientists and technologists, must provide innovative technology and develop the necessary markets.

Meanwhile, all of us as consumers need to demand products that generate fewer greenhouse gas emissions, both when they are made and when they are used. We must also recognize the need to make changes in the way that we do things, and in the way that we live our lives.