'Climate change is undeniably real, caused by human activities, and has serious consequences'

Robert McCredie, Lord May of Oxford, OM AC Kt, former President of the Royal Society (2000-2005). (Photo courtesy Office of the President)

Over the wider sweep of Earth's history, levels of carbon dioxide, and the consequent climate, have seen huge swings. Even over Homo sapiens' tenancy of the planet, ice ages have come and gone. Noting that the past 10 millennia have been unusually steady, some people have indeed argued that the beginnings of agriculture and the subsequent development of cities and civilisations is a consequence, not a coincidence.

After the 1780s, as industrialization drove up the burning up of fossil fuels in the developed world, carbon dioxide levels rose. At first the rise was slow. It took about a century and a half to reach 315 ppm. Accelerating during the 20th century, levels reached 330 ppm by the mid-1970s; 360 ppm by the 1990s; 380 ppm today.

This change of magnitude by 20 ppm over only a decade has not been seen since the most recent ice age ended, ushering in the dawn of the Holocene epoch, around 10,000 years ago. And if current trends continue, by about 2050 atmospheric carbon dioxide levels will have reached more than 500 ppm, nearly double pre-industrial levels.

There are long time lags involved here, which are often not appreciated by those unfamiliar with physical systems. Once in the atmosphere, the characteristic "residence" time of a carbon dioxide molecule is a century. And the time taken for the oceans' expansion to come to equilibrium with a given level of greenhouse warming is several centuries.
It is worth noting that the last time our planet experienced greenhouse gas levels as high as 500 ppm was some 20-40 million years ago, when sea-levels were around 100 meters higher than today. The Dutch Nobelist, Paul Crutzen, has suggested that we should recognize that we are now entering a new geological epoch, the Anthropocene, which began around 1780, when industrialization began to change the geochemical history of our planet.

Such increases in the concentrations of the greenhouse gases which blanket our planet will cause global warming, albeit with the time lags just noted. In their most recent report in 2001, the Intergovernmental Panel on Climate Change (IPCC) concluded that this warming would be in the range of 1.4 to 5.8 degrees Celsius by 2100. This would be the warmest period on Earth for at least the last 100,000 years.

Many people - especially, it would seem, some economists - find it hard to grasp the significance of such a seemingly small change, given that temperatures can differ from one day to the next by 100 degrees Celsius. There is a huge difference between daily fluctuations, and global averages sustained year on year; the difference in average global temperature between today and the last ice age is only around five degrees Celsius.

The impacts of global warming are many and serious: sea level rise as mentioned above - which comes both from warmer water expanding, and also from ice melting at the poles; changes in availability of fresh water in a world where human numbers already press hard on available supplies in many countries; and the increasing incidence of extreme events - floods, droughts, and hurricanes - the serious consequences of which are rising to levels which invite comparison with "weapons of mass destruction."

In particular, recent studies, made before Katrina, suggest that increasing ocean surface temperature, the source of a hurricane's energy, will have little effect on the frequency of hurricanes, but strong effects on their severity. The estimated damage inflicted by Katrina is equivalent to 1.7 percent of U.S. GDP this year, and it is conceivable that the Gulf Coast of the U.S. could be effectively uninhabitable by the end of the century.
The timescales for some important non-linear processes involved in climate change are uncertain. As the polar ice caps melt, the surface reflectivity is altered, causing more warming and faster melting. The timescale for the ice cap to disappear entirely (a few decades?, a century?, longer?) is unclear. As northern permafrost thaws, large amounts of methane gas are released, further increasing global warming, as methane is a more efficient greenhouse gas than carbon dioxide. Nearer home, increased precipitation in the North Atlantic region, and increased fresh water run-off, will reduce the salinity of surface water.

Water will therefore be less dense and will not sink so readily. Such changes in marine salt balance have, in the past, modified the fluid dynamical processes which ultimately drive the Gulf Stream, turning it off on decadal time-scales.

I should emphasize, however, that current thinking sees this as unlikely within the next century or more. But it is worth reflecting that the Gulf Stream, in effect, transports "free" heat towards the British Isles amounting to roughly 30,000 times the total power generation capacity of the UK. These nonlinear and potentially catastrophic events are less well understood than is the direct warming caused by increased greenhouse gases. But their potential impacts are great, and should be included in risk assessments.

On a more directly biological note, some other effects of climate change are noted in two recent Royal Society reports. One deals with the adverse impacts on marine biodiversity of the increase in acidity of the world's oceans, caused by absorbing carbon dioxide.

The other addresses the interplay between climate change and crop production, unhappily emphasizing that "Africa is consistently predicted to be among the worst hit areas across a range of future climate change scenarios."

This echoes the disconnect between the two central themes - Climate Change and Sustainable Development in Africa - of the UK's G8 Presidency. On the one hand, solemn promises were made to increase aid and support development in Africa, while on the other hand the lack of agreement on measures to curb greenhouse gas emissions means that increasing amounts of aid will be spent on tackling the consequences of climate change.

Hungry goats in Sudan feed on a single acacia tree in the desert. © FAO

So what should we be doing? One thing is very clear. The magnitude of the problem we face is such that there is no single answer, but rather a wide range of actions must be pursued. Broadly, I think these can be divided into four categories.

First, we can adapt to change: stop building on flood plains; start thinking more deliberately about coastal defences and flood protection, recognizing that some areas should, in effect, be given up. In Holland, one quarter of which lies below sea-level, there are already plans for houses designed to float on seasonally flooded areas.

Second, we can reduce inputs of carbon dioxide by reducing wasteful energy consumption. There are studies, for example, both in the US and in the UK, which demonstrate we can design housing which consumes roughly half current energy levels without significantly reducing living standards.

Third, we could capture some of the carbon dioxide emitted in burning fossil fuels, at the source, and sequester it - burying it on land or under the seabed.

Fourth, we could move toward renewable sources of energy, which do not put greenhouse gases into the atmosphere. These include geothermal, wind, wave, and water energy; solar energy from physics-based or biology-based devices; fission, currently generating seven percent of all the world's energy, and - despite its problems - surely playing a necessary role in the medium-term; fusion, a realistic long-term possibility; biomass - assuming that the carbon dioxide you put into the atmosphere was carbon dioxide you took out when you grew the fuel.

Some of these renewables are already being used, others are more futuristic. In total, they currently account for only three percent of the world's energy. In particular, Pacala and Socolow have presented a scheme of some 15 "stabilization wedges", each one of which would be sufficient to prevent a billion metric tons of carbon being emitted by around 2050. All 15 wedges are based on proven technologies. They fall into three broad categories: energy demand, energy supply, and capture and sequestration of carbon dioxide emissions.

Greenhouse gas emissions stream from the stacks at China's coal-fired Jinzhushan power plant in Hunan province. (Photo courtesy Hunan Datang Xianyi Technology Co Ltd)

Pacala and Socolow estimate that any seven of the 15, if implemented promptly and strenuously, could hold emissions at around 2010-2015 levels. Not one of these is easy or uncontroversial But the scheme does illustrate that we could get there, if we put our minds to it, although certainly not with any single, simple technological fix.

Are we likely to do this?

We made a good start, with the setting up of the IPCC in 1988. The IPCC brings together the world's top scientists in disciplines related to climate change; some 1,250 authors and reviewers from 56 countries were involved in the preparation of its Third Assessment Report in 2001. It deliberately seeks out dissenting voices, and is very careful to set out the degree of uncertainty in its findings. It has indeed created a lexicon of terminology for this purpose.

Following the first report of the IPCC in 1990, the Earth Summit in Rio de Janeiro in 1992 addressed the issue of climate change. The consequent UN Framework Convention on Climate Change (UNFCCC) has signatories from more than 180 countries, including President George H.W. Bush for the USA.

It stated that the Parties to the Convention should take "Precautionary measures to anticipate, prevent or minimize the causes of climate change and mitigate its adverse effects. Where there are threats of irreversible damage, lack of full scientific certainty should not be used as a reason for postponing such measures."

All nations need to take part in such reductions in emissions of carbon dioxide. There are very large differences among the levels emitted by different countries. Measured in tons of carbon input to the atmosphere per person each year, the variation is from about 5.5 for the USA, 2.2 for Europe, 0.7 for China and 0.2 for India, down to lower levels for many developing countries.

For the past several decades, the developed world has been moving - to different degrees in different countries - from coal to oil, gas and, to a small extent, renewables. The resulting lower carbon dioxide emissions per energy unit is known as "decarbonization."

With the rapid growth in energy use that is set to continue in industrializing countries like China and India, where supplies of coal are far more abundant than oil or gas, the next few decades are likely to see unhelpful "recarbonization." Indeed, China, with its huge population, is expected to surpass the USA as the world's largest carbon emitter by around 2025.

Not surprisingly, there exists a climate change "denial lobby," funded to the tune of tens of millions of dollars by sectors of the hydrocarbon industry, and highly influential in some countries. This lobby has understandable similarities, in attitudes and tactics, to the tobacco lobby that continues to deny smoking causes lung cancer, or the curious lobby denying that HIV causes AIDS.

Earlier, when some aspects of the science were less well understood, they denied the existence of evidence that human inputs of carbon dioxide and other greenhouse gases were causing global warming. More recently, there is acknowledgement of anthropogenic climate change, albeit expressed evasively, but accompanied by arguments that the effects are relatively insignificant, and/or that we should wait and see, and/or that technology will fix it anyway.

But make no mistake, climate change is undeniably real, caused by human activities, and has serious consequences. This has been reaffirmed, in the light of increasing scientific understanding, in the most recent report of the IPCC in 2001, by the U.S. National Academy of Sciences in its 2001 report, and most recently by the above-mentioned statement from the Science Academies of all G8 countries, along with China, India and Brazil.

This latter statement calls on the G8 nations to "Identify cost-effective steps that can be taken now to contribute to substantial and long-term reduction in net global greenhouse gas emission [and to] recognize that delayed action will increase the risk of adverse environmental effects and will likely incur a greater cost."

On November 28, 2005 the Eleventh Session of the Conference of the Parties to the UNFCCC will meet in Montreal. The UNFCCC does not identify targets for atmospheric concentrations, but rather specifies only that emissions should have been reduced to 1990 levels by 2000. The Kyoto Protocol extends this, setting targets for reducing emissions relative to 1990 levels by 2008-2012.

Both the UNFCCC and the Kyoto Protocol are political treaties, which explicitly state that the developed countries should lead the way in tackling climate change because they have been largely responsible for the rise in greenhouse gas concentrations so far. In particular, it is likely there will be an argument in Montreal over whether new targets for reducing emissions should be set, beyond the first period of the Kyoto Protocol. The United States prevented a discussion of new targets at the previous meeting, in December 2004.

The Montreal meeting could be constructive if there at least emerged agreement to initiate a study of target levels for atmospheric concentrations, as a basis for discussing appropriate plans of action.

More difficult will be that countries must recognize the need to sever the link between economic growth and increasing emissions of greenhouse gases. No country, including the UK and U.S., has yet managed to achieve this, mainly because growth currently means increased use of energy generated from fossil fuels.

Appropriately constructed economic instruments, such as a carbon tax, could help motivate a reappraisal of this perverse message. Ultimately, we need to acknowledge that the increasing incidence and/or severity of extreme events, such as floods, heatwaves, droughts, hurricanes, and the like, is associated with climate change, and the consequent costs to national economies seem likely to exceed those estimated for implementing, for example, Pacala and Socolow's seven wedges.

Initiating such a study of target levels in Montreal should not diminish the pressure for all countries to start cutting emissions now. Small actions now will, given the nature of the non-linear dynamical processes at work, be more important than big actions later.

The UK already seems likely to miss its target for the Kyoto Protocol, because emissions have risen for the past two years, owing to the UK not getting to grips with the difficult questions of meeting demand for electricity and transport without burning more and more fossil fuels.

By the same token, emissions of greenhouse gases by the U.S. are currently 20 percent higher than in 1990, compared with the target assigned to it in Kyoto of a cut of sevenpercent. President George W. Bush's failure to follow through on the commitments his father made on behalf of the U.S is underlined by his failure even to mention climate change, global warming or greenhouse gases in his 2,700-word speech when welcoming the new U.S. Energy Act in August 2005, just weeks after signing the Gleneagles G8 communiqué.

In short, we have here a classic example of the problem or paradox of co-operation - also known as the Prisoner's Dilemma or occasionally the Tragedy of the Commons - referred to at the outset - the science tells us clearly that we need to act now to reduce inputs of greenhouse gases; but unless all countries act in equitable proportions, the virtuous will be economically disadvantaged whilst all suffer the consequences of the sinners' inaction.

In this sense, the climate change disaster which looms this century is an appallingly large-scale experiment in the social sciences.

If this experiment is to end in success for humankind, then it is essential that progress be made at the Montreal meeting. We need countries to initiate a study into the consequences of stabilizing greenhouse gas concentrations at, below, or above twice pre-industrial levels, so that the international community can assess the potential costs of their actions or lack of them. Such an analysis could focus the minds of political leaders, currently worried more about the costs to them of acting now than they are by the consequences for the planet of acting too little, too late.

Lord Robert May of Oxford stood down at the end of his five-year tenure as President of the Royal Society on November 30. He is succeeded by Lord Martin Rees of Ludlow.

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