The science and politics of global climate change

Basic introduction to greenhouse warming

Sunlight heats the surface of the earth. The warmer this gets,the more heat it emits back to space as infra-red radiation, so the temperature of the surface of the earth adjusts itself until the energy from sunlight is balanced by the heat emitted. Molecules of certain gases in the atmosphere - such as water vapour, carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and freons (CFCs), can absorb some of this infra-red radiation and then emit it back to the surface of the earth. This consequently becomes a little warmer and emits more infra-red radiation, until enough heat escapes past the greenhouse gases, such that the sunlight energy is once again balanced by the heat emitted to space out of the top of the atmosphere. As these gases play a similar role to the glass in a greenhouse, this is known as the "greenhouse effect", and its basic physics is well understood.

To appreciate the importance of this, we only need to observe that the surface temperature of the earth is comfortable for life wheras the surface of Venus is far too hot for life (600C hotter than earth) and the surface of Mars is far too cold. Although Mars is further from the Sun, this cannot by itself explain this great difference, which is largely due to the great abundance of greenhouse gases in the atmosphere of Venus and the lack of them on Mars. Moreover the temperature of the earth has been fairly stable for 4 billion years despite increasing solar output, since this was compensated by a decreasing greenhouse effect as life gradually removed CO₂ from the atmosphere and stored it as organic material in the rocks, soils and ocean sediments. Now humans have suddenly discovered these "fossil fuels" and are returning the CO₂ very rapidly to the atmosphere, where it will warm the planet. Graphs showing how both atmospheric CO₂ and global average temperature have risen over the last century (as shown below) are now well known. The warming rate has increased in the last few years and we are already beginning to observe some strange climate phenomena - for example flooding in the USA and Europe, and droughts causing forest fires in South East Asia and Siberia (see section on Novosibirsk conference).

The history of the global climate deduced from analysing bubbles trapped in Antarctic and Greenland ice cores shows that over the last 200,000 years there is a clear correlation between the global temperature and atmospheric Carbon Dioxide (CO₂): when the CO₂ rises suddenly the temperature also rises suddenly, as shown by the graphics above. During the ice ages the global temperature was about 5 ^o C colder and the CO₂ concentration in the atmosphere was 210ppm (parts per million) compared to 290ppm during interglacial periods.

Since the industrial revolution CO₂ in the atmosphere has already risen from 290 to 365ppm due to fossil fuel burning and the temperature has risen about 0.6 ^o C. The temperature rise lags behind the CO₂ rise due to the large heat capacity of the oceans, so even if we stabilise greenhouse gas concentrations in the atmosphere now the temperature would continue to rise for several decades. Global Climate Models (GCMs) on supercomputers can now match current climate changes quite well, if the local cooling effects of sulphate aerosols are included in the model as well as greenhouse warming. They predict an equilibrium global average temperature rise of about 2 -5 C if we double the pre-industrial CO₂ concentration. The table below summarises some basic figures about CO₂ and global warming

The scale of the impact of such temperature rises is shown by the Intergovernmental Panel on Climate Change (IPCC) prediction that about 17% of Bangladesh, and over a hundred million people’s homes worldwide, will be under the sea by the year 2050.

However such predictions are mostly based on "equilibrium" global climate models (GCMs) which assume a gradual warming - such models cannot explain the very sudden warming observed in the ice-core data at the ends of each ice age. These sudden changes are likely to be caused by climate feedback processes. A list of climate feedback processes is shown in the figure (right), which shows for each component of the earth system both how it might be affected by global climate change, and also how it might in turn further change the global climate. The physical feedback processes - including the reflection of sunlight by changing distributions of clouds and sea ice, the interaction between greenhouse warming and stratospheric ozone depletion, and the effect of changing ocean currents, are not easy to predict but at least they are usually included in most GCMs. However both terrestrial vegetation and marine phytoplankton also play critical roles in controlling the global climate through biogeochemical feedback processes. These are difficult to predict and so are not yet included in the GCMs. There is a risk that a combination of such positive biogeochemical feedbacks might greatly amplify the greenhouse warming effect of anthropogenic CO₂ emissions.

The deep ocean can store about 50 times more CO₂ than the atmosphere, and is therefore a large potential sink for CO₂, because this reacts with alkaline seawater to form bicarbonate (HCO₃^-) ions. However the mixing between the surface water layer and the deep ocean is very slow, because the surface layer is heated by the sun and warm water sitting on top of cold water is physically stable. Two natural processes help to "pump" atmospheric CO₂ into the deep ocean. The "solubility pump" (so called because cold water has a higher solubility for CO₂ than warm water) is part of the global "thermohaline circulation", which is mainly driven by the sinking of cold salty surface water formed in the North Atlantic. To balance this, deep water returns to the surface in equatorial regions. However as the climate gets warmer the surface water will become physically more stable and recent models suggest that the "thermohaline circulation" will stop altogether if atmospheric CO₂ exceeds 650ppm - this would cause cooling of north-west Europe which derives it’s heat from the Gulf Stream, but would also reduce the "solubility pump" and hence amplify greenhouse warming elsewhere -itself a positive feedback.

The "biological pump" is driven by the sinking of biological particles from the surface to the deep water -these contain organic carbon derived from CO₂ fixed by photosynthesis in the surface layer. The growth of ocean phytoplankton is controlled principally by the supply of nutrients- nitrate, phosphate, sometimes iron, which are constantly removed from the surface mixed layer by the same sinking particles. Other marine organisms in the deep sea transform these particles back to dissolved nutrients and CO₂, which are then brought back to the surface by upwelling of deep water, driven by the "thermohaline circulation". So if the circulation is reduced due to warming, less phytoplankton will grow and the "biological pump" will remove less CO₂ from the atmosphere, although there will also be less upwelling of CO₂. It is difficult to predict the size of this feedback process but is certainly not zero as assumed by most of the current models.

In addition phytoplankton emit Dimethyl Sulphide (DMS), which reacts with oxygen in the atmosphere to produce sulphur dioxide. This acidic gas forms tiny droplets which help to seed clouds over the ocean, and these reflect sunlight thus cooling the planet. Measurements of methane sulphonic acid (MSA, which is derived from DMS) in ice core bubbles indicate that there were more phytoplankton in the polar oceans during the ice ages, as expected from the theory above. Therefore as the climate gets warmer there will be less seeding of clouds over the ocean - clearly a positive feedback.

Returning to the land, it is clear that the distribution of forests will change as a consequence of increased greenhouse warming. As the climate warms, climate models predict that more trees will grow in northern Siberia and Canada, offsetting the loss of forests further south and in the tropics. However the destruction of forests by fires due to drought, as we witnessed ourselves on the "Climate Train" in southern Siberia (see satellite image with our Novosibirsk conference), may be much faster than the slow growth of new trees in the north, thus releasing a sudden pulse of CO₂ into the atmosphere to add to our emissions from fossil fuel burning. This problem is not taken into account in the current "equilibrium" climate models.

As well as the large amount of carbon stored by forests, we also need to consider two other processes by which trees can affect the global climate. The first process is evapotranspiration - trees pump a lot of water into the atmosphere which cools the local climate by producing low-level clouds which reflect sunlight. If the overall growth of trees increases this could be a negative climate feedback, but this may be offset by a positive physiological feedback: when the atmospheric CO₂ concentration rises each tree responds by reducing the width of the stomata through which it exchanges gases, thereby reducing evapotranspiration. The second process is the albedo effect: forests absorb much more sunlight than grasslands, especially when covered with snow. This warming effect may be particularly important during spring in Siberia if the treeline moves northwards as a consequence of greenhouse warming, maybe causing a temperature increase of over 10 degrees during the month of April.

Large quantities of CO₂ are also released when peat either burns directly or is respired by microorganisms due to drying and subsequent aeration of the soil in southern Siberia when the climate warms. However in northern Siberia, if permafrost melts yet the ground remains waterlogged, anaerobic, methane rather than CO₂ may be released. Methane is a much more powerful greenhouse gas than CO₂ although its lifetime is shorter: after a few years in the atmosphere most of it oxidises to become CO₂. Methane may also be released by flooded coastal wetlands or shelf-sea sediments (methane hydrates) affected by changing sea level due to greenhouse warming. The ice core data shows sudden increases of atmospheric methane at the end of each ice age, and we can expect a similar positive biogeochemical climate feedback in the future. It was concern about the potentially catastrophic effects of the combination of such processes, which led so many scientists to call upon the world community to get together to reduce anthropogenic emissions of greenhouse gases.

Before discussing the politics of climate change, it is helpful to make some basic calculations to illustrate the scale of the problem. Currently, each year about 6 billion tonnes of carbon is emitted to the atmosphere as CO₂ from fossil fuel burning. Of this about 3.5 billion tonnes remains in the atmosphere, about 2 billion tonnes enters the ocean, and about 0.5 may be taken up by increased growth of northern temperate forests (there is considerable uncertainty about this last figure). Therefore if we wish to stabilise CO₂ concentrations at the current level, we have to stop emitting the 3.5 billion tonnes which currently accumulates in the atmosphere each year, which would mean an immediate 60% cut in emissions. There are also about six billion people in the world, so currently we emit on average one tonne per person per year, and would have to reduce this to 0.4 tonnes per person per year. However, this average hides enormous inequity between rich and poor countries. The USA contains 4% of the world’s population but emits 25% of the CO₂, or 5.42 tonnes of carbon per capita in 1995. The equivalent figure for the European Union is 2.33, for Russia 2.85, for China 0.68, for India 0.23 and for the World 1.07. Meanwhile the percentage change in per-capita emissions from 1990 to 1995 for the USA was +1.2%, for the EU -3.4%, for Russia -30%, for China +20%, and for India +21%. Remember also that the populations of India, China and the USA are still increasing significantly (in that order). More figures are given at the end in the analysis of the Kyoto protocol.

Clearly it will be a hard task to persuade everybody to agree to emit only 0.4 tonnes per capita, but many environmental and business organisations assert that by using new technology to produce renewable energy and improve the efficiency of energy use, it is not really so difficult to reduce emissions. There already exist many such technologies: Solar power (including passive solar heating as well as photovoltaics), wind, wave and tidal power (there is a large scope for offshore windmills etc. which don’t change the landscape), energy from renewable biomass, Combined Heat and Power (CHP) stations for cities, etc.. On the demand side, most buildings could also be made much more energy efficient, and this is much cheaper for new buildings if they are originally designed to include energy-saving features. Most of these measures would be commercially viable now if there were taxes or quotas controlling fossil fuel CO₂ emissions, of sufficient magnitude to stabilise atmospheric concentrations at a sustainable level. In other words, burning fossil fuel should be made more expensive because the "external" cost of atmospheric pollution and climate change is not taken into account, and if politicians agreed to use such economic instruments then the clean energy industry would grow rapidly. The money collected from taxes can be used to lower other taxes - i.e. we need a shift from taxing people’s labour to taxing resources, which would also help to reduce unemployment.

In the transport sector, the fastest growing source of CO₂ emissions, finding a technological solution is more difficult because currently cars, buses, lorries and airplanes have to be run on liquid fuel. Although there is much research into using clean hydrogen fuel made with electricity which can be produced from renewable sources, and also using fuels made from renewable biomass sources, it is likely to be several decades before these are widespread, and using hydrogen for aircraft fuel raises safety concerns. Since our cities are already clogged by traffic and more and more countryside is disappearing under tarmac, it makes more sense to focus on changing our lifestyles -promoting instead public transport, bicycling, walking, and changing the way we work by using telecommunications to reduce the need to travel. Such measures are already being implemented in many countries.

Aircraft emissions, however, are growing more rapidly than any other sector. If we wish to leave a comfortable planet for our children, the jet-setting lifestyle cannot continue, but it is a hard task to persuade people to give up their short breaks and cushy business meetings in exotic locations. In organising the "Climate Train" to try to encourage more sustainable travel, we knew we had picked the toughest nut to crack.

At COP1 they agreed the "Berlin Mandate" which required Annex 1 countries to commit themselves to legally binding targets to reduce their own greenhouse gas emissions at COP3- these targets were to become the Kyoto protocol. The developing countries made no such commitment, arguing that the industrialised countries emissions were higher and that they were responsible for most of the CO₂ already accumulated in the atmosphere, as it has a lifetime of about 100 years. However developing countries emissions are rising very rapidly particularly in East Asia, and may soon be greater than the emissions from Annex 1 countries, so clearly unless they are also restrained the problem cannot be solved. Shortly before Kyoto the US Senate passed a resolution that they would refuse to ratify any protocol which did not include "meaningful commitments from developing countries", arguing that a global problem required a global solution.

The critical stumbling block is that the parties have agreed neither any long-term target for atmospheric greenhouse gas concentrations, nor any fundamental principle by which to allocate future quotas between countries. The first straightforward but short-term proposal was that of the Alliance of Small Island States (AOSIS), backed by the Climate Action Network (CAN) of environmental NGOs, which suggested an equal 20% percentage reduction of CO₂ emissions from 1990 levels for each Annex 1 country by the year 2005. The European Union later advocated a 15% reduction by 2010. However to allocate reductions proportional to previous emissions levels still gives a higher quota to countries with higher emissions in the base year: in 1990 the per capita emissions in the USA were almost twice those of western Europe, and much higher than per capita emissions in most developing countries. Clearly this is not an equitable principle which could be applied globally or in the long term, and it broke down even in Kyoto when various Annex 1 countries argued that there were special reasons why it was difficult for them all to meet the same proportional target. Without a clear equitable principle which could apply to all countries, it was hard to defeat such "special case" arguments and consequently the emissions reductions in the Kyoto protocol (see summary at the end of this report) are arbitrary, and the targets for Australia, New Zealand, Russia and Ukraine seem particularly high.

The most obvious equitable principle for allocating quotas is that each person in the world should be entitled to emit an equal amount of greenhouse gases to the atmosphere which we must all share. Since the current inequity between the per capita emissions of the richest and the poorest countries is so great this could not be achieved overnight, so the Global Commons Institute (GCI) proposed the flexible framework of "Contraction and Convergence", whereby the total global emissions would gradually contract towards a level that would stabilise the CO₂ concentration at a safe level (e.g. 450ppm), whilst the proportion of this "cake" allocated to each country would gradually converge towards equal per capita levels by a fixed date (e.g. 2045). GCI’s proposal was recently backed by the Group of African Nations and several other countries, and also by the parliamentarians organisation "Global Legislators for a Balanced Environment". The graph shows the historical CO₂ emissions and future allocations under various stabilisation scenarios and contraction rates for the main groups of countries. Note that Western Europe, Japan, Australia, Canada etc. are included in the green band, wheras Russia and Eastern Europe are in the blue band.

For more explanation of this "breathing" graphic, see GCI's web site

It has also been proposed, most enthusiastically by the US, that emissions quotas should be tradable between countries. In theory the market would then ensure that the price of pollution was the same everywhere, leading to the most "efficient" solution to the problem. However trading is only effective if the original quotas given to all countries are both fair and demanding, as they would be under GCI’s "Contraction and Convergence". If the quotas are arbitrary, as in the Kyoto protocol (see summary at end), then "hot air" trading may result, in which a country sells quota it did not otherwise intend to use for itself, thereby raising global emissions. Another problem is that the developing countries have not yet agreed to any quotas. To get around this Joint Implementation (which became the "Clean Development Mechanism" in the Kyoto protocol) is a scheme whereby an industrialised country pays for projects to reduce emissions within a developing country, and gets emissions credits in return. However this depends on hypothetical "might have been" scenarios which offer great scope for false accounting. The details of trading mechanisms are due to be negotiated at COP4.

Although CO₂, CH4, N2O and CFCs all add significantly to greenhouse warming, many scientists assert that we do not yet have sufficient data to include the emissions of CH4 and N2O, most of which are from agricultural sources and are much harder to quantify than CO₂ from burning fossil fuels. Moreover each gas has a different lifetime in the atmosphere which makes comparison of their Global Warming Potentials (GWPs) in a common "basket" approach dependent on an arbitrary time horizon. Another critical question is whether to include CO₂ emissions or "sinks" from deliberate land-use changes, which are also hard to quantify. Both the "six-gas basket" and "enhancement of sinks" were included in the Kyoto protocol but these details were also postponed for COP4.

Another contentious issue is how to include the "bunker fuels" from international aviation and shipping, which are rising rapidly but currently not allocated to any country. Aircraft fuel is also exempt from any fuel taxes under the regulations of the International Civil Aviation Organisation (ICAO). We had hoped that our "Climate Train" would help to focus attention on this "loophole" in the protocol, and this is discussed further in the next chapter.

Although the agreements are signed by government ministers, they can spend little time focusing on climate change and form few of the thousands of delegates at the convention. For most meetings many of the poorer countries send either officials from their meteorological organisation, or their local ambassadors, the former knowing a lot about climate but little about politics, the latter knowing little about climate and tending to lose sight of the real issues behind endless legal minutiae. So it is widely acknowledged that without the lobbying from Non-Governmental Organisations (NGOs), the process would advance even more slowly.

At COP1 in Berlin, the international youth environmental organisation "ASEED" organised a gathering of over 600 environmental activists camped outside the main conference, who grabbed the attention of the media with simple actions, and were very influential in forcing the government delegates to do something, even locking them inside the building until they reached a basic agreement! At COP2 in Geneva there was no such gathering and there was little significant agreement, except the endorsement of the recent IPCC scientific assessment. Even this obvious step had been strongly opposed by the many lobbying organisations representing the fossil fuel industry, with the support of some oil-producing Gulf states, who played every trick possible to confuse the issue and stall the negotiation process. Although the fossil fuel lobby can afford to send hundreds of delegates to each meeting, they are now becoming more and more discredited. Moreover they have recently been outnumbered by delegates of business NGOs representing smaller industries promoting renewable energy technologies and/or energy efficiency.

The strange atmosphere inside vast UN meetings often seems far removed from the real climate, sun, wind and rain, and from most of the people whose future life is being decided. Professional lobbyists who have spent a long time inside the process and become accustomed to the reams of documents and procedural minutiae may gradually lower the expectations of what they really set out to achieve. Although the "Climate Train" did not set out with any particular lobbying position, because it was intended to be open to anybody who wished to travel by train and boat to Kyoto, we hoped that by trying to show the link between the scale of the problem, and our own lifestyles, we might bring some fresh viewpoints and enthusiasm to the Convention.