KYOTO : OU R LAS T CHANC E
cent of the carbon dioxide currently released into the atmosphere is expected to take many decades to be removed. I t is therefore the concentrations of greenhouse gases i n the atmosphere, i n other words the extent o f accumulation of emissions, which must be focussed on.
Atmospheric concentrations of greenhouse gases have grown significantly since pre-industrial times as a result of human activities. CO2 concentrations have grown from about 280 to almost 360 parts per million volume (ppmv), methane (CH4) from 700 to 1720 parts per billion volume (ppbv), and nitrous oxide (N2O) from about 275 to about 310ppbv.2 I f business continues as usual, the concentrations of greenhouse gases, translated into their carbon-dioxide equivalents, are set to rise to 560ppmv by 2030, double pre-industrial levels, taking levels of long-lived greenhouse gases higher than they have been for several million years.3 A second doubling by 2100 would take us to HOOppmv - four times pre-industrial levels. The consequences would be severe, and wholly unpredictable.
The threat to life Rising temperatures are already the clearest sign of climate change. So far, according to the IPCC, global average temperatures have risen 0.6QC above the pre-industrial average. As Sir John Houghton, the co-chair of the Scientific Working Group of the IPCC, told me, the IPCC's latest coupled ocean-atmosphere models show that i n the second half of the next century, for business as usual, "we would see a global average increase of 2.5QC, with perhaps 4°C over land masses, particularly i n the northern high latitudes, 3-4QC over parts of the Arctic or Antarctic, and possibly substantial regional variations from the global average." I f the increases i n temperature seem modest, i t should be noted that a 3-5QC cooling brought on the most recent
Worst-of-the-century climatic extremes Droughts: South and Eastern UK 1990-1992
Siberia and Poland
Floods: Eastern Australia
Thailand and Cambodia August-Sept. 1991 Cuba February 1992 Papua New Guinea June 1992 Pakistan: Indus September 1992 US Midwest June-August 1993 Northwest Europe December 1993 Southern China May 1994 US Southeast July 1994 Northwest Europe Jan-Feb 1995 Storms: Bangladesh (139,000 dead) May 1991
Samoas (Cyclone Val)
US East Coast
Madagascar (Cyclone Geralda) February 1994
Source: J.Leggett (Ed.), Climate Change and the Financial Sector, Munich 1996.
ice age. What is more, Houghton believes that a second doubling of pre-industrial levels of CO2, which would occur by the end of the twenty-first century, would lead to a rise of 5QC, "with a possibility o f i t being closer to 10QC temperature rise". As Houghton says, "That would be very serious indeed."
While most of the world warms, however, Northern Europe could be plunged into much colder weather because globally higher temperatures could cause the sudden collapse o f the northern spread o f the Gulf Stream, which Ben Matthews, cli matologist at the European Study o f Carbon i n the Ocean, Biosphere and Atmosphere, believes might switch off altogether after 650ppmv. On a business-as-usual scenario this could well happen by the end of the next century.
Other effects of climate change could be equally severe. Many natural ecosystems wil l not be able to adjust fast enough to a rapidly warming world - leading to sharp increases in the already alarming rate of species extinction.
Because of the melting of continental glaciers, and the thermal expansion of the water, sea levels could rise by 0.5-1 metre i f we reach double pre-industrial levels of CO2, according to Sir John Houghton, making low-lying islands, such as the Maldives, uninhabitable. Most worrying o f all , Mark Meier o f the University of Colorado estimates that, were just one-third of the East Antarctic ice-sheet to slip into the sea, the melt would raise sea-levels by 30 metres and completely inundate low-lying land and coastal cities. The portents are not encouraging. Global sea levels have already risen by between 10 and 25 cm, which is significantly higher than the rate averaged over the last several thousand years.4 Worse still, a startling 2.5QC warming i n Antarctica has been reported since 1940, the fastest on record, leading to the disintegration o f Antarctic ice-sheets.5
The threats to fresh water supplies (which are already under pressure), from higher evaporation rates, melting glaciers and snow, and falls i n precipitation, could be very significant. Most continents have already experienced a drought-of-the-century since 1990. Climatic insecurity could cause havoc for farmers who would find i t increasingly difficult to know when to reap and when to sow. A clear danger to food security would be posed first, by proliferating droughts, which the IPCC's models suggest could lead, for example, to soils i n Europe losing up to 50 per cent of their moisture once CO2 equivalent levels double; second, by proliferating floods as violent storms increase and as sea levels rise, drowning valuable arable land; and third, by proliferating pests, which could spread 200 kilometres further north for every PC temperature rise. This would clearly exacerbate existing problems such as chronic malnutrition, which 700 mil lion people already endure. A startling indication of how vulnerable we are to climate change came i n June 1991, when the worst floods so far this century burst across the Yangtze plain. China, which faces the challenge of feeding a quarter of the world's population with 8 per cent of the world's cultivable land, lost 20 per cent of its croplands.6
Climate change is also likely to have adverse impacts on human health, with significant loss of life. Direct health effects include increases i n mortality and illness due to an anticipated increase in the intensity and duration of heat waves and aggravated air pollution. Indirect effects of climate change include increases in the potential transmission o f vector-borne infectious diseases, such as malaria, dengue, yellow fever and some viral encephalitis. Perhaps more catastrophic would be the inevitable flooding o f nuclear and chemical dumps, many of which are on coasts.
Climate change also poses a very real threat o f societal destabilization and conflict. The effect o f drowning coastlines could lead to hundreds o f millions of climate refugees, more than the world has yet seen i n the course of the twentieth cen-
The Ecologist, Vol . 27, No. 6, November/December 1997 KYOTO : OU R LAS T CHANC E
tury. Where would these refugees go? How would they be cared for? A severe disruption o f the world's food supplies through floods, droughts, crop failures and diseases brought about by climate change could trigger famines, wars and civi l disorder i n many countries. As the former U N Secretary General Boutros Boutros-Ghali has said: "The next war in the Middle East wil l be fought over water, not politics."
clouds are o f the low, bright variety, they wil l reflect more of the sun's heat into space. However, i t is equally possible that the clouds that form could tend more towards the higher, cirrus type, i n which case they would reflect less o f the sun's heat than is the case at present and this could magnify warming five-or-six fold. Similarly, as snow and ice continue to melt, there wil l be fewer white areas on Earth to reflect the sun's heat directly back to space. According to one model, this could lead to a warming of up to 2.2-C.11
One of the central predictions of the climate scientists is that weather extremes wil l become more frequent, with significant consequences for human infrastructure and economies. According to Dr Jeremy Leggett, Chief Executive of The Solar Century and former scientific director of Greenpeace, "Given only a slight increase i n the scope for windstorms, droughtrelated wildfires, and floods, the $1.4 trillion insurance industry would be in danger of global collapse, with knock-on economic consequences which are completely ignored i n most analyses of climate change."7 Property-catastrophe losses have already been enormous i n recent years. I n 1995, weather extremes caused $100 billion worth of damage, with costs to insurance companies amounting to $9 billion.8 I f this seems a lot, just imagine the economic consequences were the world's big cities, many of which are on coasts, like New York and Bombay, to be flooded. The cumulative costs of climate change, based even on conservative estimates, would be enormous. They too, however, could be dwarfed i f certain often neglected positive feedbacks, provoked by global warming, were to occur.
Sir John Houghton, co-chair, Scientific Working Group o f the UN's IPCC.
A number of oceanic feedbacks wil l all lead to an increase i n CO2 i n the atmosphere. As the oceans warm, dissolved organic carbon wil l decompose more rapidly, releasing increasing quantities of CO2, and the ocean's ability to draw down CO2, currently 2 billion tonnes every year, wil l also be eroded for a number of reasons.12 First, CO2 is less soluble i n warm water than i n cold. Second, as the research of Ben Matthews shows, with warmer temperatures, the thermohaline circulation wil l
Positive feedbacks A degree of climate change far worse than even the most pessimistic predictions have so far indicated could be triggered by the reactions and interactions of the planet's land, ocean and ice masses in response to the rise in temperatures which we have already initiated, which could, in turn, provoke a significant increase in greenhouse gas concentrations and temperatures.
slow. This wil l reduce the amount of CO2 usually taken down from the surface to the deep ocean, from which, in addition, less nutrients wil l be supplied to the oceans' major absorber of CO2, ocean plankton, whose numbers wil l consequently fall and CO2 levels rise accordingly. Furthermore, i f there are fewer plankton, they wil l no longer generate sufficient dimethyl-
Climate change poses a very real threat of societal destabilization and conflict. The effect of drowning coastlines could lead to hundreds of millions of climate refugees, more than the world has yet seen in the course of the twentieth century.
There are a number o f pos-
sible biospheric feedbacks. I n a warmer world, plants wil l respire more rapidly, releasing more CO2 into the atmosphere. With global warming, forests which do not adapt rapidly enough to rising temperatures wil l rot, releasing large quantities o f CO2 and methane. The land sink could further be impoverished as forests become increasingly dry, resulting i n increasingly frequent forest fires, which wil l release millions o f tonnes of CO2.
sulphide to form cloud condensation nuclei, which create bright white clouds that reflect sunlight. The planet wil l therefore warm still further. According to a climatologist at the University of East Anglia, who prefers to remain anonymous, "I f you took away this plankton-clouds effect, you could see a warming of the order of maybe 5°C i n the Southern Ocean." Some scientists suggest that the oceans' absorptive capacity could be reduced by 50 per cent as the ocean circulation system slows down.13
Warming wil l also accelerate decomposition rates of CO2 stocks stored i n tundra soils, allowing the stored carbon to be released. Similarly, as permafrost melts and peat bogs warm, large quantities of methane (which traps 63 times more heat than does CO2) wil l find their way into the atmosphere, further adding to climate change. Annual liberation of as little as 1 per cent per year of either CO2 or methane stored i n the top metre of soils in tundra or peat could double the current rate of increase in the equivalent of atmospheric CO2.9 As sea levels rise, coastal vegetation wil l be flooded, releasing methane and nitrous oxide. I n a warmer world there wil l also be more evaporation, and so more water vapour in the atmosphere, adding significantly to the warming, possibly by as much as 1.8QC.10
One o f the most important potential atmospheric feedbacks relates to changed cloud cover. I t is thought that the Earth wil l become cloudier as temperatures rise (something which has already been measured throughout this century). I f these extra
I n the opinion of James Lovelock, atmospheric scientist and father o f the Gaia theory, the burden of added greenhouse gases could well be taking the planet close to the limits within which i t can operate as a self-regulating system. According to climate change author Peter Bunyard, 'when CO2 concentrations reach 400ppmv, Lovelock fears the algal system could collapse and the surface temperatures rise quickly. Should the concentrations rise to 700ppmv, then Gaian terrestrial regulation may collapse. A t that stage, Lovelock tells us, we are i n uncharted waters. How disturbing then, that we are within a century of taking ourselves into those waters.'
What is being presented here is the very worst case scenario. The point is not that i t wil l happen, only that i t could happen. I n the words o f Dr Jeremy Leggett, "a snowballing synergism of feedbacks is possible i f our luck is out." The uncertainty involved, however, apparently explains the IPCC's relative neglect of the importance of positive feedbacks. Sir John
The Ecologist, Vol . 27, No . 6, November/December 1997