Recent uncertainties

An article of 10 July 2004 in New Scientist was headed 'Peat bogs harbour carbon time bomb'. Research in the University of Wales at Bangor indicates that 'The world's peatland stores of carbon are emptying at an alarming rate' (Chris Freeman). Peat bogs store huge quantities of carbon and the evidence is that this is leaching into rivers in the form of dissolved organic carbon (DOC) at the rate of about 6 per cent per year. Bacteria in rivers rapidly convert DOC into CO2 that is released into the atmosphere. Recent research shows that DOC in Welsh rivers has increased 90 per cent since 1988. Freeman predicts that, by the middle of the century, DOC from peat bogs could be as great a source of atmospheric CO2 as the burning of fossil fuels. It appears to be another feedback loop in that an increase in CO2 in the atmosphere is absorbed by vegetation which in turn releases it into the soil moisture. There it feeds bacteria in the water which, in turn, breaks down the peaty soil allowing it to release stored carbon into rivers. Global warming is causing peat bogs to dissolve.

The uncertainty with perhaps the greatest potential to derail current predictions about global warming is the role of the clouds, described by New Scientist as 'the wild card in global warming predictions. Add them to climate models and some frightening possibilities fall out' (Fred Pierce, New Scientist, 24 July 2004). The worry is that global warming will either reduce the global level of cloud cover or change the character of the clouds and their influence on solar radiation. Recent modelling conducted by James Murphy of the Met Office Hadley Centre for Climate Prediction has factored in a range of uncertainties in cloud formations such as cloud cover, the lifetime of clouds and their thickness. The model suggested that warming could reach up to 10°C on the basis of a doubling of atmospheric CO2 which is widely regarded as inevitable. David Stainforth of Oxford University warns of the possibility of a 12°C rise by the end of the century. Cirrus clouds are the most efficient at reflecting heat back to Earth and these are becoming more prevalent. It is expected that the next range of predictions by the IPCC due in 2007 will take account of feedback from cloud cover and produce significantly higher worst case temperature scenarios (from New Scientist, 24 July 2004, pp. 45-47).

Another cause for concern stems from research finding from the Universities of Sheffield and Bristol. In the Eocene epoch 50 million years ago there was a catastrophic rise in temperature with seas 12°C warmer than today. The evidence comes from oxygen trapped in the shells of marine fossils. This leaves a distinct isotope pattern which gives an indication of the sea temperature at a given time. Evidence from plant fossils has shown that CO2 levels were similar to the present day and therefore could not have been responsible for that level of warming. It transpires that this was due to emissions of methane, ozone and nitrous oxide, all more powerful greenhouse gases than CO2. At the time the Earth was carpeted with wetlands which produced high levels of methane which led to runaway warming. At the present time it is cattle, rice fields and termites which are major sources of the gas. According to Professor Beerling of Sheffield University: 'Methane is being produced in increasing amounts thanks to the spread of agriculture in the tropics. Rice is a particularly intensive source. Car exhaust gases and nitrogen fertilisers are also increasing other gases' (The Observer, 11 July 2004). With a predicted steep rise in emissions from transport over the next decades, the latter point is a serious cause of concern.

It is sobering to compare how, according to the UN, different countries are making progress or otherwise in cutting their CO2 emissions. It should be noted that the improvement in the case of Russia is due to the collapse of its heavy industry since 1990 (Figure 2.4).

Up to now the focus has been on limiting CO2 emissions almost to the exclusion of other greenhouse gases. It is time to spread the net more widely if there is not to be a rerun of the Eocene catastrophe.

United States Russia

European Union Japan

China India

Figure 2.4

CO2 emissions by principal nations (UNFCCC 2004)


USA EU China Russia Japan India

1990 2002 1994 only







2001 (both China figures include Hong Kong)

SOURCES: UNFCCC (China figures from IEA)

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