Charles Keeling had established by the early 1960s that CO 2 levels were in fact rising. But the link between CO2 and climate change still needed to be established. We knew that, in general, CO2 is a component in the climate system, but it doesn't necessarily follow
8 See for example A. Meyer, Contraction and Convergence: The Global Solution to Climate Change, Schumacher Briefings 5 (Totnes: Green Books, 2000), p. 28.
9 Carbon Positive, 'West exporting emissions to China,'. See http://www.carbon-positive.net.
(climate being a complicated thing) that the observed change in CO2 has or would lead to climate change, let alone that if it did, the changes implied would be dramatic or dangerous. But by around 1990, we also started to have strong evidence that in fact the world had warmed, by around 0.6 °C, during the twentieth century. There were many efforts from 1979 onwards to firm up the state of knowledge, organised primarily by the UN's World Meteorological Organization (WMO). This included: palaeoclimatic research building up a picture of past climate changes; the development of models, known as general circulation models, to simulate existing climate and thus the effect of increased GHG concentrations; research on the interaction between the atmosphere and the oceans, known to be crucial to the global carbon cycle; and a focus on possible alternative explanations (such as sunspots or natural climatic variation) for the observed rise in global average temperatures.
Increasingly, a series of measures of past climates (other than direct measurements) showed a decisive upswing in CO2 levels and global temperatures from shortly after the time of Watt's invention. These measures include older temperature records plus a series of proxies for temperature found, for example, in tree rings or ice cores. The result of combining these measures has produced what has become known as the 'hockey stick'. When all this evidence is put together, we get a picture of relatively stable temperatures for much of the last millennium, and then a sharp upward trend from around 1900 onwards (there is of course a time-lag between emissions and their effects).
Throughout this period there was (and continues to be, as the recent so-called 'climategate' controversy shows) a small but vocal group of companies with a clear stake in ensuring that climate science doesn't support the case for dramatic cuts in fossil fuel use, while scientists such as Fred Singer and Richard Lindzen have made a name for themselves in spreading doubt about the robustness of the scientific consensus on climate change.10 More on this in the next chapter.
In the later period, the state of knowledge was organised through the Intergovernmental Panel on Climate Change (IPCC), established by the WMO and United Nations Environmental Programme (UNEP) jointly in 1988. The IPCC's assessment reports (there have now been four of them) have marked key stages in the consolidation of both the
10 P. Newell, Climate for Change: Non-State Actors and the Global Politics of the Greenhouse (Cambridge: Cambridge University Press, 2000), pp. 81-2, 101.
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