ABSTRACT
Until very recently, the atmospheric concentrations of C02 had been increasing and accelerating since regular measurements began in 1958. Only in the mid-1990s has there been a levelling-off, probably because of the world-wide recession, the run-down of industry in the former Soviet bloc and the substitution of gas for coal. This pause is likely to be only temporary; if the concentrations resume their upward trend, they will eventually lead to significant climate changes. The important questions concern the likely magnitude and timing of these events. Are they likely to be so large and imminent as to warrant immediate remedial action, or to be sufficiently small and delayed, so that we can live with them or adapt to them?
