The symposium's conclusions

The symposium's conclusions

Among the conclusions reached, the most significant was a new assessment of the link between the concentration of greenhouse gases in the atmosphere and the increase in global temperature levels. Some researchers have argued that the most seriousconsequences of global warming might be avoided if global average temperatures rose by no more than 2 °C (3.6 °F) above pre-industrial levels (1.4 °C above present levels). It had generally been assumed that this would occur if greenhouse gas concentrations rose above 550 ppm carbon dioxide equivalent by volume. This concentration was, for example, informing government in certain countries, including the European Union.^[22]

The conference concluded that, at the level of 550 ppm, it was likely that 2 °C would be exceeded, according to the projections of more recent climate models. Stabilising greenhouse gas concentrations at 450 ppm would only result in a 50% likelihood of limiting global warming to 2 °C, and that it would be necessary to achieve stabilisation below 400 ppm to give a relatively high certainty of not exceeding 2 °C.^[23]

The conference also claimed that, if action to reduce emissions is delayed by 20 years, rates of emission reduction may need to be 3 to 7 times greater to meet the same temperature target.^[23]

Proceedings of the symposium were published in 2011, in an open-access special issue of the Royal Society's Philosophical Transactions A.^[24]

Reactions to the symposium

As a result of changing opinion on the "safe" atmospheric concentration of greenhouse gases, to which this conference contributed, the UK Government changed the target in theClimate Change Act from 60% to 80% by 2050.^{[25][not in citation given]}