2. What is dangerous climate change?

The term ‘dangerous climate change’ is more than just a qualitative one, and was introduced legally in the 1992 UN Framework Convention on Climate Change (UNFCCC). Specifically, this calls for the stabilisation of greenhouse gases so as to ‘prevent dangerous anthropogenic interference with the climate system’. The Framework Convention also proposed that this needed to be achieved within a time-frame that ensured food production was not threatened, that permitted ecosystems to adapt naturally, and that allowed economic development to continue in a sustainable manner. More recently, in 2004, the European Climate Forum highlighted some more specific indicators of dangerous climate change that include: circumstances that could lead to global and unprecedented consequences, extinction of iconic species (for example, the Polar Bear), loss of entire ecosystems or human cultures, a threat to water resources, and a significant rise in mortality rates.

Some of the greatest concerns, with respect to dangerous climate change, involve the crossing of particular thresholds or ‘tipping points’. Examples include the collapse and melting of the Greenland or West Antarctic ice sheets, leading to wholesale, catastrophic sea-level rise, and a shutdown or significant slow-down in the Gulf Stream (or more correctly, the Atlantic Thermohaline Circulation or ATHC), spawning bitterly cold winters in the UK and Europe. Recent observations support acceleration in the rate of ice sheet melting at both poles and a dramatic reduction in the strength of the ATHC. Evaluation of these observations and their potential impacts and implications form the basis of this report.