Policy implications: redefining dangerous climate change

The group's research on actual thresholds (tipping points) in the Earth's climate system led them to re-examine how dangerous anthropogenic interference (DAI) in the climate system is defined. Most efforts to define this are usually framed in terms of global annual mean surface temperature change with 2°C above preindustrial being the most widely accepted climate policy 'target'. Yet, no actual large-scale threshold (or 'tipping point') in the climate system (of which there are probably several) has been clearly linked to 2°C global warming. Of those that can be indirectly linked to global temperature change, the dangerous levels are necessarily imprecise and vary, with estimates ranging from ~1°C above preindustrial upwards. In this context, some alternative approaches to defining dangerous climate change have been offered in the paper beyond 2°C: redefinding dangerous climate change for physical systems published in WIREs Climate Change March 2011.