Rapid action allows controlled change
The IPCC tells us we have a choice about the sort of world we have. We can have ‘controlled’ climate change, and aim to keep temperatures within the “safe” range that has prevailed for thousands of years, or we can continue on our current road to un-controlled or ‘run-away’ climate change.
Controlled climate change means global warming of no more 2°C, a consequent sea level rise of up to 2 meters by 2100, and a move to the stabilization of CO2 at less than 350 ppm.
The other choice is run-away climate change:
- Rapid, non-linear change to a new, much hotter, climate regime (IPCC 2007).
- Large temperature increases (6-7°C).
- Sea level rises of 7m to a possible 25m.
- Desertification of several major ecosystems: tropical forests and major granaries via drought, upper ocean waters via acidification.
- Massive species loss.
- Submerging of the most populous coastal cities.
- Large loss of human life and enormous changes in the world’s political and economic geography.
This occurs when stabilising influences on the climate (e.g. oceans absorbing CO2) are outweighed by de-stabilising effects, such as methane and CO2 releases from melting tundra).
We lose any chance to control changes if we go 2°C above pre-industrial global mean temperatures, i.e. 1.2°C above current. Some ‘tipping-points’ may occur before that point, some after.
To avoid crossing this tipping point we need average global per capita emissions of no more that 2t CO2e per person per annum by 2050. Current averages are 24t CO2e per person in the USA and 4t CO2e in China.
Controlled climate change may be within the adaptive capacity of modern societies. Run-away climate change is not.