The AVOID programme has demonstrated that limiting global warming to 2 °C above pre-industrial (1750) levels, until at least the year 2500, crucially affects the amount of mitigation that's needed.
A 'business-as-usual' scenario with no mitigation would see greenhouse gases rising throughout the century and a global temperature increase of up to 4 °C. However, in a strong mitigation scenario, emissions are cut so they fall year on year until they reach a low, stable level.
The AVOID results show that it is possible to restrict warming to 2 °C or less during the 21st century with at least a 50% probability. For example, if emissions peaked in 2016 followed by a 4% rate of reduction, the warming target would stay below 2 °C. If emissions peaked a few years later, for example in 2020, it would still be possible to limit warming to 2 °C by 2100. However, steeper reductions would be necessary after that peak year.
What is the feasibility of emissions reductions?
Limiting global temperature rise to just under 2 °C is possible yet still very challenging and will require cooperation and organisation on global, national and regional scales. Stabilising greenhouse gas concentrations in the atmosphere at sufficiently low levels will limit global temperatures rise to under 2 °C until at least 2500. This would be a potentially major breakthrough in stopping the escalation of climate change.
Implementing reduction technologies
A range of reduction measures throughout human activity is necessary to achieve the 2 °C warming limit.
The largest contributor to greenhouse gases is the energy sector. Renewable energy sources such as wind, solar and biomass, and advanced fuels such as bio-energy, are expected to play an especially important role in meeting the demand for low carbon energy. Nuclear and coal power will also continue to play a role in the near term, while carbon capture and storage may ensure emissions stability. Each has drawbacks, either in terms of land utilisation, waste management and proliferation risks, or coal extraction.
Carbon capture and storage
Carbon capture and storage (CCS) technology, by which greenhouse gas emissions from burning fossil fuels is pumped underground, is still under development. If CCS can be developed and deployed over the next few decades, some continued exploitation of fossil fuels may be viable.
The costs of mitigation
All emissions-reduction measures will cost, but the long-term goal of avoiding large-scale damage from climate change makes it cheaper in the long run. Some mitigation has other positive environmental impacts, such as reduced pollution. Mitigation technologies can be combined, for example bio-energy and CCS, which could produce negative emissions. There are currently many unanswered questions regarding the long-term costs of the more experimental mitigation technologies, and more research is necessary.
Last updated: 17 December 2013