5.12 Can we avoid a 2°C temperature rise?

The answers to the previous four questions explain the basis for the answer given here, which is that it's going to be difficult to avoid 2°C rise by 2100. It all very much depends on the global carbon budget.

The current focus of the policy debate is for a global peak in 2015, reductions of 3% each year leading to a 50% global reduction by 2050 – for a 50/50 chance of avoiding a 2°C increase. But recent work (see Section 5.10 – ‘How do you work out a carbon budget?’) suggests that global reductions of 80% are required.

If even a 50% reduction equates to 80% reductions for developed countries, if we are to give any space to developing countries to develop, then an 80% global reduction must come close to a requirement for full decarbonisation for developed countries by 2050 at the latest. Annual reductions will have to be much more than the 3% usually talked about, with some studies concluding that the challenge for developed countries is for reductions of at least 6% a year after a 2015 peak.

2015 is therefore a useful threshold for evaluating the likely effectiveness of proposed emission reduction measures. Most of the large-scale technology solutions that are proposed (e.g. new nuclear power stations, carbon capture and storage for coal and gas-fired power stations, hydrogen fuel for cars, large-scale shift to electric transport from low-carbon sources, alternatives to kerosene for aviation fuel and so on) are unlikely to make any impact on emission reductions (at least in the UK) before 2020–2025 at the earliest. At least five years too late.

The biggest tool in the box in the short term is behaviour change, with all of the political controversy that brings.

According to the Global Carbon Project's annual carbon budget, current global efforts to bring about reductions in CO₂ emissions are putting us on a course for 4–6°C increases in global temperature.

Adapting to the inevitable impacts of climate change is essential. The further 1.2°C that will take us to 2°C is part of that inevitability. Beyond that depends on serious efforts through international policy development, regions (including coalitions of the willing), countries, business and individuals.

Mitigate for 2°C but adapt for 4°C is becoming an increasingly voiced message over the last two years or so.

• Journalist George Monbiot gives a personal view after a meeting in Copenhagen in March 2009.