IPCC WGIII AR4 report analyzes mitigation options of climate change

4 May 2007

At a climate conference in Bangkok, the UN’s Intergovernmental Panel on Climate Change (IPCC) has released the third and final volume of its Fourth Assessment Report (AR4) “Climate Change 2007”. This volume, prepared by the IPCC’s Working Group III (WGIII), analyses climate change mitigation options for the main economic sectors in the near-term, and provides information on long-term mitigation strategies for various stabilization levels.

Global greenhouse gas (GHG) emissions have grown by 70% between 1970 and 2004, states the report. The largest growth in global GHG emissions has come from the energy supply sector—an increase of 145%. The growth in direct emissions in this period from transport was 120%. Under the “business as usual” scenario, GHG emissions would rise by between 25% and 90% over the next 25 years.

Stabilization of atmospheric GHG levels is possible at a reasonable cost, according to the report. Current GHG concentration is equivalent to a CO₂ level of 425 ppm. Stabilization to a level between 445 and 535 ppm CO₂ by 2030 (“short and medium term”) would cost up to 3% of global GDP. Smaller GHG reductions could even stimulate economic growth.

GHG concentrations of 445-490 ppm are believed to allow to control the temperature rise to 2.0-2.8°C. The policy of the European Union is to keep the temperature increase below 2°C, thus requiring a stabilization at about 450 ppm.

A number of mitigation technologies are discussed, such as carbon capture and storage in fossil fuel power plants, and nuclear power. The following mitigation options are envisioned for the transport sector:

• Improved vehicle efficiency measures, leading to fuel savings, have net benefits for light-duty vehicles, but the market potential is lower than the economic potential due to the influence of such consumer considerations as performance and size. There is not enough information to assess the mitigation potential for heavy-duty vehicles.
• Biofuels might play an important role in addressing GHG emissions, depending on their production pathway. Biofuels used as gasoline and diesel fuel additives/substitutes are projected to grow to 3% of total transport energy demand in 2030.
• Modal shifts from road to rail and inland waterway shipping and from low-occupancy to high-occupancy passenger transportation, as well as land-use, urban planning and non-motorized transport offer opportunities for GHG mitigation, depending on local conditions and policies.
• Medium term mitigation potential for CO₂ emissions can also come from the aviation sector.
• Realizing emissions reductions in the transport sector is often a co-benefit of addressing traffic congestion, air quality and energy security.

Government policies and measures that could be implemented in the transportation sector include mandatory fuel economy, biofuel blending and CO₂ standards; taxes on vehicle purchase, registration, use and motor fuels, road and parking pricing; influence mobility needs through land use regulations, and infrastructure planning; investment in attractive public transport facilities and non-motorized forms of transport.

The report also discusses the GHG stabilization strategies in the long term, by 2050, and indicates that making development more sustainable by changing development paths can make a major contribution to climate change mitigation.

The previous volumes of the AR4 report dealt with the scientific basis of climate change, and with future impacts.

Source: IPCC (WGIII Summary for Policymakers)