Climate Change 2007 Update

8. What actions can be taken to reduce greenhouse gas emissions?

• 8.1 What is the cost of mitigation?
• 8.2 How can changes in lifestyle and behaviour patterns contribute?
• 8.3 What are the co-benefits of mitigation?
• 8.4 How can different sectors reduce emissions?
• 8.5 What are the longer term implications of mitigation actions?

8.1 What is the cost of mitigation?

Mitigation measures aim to reduce greenhouse gas emissions and can help avoid, reduce or delay many impacts of climate change.

Mitigation measures entail a certain cost. However, they also provide economic benefits by reducing the impacts of climate change and the associated costs. In addition, they can bring economic benefits by reducing local air pollution and energy resource depletion.

The mitigation potential can be assessed either by looking at technological and regulatory options for specific sectors (“bottom-up”), or by looking at the economy as a whole (“top-down”). Both bottom-up and top-down studies indicate that there is substantial economic potential for the mitigation of global greenhouse gas emissions over the coming decades, that could offset the projected growth of global emissions or reduce emissions below current levels.

Even if the benefits of avoided climate change are not taken into account, there are a number of opportunities whose benefits, such as reduced energy costs and reduced local pollution, equal or exceed their costs to society. Just by implementing those mitigation measures, emissions of greenhouse gases could be reduced by about 6 GtCO₂-eq per year in 2030 (for reference, emissions in 2000 were 43 GtCO₂-eq).

Incentives for mitigation would increase if the benefits of avoided climate change were taken into account and a “carbon price” was established for each unit of greenhouse gas emission. Indeed policies can provide a real or implicit “price of carbon”, for instance through taxes, regulations or emission trading schemes: the higher the “carbon price” the greater the incentive for producers and consumers to invest in products, technologies and processes which emit less greenhouse gases. For instance, at a “carbon price” of 100$ per ton CO₂-equivalent, emissions could be reduced by 16 to 31 GtCO₂-eq/yr.

This assumes that the market is functioning efficiently, that implementation barriers are removed and that all sectors contribute to the overall mitigation efforts.

Stabilizing global greenhouse gas concentrations around 445-535 ppm of CO₂-eq (in 2005, this was about 455 ppm) would cause less than a 3% decrease of the global GDP in 2030, while stabilizing them at 590-710 ppm of CO₂-eq could even bring a small GDP increase. However these costs vary significantly between regions.

Studies indicate that costs may be lower if:

• Revenues from carbon taxes and emission permits are used to promote low-carbon technologies or to replace other existing taxes
• Mitigation policies include all greenhouse gases and carbon sinks
• Mitigation policies address market inefficiencies such as distortionary taxes and subsidies.

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Table SPM-4. Estimated global macro-economic costs in 2030

8.2 How can changes in lifestyle and behaviour patterns contribute?

Changes in lifestyles and consumption patterns that emphasize resource conservation can contribute to developing a low-carbon economy that is both equitable and sustainable. Education and training programmes can lead to the acceptance of energy efficiency and bring significant reductions in greenhouse gas emissions:

• In buildings, changes in occupant behaviour, cultural patterns and consumer choice can reduce energy consumption.
• In cities, urban planning and education can reduce car usage and promote efficient driving habits.
• In industrial organizations, staff training, reward systems, regular feedback, and documentation of existing practices can reduce energy use.

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8.3 What are the co-benefits of mitigation?

Not only do mitigation measures help reduce or delay impacts of climate change, they also have other beneficial effects, for instance on energy use and local air pollution.

Reduced air pollution resulting from the reduction of greenhouse gas emissions could have substantial health benefits and thereby offset part of the cost of mitigation.

Mitigation actions can also improve energy security and agricultural production while reducing pressure on natural ecosystems.

However, mitigation in one country or group of countries could lead to higher emissions elsewhere (“carbon leakage”) or effects on the global economy (“spill-over effects”). More...

8.4 How can different sectors reduce emissions?

For different sectors of human activities a number of key technologies and practices are currently commercially available that could contribute to climate change mitigation
(see Table SPM-3 for more details).

• Energy Supply: Energy infrastructure investments decisions will have long term impacts on greenhouse gas emissions, because of the long life-times of energy infrastructure. They can create opportunities to achieve emission reductions by 2030, notably through:
  
  • investing in the reduction of energy consumption rather than in new energy supply infrastructure
  • switching from coal to gas;
  • nuclear power, although safety, weapons proliferation and waste management remain as constraints;
  • renewable energy (hydro, solar, wind, geothermal and bioenergy);
  • combined heat and power generation,
  • application of Carbon Capture and Sequestration (CCS) technologies.

An increase in the price of fossil fuel could make low-carbon alternative more competitive, but could also lead to the use of high-carbon alternatives such as oil sands and heavy oils.

• Transport: There are multiple mitigation options in the transport sector, such as more fuel efficient vehicles, hybrid vehicles, cleaner diesel engines, biofuels, shift from road transport to rail and public transport, alternatives such as cycling and walking, and urban planning that reduces the need for road transport. However, mitigation efforts may be counteracted by the growth in the sector as well as barriers such as consumer preferences and lack of policy frameworks.
• Buildings: Energy efficiency options for new and existing buildings could considerably reduce CO₂ emissions with net economic benefit, though many barriers against tapping this potential remain. Available options include efficient lighting, appliances, heating and air conditioning, improved insulation, solar heating and cooling, as well as recycling or using alternatives for fluorinated gases in refrigeration.
• Industry: The mitigation potential is highest in energy intensive industries. Methods include the use of more efficient electrical equipment, heat and power recovery, recycling, and control of non-CO₂ gas emissions. Many industrial facilities in developing countries are new and include the latest technology. However, upgrading the many older, inefficient facilities remaining in both industrialized and developing countries could deliver significant emission reductions
• Agriculture: Agricultural practices collectively can make a significant contribution at low cost by increasing the amount of carbon stored away in soil (carbon sinks), by reducing methane and nitrous oxide emissions, by producing crops for energy use, by improving rice cultivation techniques and livestock and manure management to reduce methane emissions and by improving fertilizer application to reduce nitrous oxide emissions. However, biomass production for energy may compete with other land uses and have both positive and negative impacts on the environment and on food security.
• Forestry: Forest-related mitigation activities such as afforestation, reforestation, improved forest management, reduced deforestation, and use of forestry products to replace fossil fuels can considerably reduce greenhouse gas emissions and help capture CO₂ from the atmosphere. Such efforts can also improve sustainable development and adaptation to climate change. Most of the potential lies in the tropical regions, and could notably be achieved by reducing deforestation.
• Waste: The post-consumer waste sector is a small contributor to global greenhouse gas emissions (<5%), yet it can contribute to mitigation efforts at low cost through landfill methane recovery, waste incineration with energy recovery, composting, recycling, and waste minimization.

Large-scale geo-engineering options, such as ocean fertilization to remove CO₂ directly from the atmosphere, or blocking sunlight by bringing material into the upper atmosphere, remain largely speculative and unproven, with the risk of unknown side-effects. More...

8.5 What are the longer term implications of mitigation actions?

In order to stabilize the concentration of greenhouse gases in the atmosphere by 2100 or beyond, emissions would have to stop increasing and then decline. The lower the stabilization level aimed for, the more quickly this decline would need to occur. Mitigation efforts over the next two to three decades will have a large impact on the stabilization level in the longer term.

Mitigation scenarios have been assessed for six different stabilization levels (Category I to VI, as illustrated in table SPM-5 and figure SPM-8).

• On the one hand, to achieve low stabilization at less than 490 ppm CO₂-eq (Category I) would imply that emissions stop increasing and start declining before 2015. This could lead to a global mean temperature increase of about 2 to 2.4°C above pre-industrial levels.
• On the other hand, a delayed decline in emission, for instance starting between 2060 and 2090, could lead to a stabilization level of up to 1030 ppm CO₂-eq (Category VI) which could lead to a global mean temperature increase of about 4.9 to 6.3°C above pre-industrial levels.

These stabilization levels of greenhouse gases in the atmosphere can be achieved by deploying currently available technologies and technologies that are expected to be commercially available in the coming decades. Increased energy efficiency measures, as well as world-wide investments and deployment of low-emission technologies and research into new energy sources will be necessary to achieve stabilization. It will require effective incentives for the development, acquisition, deployment and diffusion of technologies and for addressing related barriers.

By 2050, for low stabilization levels, estimates indicate that mitigation efforts could lead to a global GDP reduction of up to 5.5%. However, costs may differ significantly between regions.

Table SPM-6: Estimated global macro-economic costs in 2050 relative to the baseline for least-cost trajectories towards different long-term stabilization targets

Choices about the scale and timing of greenhouse gas mitigation imply risk management decisions. It involves balancing the economic costs of rapid emission reductions against the climate risks of delayed action. Delayed emission reduction measures would lead to investments in more emission-intensive infrastructure which significantly limits the opportunities to achieve lower stabilization and increases the risk of more severe climate change impacts. More...