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
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
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
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
per year in 2030 (for reference, emissions in 2000 were 43
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
emissions could be reduced by 16 to 31
This assumes that the market is functioning efficiently, that
implementation barriers are removed and that all sectors
contribute to the overall mitigation efforts.
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
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
- Mitigation policies include all
greenhouse gases and
- Mitigation policies address market inefficiencies such
as distortionary taxes and
Table SPM-4. Estimated global macro-economic
costs in 2030
8.2 How can changes in lifestyle and behaviour patterns contribute?
Public transport can help reduce greenhouse gas emissions.
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
- 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.
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
while reducing pressure on natural
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”).
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
- Energy Supply: Energy infrastructure
investments decisions will have long term impacts on
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
- switching from coal to gas;
- nuclear power, although safety, weapons
proliferation and waste management remain as
- 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
- 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
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
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.
production for energy
may compete with other
land uses and have both
positive and negative impacts on the environment and on food
- Forestry: Forest-related mitigation
activities such as
forest management, reduced
deforestation, and use
of forestry products to replace
fossil fuels can
emissions and help capture CO2 from the
efforts can also improve
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
recovery, waste incineration with energy recovery,
composting, recycling, and waste minimization.
Large-scale geo-engineering options, such as ocean
fertilization to remove
directly from the
atmosphere, or blocking
sunlight by bringing material into the upper atmosphere, remain
largely speculative and unproven, with the risk of unknown
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
- 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
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
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
Table SPM-6: Estimated global macro-economic
costs in 2050 relative to the baseline for least-cost
trajectories towards different long-term stabilization
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