From the report

Here we excerpt material from the Summary for Policymakers. The full text of the summary is available at www.ipcc.ch

What’s the cost?

The following table shows some long-term stabilisation scenarios and their estimated macroeconomic costs in 2030 for least-cost trajectories.

Stabilisation target(CO₂–equivalent,parts per million)	Projected global temperature increase (above pre-industrial)	CO₂ emissions peak when?	Change in global CO₂ emissions in 2050 over current (year 2000) levels	Median global GDP reduction (%)	Range of global GDP reduction (%)	Reduction of average annual global GDP growth rates (percentage points)
445–490 ppm	2.0–2.4 °C	2000–2015	Cut of 50–85%	Not available	Less than 3	Less than 0.12
490–535 ppm	2.4–2.8 °C	2000–2020	Cut of 30–60%	Not available	Less than 3	Less than 0.12
535–590 ppm	2.8–3.2 °C	2010–2030	Cut of 30% to increase of 5%	0.6	0.2–2.5	Less than 0.1
590–710 ppm	3.2–4.0 °C	2020–2060	Increase of 10–60%	0.2	-0.6–1.2	Less than 0.06

Global investment in energy infrastructure is projected to be at least US $20 trillion between now and 2030. Such decisions will have long term impacts on greenhouse gas emissions.
Investing in energy efficiency is often cheaper than increasing energy supply.

Improved vehicle efficiency generally brings benefits (lower costs) but other consumer considerations, such as performance and size, come into play. "Market forces alone, including rising fuel costs, are therefore not expected to lead to significant emission reductions."
Worldwide, biofuels are projected to be 3% of transport fuel by 2030, but changes in fuel prices and technology developments might boost this to about 5–10%.
The growth of CO₂ emissions from aviation is expected to be only partially offset by improved fuel efficiency.

Energy efficiency options for new and existing buildings could significantly reduce CO₂ emissions and save money.
By 2020, about 30% of the projected greenhouse gas emissions globally in the building sector can be avoided "with net economic benefit."

The mitigation potential here is predominantly in energyintensive industries. "Full use of available mitigation options is not being made in either industrialised or developing nations."

A large proportion of the mitigation potential in this sector is in "soil carbon management" so that soil and vegetation act as greater carbon sinks.
Current technological options identified include: improved crop and grazing land management, restoration of cultivated peaty soils and degraded lands, improved livestock and manure management to reduce methane (CH₄) emissions, and improved nitrogen fertiliser application techniques to reduce nitrous oxide (N₂O) emissions.

About 65% of the mitigation potential of this sector is in the tropics, and 50% of the total could be achieved by "reducing emissions from deforestation".

Post-consumer waste contributes less than 5% of global greenhouse gas emissions but mitigation action is possible at "low cost" and can promote sustainable development.

"Changes in lifestyles and consumption patterns that emphasise resource conservation can contribute to developing a low-carbon economy that is both equitable and sustainable."