Climate Change 2001: Mitigation

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Intergovernmental Panel on Climate Change

2003

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Introduction

1. This report assesses the scientific, technical, environmental, economic and social aspects of the

mitigation of climate change. Research in climate change mitigation1 has continued since the

publication of the IPCC Second Assessment Report (SAR), taking into account political changes

such as the agreement on the Kyoto Protocol to the United Nations Framework Convention on

Climate Change (UNFCCC) in 1997, and is reported on here. The Report also draws on a number of

IPCC Special Reports, notably the Special Report on Aviation and the Global Atmosphere, the

Special Report on Methodological and Technological Issues in Technology Transfer (SRTT), the

Special Report on Emissions Scenarios (SRES), and the Special Report on Land Use, Land Use

Change and Forestry (SRLULUCF).

2. Climate change is a problem with unique characteristics. It is global, long-term (up to several

centuries), and involves complex interactions between climatic, environmental, economic, political,

institutional, social and technological processes. This may have significant international and

intergenerational implications in the context of broader societal goals such as equity and sustainable

development. Developing a response to climate change is characterized by decision-making under

uncertainty and risk, including the possibility of non-linear and/or irreversible changes (Sections

1.2.5, 1.3, 10.1.2, 10.1.4, 10.4.5).

3. Alternative development paths4 can result in very different greenhouse gas emissions. The

SRES and the mitigation scenarios assessed in this report suggest that the type, magnitude, timing

and costs of mitigation depend on different national circumstances and socio-economic, and

technological development paths and the desired level of greenhouse gas concentration stabilization

in the atmosphere (see Figure SPM.1 for an example for total CO2 emissions). Development paths

leading to low emissions depend on a wide range of policy choices and require major policy

changes in areas other than climate change (Sections 2.2.2, 2.3.2, 2.4.4, 2.5).

4. Climate change mitigation will both be affected by, and have impacts on, broader socio-

economic policies and trends, such as those relating to development, sustainability and equity.

Climate mitigation policies may promote sustainable development when they are consistent with

such broader societal objectives. Some mitigation actions may yield extensive benefits in areas

outside of climate change: for example, they may reduce health problems; increase employment;

reduce negative environmental impacts (like air pollution); protect and enhance forests, soils and

watersheds; reduce those subsidies and taxes which enhance greenhouse gas emissions; and

induce technological change and diffusion, contributing to wider goals of sustainable development.

Similarly, development paths that meet sustainable development objectives may result in lower

levels of greenhouse gas emissions (Sections 1.3, 1.4, 2.2.3, 2.4.4, 2.5, 7.2.2, 8.2.4).

5. Differences in the distribution of technological, natural and financial resources among and within

nations and regions, and between generations, as well as differences in mitigation costs, are often

key considerations in the analysis of climate change mitigation options. Much of the debate about

the future differentiation of contributions of countries to mitigation and related equity issues also

considers these circumstances5. The challenge of addressing climate change raises an important

issue of equity, namely the extent to which the impacts of climate change or mitigation policies

create or exacerbate inequities both within and across nations and regions. Greenhouse gas

stabilization scenarios assessed in this report (except those where stabilization occurs without new

climate policies, e.g. B1) assume that developed countries and countries with economies in

transition limit and reduce their greenhouse gas emissions first.

6 Emissions from all regions diverge from baselines at some point. Global emissions diverge earlier

and to a greater extent as stabilization levels are lower or underlying scenarios are higher. Such

scenarios are uncertain, do not provide information on equity implications and how such changes

may be achieved or who may bear any costs incurred. This usage differs from that in the

UNFCCC, where climate change refers to a change of climate that is attributed directly or indirectly

to human activity that alters the composition of the global atmosphere and that is in addition to

natural climate variability observed over comparable time periods.