Executive summary

This chapter identifies four types of inter-relationships between adaptation and mitigation:

• Adaptation actions that have consequences for mitigation,
• Mitigation actions that have consequences for adaptation,
• Decisions that include trade-offs or synergies between adaptation and mitigation,
• Processes that have consequences for both adaptation and mitigation.

The chapter explores these inter-relationships and assesses their policy relevance. It is a new chapter compared to the IPCC Third Assessment Report and is based on a relatively small, albeit growing, literature. Its key findings are as follows.

Effective climate policy aimed at reducing the risks of climate change to natural and human systems involves a portfolio of diverse adaptation and mitigation actions (very high confidence).

Even the most stringent mitigation efforts cannot avoid further impacts of climate change in the next few decades (Working Group I Fourth Assessment Report, Working Group III Fourth Assessment Report), which makes adaptation unavoidable. However, without mitigation, a magnitude of climate change is likely to be reached that makes adaptation impossible for some natural systems, while for most human systems it would involve very high social and economic costs (see Chapter 4, Section 4.6.1 and Chapter 17, Section 17.4.2). Adaptation and mitigation actions include technological, institutional and behavioural options, the introduction of economic and policy instruments to encourage the use of these options, and research and development to reduce uncertainty and to enhance the options’ effectiveness and efficiency [18.3, 18.5]. Opportunities exist to integrate adaptation and mitigation into broader development strategies and policies [18.6].

Decisions on adaptation and mitigation are taken at different governance levels and inter-relationships exist within and across each of these levels (high confidence).

The levels range from individual households, farmers and private firms, to national planning agencies and international agreements. Effective mitigation requires the participation of major greenhouse-gas emitters globally, whereas most adaptation takes place from local to national levels. The climate benefits of mitigation are global, while its costs and ancillary benefits arise locally. In most cases, both the costs and benefits of adaptation accrue locally and nationally [18.1, 18.4, 18.5]. Consequently, mitigation is primarily driven by international agreements and ensuing national public policies, possibly complemented by unilateral and voluntary actions, whereas most adaptation involves private actions of affected entities, public arrangements of impacted communities, and national policies [18.1, 18.7].

Creating synergies between adaptation and mitigation can increase the cost-effectiveness of actions and make them more attractive to stakeholders, including potential funding agencies (medium confidence).

Analysis of the inter-relationships between adaptation and mitigation may reveal ways to promote the effective implementation of adaptation and mitigation actions together [18.5]. However, such synergies provide no guarantee that resources are used in the most efficient manner when seeking to reduce the risks to climate change [18.7]. In addition, the absence of a relevant knowledge base and of human, institutional and organisational capacity can limit the ability to create synergies. Opportunities for synergies are greater in some sectors (e.g., agriculture and forestry, buildings and urban infrastructure) but are limited in others (e.g., coastal systems, energy, health). A lack of both conceptual and empirical information that explicitly considers both adaptation and mitigation makes it difficult to assess the need for and potential of synergies in climate policy [18.3, 18.4, 18.8].

It is not yet possible to answer the question as to whether or not investment in adaptation would buy time for mitigation (high confidence).

Understanding the specific economic trade-offs between the immediate localised benefits of adaptation and the longer-term global benefits of mitigation requires information on the actions’ costs and benefits over time. Integrated assessment models provide approximate estimates of relative costs and benefits at highly aggregated levels, but only a few models include feedbacks from impacts. Intricacies of the inter-relationships between adaptation and mitigation become apparent at the more detailed analytical and implementation levels [18.4, 18.5, 18.6]. These intricacies, including the fact that specific adaptation and mitigation options operate on different spatial, temporal and institutional scales and involve different actors with different interests, beliefs, value systems and property rights, present a challenge to designing and implementing decisions based on economic trade-offs beyond the local scale. In particular the notion of an ‘optimal mix’ of adaptation and mitigation is difficult to make operational, because it requires the reconciliation of welfare impacts on people living in different places and at different points in time into a global aggregate measure of well-being. [18.4, 18.7]

People’s capacities to adapt and mitigate are driven by similar sets of factors (high confidence).

These factors represent a generalised response capacity that can be mobilised for both adaptation and mitigation. Response capacity, in turn, is dependent on the societal development path chosen. Enhancing society’s response capacity through the pursuit of sustainable development is therefore one way of promoting both adaptation and mitigation [18.6]. This would facilitate the effective implementation of both options, as well as their mainstreaming into sectoral planning and development. If climate policy and sustainable development are to be pursued in an integrated way, then it will be important not simply to evaluate specific policy options that might accomplish both goals but also to explore the determinants of response capacity that underlie those options as they relate to underlying socio-economic and technological development paths [18.6, 18.7].