TS 6.2 Future research needs

Impacts under different assumptions about future development pathways

Most AR4 studies of future climate change are based on a small number of studies using SRES scenarios, especially the A2 and B2 families [2.3.1]. This has allowed some limited, but incomplete, characterisation of the potential range of futures and their impacts [see Section 4 on key future impacts in all core chapters].

Scenarios are required:

• to describe the future evolution of the world under different and wide-ranging assumptions about how societies, governance, technology, economies will develop in future;
• at the regional and local scales appropriate for impacts analysis;
• which allow adaptation to be incorporated into climate-change impact estimates;
• for abrupt climate change such as the collapse of the North Atlantic Meridional Overturning Circulation, and large sea-level rises due to ice sheet melting [6.8];
• for beyond 2100 (especially for sea-level rise) [6.8, 11.8.1].

Increasingly, climate modellers run model ensembles which allow characterisation of the uncertainty range for each development pathway. Thus, the impacts analyst is faced with very large quantities of data to capture even a small part of the potential range of futures. Tools and techniques to manage these large quantities of data are urgently required [2.3, 2.4].

Damages avoided by different levels of emissions reduction

Very few studies have been carried out to explore the damages avoided, or the impacts postponed, by reducing or stabilising emissions, despite the critical importance of this issue for policy-makers. The few studies which have been performed are reviewed in Chapter 20 of this Report [20.6.2] and show clearly the large reductions in damages which can be achieved by mitigating emissions [T20.4]. Existing research has emphasised the global scale, and studies which are disaggregated to the regional, and even local, scale are urgently required.

Climate-science-related research needs

Two of the most important requirements identified relate to research in climate change science, but have been clearly identified as a hindrance to research in impacts, adaptation and vulnerability.

• The first is that our understanding of the likely future impacts of climate change is hampered by lack of knowledge regarding the nature of future changes, particularly at the regional scale and particularly with respect to precipitation changes and their hydrological consequences on water resources, and changes in extreme events, due in part to the inadequacies of existing climate models at the required spatial scales [T2.5, 3.3.1, 3.4.1, 4.3].
• The second relates to abrupt climate change. Policy-makers require understanding of the impacts of such events as the collapse of the North Atlantic Meridional Overturning Circulation. However, without a better understanding of the likely manifestation of such events at the regional scale, it is not possible to carry out impacts assessments [6.8, 7.6, 8.8, 10.8.3].

Observations, monitoring and attribution

Large-area, long-term field studies are required to evaluate observed impacts of climate change on managed and unmanaged systems and human activities. This will enable improved understanding of where and when impacts become detectable, where the hotspots lie, and why some areas are more vulnerable than others. High-quality observations are essential for full understanding of causes, and for unequivocal attribution of present-day trends to climate change [1.4.3, 4.8].

Timely monitoring of the pace of approaching significant thresholds (such as abrupt climate change thresholds) is required [6.8, 10.8.4].

Multiple stresses, thresholds and vulnerable people and places

It has become clear in the AR4 that the impacts of climate change are most damaging when they occur in the context of multiple stresses arising from the effects, for example, of globalisation, poverty, poor governance and settlement of low-lying coasts. Considerable progress has been made towards understanding which people and which locations may expect to be disproportionately impacted by the negative aspects of climate change. It is important to understand what characteristics enhance vulnerability, what characteristics strengthen the adaptive capacity of some people and places, and what characteristics predispose physical, biological and human systems to irreversible changes as a result of exposure to climate and other stresses [7.1, B7.4, 9.1, 9.ES]. How can systems be managed to minimise the risk of irreversible changes? How close are we to tipping points/thresholds for natural ecosystems such as the Amazon rain forest? What positive feedbacks would emerge if such a tipping point is reached?

Climate change, adaptation and sustainable development

The AR4 recognised that synergies exist between adaptive capacity and sustainable development, and that societies which are pursuing a path of sustainable development are likely to be more resilient to the impacts of climate change. Further research is required to determine the factors which contribute to this synergy, and how policies to enhance adaptive capacity can reinforce sustainable development and vice versa [20.9].

Further understanding of adaptation is likely to require learning-by-doing approaches, where the knowledge base is enhanced through accumulation of practical experience.

The costs of climate change, both the costs of the impacts and of response (adaptation and mitigation)

• Only a small amount of literature on the costs of climate change impacts could be found for assessment [5.6, 6.5.3, 7.5]. Debate still surrounds the topic of how to measure impacts, and which metrics should be used to ensure comparability [2.2.3, 19.3.2.3, 20.9].
• The literature on adaptation costs and benefits is limited and fragmented [17.2.3]. It focuses on sea-level rise and agriculture, with more limited assessments for energy demand, water resources and transport. There is an emphasis on the USA and other OECD countries, with only a few studies for developing countries [17.2.3].

Better understanding of the relative costs of climate change impacts and adaptation allows policy-makers to consider optimal strategies for implementation of adaptation policies, especially the amount and the timing [17.2.3.1].