The ability to adapt to adverse impacts and exploit opportunities as they emerge is significant. However, present uncertainties with regard to the magnitude and even the sign of the impacts, which characterize almost all of the conclusions reported in this chapter, often will hinder such efforts. These uncertainties stem from uncertainties concerning how climate may change in the future (a subject considered in Chapter 3) and how the natural resource base may respond to such changes. In some cases, the combination of these uncertainties may mean that we are unsure about whether the total effect is broadly positive or negative. To illustrate, Table 13-8 shows the estimated effect of a wide range of possible climate futures on wheat yields in different regions of Europe. In half of the regions, yield responses range from negative to positive.

Table 13-8: Minimum, maximum, and median estimates of changes in water-limited wheat yield (t ha-1) from baseline climate derived from running 24 climate change scenarios for 2050 through EuroWheat model. Estimates are summaries for selected regions in Europe (Harrison and Butterfield, 1999). Result for HadCM2 scenario also is shown.
	Summary of 24 Scenarios
Region	Minimum	Maximum	Median	HadCM2
Nordic countries	0.7	3.5	2.1	2.8
British Isles	0.9	2.6	1.7	1.8
Germany + Benelux	0.7	2.5	1.7	2.1
Alpine countries	1.5	3.2	2.1	2.8
France	-1.5	3.0	1.3	1.5
Portugal + Spain	-0.9	4.5	1.4	1.2
Italy + Greece	0.7	3.6	1.7	1.8
Poland	-0.5	2.2	1.3	1.7
Central Europe	-1.7	2.6	1.7	1.7
Bulgaria + Romania	-2.9	2.3	1.0	0.8

Low-probability/high-consequence events (sometimes termed �surprises�) such as collapse of the thermohaline circulation of the North Atlantic (Hulme and Carter, 2000) also need to be considered (see Chapters 3 and 19). Therefore, caution must be exercised in interpreting currently available information, and there must be recognition that much more research is needed. This might include identifying flexible actions that are robust to a range of possible futures.

Further investigation is needed to understand how European climate is likely to change under various emission trends, as well as what the implications of these changes would be for Europe�s human and ecological systems. There is a need to analyze outputs from climate models that relate to extreme events. The biophysical impacts of climate change on European water, soil, and land resources have been quite thoroughly researched, but we know less about their socioeconomic consequences (e.g., in agriculture, fisheries, nature conservation, transport systems, and tourism). Improved knowledge of European coastal systems is required for their sustainable management. A key research challenge is to evaluate the feasibility, costs, and benefits of potential adaptation options, measures, and technologies. In general, research programs could benefit from more integration between basic studies of the Earth system, climate change modeling, impact and adaptation assessments, and mitigation/policy analysis. Key research challenges include:

• Transboundary regional impact assessment of various natural and socioeconomic systems
• Transboundary monitoring of impacts on sensitive ecosystems
• Better understanding of likely changes in extreme weather events
• Quantification of natural and technological hazards resulting from climate change (especially flooding)
• Guidelines for water management decisions for different regions under climatic uncertainty
• Changes in European legislation for adaptation to and/or mitigation of climate change impacts.

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