Individual sectors and resources will not be affected in isolation but in interaction with one another. The direct effects of climate change include shifts in geographic distribution of ecosystems, changes in sea and river ice, thaw of permafrost, and changes in coastal areas. Indirect effects include feedbacks to the climate system through less ice and snow reflectivity, changes in sea ice and ocean circulation, and ecological sources and sinks of CO2 and CH4. Improvements are needed in modeling of future sea-ice distribution and thickness because of their importance as drivers for other physical and ecological systems, economics, and transportation. There is uncertainty about whether changes in tundra will cause it to act as a source or a sink for CO2. This issue needs to be resolved.
There is a variety of positive and negative shifts in opportunities for shipping, the oil industry, fishing, mining, and tourism, as well as coastal infrastructure and the movement of populations. These impacts will lead to further interactions and potential changes in trade and strategic balance. The health consequences of these shifts will depend on human capacity to adapt.
The Arctic is more vulnerable than the Antarctic because of its sensitive and fragile ecosystems and the impacts on traditional lifestyles of indigenous peoples and because climate changes are expected to be greater. An integrated impact assessment using multiple stress models is required for the Arctic. When associated with baseline monitoring, it should be possible to distinguish natural variability from human impacts.
Further analysis should focus on particularly sensitive zones and activities, vulnerable species, marginal communities, and estimates of economic impacts. To improve biological components of regional and global models, it is important to understand how, when, and where productivity in the Southern Ocean will change with global warming (IPCC 1996, WG II, Section 8.3.2). More certainty is required regarding the future behavior of the marine-based West Antarctic Ice Sheet and ice balance of the continent. Changes have the potential to substantially alter sea level and southern hemispheric climate, but the time frame needs to be defined.
Most human and natural systems in the Arctic and the Antarctic Peninsula are extremely sensitive to temperature. Future global warming is expected to be greatest in these areas. Large reductions in sea ice, permafrost, and tundra will disrupt many natural systems and change species composition over land and in the polar oceans. These areas appear to be vulnerable to climate change, although the number of people directly affected would be relatively small. However, most are indigenous people, who lead traditional lifestyles and have few adaptive strategies that can be implemented. Antarctica is less vulnerable because the temperature changes envisioned over the next century are likely to have little impact, and few people are involved.
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