This is Section 1.2 of the Arctic Climate Impact Assessment
Authors: Henry Huntington, Gunter Weller. Contributing Authors: Elizabeth Bush,Terry V. Callaghan,Vladimir M. Kattsov, Mark Nuttall
There are four compelling reasons to examine arctic climate change. First, the Arctic, together with the Antarctic Peninsula, experienced the greatest regional warming on earth in recent decades, due largely to various feedback processes.Average annual temperatures have risen by about 2 to 3 ºC since the 1950s and in winter by up to 4 ºC.The warming has been largest over the land areas.There are also areas of cooling in southern Greenland, Davis Strait, and eastern Canada. The warming has resulted in extensive melting of glaciers, thawing of permafrost, and reduction in extent of sea ice in the Arctic Ocean.The warming has been accompanied by increases in precipitation, but a decrease in the duration of snow cover.These changes have been interpreted to be due at least in part to anthropogenic intensification of the global greenhouse effect, although the El Niño– Southern Oscillation and the inter-decadal Arctic Oscillation also affect the Arctic. The latter can result in warmer and wetter winters in its warm phases, and cooler, drier winters in its cool phases (see Chapter 2).
Second, climate projections suggest a continuation of the strong warming trend of recent decades, with the largest changes coming during winter months. For the B2 emissions scenario used by the Intergovernmental Panel on Climate Change (IPCC) and in the ACIA (see section 1.4.2), the five ACIA-designated general circulation models (GCMs; see section 1.4.2) project an additional warming in the annual mean air temperature of approximately 1 ºC by 2020, 2 to 3 ºC by 2050, and 4 to 5 ºC by 2080; the three time intervals considered in this assessment (see Figs. 1.4 and 1.5).Within the Arctic, however, the models do show large seasonal and regional differences; in fact, the differences between individual models are greatest in the polar regions.The reduction in or loss of snow and ice has the effect of increasing the warming trend as reflective snow and ice surfaces are replaced by darker land and water surfaces that absorb more solar radiation. At one extreme, for example, the model of the Canadian Centre for Climate Modelling and Analysis projects near-total melting of arctic sea ice by 2100. Large winter warming in the Arctic is likely to accelerate already evident trends of a shorter snow season, retreat and thinning of sea ice, thawing of permafrost, and accelerated melting of glaciers
Third, the changes seen in the Arctic have already led to major impacts on the environment and on economic activities. If the present climate warming continues as projected, these impacts are likely to increase, greatly affecting ecosystems, cultures, lifestyles, and economies across the Arctic (see Chapters 10 to 17). On land, the ecosystems range from the ecologically more productive boreal forest in the south to the tundra meadows and unproductive barrens in the High Arctic (Fig. 1.6). Reindeer herding and, to a lesser extent, agriculture are among the economic activities in terrestrial areas.Tourism is an increasing activity throughout the region. Some of the world’s largest gas, oil, and mineral deposits are found in the Arctic. In the In the Arctic there are few cities and many rural communities. Indigenous communities throughout the Arctic depend on the land, lakes and rivers, and the sea for food and income and especially for the vital social and cultural importance of traditional activities.The cultural diversity of the Arctic is already at risk, and this may be exacerbated by the additional challenge posed by climate change.The impacts of climate change will occur within the context of the societal changes and pressures that arctic indigenous residents are facing in their rapid transition to the modern world.The imposition of climate change from outside the region can also be seen as an ethical issue, in which people in one area suffer the consequences of actions beyond their control and in which beneficial opportunities may accrue to those outside the region rather than those within.
Fourth, climate change in the Arctic does not occur in isolation.The Arctic is an important part of the global climate system; it both affects and is affected by global climate change. Changes in climate in the Arctic, and in the environmental parameters such as snow cover and sea ice that affect the earth’s energy balance and the circulation of the oceans and the atmosphere, may have profound impacts on regional and global climates. Understanding the role of the Arctic and the implications of projected changes and their feedbacks, regionally and globally, is critical to assessing global climate change and its impacts. Furthermore, migratory species provide a direct biological link between the Arctic and lower latitudes, while arctic resources such as fish and oil play an economic role of global significance. Impacts on any of these may have global implications.
UV radiation (1.2.2)
The case for assessing UV radiation is similarly compelling. Stratospheric ozone depletion events of up to 45% below normal have been recorded recently in the Arctic. Dramatic change in the thickness of the stratospheric ozone layer and corresponding changes in the intensity of solar UV radiation were first observed in Antarctica in the mid-1980s.The depletions of ozone were later found to be the result of anthropogenic chemicals such as chlorofluorocarbons reaching the stratosphere and destroying ozone. Ozone depletion has also been observed in the Arctic in most years since 1992. Owing to global circulation patterns, the arctic stratosphere is typically warmer and experiences more mixing than the antarctic stratosphere.
The ozone decline is therefore more variable in the Arctic. For example, severe arctic ozone depletions were observed in most of the last ten springs, but not in 2002 owing to early warming of the stratosphere.
Although depletion of stratospheric ozone was expected to lead to increased UV radiation at the earth’s surface, actual correlations have become possible only recently because the period of instrumental UV measurement is short. Goggles found in archaeological remains in the Arctic indicate that UV radiation has been a fact of human life in the Arctic for millennia. In recent years, however, UV radiation effects, including sunburn and increased snow blindness, have been reported in regions where they were not observed previously.
Future increases in UV-B radiation of 20 to 90% have been predicted for April for the period 2010 to 2020. Ultraviolet radiation can have a variety of harmful impacts on human beings, on plants and animals, and on materials such as paints, cloths, and plastics. Ultraviolet radiation also affects many photochemical reactions, such as the formation of ozone in the lower atmosphere. In the Arctic, human beings and ecosystems have both adapted to the very low intensity of the solar UV radiation compared with that experienced at lower latitudes.The low intensity of UV radiation in the Arctic is a consequence of the sun never reaching high in the sky as well as the presence of the world’s thickest ozone layer.The Arctic as a whole may therefore be particularly susceptible to increases in UV radiation.
Other factors that affect the intensity of UV radiation include cloudiness and the amount of light reflected by the surface. Climate change is likely to affect atmospheric circulation as well as cloudiness and the extent and duration of snow and ice cover, which in turn will affect UV radiation.Thus, UV radiation is both a topic of concern in itself and also in relation to climate change.
Chapter 1: Introduction to the ACIA1.1 An Introduction to the Arctic Climate Impact Assessment
1.2. Why assess the impacts of changes in climate and UV radiation in the Arctic?
1.3. The Arctic Climate Impact Assessment
1.4. The assessment process
1.5. The Arctic: geography, climate, ecology, and people
1.6. An outline of the assessment
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