Evidence and Implications of Dangerous Climate Change in the

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Arctic: 2° is too much!

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WWF International Arctic Programme

2005

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Understanding Dangerous Climate Change

Arctic Climate Change with a 2°C Global Warming

Climate Change and Arctic Vegetation

Impact Studies of a 2°C Global Warming on the Arctic Sea Ice Cover

Responding to Global Climate Change: The View of the Inuit Circumpolar Conference on the Arctic

Climate Impact Assessment

Abstract

Climate models used to predict the consequences of increased greenhouse gas (GHG)

concentrations all exhibit a warming over the Arctic that is larger than the global mean warming.

Results from six global climate models (GCMs), forced with four different GHG and aerosol

emission scenarios indicate, that the earth will have warmed by 2°C relative to pre-industrial

temperatures by between 2026 and 2060. These same GCMs predict, for a global warming of 2°C,

an area-mean annual temperature increase over the Arctic (60-90°N) of between 3.2° and 6.6°C.

Arctic warming is greatest in winter (4°-10°C) and least in summer (1.5°-3.5°C). The amount that

Arctic climate has warmed by the time of a 2°C global warming appears to be independent of the

rate of warming: simulations that warm globally by 2°C by the 2020s or 2030s do not necessarily

produce a warming in the Arctic that is different from those that achieve a 2°C warming by the

2040s or 2050s. However, faster global warming is associated with greater rates of temperature

change (up to 1.5°C/decade) over the Arctic. Area-mean precipitation increases in all seasons,

leading to increased winter and early spring snow depth. More precipitation falls as rain rather than

snow in summer. These changes will combine to change river basin hydrology. Spatial patterns of

change in the Arctic are highly model-dependent. In general, warming is greatest in winter over the

Arctic Ocean, especially where each model experiences large changes in sea ice.

Warming over the North Atlantic and Greenland Sea is reduced or even reversed, most often due to

reduced thermohaline circulation strength. The greatest warming in summer occurs over the

continents. Differences in simulated climate changes between the models are larger over the Arctic

than other comparably-sized regions of the globe. GCMs simulate different present-day and future

sea ice, snow, clouds and ocean circulation. Complex interactions between these processes, along

with relatively large natural variability over decades, lead to the wide range of simulated changes

over the Arctic region.