Elements of Climate Change

Most models predict that future climate change could include:

• higher maximum temperatures and more hot days in nearly all land areas;
• more intense precipitation events over many Northern Hemisphere middle to high latitude land areas;
• higher minimum temperatures and fewer cold days and frost over virtually all land areas;
• reduced diurnal temperature range across most land areas;
• summer continental drying in some areas and associated drought risks.

Temperature

The globally averaged surface air temperature is estimated to increase from 1990 to 2100 by between 1.4°C and 5.8°C. Climate models cannot yet provide a detailed picture of regional climate change, but it is likely that nearly all land areas, particularly those at high latitudes in the winter season, will warm more rapidly than the global average. Most notable is the warming in the northern regions of North America, and northern and central Asia. In contrast, the warming is less than the expected global mean over South and Southeast Asia in summer and southern South America in winter. The surface temperature is likely to rise least in the North Atlantic and the circumpolar Southern Ocean.

Precipitation

Globally-averaged water vapour and precipitation are projected to increase along with the warming. It is expected that precipitation will increase over northern middle and high latitudes and Antarctica in winter. At low latitudes both regional increases and decreases of rainfall over land areas are expected. Larger year-to-year variations are likely over those areas where the mean precipitation is predicted to increase.

Cryosphere

At high latitudes in the Northern Hemisphere snow cover and sea-ice extent will continue to decrease. Glaciers and ice caps are projected to continue their widespread retreat. Over Greenland, the ice sheet is expected to lose mass as a result of ice melt runoff and iceberg calving. Only the Antarctic ice sheet is likely to gain in mass because of greater precipitation.

Sea level Rise

Global mean sea level is projected to rise between 0.09 and 0.88 m above the 1990 level by 2100. This rise is due primarily to thermal expansion of the warmer oceans combined with melting of glaciers and ice sheets. The global mean temperature and sea level would continue to increase beyond 2100 because of the slow thermal response of the oceans, even if carbon dioxide concentrations in the atmosphere had stabilized by then.

Rising sea levels are expected to have severe effects on many low-lying areas, forcing populations to move inland to higher levels.

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