Global mean annual temperature change relative to 1980-1999 (°C) Table TS.4. Examples of regional impacts [T20.9]. See caption for Table TS.3.

Table TS.3. (cont.) Edges of boxes and placing of text indicate the range of temperature change to which the impacts relate. Arrows between boxes indicate increasing levels of impacts between estimations. Other arrows indicate trends in impacts. All entries for water stress and flooding represent the additional impacts of climate change relative to the conditions projected across the range ofSRES scenarios A1FI, A2, B1 and B2. Adaptation to climate change is not included in these estimations. For extinctions, 'major' means ~40 to ~70% of assessed species.

The table also shows global temperature changes for selected time periods, relative to 1980-1999, projected forSRES and stabilisation scenarios. To express the temperature change relative to 1850-1899, add0.5°C. More detail is provided in Chapter 2 [Box 2.8]. Estimates are for the 2020s, 2050s and 2080s, (the time periods used by the IPCC Data Distribution Centre and therefore in many impact studies) and for the 2090s. SRES-based projections are shown using two different approaches. Middle panel: projections from the WGIAR4 SPM based on multiple sources. Best estimates are based on AOGCMs (coloured dots). Uncertainty ranges, available only for the 2090s, are based on models, observational constraints and expert judgement. Lower panel: best estimates and uncertainty ranges based on a simple climate model (SCM), also from WGI AR4 (Chapter 10). Upper panel: best estimates and uncertainty ranges for four CO2-stabilisation scenarios using an SCM. Results are from the TAR because comparable projections for the 21st century are not available in the AR4. However, estimates of equilibrium warming are reported in the WGIAR4 for CO2-equivalent stabilisation18. Note that equilibrium temperatures would not be reached until decades or centuries after greenhouse gas stabilisation.

Table TS.3. Sources: 1,3.4.1; 2,3.4.1, 3.4.3; 3,3.5.1; 4,4.4.11; 5,4.4.9,4.4.11, 6.2.5,6.4.1; 6,4.4.9,4.4.11, 6.4.1; 7,4.2.2,4.4.1,4.4.4 to 4.4.6,4.4.10; 8,4.4.1, 4.4.11; 9,5.4.2; 10,6.3.2,6.4.1,6.4.2; 11,6.4.1; 12,6.4.2; 13,8.4,8.7; 14,8.2,8.4,8.7; 15,8.2,8.4,8.7; 16,8.6.1; 17,19.3.1; 18,19.3.1,19.3.5; 19,19.3.5 Table TS.4. Sources: 1, 9.4.5; 2, 9.4.4; 3,9.4.1; 4,10.4.1; 5, 6.4.2; 6,10.4.2; 7,11.6; 8,11.4.12; 9,11.4.1,11.4.12; 10,11.4.1,11.4.12; 11,12.4.1; 12, 12.4.7; 13,13.4.1; 14,13.2.4; 15,13.4.3; 16,14.4.4; 17,5.4.5,14.4.4; 18,14.4.8; 19,14.4.5; 20,15.3.4,21,15.4.2; 22,15.3.3; 23,16.4.7; 24,16.4.4; 25,16.4.3

18 Best estimate and likely range of equilibrium warming for seven levels of CO2-equivalent stabilisation from WGI AR4 are: 350 ppm, 1.0°C [0.6-1.4]; 450 ppm, 2.1°C

[1.4-3.1]; 550 ppm, 2.9°C [1.9-4.4]; 650 ppm, 3.6°C [2.4-5.5]; 750 ppm, 4.3°C [2.8-6.4]; 1,000 ppm, 5.5°C [3.7-8.3] and 1,200 ppm, 6.3°C [4.2-9.4].

Phenomenon5 and direction of trend

Likelihood of future trends based on projections for 21st century using SRES scenarios

Examples of major projected impacts by sector

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