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— range of changes from seven pre-TAR AOGCMs for the A2 emissions scenario

— range of changes from 15 recent AOGCM simulations for the A2 emissions scenario

^m 95% confidence limits on modelled 30-year natural variability based on HadCM3 millennial control simulation 95% confidence limits on modelled 30-year natural variability based on CGCM2 millennial control simulation

Figure TS.3. Range of winter and summer temperature and precipitation changes up to the end of the 21st century across recent (fifteen models-red bars) and pre-TAR (seven models - blue bars) AOGCM projections under the SRES A2 emissions scenarios for thirty-two world regions, expressed as rate of change per century. Mauve and green bars show modelled 30-year natural variability. Numbers on precipitation plots show the number of recent A2 runs giving negative/positive precipitation change. DJF: December, January, February; JJA: June, July, August. [F2.6, which includes map of regions]

Non-climate scenarios

While the CCIAV studies reported in the TAR typically applied one or more climate scenarios, very few applied contemporaneous scenarios of socio-economic, land-use or other environmental changes. Those that did used a range of sources to develop them. In contrast, AR4 studies which include SRES assumptions may now have several estimates, taking into account different storylines. The role of non-climate drivers such as technological change and regional land-use policy is shown in some studies to be more important in determining outcomes than climate change [2.4.6].

Scenarios of CO2 concentration are required in some studies, as elevated concentrations can affect the acidity of the oceans and the growth and water use of many terrestrial plants. The observed CO2 concentration in 2005 was about 380 ppm and was projected in the TAR using the Bern-CC model to rise to the following levels by the year 2100 for the SRES marker scenarios - B1: 540 ppm (range 486-681 ppm); A1T: 575 (506-735); B2: 611 (544-769); A1B: 703 (617-918); A2: 836 (735-1,080); A1FI: 958 (824-1,248) ppm. Values similar to these reference levels are commonly adopted in SRES-based impact studies [2.4.6.2]. Moreover, a multi-stressor approach can reveal important regional dependencies between drivers and their impacts (e.g., the

Global mean annual temperature change relative to 1980-1999 (°C) 12 3 4

Global mean annual temperature change relative to 1980-1999 (°C) 12 3 4

CO2 stabilisation: TAR

(560 ppm C02 eq.)

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