TABLE 5-1 Characteristics of Post-Third Assessment Report (TAR) Stabilization Scenarios and Resulting Long-Term Equilibrium Global Average Temperature and the Sea-Level Rise Component from Thermal Expansion Only

Category

CO2 Concentration at Stabilization (2005 = 379 ppm)b

CO2-Equivalent Concentration at Stabilization Including GHGs and Aerosols (2005 = 375 ppm)b

Peaking Year for CO2 Emissionsa,c

Change in Global CO2 Emissions in 2050 (Percent of 2000 Emissions)a,c

Global Average Temperature Increase above Preindustrial Level at Equilibrium, Using “Best Estimate” Climate Sensitivityd,e

Global Average Sea-Level Rise above Preindustrial Level at Equilibrium from Thermal Expansion Onlyf

Number of Assessed Senarios

 

ppm

ppm

Year

Percent

°C

Meters

 

I

350-400

445-490

2000-2015

−85 to −50

2.0-2.4

0.4-1.4

6

II

400-440

490-535

2000-2020

−60 to −30

2.4-2.8

0.5-1.7

18

III

440-485

535-590

2010-2030

−30 to +5

2.8-3.2

0.6-1.9

21

IV

485-570

590-710

2020-2060

+10 to +60

3.2-4.0

0.6-2.4

118

V

570-660

710-855

2050-2080

+25 to +85

4.0-4.9

0.8-2.9

9

VI

660-790

855-1130

2060-2090

+90 to +140

4.9-6.1

1.0-3.7

5

aThe emission reductions to meet a particular stabilization level reported in the mitigation studies assessed here might be underestimated because of missing carbon-cycle feedbacks.

bAtmosphere CO2 concentrations were 379 parts per million (ppm) in 2005. The estimate of total CO2-equivalent concentration in 2005 for all long-lived greenhouse gases (GHG) is about 455 ppm, and the corresponding value including the net effect of all anthropogenic forcing agents is 375 ppm CO2-eq.

cRanges correspond to the 15th to 85th percentile of the post-TAR scenarios distribution. CO2 emissions are shown so multigas scenarios can be compared with CO2-only scenarios.

dThe best estimate of climate sensitivity is 3°C.

eNote that global average temperature at equilibrium is different from expected global average temperature at the time of stabilization of GHG concentrations due to the inertia of the climate system. For the majority of scenarios assessed, stabilization of GHG concentrations occurs between 2100 and 2150.

fEquilibrium sea-level rise is for the contribution from ocean thermal expansion only and does not reach equilibrium for at least many centuries. These values have been estimated using relatively simple climate models (one low-resolution AOGCM [Atmosphere-Ocean General Circulation Model] and several EMICs [Earth System Models of Intermediate Complexity] based on the best estimate of 3°C climate sensitivity) and do not include contributions from melting ice sheets, glaciers, and ice caps. Long-term thermal expansion is projected to result in 0.2 to 0.6 m per degree Celsius of global average warming above preindustrial levels.

SOURCE: IPCC 2007a, p. 20, Table SPM.6. Reprinted with permission; copyright 2007, Intergovernmental Panel on Climate Change.



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