Climate Scenario 1 Expected Climate Change

This scenario provides the basis for chapter 4 in this volume, by John Podesta and Peter Ogden, on the expected consequences of climate change for national and international security over the next thirty years. It accepts the temperature change projected in the AR4 for emissions scenario A1B,

Table 3-1. Global Average Surface Warming and Sea Level Rise Relative to 1990 for the Plausible Scenarios of Climate Change

Climate scenario

Start year

End year

Warming

Basis for warming

Sea level rise

Scenario 1 (expected)

1990

2040

1.3°C (2.3°F)

Model average for A1B emission scenario in 2040

0.23 m (0.75 ft)

Scenario 2 (severe)a

1990

2040

2.6°C (4.7°F)

Double the model average for A1B in 2040

0.52 m (1.7 ft)

Scenario 3 (catastrophic)a

1990

2100

5.6°C (10.1 °F)

Double the model average for A1B in 2100

2.00 m (6.6 ft)

Source: Author's compilation.

a. Projections for scenarios 2 and 3 are unique to this study and are meaningful only within the context of this study.

Source: Author's compilation.

a. Projections for scenarios 2 and 3 are unique to this study and are meaningful only within the context of this study.

resulting in warming of 1.3°C (2.3°F)) relative to 1990 (table 3-1). Attendant impacts described for this temperature change are also accepted, except for sea level rise, which is assessed separately as described below. The AR4 projects impacts for the 2020s, 2050s, and 2080s. Where relevant, scenario 1 assumes that impacts intermediate to those described for the 2020s and 2050s represent impacts thirty years from the present.

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