Damage and adaptation

As stated above, it is unlikely that global warming resulting from a doubling of CO2 equivalents can or will be prevented. The IPCC's central estimate of this warming is 2.5°C, and it is likely to be realized by 2050 under business-as-usual or 70-80 years later under IPCC's scenario of 'accelerated policies' to mitigate it (Cline 1992:36). Nordhaus (1991a:933), Cline (1992:132) and Fankhauser (1992:43, Table 15) estimate the 'damage' caused by this level of warming at 1-2 per cent of world GDP, but it is clear from their detailed figures that these costs might better be termed 'damage and adaptation' costs. Thus Table 12.1 reproduces Fankhauser's and Cline's 'damage' costs for doubling CO2 equivalents and Cline's estimates for (much higher) long-term warming, from which it is clear that several entries (e.g. construction of dykes, electricity requirements and migration) actually represent the costs of adapting to climate change rather than the costs of damage associated with it.

This distinction is important because the costs of damage and adaptation are not independent. In particular, incurring costs of adaptation may reduce the costs of damage. Indeed it should do so by more than the cost of adaptation if adaptation is economically rational. Dykes are built to protect land from sea-level rise. Air-conditioning in hot climates may reduce death and morbidity from heat stress (a significant item in Cline's damage costs). With the exception of the figures on sea-level rise, it is not clear in any of the estimates how far it has been possible to take these trade-offs into account.

Table 12.1 Estimates of annual damage and adaptation costs from global warming incurred by the US economy at 1990 scale (billions of 1990 dollars)

Fankhauser" (2*CO2 warming)

Cline

Cline

(long term)

Agriculture 8.4

Forest loss -2.0

Species loss 7.3 Sea-level rise

Coastal defences 0.2

Wetlands loss 9.5

Drylands loss 2.4 Electricity requirements Non-electric heating

Human amenityc 7.7

Human life 18.9

17.5

64.1

33.0

Fankhausera (2*CO2 warming)

(long term)

Human morbidity

+

+

+

Migration

0.6

0.5

2.8

Hurricanes

0.2

0.8

6.4

Tourism

1.7

4.0

Water supply

15.6

7.0

56.0

Urban infrastructure

0.1

0.6

Air pollution

7.3

Tropospheric ozone

3.5

19.8

Other

+

+

Total (billion 1990 $)

76.1

61.6

335.7

Total (% GNP)

1.3

1.1

6.0

Sources: Cline 1992:131, Table 3.4; Fankhauser 1992:44, Table 16

Notes: aIn the source the figures given are in 1988 $. They have been scaled up in the column below by the ratio of

1990 to 1988 GDP. bSource indicates (further) unquantified costs of the sign shown.

cThis entry in Fankhauser corresponds to the previous two rows in Cline. Cline indicates further unquantified costs under this heading as shown.

Sources: Cline 1992:131, Table 3.4; Fankhauser 1992:44, Table 16

Notes: aIn the source the figures given are in 1988 $. They have been scaled up in the column below by the ratio of

1990 to 1988 GDP. bSource indicates (further) unquantified costs of the sign shown.

cThis entry in Fankhauser corresponds to the previous two rows in Cline. Cline indicates further unquantified costs under this heading as shown.

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