This Appendix describes the methods used in this report to make sea level rise projections for the SRES scenarios for the 21st century. The results are discussed in Section 11.5.1.2 and shown in Figure 11.12 and Appendix II.

Global-average sea-level rise h(t) is a function of time t and is expressed relative to the level in 1990. It comprises several components, which are all zero at 1990:

The components are sea-level rise due to:

X thermal expansion.

g loss of mass of glaciers and ice caps.

G loss of mass of the Greenland ice sheet due to projected and recent
climate change.

A loss of mass of the Antarctic ice sheet due to projected and recent
climate change.

I loss of mass of the Greenland and Antarctic ice sheets
due to the ongoing adjustment to past climate change.

p runoff from thawing of permafrost.

s deposition of sediment on the ocean floor.

The components X, g, G and A are estimated for each of 35 SRES scenarios using the projections of an upwelling-diffusion energy-balance (UD/EB) model calibrated separately for each of seven AOGCMs (Appendix 9.1).

Thermal expansion X is obtained directly from the thermal expansion X _{m}
(t) projected by the UD/EB model:

No uncertainty is included in this term, because the uncertainty is sufficiently
represented by the use of a range of AOGCMs. The term g from glaciers and ice
caps is estimated using the global average temperature change T_{m}(t)
projected by the UD/EB model. First, we obtain the loss of mass gu with respect
to the glacier steady state without taking contraction of glacier area into
account.

where *g _{1990}* is the sea-level rise from glaciers and ice caps
up to 1990 calculated from AOGCM results without contraction of glacier area,

for g_{u} and g_{s} in metres. Third, we calculate the change
since 1990.

The uncertainty *g(t)*
on this term is calculated assuming an uncertainty of ±40% (standard
deviation) in the mass balance sensitivities, as discussed in Section
11.5.1.1.

The term G from the Greenland ice sheet is calculated according to

where dB_{G}/dT_{g} is the sensitivity of the Greenland mass
balance to global-average temperature change, expressed as sea level equivalent
(from Table 11.12). The uncertainty on this term
comprises two components, as discussed in Section 11.5.1.1.
The first uncertainty is a mass balance uncertainty

where *m _{G}*
= 0.05 mm/yr/°C and T

The term *A* from the Antarctic ice sheet is calculated according to

where d*B _{A}*/d

where *m _{A}*
= 0.08 mm/yr/°C and

The uncertainties on the above terms are combined in quadrature:

The remaining terms are calculated assuming they contribute to sea-level rise at a constant rate, independent of AOGCM and scenario, thus:

The rates each have a range of uncertainty. For d*I*/d* _{t}*,
this is 0.0 to 0.5 mm/yr (Section 11.3.1, Table
11.9), for d

and the maximum is

In these formulae, *h _{v}*
has been doubled to convert from an uncertainty to a range, following Box
11.1.

Table 11.17: Parameters used in sea-level
projections to simulate AOGCM results. |
|||||||

AOGCM | T1990 (°C) |
g1990 (m) |
.Bg/.Tg (mm/yr/°C) |
dBG /dTg (mm/yr/°C) |
dBA/dTg (mm/yr/°C) |
.TG /Tg | .TA/Tg |

CSIRO Mk2 | 0.593 | 0.022 | 0.733 | 0.157 | -0.373 | 2.042 | 1.120 |

CSM 1.3 | 0.567 | 0.021 | 0.608 | 0.146 | -0.305 | 3.147 | 1.143 |

ECHAM4/OPYC3 | 0.780 | 0.027 | 0.608 | 0.029 | -0.478 | 1.153 | 1.484 |

GFDL_R15_a | 0.635 | 0.015 | 0.576 | 0.029 | -0.177 | 1.879 | 0.799 |

HadCM2 | 0.603 | 0.027 | 0.613 | 0.096 | -0.214 | 1.441 | 1.239 |

HadCM3 | 0.562 | 0.021 | 0.622 | 0.096 | -0.354 | 1.443 | 1.288 |

DOE PCM | 0.510 | 0.017 | 0.587 | 0.136 | -0.484 | 2.165 | 1.618 |

Other reports in this collection |