Lack of adequate data sets means we can not ascertain whether there have been changes in the magnitude and/or frequency of storm surges (aperiodic changes associated with major meteorological disturbances resulting in sea level changes of up to several metres and lasting a few hours to days) in many regions of the world. Zhang et al. (1997, 2000) performed a comprehensive analysis of hourly tide gauge data from the east coast of North America, and concluded that there had been no discernible secular trend in storm activity or severity during the past century. European analyses include that of Woodworth (1999b), who found no significant increase in extreme high water level distributions from Liverpool from 1768 to 1993 to those from later epochs, other than what can be explained in terms of changes in local tidal amplitudes, mean sea level and vertical land movement. Vassie (reported in Pugh and Maul, 1999) and Bijl et al. (1999) concluded that there was no discernible trend over the last century in the statistics of non-tidal sea level variability around the UK and the eastern North Sea (Denmark, Germany and the Netherlands), above the considerable natural sea level variability on decadal time-scales. In South America, D’Onofrio et al. (1999) observed a trend of extreme levels at Buenos Aires of 2.8 mm/yr over 1905 to 1993. On the basis of available statistics, the South American result is consistent with the local mean sea level trend.

Table 11.11: Sea level rise from thermal expansion from AOGCM experiments following the IS92a scenario for the 21st century, including the direct effect of sulphate aerosols. See Chapter 8, Table 8.1 and Chapter 9, Table 9.1 for further details of models and experiments. See Table 11.2 for thermal expansion from AOGCM experiments for the 20th century.
Experiment	.Tg (°C)	Sea level rise (m)
	1990 to 2090a	1990 to 2040	1990 to 2090a
CGCM1 GS	3.7	0.12	0.37
CGCM2 GS	3.6	0.11	0.33
CSIRO Mk2 GS	2.7	0.11	0.28
ECHAM4/OPYC3 GSb	—	0.11	—
GFDL_R15_a GSc	—	0.13	—
GFDL_R15_b GS	3.2	0.12	0.29
GFDL_R30_c GS	2.8	0.12	0.31
HadCM2 GS	2.5	0.07	0.20
HadCM3 GSIO	2.8	0.07	0.20
MRI2 GS	1.5	0.04	0.09
DOE PCM GS	1.9	0.07	0.17
a An end date of 2090, rather than 2100, is chosen to match the last available date in some of the experiments. b This experiment ends at 2050. c This experiment ends at 2065. Tg Global average surface air temperature change.

Variations in surge statistics can also be inferred from analysis of meteorological data. Kass et al. (1996) and the WASA Group (1998) showed that there are no significant overall trends in windiness and cyclonic activity over the North Atlantic and north-west Europe during the past century, although major variations on decadal times-scales exist. An increase in storminess in the north-east Atlantic in the last few decades (Schmith et al., 1998) and a recent trend towards higher storm surge levels on the German and Danish coasts (Langenberg et al., 1999) is consistent with natural variability evident over the last 150 years. Pirazzoli (2000) detected evidence for a slight decrease in the main factors contributing to surge development on the French Atlantic coast in the last 50 years. Correlation between the frequency of Atlantic storms and ENSO was demonstrated by Van der Vink et al. (1998).

Table 11.12: Calculations of glacier melt from AOGCM experiments following the IS92a scenario for the 21st century, including the direct effect of sulphate aerosols. See Tables 8.1 and 9.1 for further details of models and experiments.
Experiment	B (mm/yr) 1990	Tg (°C) 1990 to 2090	Sea level rise (m) 1990 to 2090		ðB/ðTg (mm/yr/°C)
			Constant area	Changing area
CGCM1 GS	0.43	3.7	0.15	0.11	0.65
CSIRO Mk2 GS	0.52	2.7	0.15	0.11	0.73
CSM 1.3 GS	0.45	1.8	0.10	0.07	0.61
ECHAM4/OPYC3 GSa	0.56	–	–	–	0.64
GFDL_R15_a GSb	0.42	–	–	–	0.58
GFDL_R15_b GS	0.44	3.2	0.13	0.09	0.54
GFDL_R30_c GS	0.33	2.8	0.12	0.08	0.53
HadCM2 GSc	0.44	2.5	0.11	0.08	0.61
HadCM3 GSIO	0.31	2.8	0.11	0.08	0.62
MRI2 GS	0.22	1.5	0.06	0.05	0.60
DOE PCM GS	0.42	1.9	0.09	0.06	0.59
a This experiment ends at 2050. b This experiment ends at 2065. c Similar results for constant area were obtained for an ensemble of HadCM2 GS experiments by Gregory and Oerlemans (1998). B Global glacier mass balance for constant glacier area, expressed as sea level equivalent. B/ðTg Sensitivity of global glacier mass balance for constant glacier area, expressed as sea level equivalent, to global average surface air temperature change. Tg Global average surface air temperature change.

Increases in wave heights of approximately 2 to 3 m over the period 1962 to 1985 off Land’s End, south-west England (Carter and Draper, 1988), increases in wave height over a neighbouring area at about 2%/yr since 1950 (Bacon and Carter, 1991, 1993) and wave height variations simulated by the Wave Action Model (WAM) (Günther et al., 1998) are all consistent with decadal variations over most of the north-east Atlantic and North Sea. This variability could be related to the NAO (Chapter 2, Section 2.6.5).

Table 11.13: Calculations of ice sheet mass changes using temperature and precipitation changes from AOGCM experiments following the IS92a scenario for the 21st century, including the direct effect of sulphate aerosols, to derive boundary conditions for an ice sheet model. See Tables 8.1 and 9.1 for further details of models and experiments.
Experiment	Greenland					Antarctica
	Sea level rise (m) 1990 to 2090	Sensitivity (mm/yr/ °C)		T/Tg	1/P dP/dT (%/°C)	Sea level rise (m) 1990 to 2090	Sensitivity (mm/yr/ °C)		T/ Tg
		dB/dTg	dB/dT				dB/dTg	dB/dT
CGCM1 GS	0.03	0.13	0.10	1.3	2.7	– 0.02	– 0.12	– 0.11	1.1
CSIRO Mk2 GS	0.02	0.16	0.08	2.0	5.9	– 0.07	– 0.37	– 0.33	1.1
CSM 1.3 GS	0.02	0.15	0.05	3.1	7.8	– 0.04	– 0.31	– 0.27	1.1
ECHAM4/OPYC3 GS a	–	0.03	0.03	1.2	6.5	–	– 0.48	– 0.32	1.5
GFDL_R15_a GS b	–	0.12	0.06	1.9	4.1	–	– 0.18	– 0.22	0.8
HadCM2 GS	0.02	0.10	0.07	1.4	4.0	– 0.04	– 0.21	– 0.17	1.2
HadCM3 GSIO	0.02	0.09	0.06	1.4	4.5	– 0.07	– 0.35	– 0.28	1.3
MRI2 GS	0.01	0.08	0.05	1.6	4.4	– 0.01	– 0.14	– 0.12	1.2
DOE PCM GS	0.02	0.14	0.06	2.2	5.6	– 0.07	– 0.48	– 0.30	1.6
a This experiment ends at 2050. b This experiment ends at 2065. dB/dTg Ice-sheet mass balance sensitivity to global-average surface air temperature change, expressed as sea level equivalent. dB/dT Ice-sheet mass balance sensitivity to surface air temperature change averaged over the ice sheet, expressed as sea level equivalent. T/Tg Slope of the regression of surface air temperature change averaged over the ice sheet against global-average change. 1/P dP/dT Fractional change in ice-sheet average precipitation as a function of temperature change.

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