Storm surges – the case of Hamburg, Germany

Hans von StorchInstitute for Coastal Research

GKSS Research Center, Geesthacht

Parallel 26: Global environmental change, natural disasters, and their implications for human security in coastal areas, 11. November 2006

Historically, the coast was a place of danger (and some opportunities) for humans.

The first priority was to defend against storm surges. Life was adapted to this risk.

Nowadays, people consider themselves safe from the dangers of the sea, and are concerned about the health and the opportunities related to the coastal seas.

Hamburg – storm surges

In the early 90s, the specter of Global Warming entered the perception of people. Storm got worse.

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Proxy for storm activity in the North Sea region (after Alexandersson, SMHI, 2003)

•Scientists related worsening of storm climate to GHG emissions (warmer world > more water vapor > more energy for storms > situation will continue to worsening).

•Insurance companies supported the claims.

•Media took up the message, which is consistent with cultural pre-conception of humans changing climate to become worse.

•Nowadays widely accepted among media and lay-people that storms are getting worse. However, the claim is false.

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Proxy for storm activity in the North Sea region (after Alexandersson, SMHI, 2003)

Bärring, 2005; blue - Lund; red – Stockholm

Where does the enhanced storm surge levels Hamburg come from?• Sea level rise – a few centimeters• Intensification of storm activity

1960-1995

• What else has happened in the coastal/estuarine environment?

The tidal change is due to coastal protection measures and modifications of the tributaries, and to the deepening of the shipping channel. These measure also had an effect on the heights of severe storm surges – estimates are 45 cm caused by measures of coastal defense and 15 cm by deepening the shipping channel (Haake, 2004: 27).

Difference in storm surge heights – mouth of Elbe estuary and Hamburg, 1900- 2005

• Thus, so far, global warming had no discernible impact on the storm surge risk in Hamburg.

• Will it have an effect?

Katja Woth

Global scenario

Dynamical Downscaling

Model of North Sea hydrodynamics

Empirical “localization”

Tide gauge St. Pauli

Joint work with regional authorities.

Regional and lcoal effect of expected anthropogenic climate change (A2 and

B2)

Scenarios 2030, 2085

Only the effect of anthropogenic climate change (A2, B2)

- No effect of water works.

Conclusions• For storm surge risk in Hamburg, modifications of

the estuary are presently more important than anthropogenic climate change; in the distant future they may be of comparable significance.

• Public perception is changing to: Storm surge risk is mostly related to GHG emissions. Thus storm surge risk can be controlled by regulating these emissions.

• Vulnerability enhanced by framing storm surge risk as GHG problem and not as natural hazard exaggerated by regional modifications.

• Sloppy talking about Global Warming has detrimental effect on better adaptation.

• The same true for Hurricane hazard?