MET OFFICE News
Release issued by COI News Distribution Service. 23 September 2008
Critical research
findings that will help plan future flood risk in the Thames
Estuary are revealed today as part of the Environment
Agency's Thames Estuary 2100 Project - a project that
considers an adaptive approach for planning for future flood risk
in the Estuary.
The results, released today at the international conference
Climate change impacts and adaptation: Dangerous rates of change
at Exeter University, confirm that current Government predictions
and previous flood scenarios are realistic and have gone a long
way to reducing the uncertainty around maximum water levels.
The key findings from this new research are:
* Sea level rise in the Thames over the next century due to
thermal expansion of the oceans, melting glaciers and polar ice is
likely to be between 20cm and 90cm.
* There remains much uncertainty over the contribution of polar
ice melt to increasing sea level rise. At the extreme, it may
cause sea level to rise by a total of up to 2 metres (including
thermal expansion).
* Climate change is less likely to increase storm surge height
and frequency in the North Sea than previously thought.
* Future peak freshwater flows for the Thames, at Kingston for
instance, could increase by around 40% by 2080.
Crucially, in terms of the Thames estuary, this research means that:
* Current Government predictions for sea-level rise in the Thames
Estuary are realistic.
* the Environment Agency's Thames Estuary 2100 project is
using the best available climate change science to plan with
confidence for future flood management on the Thames Estuary
* previous worst-case scenario of increases in maximum water
levels can be revised down from 4.2 metres to 2.7 metres. Such a
reduction in worst case scenario for this century means that a
tide-excluding estuary barrage is unlikely to be necessary to
manage flood risk this century.
Speaking about the results, Dr Jason Lowe, Head of Mitigation at
the Met Office said: "Having greater clarity on things such
as storm surge frequency is tremendously valuable and not just
from a scientific point of view. This research will help to direct
investment where it is most needed to manage the impacts of
climate change."
Tim Reeder, Regional Climate Change Programme Manager for the
Environment Agency Thames Region said: "This research enables
the Environment Agency to continue to plan flood management
investment with confidence. By narrowing previous uncertainty we
now have an improved understanding of how climate change will
affect the Thames Estuary and can develop realistic and
cost-effective options, which will meet future needs. These are
cutting-edge results and demonstrate the value of the Government
engaging with the world-class scientists we have here in the UK."
The Environment Agency commissioned climate scientists from the
Met Office Hadley Centre, the Proudman Oceanographic Laboratory
and the Centre for Ecology and Hydrology to investigate what
impact climate change will have on the area over the next 100 years.
The study was commissioned to reduce climate change
uncertainties, in particular the future frequency and height of
North Sea storm surges on the Thames Estuary. In addition, the
group answered other key questions to assist the Environment
Agency to plan future flood-management investment with confidence:
* By how much the thermal expansion of the oceans as they warm
would increase sea levels in the Thames estuary?
* By how much sea levels in the estuary might rise due to polar
ice melt?
* By how much freshwater flows in the Thames are likely to increase?
ENDS
For further information contact Met Office press office 01392
886655 or Hayley Willoughby at the EA press office 01189 535555
Notes to Editors:
Sea level rise
The maximum likely contribution of sea level rise is broadly the
same as the guidance given by Defra in 2006 (0.94 metres by 2100).
This means previous assumptions on sea level rise based upon Defra
guidance are realistic. (Note: these figures include changes in
land levels.)
Polar ice melt
The potential for sea level rise to be further increased by polar
ice melt was factored in to the original worst case scenario of
4.2 metres maximum water levels. This had taken an extremely
precautionary approach for worst case ice cap melt. The increase
of 2 metres (including thermal expansion) from this study can now
be taken as the contribution of sea level rise in a revised worst
case scenario, using more recent, albeit still highly uncertain
ice sheet dynamics science.
Storm surge
The EA also factored an increase in maximum water levels due to
increased heights of storm surge into previous worst case planning
scenarios. The results of these studies suggest that it is
unlikely that we will see an increase in maximum water levels
through this source.
Worst case scenario
The TE2100 worst case scenario for increases in maximum water
levels in the Thames this century is now revised down to 2.7
metres including surge. Although the research suggests that storm
surges are less likely to contribute to any increase in maximum
water levels, a precautionary extreme value of 0.7 metres is included.
This worst case scenario is highly unlikely to occur as is it is
derived from a combination of extreme values for thermal
expansion, polar ice melt, and storm surge. Further research is
needed to try and understand the probability of all these extremes
occurring, but this study allows us to understand the maximum
levels that could plausibly happen, and therefore set the outer
range for planning for the future.
Estuary responses to managing water levels
Under the previous worst case scenario, which was accepted as
very unlikely, the only option available to manage maximum water
levels by the end of the century was an estuary barrage. With the
revised assessment (again very unlikely) it should be possible to
manage water levels through other more sustainable means without
resorting to a tide excluding barrage.
Freshwater flows
Previous planning was based on a 20% increase in river flows over
the century based on UKCIP02. As a result, flood management
options will be sensitivity tested against the potential increase
to 40%. The contribution of freshwater flow to flood risk is low
apart from in the western reaches of the estuary, where there is
less tidal influence.