Re: [asa] IPCC 1995 draft myths

From: Rich Blinne <>
Date: Fri Dec 22 2006 - 09:16:37 EST

On 12/21/06, PvM <> wrote:
> Nowhere do IPCC rules explicitly address the question of when a
> report chapter becomes final (i.e., when all changes must cease).
> Therefore, Santer et al. correctly understood that the Working Group
> Chairs and the Plenary meeting itself would define the endpoint
> of the revision process.

In retrospect, the final version of chapter 8 was more accurate. One
could argue that this like the inclusion of the infamous hockey stick
in the 2001 IPCC was ahead of the curve, but again with the benefit of
time we see that both of those decisions were vindicated. There is now
rumblings that the draft language that got leaked by the Telegraph may
be revised upward in a similar fashion.

A new study has called into to question both the 2001 and the proposed
2007 sea rise estimates.
Submitted on September 22, 2006
Accepted on December 4, 2006

A Semi-Empirical Approach to Projecting Future Sea-Level Rise
Stefan Rahmstorf 1*
1 Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany.

A semi-empirical relation is presented which connects global sea level
rise to global mean surface temperature. It is proposed that for time
scales relevant to anthropogenic warming, the rate of sea level rise
is approximately proportional to the magnitude of warming above the
pre-industrial temperature. This holds to good approximation for
temperature and sea level changes during the 20th Century, with a
proportionality constant of 3.4 mm/yr/C. When applied to future
warming scenarios of the Intergovernmental Panel on Climate Change,
this relationship results in a sea level rise in 2100 of 0.5 - 1.4 m
above the 1990 level.
From the New Scientist article about this study that says the Janice's
favorite section may be revised higher than the 2001 estimate! Note
the author of the study is the lead author of the paleoclimate
section. See
Shorelines may be in greater peril than thought
19:00 14 December 2006 news service
David L Chandler

Previous estimates of how much the world's sea level will rise as a
result of global warming may have seriously underestimated the
problem, according to new research.

The study, published in Science, uses a new "semi-empirical" method
instead of relying purely on computer modelling. While some modelling
significantly underestimates the amount of sea-level rise that has
already been seen over the last century, the new method matches the
observed rise very closely, says Stefan Rahmstorf, at the Potsdam
Institute for Climate Impact Research, Germany, who conducted the new

The existing computer model deviates even more from the actual
observations built into the new estimates included in a draft of the
next report of the Intergovernmental Panel on Climate Change, due to
be released in February 2007.

The draft report says newer climate models now suggest a rise only
half as great as projected in the previous IPCC report. But that draft
may be revised before its release to reflect the new research that
suggests the rise will be greater than the IPCC's previous estimate,
Rahmstorf told New Scientist.

Capital cities

For a given amount of warming, Rahmstorf says, the rise in sea level
"could well be twice as much as was so far expected, based on the last
IPCC report".

At the top of the range of possible temperature rises estimated by the
last IPCC report, the rise could be as great as 140 centimetres by
2100. That would be bad new for cities like London and New York, which
lie close to sea level, and would leave them facing an increased risk
of devastating storm surges. Even the lowest predicted temperature
rises would cause a 50 cm rise, Rahmstorf says.

The predictions in the previous IPCC report its third ranged from
9 cm to 88 cm by 2100, and the initial draft of the next report was to
cut those figures in half. But Rahmstorf, who is a lead author of the
paleoclimate section of the upcoming report, says he hopes his new
results will be incorporated before IPCC 4 is officially released in
February 2007.

Search for meaning

Rahmstorf says there are so many possible factors and feedback
mechanisms that affect sea level that it is almost impossible to
derive a meaningful model of future rises from purely physical
modelling. Instead, he uses a method similar to that used for
calculating tide tables.

The method relies on actual observations of past changes in sea level,
and their correlation with temperature changes, to derive an estimate
of the amount of increase expected for a given temperature change.

Rahmstorf acknowledges that the simple linear extrapolation derived
using the new semi-empirical method will not hold good over a
timescale of millennia, but he argues that it is a good approximation
for the next century. However, the strongest conclusion of the new
work, he says, is that uncertainties in sea level rise predictions are
far greater than expected.

"We should not take this risk," Rahmstorf says. "We should start with
very effective emission reduction measures. The global temperature
increase should be kept to under 2C."

"We still have some work to do to improve our comprehensive physical
models, especially for ice sheets," says Richard Alley, at Penn State
University, who specialises in ice sheets and glaciers. "But given the
difficulties with modelling ice sheets etc., Rahmstorf's approach is
clever and useful."

To unsubscribe, send a message to with
"unsubscribe asa" (no quotes) as the body of the message.
Received on Fri, 22 Dec 2006 07:16:37 -0700

This archive was generated by hypermail 2.1.8 : Fri Dec 22 2006 - 09:17:30 EST