Download Professor Mark Merrifield, Director, Sea Level Centre

RESPONSE FROM PROFESSOR MARK MERRIFIELD – 29/7/11
Oceanography Department at the University of Hawaii
Director, Sea Level Centre, University of Hawaii
1.
Do you agree with the premise of The Australian’s article, which is that analysis of tidal
gauges in Australia, as demonstrated in research published by Phil Watson, shows that
sea-levels were rising at a decelerating rate in Australia between 1940 and 2000, and that
the research paper calls into question the projected rise in sea-levels attributed to climate
change?
Yes and no. I agree that sea level around Australia and New Zealand exhibited the
deceleration as described in the Watson article. I don't agree that that result can be used to
call into question global sea-level rise projections.
2.
What is your view of Mr Watson’s methodology and findings in his journal article?
I thought the methodology was sound and the findings were supported by the tide gauge
data.
4. The article quotes Dr Howard Brady as saying ‘the divergence between the sealevel trends from models and sea-level trends from the tidal gauge records was now so
great “it is clear there is a serious problem with the modelling”’. Do you agree with Dr
Brady’s assertion that this report calls into question the projections of the IPCC?
No, Dr. Brady is comparing apples and oranges. The Watson article highlights changes in
regional sea level, not global average sea level. There's an important distinction, which
I felt Mr. Watson tried to emphasize. Regional sea level variations largely result from
changes in wind patterns and ocean circulation that are components of natural climate
variability.
Global average sea level is affected by changes in net ocean heat content and land-based
ice melt which are strongly influenced by warming trends. A simple analogy is a tub of
water that is slowly being filled by a spigot while at the same time is being sloshed about.
The sloshing motions don't affect the amount of water in the tub, but would certainly affect
a measurement of water level anywhere in the tub (the regional equivalent). An average of
the water level everywhere in the tub would provide a measure of the water input from the
spigot. Analyses of global sea level using tide gauges are concerned with this average, and
the challenge is to average out the regional sloshing to get to the global average. This was
not the intent of Mr. Watson's paper and his results do not address global sea level..
5.
Do you agree with the journalist’s analysis of Mr Watson’s research paper, particularly
that the research ‘... calls into question one of the key criteria for large-scale inundation
around the Australian coast by 2100 – the assumption of an accelerating rise in sea levels
because of climate change’?
No. There is no basis for that argument.
6.
How do Mr Watson’s results compare with other evidence available about sea-level rise
in the 20th century? Does most hard evidence point to an acceleration in sea-level rise, a
steady increase or a decelerating rate of sea-level rise?
The results are similar to other studies that highlight differences between regional and
global sea level changes. Studies of global sea-level rise over the past several centuries
show a long-term acceleration that is most noticeable since the early 1900s.
7.
Do you think the Houston and Dean study casts doubt on the IPCC’s modelling and
forecasts for sea level rise?
No. Their study also pertains largely to regional sea level changes. Their attempts to infer
global sea level changes I found to be misleading.
8.
Could you please send us the details of your titles and expertise in this field.
I'm a professor in the Oceanography Department at the University of Hawaii specializing in
sea level, waves, and coastal processes. I've been the Director of the University of Hawaii
Sea Level Center (UHSLC) since 1997. The UHSLC is a NOAA funded program to collect,
analyze and serve tide gauge observations from a global network for climate and
oceanographic research. For the past 6 years I've chaired the Global Sea Level Observing
System (GLOSS) Group of Experts. GLOSS is an international program that is concerned with
the establishment of global and regional sea level networks for scientific research and in
support of operational needs.