Friday, June 15, 2012

5179.txt

cc: Mike Wallace <wallaceatXYZxyzos.washington.edu>, Phil Jones <p.jonesatXYZxyz.ac.uk>
date: Fri, 16 May 2008 13:42:24 +0100
from: John Kennedy <john.kennedyatXYZxyzoffice.gov.uk>
subject: Re: Press release
to: David Thompson <davetatXYZxyzos.colostate.edu>

All,

I've attached the latest version of the press release. I've stripped off
the additional information and removed some of the text about keying in
new data.

The press office and other interested parties haven't seen it yet, which
is the next stage.

John

On Wed, 2008-04-30 at 10:50 +0100, David Thompson wrote:
>
>
> All,
>
>
> I've made a few tweaks to Mike's version. Text is below.
>
>
> I was also uncomfortable with the Hadley Centre propaganda. I think it
> would have been a lightning rod for the critics.
>
>
> -Dave
>
>
> Using a novel technique to remove the effects of temporary
> fluctuations in global temperature due to El Niño and transient
> weather patterns, researchers at Colorado State University, the
> University of Washington, the UK Met Office and the University of East
> Anglia have highlighted a number of sudden drops in global
> temperature.
>
>
> Most of these drops coincide with the eruptions of large tropical
> volcanoes and are evident in temperatures measured over both the
> world's land and ocean areas. But the largest drop, occurring towards
> the end of 1945, is unrelated to any known volcanic eruption and is
> not apparent over land. It appears to arise from an artificial and
> temporary cooling caused by an abrupt change in the mix of US and UK
> ships reporting temperatures at the end of the Second World War.
>
>
> The majority of sea temperature measurements available in
> international data bases between 1941 and 1945 are from US ships. The
> crews of US ships measured the temperature of the water before it was
> used to cool the ships engine. Because of warmth coming from the ship,
> the water was often a little warmer than the true sea temperature. At
> the end of 1945 the number of US observations in the data base dropped
> rapidly while the number of UK observations increased. UK ships
> measured the temperature of water samples collected using special
> buckets. Wind blowing past the buckets as they were hauled onto the
> deck often caused these measurements to be cooler than the actual sea
> temperature. The sudden drop in global-mean temperatures at the end of
> World War 2 is due to the sudden but uncorrected change from US engine
> room measurements - which are biased warm - to UK measurements - which
> are biased cool.
>
>
> Although the drop in 1945 is large in climate-change terms � abouut
> 0.3°C � its effect is likely to be largest during the period

> immediately after the Second World War and very small by the 1960s,
> when better-insulated buckets came into use and a there was a more
> varied mix of measurements from different national merchant shipping
> fleets. Correcting the drop will change the character of middle
> century temperature variablity during the period following World War
> 2, but it is expected to have little effect on 20th century warming
> trends, which are corroborated by independent records of air
> temperatures taken over both land and sea.
>
>
>
> Climate researchers at the Met Office Hadley Centre are working to
> reduce the biases in the temperature datasets. In the past two years,
> many hundreds of thousands of observations have been keyed in from
> hand-written log books that were kept aboard ships in the UK navy,
> particularly for the periods of sparse marine coverage, such as the
> two World War periods. Fixing the drop is unlikely to radically alter
> our understanding of climate change, but having a more accurate record
> of the real temperature change during the mid-20th century could
> provide insight into the more subtle mechanisms that caused the early
> rise in temperatures to the 1920s and the subsequent flattening of the
> temperature curve that lasted into the early 1970s.
>
>
>
> Extra information:
>
>
> Marine temperatures are much more prone to systematic biases arising
> from changes in the way the measurements are taken and the platforms
> used than are land air temperatures. For example, since the 1970s,
> sea surface temperatures have been estimated from satellites, but
> these need considerable adjustment (sometimes in excess of 2 deg C) to
> be comparable with ship and buoy measurements. The satellite sees only
> the top millimetre of the ocean surface, while traditional ship-based
> sampling sees the top few metres. A change is gradually talking place
> across the world's oceans in the way sea surface temperature
> measurements are made during the last ten years: the number of ship-
> based measurements has reduced slightly, but there is a dramatic
> increase in the number of measurements coming from automatic
> measurements taken on fixed and drifting buoys. Work is underway to
> determine the size of the difference between the ships and buoys, as
> the bias between the two could be of the same order as that in the
> 1940s.
--
John Kennedy Climate Monitoring and Research Scientist
Met Office Hadley Centre FitzRoy Road Exeter EX1 3PB
Tel: +44 (0)1392 885105 Fax: +44 (0)1392 885681
E-mail: john.kennedyatXYZxyzoffice.gov.uk http://www.metoffice.gov.uk
Global climate data sets are available from http://www.hadobs.org



Attachment Converted: "c:\eudora\attach\DraftPressStatement_v5.doc"

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