from: Phil Jones <p.jonesatXYZxyz.ac.uk>
subject: Re: Urgent
to: "Rachel Warren" <r.warrenatXYZxyz.ac.uk>
Here's a few sentences. You can pick and choose which bits you want.
Description of HadCRUT3(v) - the dataset names. CRU does the land and the Hadley Centre
Over land regions of the world over 3000 monthly station temperature time series are used.
The basic monthly average temperature series are collected by the National Meteorological
Services around the world. Coverage is denser over the more populated parts of the world,
particularly, the United States, southern Canada, Europe and Japan. Coverage is sparsest
over the interior of the South American and African continents and over the Antarctic. The
number of available stations was small during the 1850s, but increases to over 3000
stations during the period since 1951. For marine regions sea surface temperature (SST)
measurements taken on board merchant and some naval vessels are used, supplemented by buoy
data in recent decades. As the majority come from the voluntary observing fleet, coverage
is reduced away from the main shipping lanes and is minimal over the Southern Oceans.
CRU has spent many person years assessing the long-term homogeneity of the land station
record and the Hadley Centre a similar time undertaking complementary assessments of the
homogeneity of the marine data.
Stations on land are at different elevations, and different countries estimate average
monthly temperatures using different methods and formulae. To avoid biases that could
result from these problems, monthly average temperatures are reduced to anomalies from the
period with best coverage (1961-90). For stations to be used, an estimate of the base
period average must be calculated. Because many stations do not have complete records for
the 1961-90 period several methods have been developed to estimate 1961-90 averages from
neighbouring records or using other sources of data. Over the oceans, where observations
are generally made from mobile platforms, it is impossible to assemble long series of
actual temperatures for fixed points. However it is possible to interpolate historical data
to create spatially complete reference climatologies (averages for 1961-90) so that
individual observations can be compared with a local normal for the given day of the year.
Both the component parts (land and marine) are separately interpolated (as anomalies from
1961-90) to the same 5� x 5� latitude/longitude grid boxes. The combined versions (HadCRUT3
and HadCRUT3v) take values from each component and weight the grid boxes according to their
errors in estimation, so giving greater weight to the oceanic data as errors of estimate
are generally smaller.
The gridded surface temperature products (HadCRUT3 and HadCRUT3v) extend from 1850 up to
Both HadCRUT3/HadCRUT3v and the separate land and marine grids (CRUTEM3 and HadSST2) are
used extensively within WG1 of AR4, principally within Chapter 3 on 'Observations:
Atmospheric Surface nd Climate Change', but the datasets in their various forms are used in
Chapter 1 (Historic overview of Climate Change Science), Chapter 6 (Paleoclimate), Chapter
8 (Climate Model Evaluation) and Chapter 9 (Understanding and Attributing Climate Change),
as well as in WG2.
At 19:33 17/03/2008, Rachel Warren wrote:
I went to see Simon Clegg - and ufnortunately need to trouble you
again - sorry.
Simon Clegg has emphasised that there really needs to be a section on
the CRU temp record
in the IPCC ENV research section in the ENV report. This means a
paragraph on how the CRU temp record
is put together and where it is used in IPCC. Simon insists that what
is in the 2006/5 ENV report
doesn't explain HOW the temp record is put together which is what he
wants ....ie where data
is collected from, how collated, what did CRU actually do, for how long etc ....
Can you help? I'm going to be VERY unpopular if I don't hand this in
complete on Wednesday so
please can you send me something tomorrow?
Dr Rachel Warren
Senior Research Fellow
University of East Anglia
Norwich NR4 7TJ
Telephone 01603 593912
Fax 01603 593901
Prof. Phil Jones
Climatic Research Unit Telephone +44 (0) 1603 592090
School of Environmental Sciences Fax +44 (0) 1603 507784
University of East Anglia
Norwich Email p.jonesatXYZxyz.ac.uk