cc: <t.osborn@uea.ac.uk>, <christopher.d.miller@noaa.gov>
date: Thu, 24 Oct 2002 17:14:31 +0000
from: Tim Osborn <t.osborn@uea.ac.uk>
subject: confidential assessment of GC03-512
to: <irma.dupree@noaa.gov>

Dear Irma and Chris,

Re. proposal review GC03-512, PI: David Meko "A 19th century data catalog"

First of all, I confirm that there is no conflict of interest etc.

Now to my review...



(1) Scientific Merit

Rating: Good

Comments:
I completely agree with the rationale behind improving data sets of 19th
century climate (see my comments below on "Relevance to climate change
programme"), and the proposers have identified the most relevant data
sources available for the US.  The objectives and workplan are generally
reasonable, but I have rated it "good" rather than "very good" or
"excellent" because it does not seem as scientifically innovative or
challenging as it might.  Some particular concerns are highlighted below.

I am very wary about the proposed approach of integrating the data sources
together to produce a single climate product.  Obviously the data sources
have to be used in combination, for calibration of proxy data or for
assessment of possibly dubious early instrumental data, *but* combining them
all into a single product only will be very restrictive for future use,
assessment, improvements.  Much better would be to produce intrumental-only
series for whatever length is available, and tree-ring only series for the
full length (i.e., into the late 19th and 20th centuries, despite the
availability of instrumental data for these periods).  Blending them into a
single analysis is of some, but limited, use and comparisons of different
periods and with (e.g.) model simulations can only ever be done by taking
into account error bars that vary dramatically in time and are only
estimates of the "true" errors - and the error estimates may be
underestimates if based only on residuals or covariances during the 20th
century.

No mention is made of using the 19th century data to consider key issues
such as difference between tree-ring and ground borehole temperatures (they
differ more in the 19th century, in terms of trend, than in other
centuries), possibly taking into account land-use change.  No mention is
made of using the 19th century data to assess multi-century temperature
reconstructions and why they differ.  These are issues of great importance.

No mention is investigating seasonal dependence of temperature changes,
which are greater in existing temperature products during the 19th century
than in the 20th century and which has important implications for the
calibration of proxy (including tree-ring) data against summer or annual
data and the need to more clearly define the true seasonal response of proxy
data.

Despite these concerns, the proposed work is certainly worthy of funding and
the extra items of interest that I mention above could be achieved using the
data generated here, in some future project.



(2) Relevance to climate change programme

Rating: High

Comments:
The 19th century is certainly of particular importance, not just for the
reasons outlined in the proposal but also because this century shows some of
the biggest disagreements in warming trend between various quasi-hemispheric
temperature reconstructions and between proxy and instrumental data and
between different seasons of instrumental data.  Additional data sources are
definitely required, and additional digitisation, homogenisation and
intercomparison of data sets is necessary.  For these reasons, work such as
that proposed here is essential for helping to refine answers to questions
such as how unusual is late twentieth century climate and detection of
climate change signals against the noise of natural climate variability.

Best regards

Tim


-- 
Dr. Timothy J. Osborn
Climatic Research Unit
University of East Anglia
Norwich  NR4 7TJ, UK.
Telephone: 01603 592089
Fax:       01603 507784
e-mail:    t.osborn@uea.ac.uk
homepage:  http://www.cru.uea.ac.uk/~timo

