Friday, May 18, 2012


cc: Simon Tett <>,, Gabi Hegerl <>, John Kennedy <>
date: Mon, 13 Apr 2009 09:39:12 +0100
from: Thomas Crowley <>
subject: Re: trends for n. land (summer) vs globe


thanks for the clarifications on all this - didn't claim originality on
my land detection sentence - but its good to have the original citation
for that, thanks.

this is not part of a paper - just put it together to straighten out
some of my own thoughts. seems a little thin for a paper, may try
posting on as a compromise

big divergence is during 97-98 ENSO - if it is some instrumental problem
from the ocean, perhaps clues from this time interval could unravel why

if not instrumental, then maybe an abrupt climate change bogie man came
out of the closet to cause 0.5 offset after that time - any ideas? might
be too early to look that way unless
ocean instrumental uncertainties are put to rest....

> Dear All,
> So this is how you all spend your Easter! It seems that
> I'm joining you - checking email from home.
> A couple of things
> 1. Argo floats don't go into the surface SST data as they
> don't measure at the surface. They stop some metres down,
> but come to the surface to transmit. What is likely causing a
> part of this divergence is the drifters. These are buoys
> that have dramatically improved the number of SST data entering
> analyses - and spatially as well. As Simon says, the HC
> are working on this. My belief is that the drifters are
> about 0.1 to 0.2 deg C cooler than the ships. We need to
> get a spatial pattern for this, and understand why. There is
> also an issue of these drfiters in the Southern Oceans. They
> get used but their 61-90 base periods could be off, as they
> basically come from interpolations from ships.
> 2. That NH summer is better for D&A has been said before.
> Wigley, T.M.L. and Jones, P.D., 1981. Detecting CO2-induced climatic
> change. Nature 292, 205-208.
> We didn't call it D&A then - just good old SNR.
> I don't have a pdf of this paper!
> Have a good Easter!
> Phil
> > I don't think ARGO goes into the SST dataset though there are a lot more
>> buoys in it. When I was at the Hadley Centre we wondered if buoys were
>> causing a slight cooling trend. [John Kennedy CCed might have some more
>> thoughts on that.]
>> Simon
>> wrote:
>>> Tom
>>> The fact that land could be shown to be warming more than ocean was a
>>> major conclusion of the AR4.
>>> It's good to see the update to 2008. Quite striking.
>>> I hate to say this, but I wonder if some of the recent behavior is
>>> spurious - the Argo floats just don't seem very consistent with earlier
>>> records not only for surface temperature but also for sea level (ie
>>> subsurface). What do you think?
>>> Susan
>>> ----- Original Message -----
>>> From: Thomas Crowley <>
>>> Date: Friday, April 10, 2009 6:10 am
>>> Subject: trends for n. land (summer) vs globe
>>>> Hi,
>>>> I am in the process of producing a new, long (733-1960) paleo
>>>> reconstruction at annual resolution for purposes of better
>>>> validation
>>>> against models. since tree rings are most sensitive to summer half-
>>>> year
>>>> temperatures, and trees usually grow on land, I am calibrating
>>>> against
>>>> 30-90N summer (land), using HadCRU data updated through 2008,
>>>> kindly
>>>> provided by Phil.
>>>> some interesting items jump out from just comparing (attached) the
>>>> instrumental reconstructions for 30-90N land, summer vs global
>>>> temps
>>>> (anomalies based on 1960-1990 mean for each data set):
>>>> 1) the n summer land changes are almost twice as large (1.5 vs.
>>>> 0.8�C)
>>>> as the global - this is not surprising because we know that land
>>>> heats
>>>> up faster than ocean, but the magnitude is quite striking.
>>>> 2) since most people still live on land, this means the human
>>>> impact
>>>> factor has been twice as large as normally assumed for close to 3
>>>> billion people
>>>> 3) the divergence between northern land and global temps seems to
>>>> be
>>>> increasing - both record show the recent decrease in temperatures,
>>>> but
>>>> on land it only started last year (2008)
>>>> 4) seven large volcanic eruptions can easily be identified in the
>>>> northern land record - this again makes sense from an energy
>>>> balance
>>>> viewpoint, as summer temperatures are more driven by thermodynamics
>>>> than
>>>> dynamics, so the signal is more easily detectable, especially given
>>>> the
>>>> added impact of maximized reflection of insolation due to high sun
>>>> angle.
>>>> 5) this suggests that northern hemisphere land (summer) might be
>>>> the
>>>> most logical data set to look at for detection of volcanic signals.
>>>> as
>>>> I have nearly finalized the new paleo reconstruction of volcanos,
>>>> it
>>>> might be interesting to re-apply detection and attribution to the
>>>> new,
>>>> longer, and (hopefully improved) data sets.
>>>> fyi, Tom
>>>> --
>>>> The University of Edinburgh is a charitable body, registered in
>>>> Scotland, with registration number SC005336.
>> --
>> Simon Tett
>> Chair of Earth System Dynamics
>> School of Geosciences
>> The University of Edinburgh
>> Tel:+44-(0)131-650-5341
>> Fax: +44 (0)131 668 3184
>> Room 351, Grant Institute,
>> The King's Buildings,
>> West Mains Road, Edinburgh EH9 3JW
>> UK
>> The University of Edinburgh is a charitable body, registered in
>> Scotland, with registration number SC005336.

The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.


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