Wednesday, May 16, 2012

4282.txt

cc: Dave Thompson <davetatXYZxyzos.colostate.edu>
date: Mon Oct 19 16:58:19 2009
from: Phil Jones <p.jonesatXYZxyz.ac.uk>
subject: Re: food for thought...
to: Dave Thompson <davetatXYZxyzos.colostate.edu>, John Kennedy <john.kennedyatXYZxyzoffice.gov.uk>, Mike Wallace <wallaceatXYZxyzos.washington.edu>

Dave,
Have had a look at these one and off today.
My suggestion would be to smooth these series then look at the results. Maybe something at
about 5 year timescale.
If there was a problem with the NH SSTs in 1969 it should also affect the SH - it doesn't.
You could also correlate your red line with gridded land data. It will be noisier, but I'd
reckon that the basic pattern would show there.
I think what you're seeing is the aerosol cooling of the NH. It's also in the SH, but
much lower amplitude.
Try a comparison with some of the global dimming/brightening series. There are a number of
papers on this my Martin Wild.
A proxy for this is the DTR - See Fig 1 in the attached. This is global. What you want is
separate ones for the NH and SH. The NH one will be steeper.
Cheers
Phil

At 22:02 16/10/2009, Dave Thompson wrote:

Dear Phil, John (cc Mike),
I've spent some more time looking at the differences between NH and SH
SSTs... and I'm increasingly convinced the global cooling in the 70s
occurred over a discrete period, and that it likely reflects some
residual data issues. Either that, or the climate system changed
abruptly in one hemisphere ~1969, but not in the other ....
So... I figured I'd bounce my latest ideas off of you folks to see
what you think... the last couple of papers were a lot of fun...maybe
there is another story that needs to be told...
I've attached three pages of figures. They are based on the corrected
SST time series John sent me, but all of the results I discuss below
are evident in HadSST2 as well. The vertical tickmarks are 0.5 K in
all figures.
Figure 1 shows NH (top), SH (middle) and the difference between NH and
SH SSTs (NH-SH). The data have not been filtered in any way. There is
some mess around WW1 and WW2, and that's to be expected. But there is
also - to my eye - a distinct drop in the difference between NH and SH
SSTs ~1969 (1969 is indicated by the dashed line).
(Note the nice thing about the difference time series is that it
filters much of the ENSO and volcanic variability.)
Is the drop also evident in the land data?
Figure 2 shows NH-SH time series of SSTs (top) and land data (bottom).
I've filtered the data for COWL, ENSO and Volcano. This makes little
difference in the case of the SST difference time series (since ENSO
and volcanos show up in both hemispheres). But it does make a
difference in the land difference time series, as the COWL pattern
shows up only in the NH. There is a weak drop in the land data ~1969.
But nothing like the SST data.
Looking at the NH only:
Figure 3 shows the land (top) and SST (bottom) time series for the NH.
Both have been filtered as per our recent paper. The drop in the NH
SST time series is very pronounced. Dominant, I'd say. Can't believe I
missed it earlier. It's not as discrete as the 45 drop. But it's
certainly rapid. To my eye, the NH land areas are doing something
similar to the NH ocean areas ~1969. But it's hard to tell for sure.
The drop is there in the land data, but it is not as large.
Looking at the SH region only:
Figure 4 shows the land (top) and SST (bottom) time series for the SH.
Both have been filtered as per our recent paper. Both seem to warm
throughout the century. Note the large drop in land variance ~WW2.
There is no evidence of the drop in 1969 that is readily apparent in
the NH SST time series in Figure 3.
Figures 5 and 6 show one attempt to find the pattern associated with
the drop. Figure 5 shows the NH-SH difference time series along with a
fit to the drop in 1969 (as a red line). Figure 6 shows the
correlations between gridded SSTs and the red line from Fig. 5 over
the period 1960-1980. It's clear no particular region is giving rise
to the drop in 1969. Rather, the entire NH appears to have cooled
rapidly relative to the SH at nearly the same time (red shading
indicates the NH cooled relative to the SH, and vice versa). I
explored a range of slightly different analyses to try and tease out
the source of the drop ... but the results always stayed the same.
The bottom line...
- To my eye, the SST difference time series in Figure 2 looks
suspicious around 1969. The difference is almost 0.5 K (tickmarks are
at 0.5 K).
- I think the NH SST time series in Figure 3 is striking... the drop
in 1969 stands out clearly above the rest of the record. A similar
drop is not evident in the SH (Figure 4), and that is why the drop
exists in the difference time series in Figure 2.
- The NH land areas might be doing something interesting around 1969
(Figure 3). But as always, they are noisy (even when filtered) and
it's hard to tell.
- I think the drop in the NH SST time series in Figure 3 is
potentially more important for interpreting long-term trends in global- mean
temperatures than the drop in 1945. It lies close to the middle
of the period extending from WW2-now...
So .... what do you think? To your eyes, does the drop in 1969 look
normal or unusual? John... have you had any luck finding any data
issues at that time? Maybe the SST data is too high in the 1960s?
-Dave
--------------------------------------------------------------------
--------------------------------------------------------------------
David W. J. Thompson
[1]www.atmos.colostate.edu/~davet
Dept of Atmospheric Science
Colorado State University
Fort Collins, CO 80523
USA
970-491-3338
Dear Phil, John (cc Mike),
I've spent some more time looking at the differences between NH and SH SSTs... and I'm
increasingly convinced the global cooling in the 70s occurred over a discrete period,
and that it likely reflects some residual data issues. Either that, or the climate
system changed abruptly in one hemisphere ~1969, but not in the other ....
So... I figured I'd bounce my latest ideas off of you folks to see what you think... the
last couple of papers were a lot of fun...maybe there is another story that needs to be
told...
I've attached three pages of figures. They are based on the corrected SST time series
John sent me, but all of the results I discuss below are evident in HadSST2 as well. The
vertical tickmarks are 0.5 K in all figures.
Figure 1 shows NH (top), SH (middle) and the difference between NH and SH SSTs (NH-SH).
The data have not been filtered in any way. There is some mess around WW1 and WW2, and
that's to be expected. But there is also - to my eye - a distinct drop in the difference
between NH and SH SSTs ~1969 (1969 is indicated by the dashed line).
(Note the nice thing about the difference time series is that it filters much of the
ENSO and volcanic variability.)
Is the drop also evident in the land data?
Figure 2 shows NH-SH time series of SSTs (top) and land data (bottom). I've filtered the
data for COWL, ENSO and Volcano. This makes little difference in the case of the SST
difference time series (since ENSO and volcanos show up in both hemispheres). But it
does make a difference in the land difference time series, as the COWL pattern shows up
only in the NH. There is a weak drop in the land data ~1969. But nothing like the SST
data.
Looking at the NH only:
Figure 3 shows the land (top) and SST (bottom) time series for the NH. Both have been
filtered as per our recent paper. The drop in the NH SST time series is very pronounced.
Dominant, I'd say. Can't believe I missed it earlier. It's not as discrete as the 45
drop. But it's certainly rapid. To my eye, the NH land areas are doing something
similar to the NH ocean areas ~1969. But it's hard to tell for sure. The drop is there
in the land data, but it is not as large.
Looking at the SH region only:
Figure 4 shows the land (top) and SST (bottom) time series for the SH. Both have been
filtered as per our recent paper. Both seem to warm throughout the century. Note the
large drop in land variance ~WW2. There is no evidence of the drop in 1969 that is
readily apparent in the NH SST time series in Figure 3.
Figures 5 and 6 show one attempt to find the pattern associated with the drop. Figure 5
shows the NH-SH difference time series along with a fit to the drop in 1969 (as a red
line). Figure 6 shows the correlations between gridded SSTs and the red line from Fig. 5
over the period 1960-1980. It's clear no particular region is giving rise to the drop in
1969. Rather, the entire NH appears to have cooled rapidly relative to the SH at nearly
the same time (red shading indicates the NH cooled relative to the SH, and vice versa).
I explored a range of slightly different analyses to try and tease out the source of the
drop ... but the results always stayed the same.
The bottom line...
- To my eye, the SST difference time series in Figure 2 looks suspicious around 1969.
The difference is almost 0.5 K (tickmarks are at 0.5 K).
- I think the NH SST time series in Figure 3 is striking... the drop in 1969 stands out
clearly above the rest of the record. A similar drop is not evident in the SH (Figure
4), and that is why the drop exists in the difference time series in Figure 2.
- The NH land areas might be doing something interesting around 1969 (Figure 3). But as
always, they are noisy (even when filtered) and it's hard to tell.
- I think the drop in the NH SST time series in Figure 3 is potentially more important
for interpreting long-term trends in global-mean temperatures than the drop in 1945. It
lies close to the middle of the period extending from WW2-now...
So .... what do you think? To your eyes, does the drop in 1969 look normal or unusual?
John... have you had any luck finding any data issues at that time? Maybe the SST data
is too high in the 1960s?
-Dave

--------------------------------------------------------------------
--------------------------------------------------------------------
David W. J. Thompson
[2]www.atmos.colostate.edu/~davet
Dept of Atmospheric Science
Colorado State University
Fort Collins, CO 80523
USA
970-491-3338

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
NR4 7TJ
UK
----------------------------------------------------------------------------

No comments:

Post a Comment