First of all, the SST drop was not a drop but a rise in the late 1941 (uncorrected on a global basis ca. 0.8 degrees), which dropped about 0.4 degree at about 1946. Actually the situation seem to have been much more complex, http://www.oceanclimate.de/English/Pacific_SST_1997.pdf and http://www.oceanclimate.de/English/Atlantic_SST_1998.pdf , as not only during that time period the conditions differed from ship to ship extremely, but continued with the increasing size and speed of the ships since the 1950s. In the vastness of the ocean space and volume, the comparability of data, summing them up in series, presumably make any adjustment speculative. It should be furthermore taken into account that only recently the New Scientist (issue 2652) reported about ‚Mysterious striped currents revealed in the oceans’. http://www.soest.hawaii.edu/soest_web/images/Maximenko_Uga_eqrec_1000px.jpg . Should this extraordinary finding not be included in any research planning before considering any adjustment of historical SST?
Indeed: # the historic data is pretty thorny; lucia at May 29, 2008 12:08 PM #

If the “suspicious” period starts earlier– say as early as 1941, when the British distracted by things like the London Blitz, even up-side false-falsifications using Cochrane-Orcutt may have disappeared. (This is primarily due to the effect on the 30 year trend used to ‘test’ the 7 year trends. The bucket-engine transition cooling makes it drop too!)

That said, in this case, the non-volcanic, non-bucket-adjustment periods is short. If it gets too short, the whole test is beyond weird.

Still, what can be said is the “weather only” during the non-stratospheric volcano period we *have* looks pretty small!

adjusticating the post 40s dip could very well
improve the hindcast of ModelE. As it is ModelE hits the 30 year trend from 1940-1970 pretty well.

I’m more interested in what will happen to the frequency of “non volcanic cold spells”

Thanks for the clarifications.

I had naively assumed that the near-surface marine air temps would be independent and relatively reliable.

Len Ornstein

I probably overstated my case a bit. My point was that there’s a lot of data available for D&A that is either long term (say 1880-present) or spatial, and thus is fairly immune to a blip in the middle. Looking at the GISS Model E 20th century ensembles, for example, it looks like they steam right past the WWII blip in global temperatures. The correction could easily improve the fit without any change to the model. I’d guess that the result would be similar with your Lumpy. However, until we actually have new data, that remains a guess.

“That is, if we look at the second derivative of GHG forcings, that should result in causing the second derivative of temperature to increase.”
Not quite. Temperature (or heat) integrates radiative forcing and transport processes, so you’d expect the second derivative of temperature to be related to the first derivative of forcing. In practice it’s hard to see the derivatives through the noise and uncertainty about initial conditions, so it’s sensible to focus on temperatures not trends. Hence my preference for large cumulative changes over long records.

What would be susceptible is an analysis like Schwartz (2007), because it relies on surface temperature and ocean heat entirely in the postwar era. In that case it’s hard to say what the net outcome will be, because ocean heat revisions for the XBT fall rate problem are apparently also forthcoming.

————–
See the 2007 CCSP report:
[http://www.climatescience.gov/Library/sap/sap1-1/finalreport/default.htm]

on this subject; e.g. Chapter 3 Sections 2.2 and 2.3 at

http://www.climatescience.gov/Library/sap/sap1-1/finalreport/sap1-1-final-chap3.pdf

and also Section 1.1 in

http://www.climatescience.gov/Library/sap/sap1-1/finalreport/sap1-1-final-chap2.pdf.

“Near-surface” air temperatures over the ocean (“Marine Air Temperatures” or MATs) are measured by ships and buoys at various heights from 2 to more than 25 meters, with poorer temporal and spatial coverage than over land (e.g., Rayner et al., 2003). To avoid the contamination of daytime solar heating of the ships’ surfaces that may affect the MAT, it is generally preferred to limit these to night MAT (NMAT)readings only. Observations of the water temperature near the ocean surface or “Sea Surface Temperatures” (SSTs) are widely used and are closely tied to MATs; ships and buoys measure SSTs within a few meters of the surface.”

The near surface air temperature and the SST are used essentially interchangeably in constructing the ocean contribution to the global average. See the rest of the discussions on this temperature interpretation there.
—————

Actually the surface measurements are very much in dispute. Micheals and McKitrick published a recent statistical analysis that suggests urbanization has contaminated the post-50s record and up to half of the reported warming may be spurious.

The counter argument has always been that land only accounts for 30% of the surface so contamination of the land record does not have a huge effect on the GMST. However, this argument is a double edged sword because it means errors in the SST record will have large effect on GMST.

Nature 453, 646-649 (29 May 2008) | doi:10.1038/nature06982; Received 28 January 2008; Accepted 4 April 2008

A large discontinuity in the mid-twentieth century in observed global-mean surface temperature

David W. J. Thompson1, John J. Kennedy2, John M. Wallace3 & Phil D. Jones4

1. Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado 80523, USA
2. Met Office Hadley Centre, Exeter EX1 3PB, UK
3. Department of Atmospheric Sciences, University of Washington, Seattle, Washington 98195, USA
4. Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK

Correspondence to: David W. J. Thompson1 Correspondence and requests for materials should be addressed to D.W.J.T. (Email: davet@atmos.colostate.edu).

Top of page
Abstract

Data sets used to monitor the Earth’s climate indicate that the surface of the Earth warmed from approx1910 to 1940, cooled slightly from approx1940 to 1970, and then warmed markedly from approx1970 onward1. The weak cooling apparent in the middle part of the century has been interpreted in the context of a variety of physical factors, such as atmosphere–ocean interactions and anthropogenic emissions of sulphate aerosols2. Here we call attention to a previously overlooked discontinuity in the record at 1945, which is a prominent feature of the cooling trend in the mid-twentieth century. The discontinuity is evident in published versions of the global-mean temperature time series1, but stands out more clearly after the data are filtered for the effects of internal climate variability. We argue that the abrupt temperature drop of approx0.3 °C in 1945 is the apparent result of uncorrected instrumental biases in the sea surface temperature record. Corrections for the discontinuity are expected to alter the character of mid-twentieth century temperature variability but not estimates of the century-long trend in global-mean temperatures.

Is the entire discussion a bit off the mark?

The argument in Nature, and by Steve McIntyre, relates to ‘instrumental biases’ in sea surface temperature measurements. Associated with those measurements are SEPARATE surface air temperature measurements. The latter ARE NOT IN DISPUTE.

Although the apparent skill of those GCMs, using dynamic atmosphere/ocean flux modules, should be affected, the trends of OBSERVED surface air temperatures should not.

What am I missing?

Len Ornstein