2010-09-23 08:55:37A new paper on mid-century cooling
John Cook


Just bumped into this new paper: An abrupt drop in Northern Hemisphere sea surface temperature around 1970 (Thompson et al 2010). It seems to suggest there was more to mid-century cooling than aerosols (emphasis mine):

The twentieth-century trend in global-mean surface temperature was not monotonic: temperatures rose from the start of the century to the 1940s, fell slightly during the middle part of the century, and rose rapidly from the mid-1970s onwards1. The warming–cooling–warming pattern of twentieth-century temperatures is typically interpreted as the superposition of long-term warming due to increasing greenhouse gases and either cooling due to a mid-twentieth century increase of sulphate aerosols in the troposphere2, 3, 4, or changes in the climate of the world’s oceans that evolve over decades (oscillatory multidecadal variability)2, 5. Loadings of sulphate aerosol in the troposphere are thought to have had a particularly important role in the differences in temperature trends between the Northern and Southern hemispheres during the decades following the Second World War2, 3, 4. Here we show that the hemispheric differences in temperature trends in the middle of the twentieth century stem largely from a rapid drop in Northern Hemisphere sea surface temperatures of about 0.3 °C between about 1968 and 1972. The timescale of the drop is shorter than that associated with either tropospheric aerosol loadings or previous characterizations of oscillatory multidecadal variability. The drop is evident in all available historical sea surface temperature data sets, is not traceable to changes in the attendant metadata, and is not linked to any known biases in surface temperature measurements. The drop is not concentrated in any discrete region of the Northern Hemisphere oceans, but its amplitude is largest over the northern North Atlantic.

It's like Trenberth's missing heat... in the 1970s! :-)

Idon't have access to the full paper however, dang paywall.

2010-09-23 08:59:55how much is that?
Dana Nuccitelli

I wonder how much of the total surface cooling that 0.3°C drop in NH SSTs can account for.  It's a bit confusing, because the cooling didn't just occur from 1968 to 1972.

If I'm interpreting correctly, they're not trying to attribute the overall cooling trend, but rather the difference between NH and SH SSTs during the 4-year period in question.

2010-09-23 18:56:40the unaccounted reason could be
Otto Lehikoinen
the 30s depression via delay, possibly.
2010-09-23 23:48:05


Reuters covers this here: 


Article mentions this is Phil Jones' first publication in Nature since  the TomskTwaddle affair. So much for all the hysterical claptrap...

2010-09-24 00:07:59Anthony Watts' take on it
John Cook


Watts has a go at it too:


His anti-science jibes leave a real sour taste in my mouth. The cheap shot about the paywall like it's Phil Jones' fault and not the official policy of Nature, well, it really elevates the tone of the debate... not! :-(

2010-09-24 01:11:33comment
Robert Way

I think we have to consider this has something to do with the changeover of the AMO... Furthermore, in the North atlantic basin something called a great salinity anomaly propagated across the ocean causing temperature anomalies of greater than -2 in their localized regions... In Labrador it hit during 1972 and subsequent Land temperatures were found to be 2 degrees colder that year.

I once again take you back to the AMO/CO2 regression under the required reading section... Things are starting to make more sense me thinks...