Hemispheric Temperature Anomalies: 1851-1980

Climate Research Unit, University of East Anglia

The Climatic Research Unit (CRU) was established in the School of Environmental Sciences (ENV) at the University of East Anglia (UEA) in Norwich in 1972.

The CRU has collected, collated and archived global climate data for over 40 years.

CRU temperature data

 

In 1987, the American Meteorological Society published a paper by Stanley Grotch of the Lawrence Livermore National Laboratory, University of California, that assessed the robustness of the CRU dataset for land and other datasets.

Monthly Weather Review, Volume 115 No. 7, July 1987, ISSN: 0027-0644; eISSN: 1520-0493

Abstract

Three data bases of gridded surface temperature anomalies were used to assess the sensitivity of the average estimated Northern Hemisphere (NH) temperature anomaly to: 1) extreme gridpoint values and 2) zonal band contributions. Over the last 100 year, removal of either the top or bottom 10% of the gridpoint anomalies in any year changes the estimated NH average anomaly by 0.1−0.2°C. Excising extensive zonal bands also produces root-mean-square changes in the estimated NH anomaly of approximately 0.1°C. The estimated NH average anomaly appears to be robust to such perturbations.

[The following link link may not be recognized by WordPresss]

Some Considerations Relevant to Computing Average Hemispheric Temperature Anomalies (Grotch, S. L., 1987)

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URL: http://journals.ametsoc.org/doi/abs/10.1175/1520-0493%281987%29115<1305%3ASCRTCA>2.0.CO%3B2

Grotch cited the paper by Jones that described the land and ocean datasets: A new compilation of monthly mean surface air temperature for the Northern Hemisphere for 1851-1984 is presented based on land-based meteorological station data and fixed-position weather ship data.

PDF: JONES, P. D., et al. Northern Hemisphere surface air temperature variations: 1851-1984. Journal of Climate and Applied Meteorology, 1986, 25.2: 161-179.

My comment:

Grotch’s paper claimed that the land (CRU) and ocean (COADS) datasets pass his tests of normality and freedom from bias. His presentation is reasonable.

However, his Figure 1 shows that the 26,000 datapoints range between plus and minus 2 degrees Celsius , while the signal (the mean temperature) ranges from approximately -0.2 C to +0.2 C over a period of 130 years, a rate of about 0.3 C per century.

The temperature increase from 1875-80 to 1935-40 was about 1.1 C, more than double the increase over the period 1851-1980. This means that the biggest change in temperature during the period was before 1950 when CO2 began to be emitted at modern levels. It also means that this rise in temperature by 1 degree C was not climate change, but merely a natural fluctuation in temperature.

The duration both 1875-80 to 1935-400 and 1935-40 to 1995-2000, is 60 years, approximately the same as the period of the Atlantic Multidecadal Oscillation (AMO).

Unfortunately, we do not know how much of the temperature change on land observed during the last 120 years was a natural response to oceanic oscillations, including the AMO.

Since no warming was observed between 1940 and 1980 and since little or no warming has been observed since about 1995 (apart from El Ninos), the 15-year period from about 1980 to 1995 is our strongest,  and perhaps only, evidence for an irreversible change in climate.

But if the warming from 1980 to 1995 was related to the warm phase of the AMO, then we can expect, first a peaking in the cycle lasting until about 2010, and then a gradual downturn in the AMO, which may have already occurred but has been masked by El Nino events.

The COADS ocean data from the period 1850-1980 revealed no global temperature trend. This may possibly reflect the crude technology in use at sea during the entire period. The change in ocean temperature was less than the errors in measurement.

Until the Argo system began to be deployed in 2000, oceanographers had to rely on ships at sea to measure the temperature of the world ocean. The ocean covers 70% of the Earth’s surface and the thermocline extends to a depth of about two kilometers. Thus, most of the heat in the biosphere is stored in and released from the ocean.

Argo buoys

From 2007, several thousand Argo buoys began to record ocean temperatures. Until then, the error bars on ocean temperature estimates were too large relative to the size of the anomalies to inspire much confidence. Grotch did not elaborate on the weaknesses of the COADS dataset, but the situation is clear from his paper.

The publication in an obscure minor journal of the AMS effectively buried Grotch’s paper until Richard Lindzen displayed his graph of CRU temperature in his lecture,

Global Warming, Lysenkoism _ Eugenics Prof Richard Lindzen, at 30:37.

 

 

 

 

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3 thoughts on “Hemispheric Temperature Anomalies: 1851-1980

  1. Reblogged this on Tallbloke's Talkshop and commented:
    Are we anywhere close to really understanding the strength of natural climate variation and how it works?

    We can easily overlook that most temperature measurements are taken on land, but over 70% of the Earth’s surface is deep water.

    Like

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