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

Data sets used to monitor the Earth's climate indicate that the surface of the Earth warmed from ∼1910 to 1940, cooled slightly from ∼1940 to 1970, and then warmed markedly from ∼1970 onward. The weak cooling apparent in the middle part of the century has been interpreted in the context of a va...

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Bibliographic Details
Published in:	Nature 2008-05, Vol.453 (7195), p.646-649
Main Authors:	Jones, Phil D, Wallace, John M, Thompson, David W. J, Kennedy, John J
Format:	Article
Language:	eng
Subjects:	Atmospheric circulation Climate change Climatology. Bioclimatology. Climate change Earth, ocean, space Exact sciences and technology External geophysics Geophysics. Techniques, methods, instrumentation and models Global temperature changes Measurement techniques Meteorology Methods Ships Studies Temperature measurements Time series
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Summary:	Data sets used to monitor the Earth's climate indicate that the surface of the Earth warmed from ∼1910 to 1940, cooled slightly from ∼1940 to 1970, and then warmed markedly from ∼1970 onward. 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 aerosols. 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 series, 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 ∼0.3 °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.
ISSN:	0028-0836 1476-4687 1476-4679