Temperature record

The temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. The most detailed information exists since 1850, when methodical thermometer-based records began. There are numerous estimates of temperatures since the end of the glaciation, particularly during the current Holocene epoch. Older time periods are studied by paleoclimatology.

Weather balloon radiosonde measurements of atmospheric temperature at various altitudes begin to show an approximation of global coverage in the 1950s. Since December 1978, microwave sounding units on satellites have produced data which can be used to infer temperatures in the troposphere.

Several groups have analyzed the satellite data to calculate temperature trends in the troposphere. Both the University of Alabama in Huntsville (UAH) and the private, NASA funded, corporation Remote Sensing Systems RSS (RSS) find an upward trend.

For the lower troposphere (TLT), UAH find a global average trend since 1978 of +0.140 °C/decade, to January 2011. RSS finds +0.148 °C/decade, to January 2011.

In 2004 Fu et al. found trends of +0.19 °C/decade when applied to the RSS dataset. Vinnikov and Grody found +0.20 °C/decade up between 1978 and 2005, since which the dataset has not been updated.

Detailed information exists since 1850, when methodical thermometer-based records began.

Proxy measurements can be used to reconstruct the temperature record before the historical period. Quantities such as tree ring widths, coral growth, isotope variations in ice cores, ocean and lake sediments, cave deposits, fossils, ice cores, borehole temperatures, and glacier length records are correlated with climatic fluctuations. From these, proxy temperature reconstructions of the last 2000 years have been performed for the northern hemisphere, and over shorter time scales for the southern hemisphere and tropics.

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