Instrumental temperature record

The instrumental temperature record provides the temperature of Earth's climate system from the historical network of in situ measurements of surface air temperatures and ocean surface temperatures. Data are collected at thousands of meteorological stations, buoys and ships around the globe. The longest-running temperature record is the Central England temperature data series, that starts in 1659. The longest-running quasi-global record starts in 1850. In recent decades more extensive sampling of ocean temperatures at various depths have begun allowing estimates of ocean heat content but these do not form part of the global surface temperature datasets.

The global average and combined land and ocean surface temperature, show a warming of 0.85 [0.65 to 1.06] °C, in the period 1880 to 2012, based on multiple independently produced datasets. This gives a trend of 0.064 ± 0.015 °C per decade over that period. The trend is faster for land than ocean, faster for Arctic regions, and faster since the 1970s than the longer period.

Most of the observed warming occurred in two periods: around 1900 to around 1940 and around 1970 onwards; the cooling/plateau from 1940 to 1970 has been mostly attributed to sulphate aerosol. Some of the temperature variations over this time period may also be due to ocean circulation patterns.

Attribution of the temperature change to natural or anthropogenic (i.e., human-induced) factors is an important question: see global warming and attribution of recent climate change.

Land air temperatures are rising faster than sea surface temperatures. Over 1979 to 2012 the trend for land was about 0.254 ± 0.050 °C per decade per CruTemp4 or 0.273 ± 0.047 per GHCN while the trend for sea surface temperatures is about 0.072 ± 0.024 °C per decade per HadISST to 0.124 ± 0.030 °C per decade per HadSST3

For 1979 to 2012, the linear warming trend for combined land and sea temperatures has been 0.155 °C [0.122 to 0.188 °C] per decade according to AR5.

The IPCC Fourth Assessment Report found that the instrumental temperature record for the past century included urban heat island effects but that these were primarily local, having a negligible influence on global temperature trends (less than 0.006 °C per decade over land and zero over the oceans).

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