Instrumental temperature record
The instrumental temperature record shows the fluctuations of the temperature of the atmosphere and the oceans since the invention of thermometers. A quasi-global record exists since about 1850. See also
temperature record.
Encyclopedia
The
instrumental temperature record shows the fluctuations of the temperature of the atmosphere and the oceans since the invention of thermometers. A quasi-global record exists since about 1850. See also
temperature record.
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The quasi-global period: from 1850
The time period for which reasonably reliable near-surface temperature records exist from actual observations from
thermometers with quasi-global coverage is generally considered to start in about 1850 - earlier records exist, but coverage and instrument standardisation are less.
In the present day most meteorological observations are taken for use in weather forecasts. Centres such as ECMWF show ; or the Hadley Centre show the coverage for the . Coverage for earlier in the 20th and 19th centuries would be significantly less. While temperature changes vary both in size and direction from one location to another, the numbers from different locations are combined to produce an estimate of a global average change.
Most of the warming occurred during two periods: 1910 to 1945 and 1976 to 2000; the cooling/plateau from 1945 to 1976 is attributed to sulphate aerosol . Attribution of the temperature change to natural or anthropogenic factors is an important question: see
global warming and
attribution of recent climate change.
The data for the record come from
thermometer measurements from land stations and ships ,
which independently show much the same warming since 1860.
The data from these stations show an average surface temperature increase of 0.6±0.2 °C during the
20th century. The Intergovernmental Panel on Climate Change concludes:
- "The best estimate of global surface temperature change is a 0.6 °C increase since the late 19th century with a 95% confidence interval of 0.4 to 0.8 °C" .
The US National Academy of Science, both in its 2002 report to President George W. Bush, and in its latest publications, has strongly endorsed evidence of an average global temperature increase in the 20th century.
There are concerns about possible uncertainties in the instrumental temperature record including the fraction of the globe covered, the effects of changing thermometer designs and observing practices, and the effects of changing land-use around the observing stations. These are being continually addressed in the literature to optimally characterize the accuracy of the record. The casual reader is warned that advocacy organizations considerably exaggerate how seriously these effects contaminate the record. On the other hand considerable skepticism should be exercized for the early years. Indeed, the argument has been advanced that pre-1880 climate models could be more accurate than the instrumental record. Methods standardization and instrument calibration have been the responsibilities of the
World Meteorological Organization and its predecessor, the International Meteorological Organization.
There exists a parallel record of marine observations from surface
ships. These too suffer from changing practices but they are at least immune to the
urban heat islandeffect. The land and marine records can be compared.
For information about the effects or otherwise of urbanization on the temperature record, see the main article:
Urban heat island effectSecondary data
Secondary evidence for temperature changes can be obtained by observing things that are predicted to be affected by temperature changes, such as variations in the
snow cover and ice extent ,
sea level rise, precipitation ,
cloud cover , El Niño and extreme weather events . For example,
satellite data shows a 10% decrease of snow cover since the late 1960s , and the Northern Hemisphere spring and summer sea-ice extent has decreased by about 10% to 15% since the 1950s and there has been a widespread retreat of mountain
glaciers in non-polar regions throughout the 20th century..
Spatial variability
The global temperature changes are not uniform over the globe, nor would they be
expected to be, whether the changes were naturally or human forced. Certain places, such as the north shore of Alaska, showing dramatic rises temperature far above the average for the globe as a whole . The
Antarctic peninsula has warmed by 2.5 °C in the past 5 decades in certain places meanwhile East Antarctic has not significantly warmed .
See also
References
- Global average temperature for the last and of trends
- Preliminary data from the last [ftp://holocene.evsc.virginia.edu/pub/mann/mannjones03.pdf 2000 years]
