Global and Hemispheric Temperature Anomalies - Land and Marine Instrumental Records

Graphics    Digital Data

Investigators

P. D. Jones¹, D. E. Parker², T. J. Osborn¹, and K. R. Briffa¹

¹Climatic Research Unit,
School of Environmental Sciences, University of East Anglia,
Norwich NR4 7TJ, United Kingdom

²Hadley Centre for Climate Prediction and Research,
Meteorological Office,
Bracknell, Berkshire, United Kingdom

DOI

10.3334/CDIAC/cli.002

Period of Record

1850-2008 (Anomalies are relative to the 1961-90 reference period means.)

Methods

These global and hemispheric temperature anomaly time series, which incorporate land and marine data, are continually updated and expanded by P. Jones of the Climatic Research Unit (CRU) with help from colleagues at the CRU and other institutions. Some of the earliest work in producing these temperature series dates back to Jones et al. (1986a,b,c), Jones (1988, 1994), and Jones and Briffa (1992). Most of the discussion of methods given here has been gleaned from the Frequently Asked Questions section of the CRU temperature data web pages. Users are encouraged to visit the CRU Web site for the most comprehensive overview of these data, other associated datasets, and the most recent literature references to the work of Jones et al.

The land portion of the database from which the Jones et al. time series are computed consists of surface air temperature (SAT) data (land-surface meteorological data and fixed-position weather ship data) from over 3000 station records that have been corrected for non-climatic errors, such as station shifts and/or instrument changes (Jones 1994).

Coverage is denser over the more populated parts of the world, particularly the United States, southern Canada, Europe and Japan. Coverage is sparsest over the interior of the South American and African continents and over the Antarctic. The number of available stations was small during the 1850s, but increases to over 3000 stations during the 1951-90 period.

The marine data used are compiled at the Hadley Centre of the United Kingdom Meteorological Office and consist of sea surface temperatures (SSTs) that incorporate in situ measurements from ships and buoys. The SST data have been corrected for different types of buckets used before 1942 (Folland and Parker 1995; Parker et al. 1994, 1995). Since the majority of the marine observations come from the voluntary observing fleet, coverage is reduced away from the main shipping lanes and is minimal over the Southern Oceans. Maps/tables giving the density of coverage through time are given for land regions by Jones and Moberg (2003) and for the oceans by Rayner et al. (2003). Both these sources, in addition to more recent work (Rayner et al., 2006), also extensively discuss the issue of consistency and homogeneity of the measurements through time and the steps that have been taken to ensure all non-climatic inhomogeneities have been removed.

The land and marine data components are combined by first interpolating each to the same 5° x 5° latitude/longitude grid boxes. The combined version takes values from each component and weights the grid boxes where both occur (coastlines and islands). The weighting method is described in detail in Jones et al. (2001). Land temperature anomalies are infilled where more than four of the surrounding eight 5° x 5°6 grid boxes are present, as discussed in Jones et al. (2001). Infilling doesn't take place when the box is ocean, except when it is covered by sea ice based on 1961-90 average conditions.

Assessing the accuracy of the resulting global and hemispheric temperature anomalies has always been of critical importance in the work of Jones et al.. Annual values are approximately accurate to +/- 0.05°C (two standard errors) for the period since 1951. They are about four times as uncertain during the 1850s, with the accuracy improving gradually between 1860 and 1950, except for temporary deteriorations during data-sparse, wartime intervals. Estimating accuracy is far from a trivial task, as the individual grid boxes are not independent of each other and the accuracy of each grid box time series varies through time (although an employed variance adjustment has reduced this influence to a large extent). The issue is discussed extensively by Brohan et al. (2006), Folland et al. (2001a,b), and Jones et al. (1997). Brohan et al. (2006) and Folland et al. (2001a,b) extend discussion to the estimate of accuracy of trends in the global and hemispheric series, including the additional uncertainties related to homogeneity corrections.

The global and hemispheric averages are now given to a precision of three decimal places to enable seasonal values to be calculated to ±0.01°C. The extra precision implies no greater accuracy than two decimal places.

Trends

Trends in annual mean temperature anomalies for the globe show relatively stable temperatures from the beginning of the record through about 1910, with relatively rapid and steady warming through the early 1940s, followed by another period of relatively stable temperatures through the mid-1970s. From this point onward, another rapid rise similar to that in the earlier part of the century is observed. The year 2008 was the tenth warmest in the global record (0.33°C above the 1961-1990 reference period mean), exceeded by 1998, 2005, 2003, 2002, 2004, 2006, 2001, 2007 and 1997. [Jones et al. (1999) report the 1961-1990 reference period means for the globe, northern hemisphere, and southern hemisphere as 14.0°C, 14.6°C, and 13.4°C, respectively.]

An additional summary of the Jones et al. temperature record (along with several other informative climate-related "Information Sheets" available from the CRU) may be found here. The 1990s were the warmest complete decade in the series. The warmest year of the entire series is 1998, with a temperature of 0.546°C above the 1961-90 mean. Thirteen of the fourteen warmest years in the series have now occurred in the past fourteen years (1995-2008). The only year in the last fourteen not among the warmest fourteen is 1996 (replaced in the warm list by 1990). The period 2001-2008 (0.43°C above 1961-90 mean) is 0.19°C warmer than the 1991-2000 decade (0.24°C above 1961-90 mean).

The northern and southern hemisphere annual trend series show some general similarities, e.g., little sign of trends before about 1900, a peak in the early 1940s, and the highest temperatures occurring after 1980; but there are several notable differences. A steady period of warming is seen for the northern hemisphere from about 1910 through the mid-1940s. For the southern hemisphere, there is less warming observed from about 1910 through 1930, with sudden and rapid warming from about 1930 through the mid-1940s. The northern hemisphere record shows gradual cooling from the mid-1940s through the mid-1970s, followed by rather steady temperature increases thereafter. The southern hemisphere shows an abrupt shift to cooler temperatures after 1945, quite variable temperatures until the mid-1960s, followed by a gradual increase over the remainder of the record.

Examining the seasonal series for the Southern Hemisphere, it is interesting to note that for all seasons, a warming trend does not commence until about 1910. All seasons show somewhat of a peak in the 1940s, like the global annual series, and steady warming after about the mid-1960s. The record warmth of 1998 still stands out as the warmest year across all seasons.

Similar to the southern hemisphere seasonal series, the seasonal series for the northern hemisphere show warming from about 1910 through the early 1940s, but thereafter until about the mid-1970s, show differences from one another. Winter and spring don't show much variation through the mid-1970s, whereas summer and fall show gradually declining temperatures. All seasons show pronounced warming from the mid-1970s onward. The northern hemisphere winter of 2008 (defined as the mean of the 3-month period December, 2007 through February, 2008) is the warmest on record at 0.70°C above 1961-90 mean.

References

• Brohan, P., J.J. Kennedy, I. Harris, S.F.B. Tett, and P.D. Jones. 2006. Uncertainty estimates in regional and global observed temperature changes: a new dataset from 1850. J. Geophysical Research 111, D12106, doi:10.1029/2005JD006548.
• Folland, C.K., and D.E. Parker. 1995. Correction of instrumental biases in historical sea surface temperature data. Quarterly Journal of the Royal Meteorological Society 121:319-367.
• Folland, C.K., N.A. Rayner, S.J. Brown, T.M. Smith, S.S.P. Shen, D.E. Parker, I. Macadam, P.D. Jones, R.N. Jones, N. Nicholls, and D.M.H. Sexton, 2001a. Global temperature change and its uncertainties since 1861. Geophysical Research Letters 28, 2621-2624.
• Folland, C.K., T.R. Karl, J.R. Christy, R.A. Clarke, G.V. Gruza, J. Jouzel, M.E. Mann, J. Oerlemans, M.J. Salinger, and S.-W. Wang, 2001b. Observed Climate Variability and Change. pp. 99-181 In: Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change (Houghton, J.T., Ding, Y., Griggs, D.J., Noguer, M., van der Linden, P.J., Dai, X., Maskell, K. and Johnson, C.A. Eds.). Cambridge University Press, Cambridge, UK, 881pp.
• Jones, P.D. 1988. Hemispheric surface air temperature variations: Recent trends and an update to 1987. Journal of Climate 1:654-60.
• Jones, P. D. 1994. Hemispheric surface air temperature variations: A reanalysis and an update to 1993. Journal of Climate 7(11):1794-1802.
• Jones, P.D., and K.R. Briffa. 1992. Global surface air temperature variations during the twentieth century: Part 1, spatial, temporal and seasonal details. The Holocene 2:165-79.
• Jones, P.D., and A. Moberg. 2003. Hemispheric and large-scale surface air temperature variations: An extensive revision and an update to 2001. J. Climate 16, 206-223.
• Jones, P.D., T.J. Osborn, and K.R. Briffa. 1997. Estimating sampling errors in large-scale temperature averages. Journal of Climate 10:2548-2568.
• Jones, P.D., M. New, D.E. Parker, S. Martin, and I.G. Rigor. 1999. Surface air temperature and its changes over the past 150 years. Reviews of Geophysics 37:173-199.
• Jones, P.D., T.J. Osborn, K.R. Briffa, C.K. Folland, E.B. Horton, L.V. Alexander, D.E. Parker, and N.A. Rayner, 2001. Adjusting for sampling density in grid box land and ocean surface temperature time series. Journal of Geophysical Research 106:3371-3380.
• Jones, P.D., S.C.B. Raper, R.S. Bradley, H.F. Diaz, P.M. Kelly, and T.M.L. Wigley. 1986a. Northern Hemisphere surface air temperature variations: 1851-1984. Journal of Climate and Applied Meteorology 25(2):161-179.
• Jones, P.D., S.C.B. Raper, and T.M.L. Wigley. 1986b. Southern Hemisphere surface air temperature variations: 1851-1984. Journal of Climate and Applied Meteorology 25(9):1213-1230.
• Jones, P.D., T.M.L. Wigley, and P.B. Wright. 1986c. Global temperature variations between 1861 and 1984. Nature 322:430-434.
• Parker, D. E., P. D. Jones, A. Bevan, and C. K. Folland. 1994. Interdecadal changes of surface temperature since the 19th century. Journal of Geophysical Research 99:14373-14399.
• Parker, D. E., C. K. Folland, and M. Jackson. 1995. Marine surface temperature: observed variations and data requirements. Climatic Change 31:559-600.
• Rayner, N.A., D.E. Parker, E.B. Horton, C.K. Folland, L.V. Alexander, D.P. Rowell, E.C. Kent, and A. Kaplan. 2003. Globally complete analyses of sea surface temperature, sea ice and night marine air temperature, 1871-2000. J. Geophys. Res. 108, 4407, doi 10.1029/2002JD002670.
• Rayner, N.A., P. Brohan, D.E. Parker, C.K. Folland, J.J. Kennedy, M. Vanicek, T. Ansell, and S.F.B. Tett. 2006. Improved analyses of changes and uncertainties in marine temperature measured in situ since the mid-nineteenth century: the HadSST2 dataset. J. Climate, 19, 446-469.