1: Global Temperature Record

Phil Jones

(this graph of HadCRUT3 is also available as Encapsulated PostScript and PDF
suitable for publication and the data are available as Comma-Separated Values)

The time series shows the combined global land and marine surface temperature record from 1850 to 2010. According to the method of calculation used by CRU, the year 2010 was the equal third (see footnote) warmest on record (with 2003), exceeded by 1998 and 2005. The years 2003, 2005 and 2010 are only distinguishable in the third decimal place. The error estimate for individual years (two standard errors is about ±0.1°C, see Brohan et al., 2006) is at least ten times larger than the differences between these three years.

The period 2001-2010 (0.44°C above 1961-90 mean) was 0.20°C warmer than the 1991-2000 decade (0.24°C above 1961-90 mean). The warmest year of the entire series has been 1998, with a temperature of 0.55°C above the 1961-90 mean. After 1998, the next nine warmest years in the series are all in the decade 2001-2010. During this decade, only 2008 is not in the ten warmest years. Even though 2008 was the coldest year of the 21st century it was still the 12th warmest year of the whole record.

This time series is compiled jointly by the Climatic Research Unit and the UK Met. Office Hadley Centre. Increased concentrations of greenhouse gases in the atmosphere due to human activities are most likely the underlying cause of warming in the 20th century. The warmth or coldness of individual years is strongly influenced by whether there was an El Niño or a La Niña event occurring in the equatorial Pacific Ocean (see Information Sheet 12).

The Inter-governmental Panel on Climate Change in its most recent report in 2007 stated:

'Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.'

'Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. This is an advance since the TAR's conclusion that "most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations". Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns'

Links

• Global temperature anomaly datasets
• CET data
• IPCC: the Intergovernmental Panel on Climate Change
• Latest IPCC report from Working Group 1

The annual global (and hemispheric) mean values for each year given on our web site differ slightly from those given on the hadobs web site. All hemispheric averages are calculated from the grid box values available in each hemisphere, weighted to account for the different surface areas represented by each grid box. The global value is the mean of the two hemispheric averages. The CRU and Met. Office (hadobs) values are identical for the monthly global and hemispheric values, but for the annual averages CRU calculates this as the average of 12 monthly values, whereas the Met. Office calculates the annual average temperature anomaly for each grid box and then the hemispheric and global means from that. If the data coverage were the same for all 12 months, the two methods should give the same result, but if the data coverage varies during the year, small differences arise between the two methods.

The key reference for this time series is:

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