This study is an extensive revision of the Climatic Research Unit (CRU) land station temperature database that has been used to produce a grid-box dataset of 5º latitude by 5º longitude temperature anomalies. The new database (CRUTEM4) comprises 5583 station records of which 4842 have enough data for the 1961-90 period to calculate or estimate the average temperatures for this period. Many station records have had their data replaced by newly homogenised series that have been produced by a number of studies particularly from National Meteorological Services (NMSs). Hemispheric temperature averages for land areas developed with the new CRUTEM4 dataset differ slightly from their CRUTEM3 equivalent. The inclusion of much additional data from the Arctic (particularly the Russian Arctic) has led to estimates for the Northern Hemisphere (NH) being warmer by about 0.1{degree sign}C for years since 2001. The NH/SH warms by 1.12/0.84{degree sign}C over the period 1901-2010. The robustness of the hemispheric averages is assessed by producing five different analyses each including a different subset of 20% of the station time series and by omitting some large countries. CRUTEM4 is also compared with hemispheric averages produced by reanalyses undertaken by the European Centre for Medium-Range Weather Forecasts (ECMWF) - ERA-40 (1958-2001) and ERA-Interim (1979-2010) datasets. For the NH, agreement is good back to 1958 and excellent from 1979 at monthly, annual and decadal timescales. For the SH agreement is poorer, but if the area is restricted to the SH north of 60{degree sign}S the agreement is dramatically improved from the mid-1970s.