A new approach to calculating Earth's global land temperature

Because of their importance as indicators of possible climate change, estimates of annual global temperatures have attracted intense scrutiny. For more than 30 years, such estimates have come from three independent groups: the University of East Anglia in England together with the UK Met Office Hadley Center; NASA's Goddard Institute for Space Sciences; and the National Oceanic and Atmospheric Administration's National Climatic Data Center. The data from all three manifest a slow rise in the mean annual global temperature over the past century. Some critics have raised doubts about possible sources of bias that might be influencing the observed trend. In response, the three groups have performed numerous corrections and checks on their calculations. For those still not convinced that the observed upward trend is real, there's now confirmation from a fourth group, the Berkeley Earth Surface Temperature project and its collaborators. Their approach differed from previous ones by including data from many more weather stations and by using a statistical fit to adjust for discontinuities in the data that are unrelated to the climate. The global temperatures, calculated so far just for land surface temperatures, agree with previous results. (R. Rohde et al., Geoinfor. Geostat: An Overview 1, 1 2013.)—Barbara G. Levi