<P> The global temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time . The most detailed information exists since 1850, when methodical thermometer - based records began . There are numerous estimates of temperatures since the end of the Pleistocene glaciation, particularly during the current Holocene epoch . Older time periods are studied by paleoclimatology . </P> <P> Weather balloon radiosonde measurements of atmospheric temperature at various altitudes begin to show an approximation of global coverage in the 1950s . Since December 1978, microwave sounding units on satellites have produced data which can be used to infer temperatures in the troposphere . </P>

How long have we been keeping weather records