The phrase "hemispheric temperature" refers to the average temperature in one half of the Earth, either the northern or southern hemisphere. It measures the overall warmth or coldness of a specific hemisphere. Full definition
One can reasonably wonder whether the key conclusion of Briffa and Osborn 1999 — «[despite] the problems associated with interpreting many of them as unambiguous measures of hemispheric temperature change, this conclusion [MBH] must surely be accepted» — would have stood up if the decline had been shown. (climateaudit.org)
1) in 1998, Mann, then an early career researcher with a background in physics, was celebrated for the first multi-century hemispheric temperature reconstruction with annual resolution. (planet3.org)
The earlier data that do exist may be used to construct a very uncertain estimate of Australian temperatures, and may also be used for the construction of global and hemispheric temperature averages on monthly and annual time scales. (bom.gov.au)