by K. Hansen, 2017 in WUWT
A quick note for the amusement of the bored but curious.
While in search of something else, I ran across this enlightening page from the folks at UCAR/NCAR [The University Corporation for Atmospheric Research/The National Center for Atmospheric Research — see pdf here for more information]:
We are first reminded that “Climate scientists prefer to combine short-term weather records into long-term periods (typically 30 years) when they analyze climate, including global averages.” As we know, these 30-year periods are referred to as “base periods” and different climate groups producing data sets and graphics of Global Average Temperatures often use differing base periods, something that has to be carefully watched for when comparing results between groups.
Then things get more interesting, in that we get an actual number for Global Average Surface Temperature:
“Today’s global temperature is typically measured by how it compares to one of these past long-term periods. For example, the average annual temperature for the globe between 1951 and 1980 was around 57.2 degrees Fahrenheit (14 degrees Celsius). In 2015, the hottest year on record, the temperature was about 1.8 degrees F (1 degree C) warmer than the 1951–1980 base period.”
Quick minds see immediately that 1.8°F warmer than 57.2°F is actually 59°F [or 15° C] which they simply could have said.
UCAR/NCAR goes on to “clarify”:
“Since there is no universally accepted definition for Earth’s average temperature, several different groups around the world use slightly different methods for tracking the global average over time, including:
NASA Goddard Institute for Space Studies
NOAA National Climatic Data Center
UK Met Office Hadley Centre”
We are told, in plain language, that there is no accepted definition for Earth’s average temperature, but assured that it is scientifically tracked by the several groups listed.