By Kip Hansen – Re-Blogged From http://www.WattsUpWithThat.com
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.
It may seem odd to the scientifically-minded that Global Average Temperature is measured and calculated to the claimed precision of hundredths of a degree Celsius without first having an agreed upon definition for what is being measured.
When I went to school, we were taught that all data collection and subsequent calculation requires the prior establishment of [at least] an agreed upon Operational Definition of the variables, terms, objects, conditions, measures, etc. involved.
A brief of the concept: “An operational definition, when applied to data collection, is a clear, concise detailed definition of a measure. The need for operational definitions is fundamental when collecting all types of data. When collecting data, it is essential that everyone in the system has the same understanding and collects data in the same way. Operational definitions should therefore be made before the collection of data begins.”
Nonetheless, after having informed the world that there is no agreed upon definition for Global Average Temperature, UCAR assures us that:
“The important point is that the trends that emerge from year to year and decade to decade are remarkably similar—more so than the averages themselves. This is why global warming is usually described in terms of anomalies (variations above and below the average for a baseline set of years) rather than in absolute temperature.”
In fact, the annual anomalies themselves differ one-from-another by > 0.49°C — an amount just slightly smaller than the whole reported temperature anomaly from 1987 to date (a 30-year climate period). [The difference between GISS June 2017 and UAH June 2017].
So, let’s summarize:
- We are told that 2015, the HOTTEST year ever, was …. what? ….. 59°F or 15° C – which is not hot except maybe in the opinion of the Inuit and other Arctic peoples — which may be a clue as to why they really talk in anomalies instead of absolute temperatures.
- Although a great deal of fuss is being made out of Global Average Temperature, there is no agreed upon definition of what Global Average Temperature actually means or how to calculate it.
- Despite the problems of #2 above, major scientific groups around the country and the world are happily calculating away on the as-yet undefined metric, each in a slightly different way.
- Luckily (literally, apparently) the important point is that although all the groups get different answers to the Global Average Surface Temperature question – we suppose it’s because of that lack of an agreed upon definition of what they are calculating — the trends they find are “remarkably similar”. [That choice of wording does not fill me with confidence in the scientific rigor of the findings — it so sounds like my term – “luckily”]. Even less reassuring is being told that the trends are “more [remarkably similar] … than the averages themselves.”
- And finally, because there is no agreed upon definition of Global Average Temperature and the results for the undefined metric from varying groups are less [remarkably] similar than the trends; even the calculated anomalies themselves from the different groups are as far apart from one another as the entire claimed temperature rise over the last 30 year climatic period.