Commentary: Don’t Be Fooled by “Global Average Temperature”

Last week was a banner week for climate crisis headlines. Washington Post: “The world is hotter than it’s been in thousands of years.” AP: “For the third time this week, Earth sets unofficial heat record.” Politico: “Scientists are freaking out about surging temperatures.”    

As anyone in the media business knows, headlines are apt to be more sensational than the reporters’ actual stories. The two climate scientists quoted in the Politico story, for example, offer accurate descriptions of meteorological events, but neither is close to “freaking out”.

To put this in some perspective, let’s imagine you are asked to produce a simple “global average temperature” at some point in time. Professional engineer Ronald Barmby, a Canadian, addresses that question in his useful book Sunlight on Climate Change (2020).

“Beyond the problem of what calculations are required in a global climate model to make it valid as science is the even bigger problem of where the historical temperature data comes from to run the models. The first big issue is how do we determine the true average temperature of the Earth, now and in recent history? It is very problematic.”

Barmby points to three major problems: “obtaining temperature series from a sphere eight thousand miles in diameter, seventy percent of whose surface is covered with water; adjusting the temperature data from locations that have become ‘heat islands’ (i.e ,pastures turned into shopping centers), and the lower accuracy of temperature recording devices in the decades back into the 19th century.”

Now to my hypothetical assignment: determining global average temperature. Let’s divide the globe into 6,912 rectangular grid boxes (the IPCC model) covering the Earth’s land and water surfaces. In the middle of each grid box, you set up an accurate thermometer well away from any “heat island”. On your chosen day, read them at noon and midnight and transmit  the 6,912 x 2=13,824 readings to a collection center. Add up the readings and divide that large number by 13,824, and you have the global average temperature for that day. Problem solved!

If we had a hundred year record of those accurately measured temperatures, we could determine how much the Earth had warmed or cooled over the hundred year period.

Reality check. There are thousands of uninstrumented grid boxes, with no thermometers reporting. So the people who invent this “global average temperature” (Climate Research Unit, East Anglia University, UK) embark on estimates, ensembles, models and statistical manipulations to produce the magical “Global Average Temperature”’. Here’s how the CRU explains it: “The uncertainties in the gridded data are represented by the 200-member HadCRUT5 ensemble, and for the global and hemispheric mean time series these have been used to estimate confidence intervals alongside the best estimates.”

Where the researchers have latitude to fill in empty box uncertainties with their own best estimates, there can be a lot of slippage. Barmby explains “One way to make the [IPCC] computer simulations match history is to carefully select which temperatures you use as history, how you may or may not correct them, and what statistical manipulations you exercise to come up with a blended global average temperature.”

As climate skeptic Steve Milloy puts it, with the limitations on data collecting over the entire globe for a century or more of time, “the notion of ‘average global temperature’ is meaningless. Average global temperature is a concept invented by and for the global warming hypothesis. It is more a political concept than a scientific one.” One might go further and call it a carefully crafted falsehood.

And one more reminder: “Climate Change” is not a Thing. Unlike temperature, pressure sea ice coverage, and precipitation, there is no metric, no instrument reading for “climate change.” No one can say that “in 1940 climate change stood at 56.5, and today it has increased to 92.4 “. It is a purposefully deceptive description concocted by the climate crisis industry to replace unreliable “global warming” which was not proceeding according to the industry’s urgent predictions.

It is universally accepted that Earth has warmed since the end of the Little Ice Age around 1850, and since 1977. There are many valid observations that support that finding, and there is little doubt but what human-caused greenhouse gas emissions have contributed to that warming.

How much those emissions have contributed, compared to natural causes, is still a matter for intense debate. Also debated is whether a warming of another one degree Celsius (as from 1900 to today, added to current temperature readings) would make Earth more or less livable for humans. Those debates are important. Breathless news stories about “global average temperatures” and “hottest month on record” are not.


John McClaughry is vice president of the Ethan Allen Institute. He earned an A.B in physics and an M.S. in nuclear engineering.


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  • John McClaughry
    published this page in EAI Commentary 2023-07-18 01:57:37 -0400