He e-mails in response to the responses:

It is noteworthy that the (correct) charts on global mean temperature do not include “error bars” around the data points– as required in good science reporting. If error bars were included, one would see them get smaller over the period 1860 to the present reflecting mankind’s ever increasing ability to measure temperature routinely with accuracy around the globe as a result of the advance of technology. Derb could weigh in here, but it is a simple principle of mathematics that the greater the number of measurements, the more accurate is the “average” value calculated, reducing the error. Consequently, it would be useful if your “hard-science professor” could cite the number of people making accurate daily surveys of temperature worldwide in decade 1860-1870 that we can use today to reliably calculate global mean temperature for those years. For completeness we need data from sub-Saharan Africa, the Yukon, Patagonia, etc. etc. Just a reminder, the transcontinental railroad was not completed until after the Civil war so in 1860 there were vast swaths of the continental United States without one settler, never mind one with a mercury thermometer dutifully and accurately recording daily temperatures. Stanley did not meet Livingston who was looking for the source of the Nile (not measuring daily temperatures) until 1871. My company has sold nano-particle measurement instruments to NIST among other clients, and, yes, we do report error-bars on calibrations of our instrument’s resolution and sensitivity.

UPDATE:

We won’t continue this all day, but hard-science prof is back:

The error bars, about which your nanofriend is complaining, are included in the graph on the National Climatic Data Center page. (It was linked in your post!)