I went to listen to Phil Jones from the Climate Research Unit, University of East Anglia the other afternoon at an I-SEE seminar.
His title was: ‘The global temperature average: a history, recent changes and their context over the Late Holocene’ and this was his Abstract:
"Global temperatures have risen during the 20th century, and have continued to rise during the present century. The warmest 5 years are the last five, with 2016 the warmest followed by 2015, 2017, 2018 and 2014. The talk will begin discussing the history of the global temperature series, highlighting some important earlier work, and also illustrating how relatively few series are required to produce it. Many more series are used, as producers want a gridded product at as small a scale as possible to look at patterns of change. The talk will further address the robustness of the record, and what the important issues are with respect to biases and homogeneity. The most important relates to the way sea surface temperatures have been taken over the course of the 20th century, and if this isn’t taken into account, the long-tern warming would be greater. The talk will then discuss the various factors that influence the climate on decadal and longer timescales. The final part of the talk will place the record from 1850 in the context of the last 2000 years, and discuss the warming in the context of the pre-industrial average, which until recently wasn’t defined."
I have never seen so many graphs, all of which pointed to continued warming. I didn't need convincing, of course. He said the current temperature average is 1.05 degrees "above the pre-industrial average". I forgot to ask what the uncertainty is in that figure. So did everyone else. My guess is that it's about ± 25%.
He was very informative on the 'how' of temperature measurement, and in its history. And about the built-in biases to data depending on the method of collection. Wooden buckets ripped over the side of ships were biased to give a low reading (canvas ones were worse) because of the cooling effect of the evaporation that took pace. A bit of 1960s physics came to mind with the mantra: "Evaporation produces cooling". Latent heat, specific heat capacity, and all that ... .
I was also reminded about the 1980s global cooling scare. Do you remember that? It was on Tomorrow's World. That was when we'd noticed the drop in solar activity since the 1960s and began to worry about a new ice age. Happily, that extra CO2 came to our rescue.