For the past decade or so, each January has produced a news headline about whether or not this year has been the hottest ever. It seems to be agreed that 2016 was the hottest ever, but with a statistically insignificant increase over 2015, and only a tiny bit above 1998. In 2015, 2016 and 1998 the spike was due to an el Nino, which subsided quickly. As I have argued before, there is no human being who has ever experienced a global average temperature, unless coincidentally, and for a moment or two. What we want to know is what our own environment has been like, if such weather details are of interest at all.
I have recommended before a most useful weather-data website, climate4you, conducted by a Norwegian scientist, Professor Ole Humlum. What he does is to assemble all the data from all the major climate dataset compilers, and provide a month-by-month summary. Since the focus at this time of the year is always on temperature, I thought it would be useful to look at what his data sources say. Humlum grades the datasets by reliability, and puts the two satellite datasets, UAH-MSU and RSS into his top category. They show December 2016 as much the same as the average up to the beginning of the 2015/2016 el Nino spike (UAH), and about where average temperature was in 1997 (RSS). Humlum uses the 1979-present period as his base, arguing that (i) 1979 was the beginning of the last strong warming period, and (ii) it is also the year when proper global data from satellites appear. He doesn’t like the older datasets because their controllers make too many ‘administrative changes’. What he has in mind is shown in the next graph.
The size of the changes, 0.7 degrees C over ten years is considerable, as are the actual number of changes, most of them slight. Fiddling with the past is all too reminiscent of Orwell’s 1984. Maybe there are good reasons, and maybe if I did a lot of work I would find them. Humlum’s point is that every time a datum is changed, the trend lines from the past are altered too. What is one to think? He argues that these changes do not seem to appear in the satellite data. though there is a new version of UAH-MSU which is eventually to supplant the original one. The changes there seem small to me. Incidentally he notes that since 2003 the average global surface air temperature has steadily drifted away in a positive direction from the average satellite temperature. He doesn’t know why, but for the moment puts the shift down to those ‘administrative changes’.
Anyway, the whole website is most interesting, and is supplemented by discussion. Just about everything you might want to find is there, with contributions, where they exist, from every dataset. It is my go-to source for weather data.
One aspect of global weather which I find particularly valuable on his website is the mapping. What exactly happened to Australia in terms of temperature over 1916? Well. you can find out by looking at Australia on his global map each month. The data come from the Goddard Institute for Space Science (GISS). Below is the world in October 2016. The colours have numerical referents in the bar on the right-hand side. We need to remember that large areas of Australia and much of the rest of the world, especially the ocean expanse, have no thermometers, so the colours in part represent extrapolations from real instruments elsewhere.
What is arresting about this image is the variation across the globe. In October, on average, Central Asia was having a most unpleasant cold spell and Australia was cooler than the ten-year average. So was Canada, but below the border most of the USA was warmer. Yes, of course you can determine an average for the whole world, but surely the spatial variation here is what we really want to know about. How has it been for us? You can go to such a map for each month, and here is my verbal summary for Australia.
January: a little cooler than the ten-year average
February: a little warmer in the northeast; a little cooler in the southwest
March: a little warmer
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