As regular readers know, I now do this little examination each year, waiting until Ole Humlum, of climate4you, has assembled the global data from all the climate datasets. Most of what follows has been distilled from his latest bulletin. As always there were excitable people who wanted to tell us, even before the end of 2017, that the year would prove to be the hottest ever, and were asking why we weren’t doing something about it. So a few preparatory remarks are in order. First, the planet has emerged from a notably cool period, often called ‘the little Ice Age’. By and large there seems to have been a slight warming since about 1850, with some later cool or static periods as well. Second, one central question is the extent to which human activities have added to the warming. The IPCC claims that more than half of the warming since 1950 is so caused. It is very difficult indeed to showroom evidence that this is so, and the IPCC’s claim is in fact a kind of consensus of opinion from those who wrote the report. Third, ‘global average warming’ which is part of the equation, is a statistical construct that has no real meaning to anyone. We experience our local weather, not anyone else’s, let alone the average for the globe. Readers will remember that just as parts of Australia were having some hot weather in January, parts of North America and Europe were having great freezes. The end of the year is often like that. It’s called weather.
In the diagram that follows, the average surface temperatures for areas on the globe are set against the average for the last ten years for the same areas. The data come from the Goddard Institute of Space Studies (GISS). Humlum uses the past decade because he thinks that going back to 1950, a cool period, gives a misleading account of ‘climate change’ (see further below). Besides, he regards the satellite temperature measurements as much the best, and they only begin in 1979 (but of course the satellite instruments measure lower troposphere temperatures, which are in the body of air above us but not at the surface, where we live).
In considering the map don’t be fooled by Mercator’s projection, which gives greatest emphasis to the Poles. It is the tropical areas that have the most weight, and you can see that there it was pretty balanced, perhaps a tad more cooling than warming. In our part of the world eastern Australia was a little warmer than average for the past ten years, while the southwest of WA was rather cooler. By and large, there wasn’t much change anywhere. The data suggest that 2017 was a little cooler on average than 2016, which was a little warmer on average than 2015. The reason is mostly the el Nino spike of 2015/16, which extended into 2017 but was replaced at the end of the year by a weak la Nina. We are back to the way things were before that el Nino. CO2 accumulations are increasing, and global air temperatures are responding mostly to the oceans. All the datasets are showing these variations.
It seems to me that el Ninos and la Ninas are responsible for most of the variation in temperature that we experience in Australia. The following data uses NOAA classifications, and runs from January 1950 to December 2017. I’m sorry the detail is so small, but I use the diagram only to show the powerful episodes.
Since 1950 there have been six really big el Ninos, and the one that has just finished was slightly larger than the one in 1998. Alongside them there have been a dozen or more smaller ones. La Ninas don’t exactly match el Ninos — eight big ones and about the same number of small ones. No one has been able to show, even theoretically, how anthropogenic global warning could produce the shift from one phase to another, a shift which has been going on for at least a hundred years (when measurements started) and almost certainly long, long before that. There is some expectation that the current weak la Nina will continue and grew more intense. If that happens we will have more cool and wet conditions on the eastern seaboard. They can’t come quickly enough for me.
A good deal of interest in climate circles surrounds ocean temperatures and ‘ocean heat content’, since about 90 per cent of the heat in the planet is contained within the oceans. Not only that, higher-than-usual air temperatures lead in time to higher-than-usual sea surface temperatures. Climate4you.com provides quite a set of sea-surface temperatures (SST). My reading is that there has been a small, but rather steady increase, and the error involved in measurement is likely to be a good deal higher. The increase, according to Argo buoys, which are accepted as the gold standard here, runs from 6.36 degrees C in 2004 to 6.38 degrees C at the beginning of 2018. Nonetheless, I would not argue that SST are decreasing.
As for ocean heat content, measuring it involves abundant averaging. We need to decide what layers of water we will regard as important. We know that the bottom of the ocean is very cold indeed everywhere, so all the attention focusses on the top and intermediate layers. We have to assume the the measuring points we have are representative of a great or lesser amount of water between the measuring point and the nearest one. And so on. If the oceans are warming, then the heat content must be higher. What does all that tell us? In my view, it leads to a summary that nothing much seems to be happening in these areas. I’ve dealt with the belief that sea-level rise is accelerating in another post, and won’t rehash that here. It is worth remembering, as we leave this topic, that if air temperatures fall, then the oceans will release some of their stored heat.
What else is there to note? Well, there have been cries (most now decently forgotten) that snow would be a thing of the past, and that children in England would never know what a snowfall was. The data don’t show anything of the sort. Northern Hemisphere snow cover has moved up and down a little in the last fifty years, but is still much as it was in the 1970s. Indeed, there was in 2017 more snow in Summer, Spring and Winter in the Northern Hemisphere then there had been in the few previous years, while in the Fall there was almost as much as there had been in those years. Sunspots? They are declining in number, which often though not always is a harbinger for colder weather. One day I’ll do a piece on sunspots, the historic use of which in agriculture is most interesting.
To conclude, 2017 was just another year, with no sign of anything of great moment one way or the other. It is perhaps best to finish with a summary from Professor Humlum himself, a cautious and rigorous scholar. The notion that he could be ‘debunked’, as one reader commented in the past, seems almost preposterous to me. This is what he says, in part, about measuring air temperature:
Usually modern surface air temperatures are compared to the so-called normal temperature, representing the so-called normal climate. This ‘normal’ temperature is calculated as the average for values recorded during a 30-year period. The period 1961-1990 is the official World Meteorological Organisation (WMO) normal period, and is therefore often the time period referred to. Another 30-year period used as reference for comparisons is 1951-1980. This is partly because the total number of meteorological stations during this period reached a maximum, and since has undergone a marked reduction in number.
Unfortunately, both these periods are dominated by the cold period 1945-1980, and almost any comparison with such a low average value will therefore appear as high or warm. This makes it difficult to decide if surface air temperatures at present are increasing or decreasing. The only thing that will be clear is that modern temperatures are higher than back in this cold period.