There is no single thermometer measuring the global temperature. Instead, individual thermometer measurements taken every day at several thousand stations over the land areas of the world are combined with thousands more measurements of sea surface temperature taken from ships moving over the oceans to produce an estimate of global average temperature every month.
Recent global surface temperatures have continued to fall in the two years following the El Niño of 2014-16. January 2018 was the coldest January since 2014 in both the CRUTEM and GISS series (fig 1). The anomalies of 0.553°C and 0.78°C above the long-term average still mean that the global picture is one of various shades of yellow and red rather than blue though (fig 2). There was an interesting cold pool across a large area surrounding the Mediterranean during the month, but apart from this it was the scale of the warmth across eastern north America and northern Asia that were the main talking points.
If you were wondering just how the recent SSW has affected things, and how temperature anomalies ended up in February, here’s a chart that I’ve put together using reanalysis data (fig 3).
In an addendum to yesterdays blog “Is it 1°C higher or not?“, I can now say yes, recent global temperature were 1°C higher than pre-industrial levels for the best part of two years or more, but in the latter part of 2017 monthly temperatures dropped below the magic +1°C, and that’s why the press releases seem to suggest things haven’t changed. In fact they have gone up and crashed back down again in that period.
Perhaps if they had used a more detailed and larger graph of changes in global temperatures in the latest news release that might have helped. And so to clarify what’s actually going on in more detail I decided to create my own graph based on the CRUTEM4 monthly data that you can freely download (fig 1).
I can now also understand why professor Stephen Belcher the Met Office chief scientist is saying that global surface temperature anomalies could reach 1.5°C above pre-industrial levels in the next 5 years. Already monthly values in the last El Niño event in early 2016 got close to 1.5°C (fig 1). He is obviously banking on the current La Niña fizzling out and a return to the strong warming we saw in 2015.
There is a natural seasonality to the monthly values and that’s why I’ve added a 12 month moving average to the graph. That 12 month moving averaged peaked at +1.25°C in early 2016 and by December 2017 it’s fallen back to +1.05°C. The linear trend for the last five years does indicate that there’s been a decadal increase of 0.547°C, which would be enough to take temperatures above 1.5°C, possibly in the next ten years rather than the five suggested by Stephen Belcher.
I’m a bit confused about this weeks press release from the Met Office concerning global warming (fig 1). I was under the impression that global temperature was already 1°C higher than they had been at the start of the industrial age (1850?) from a press release they had made over two years ago in November 2015 (fig 2). I was obviously mistaken, because if you read what professor Stephen Belcher chief scientist at the Met Office says in the latest press release, it appears that this was not the case.
I find it difficult to believe that if the global surface temperature anomaly has hovered around 1°C higher for the last two years, how it could possibly jump to be 1.5°C higher in the next five years.
A massive contrast in temperature anomalies between the exceptionally cold east of North America (-14°C), and a tongue of warm anomalies that extends from northern Russia (+17°C) southwest across Europe to Iberia, during the first six days of the New Year as you can see in this chart (fig 1).
If we do see an easterly anticyclonic spell in the next few weeks the temperatures may not be as cold as usual in the UK, because the source of that cold continental air has been very mild throughout this autumn and early winter. At the moment Moscow isn’t reporting a snow depth, because there isn’t any, which in itself is uncommon at the turn of the year (fig 1), in fact the mean temperature there has been anomalously warm since the start of November. The chart of snow and ice cover for the northern hemisphere (fig 2) illustrates the lack of snow. In the last twenty years a chart similar to this one has become a common feature of many a winter.
Here are the anomalies so far this month for our part of the northern hemisphere, as you can see there is a large positive +5°C anomaly across western Russia, so it’s no wonder there’s not much snow in Moscow (fig 3).
As far as I can see using the daily objective LWT data that I regularly download from the UEA, the 30 percent NW’ly weather types of the last month (7 November – 6 December) are the highest percentage for this period ever seen in the series since it started in 1871 (fig 1). Thirty percent may not seem high but NW’ly types are not a common LWT believe it or not.
Here are the 00 UTC weather charts for the last month (fig 2), and as you can see southerly and southwesterlies have been in short supply.
So the obvious question is with so many NW’ly days during the last month why has the weather been so mild, and not much colder? The last months CET daily mean values (9 November – 8 December) are currently a shade above average at +0.18°C above the long-term 1981-2010 average (fig 3). Even during the first eight days of December, mean temperatures across Central England are currently still +0.75°C above average.
It may have a lot to do with the sea surface temperatures around our part of the northeast Atlantic and they are currently much warmer than average (fig 4).
Here are the 12 UTC temperature anomalies for the start of December for our part of world (fig 5), which show that colder than average temperatures are in short supply even when we are currently in the grips of an Arctic northerly across the British Isles. So the answer to the question why hasn’t the last month been colder, is simply down to the fact that surface temperatures across the world are currently at record high levels, and no matter how many northerly outbreaks we seem to have seen in the last month it seems to have made little difference.