Record warmth in the UK

20°C in February!  In all the years I lived in England, I cannot remember there ever being such a warm spell so early in the year.  And it turns out in fact that this is an all time record: the warmest February day on record and the highest temperatures ever recorded in winter.  The day after was even warmer, with an all-time record of  21.2°C reached in Kew Gardens (in London).  This time last year, temperatures were below zero when the "beast of the east" plagued the country. (There are some nice images in both articles I've linked to.)

Now, a single episode of excessive heat doesn't prove global warming, any more than a single episode of extreme cold proves global warming doesn't exist.  But if you get much warmer than usual conditions, and they fit in with the long-term pattern, then they add to the evidence of global warming.  They are consistent with the hypothesis.  And if you are getting a pattern of successively higher highs and lows, this too points to a rising longer-term trend.

Below is the chart for the central England temperature anomalies, the longest continuous temperature record available anywhere.  The annual deviation from the 1961-1990 average is shown by the blue bars and the red line is a centred moved average of those data.  A couple of things to notice:

• The blue lines jump a lot from year to year.  Even the red line is fairly squiggly.  And these are annual averages: the monthly deviations from the baseline will be greater.  In this context a particularly hot or cold day or week doesn't mean much.  But a steadily rising long term trend means a lot.
• This absurdly warm spell in the UK will last just a few days, so it doesn't follow that the whole year will on average be warmer than, say, last year.  On the other hand, there's no guarantee it won't either.  And despite the "beast from the east", last year was warm enough.
• The trend is firmly up, despite the large year-to-year fluctuations.  And there's no reason for the trend to reverse direction as long as we continue to spew CO2 and methane into the atmosphere in ever increasing amounts.
• Observe how temperatures fell up to 1700, perhaps because of a string of volcanic eruptions from 1660 to 1680   But from 1700 to about 1900, although there were cyclical fluctuations, essentially the longer-term trend was flat.  Since then, it's been a more or less steady rise from decade to decade, even after downward adjustment for the urban heat island effect.  ( I defer to the experts on this: I'm doing no statistical analysis, just chart gazing)  The decline from 1950 to 1975 was prolly due to rapid industrialisation, which increased emissions of sulphur dioxide (the same stuff emitted by volcanoes).  This effect diminished as steps were taken to reduce factory SO2 emissions, and the underlying increase in CO2 started to dominate again.

Source

Dr Friedericke Otto, acting director of the Environmental Change Institute at Oxford University, said people were right to ask themselves whether the record temperatures were being driven by climate change.

"I am very confident to say that there's an element of climate change in these warm temperatures," she said.

"But climate change alone is not causing it. You have to have the right weather systems too."

[Read more here]