By Paul Homewood
There is a very muddled piece in the Sunday Times today by meteorologist Simon Lee, which attempts to link winter storms with climate change:
Every winter Britain gets hit by a series of storms. Ciara and Dennis are just the latest — but with two key differences.
The first is their strength. Our storms get their energy from temperature gradients in the atmosphere over north America. Recently that gradient has been much greater than normal.
The second is good PR. In 2015 the Met Office decided to start naming storms, which gave them a much higher media profile.
In 1993 Britain had the powerful Braer storm. In 2013-14 we faced about 12 of these weather systems. But in other years there are hardly any, which is why this year might be feeling so extraordinary to people coping with flooding, high winds and lots of rain.
A key question: why does the number vary so much?
Part of the answer lies in the jet stream, the powerful westerly wind blowing about six miles above us which, driven by that steep temperature gradient, has accelerated and got bigger. That energy feeds into our storms.
On their own, Ciara and Dennis are not symptomatic of climate change or a global weather crisis. What climate change does is to alter the likelihood of such events.
Computer models of the impact of climate change predict an increase in winter rainfall for the UK, along with warmer atmospheric temperatures and changes to the tracks followed by storms across the north Atlantic. This year may not be a sign of things to come, but we will probably see more severe winter flooding in future.
January 2020 was the warmest or second warmest on record in every global temperature dataset. It was rivalled only by 2016, when there was a strong El Niño event in the Pacific that temporarily raised global temperatures. Given that there is no El Niño this year, these record global temperatures — up to 1.5C above pre-industrial levels — are a cause for concern.
It emphasises the rapid warming of the planet. These record temperatures are consistent with recent events such as the Australian wildfires, the rising temperatures in the Antarctic and the unprecedented lack of ice and snow in parts of Europe.
What does this mean for Britain’s weather? So far the world has seen warming of about 1C. That is going to continue and the best guess is that the world could be 4C-6C warmer by 2080.
That may not sound much – but multiplied by the area of the planet it means that the atmosphere will hold an enormous amount more energy.
That energy will not only be felt as heat. It will also power our weather like never before. That means more and bigger storms, stronger winds and changes in the temperature of the oceans, which will make the sea levels rise. If our weather is exciting now, it may soon be overwhelming.
Simon Lee is a meteorologist at Reading University
Let’s take it apart:
1) He is right that storms get their energy from temperature gradients in the atmosphere over north America. However global warming theory (and observations) tell us that this gradient should be getting less, not greater, because the Arctic has warmed faster than temperate latitudes.
Lower troposphere temperature anomalies from UAH, however, show a much more complex picture. Alaska and Greenland were much colder than average during January, but tucked between them is a warmer than normal area in eastern Canada:
https://www.nsstc.uah.edu/climate/
This is a classic example of a meridional jet stream, where it loops around, rather than flowing in a straighter zonal fashion. For more detail, see here.
In simple terms, Alaska and Greenland have been stuck to the polar side of the jet stream, whilst Canada has been to the south.
Global Jet Stream
Meridional jet stream patterns are a normal meteorological event, and have nothing to do with global warming. As well as being responsible for atmospheric blocking, they can also speed up the jet stream.
And because of the looping, they can bring the jet stream further south than normal, as has happened this month, along with associated storms where they can have more impact.
2) He then goes on to suggest that storms such as Ciara and Dennis are becoming more frequent.
Yet, according to the Met Office, storminess has actually declined since the 1990s.
https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/joc.6213
3) Finally he invokes those climate models, which tell us we will end up with wetter winters, thus implying that this month’s storms have been made more likely by global warming. Lots of maybes and probablies.
But again the data does not support this conjecture:
https://www.metoffice.gov.uk/research/climate/maps-and-data/summaries/index
The rest of the article is no more than childish imaginings of apocalypse, hardly worth commenting on.
Overall, Lee tries to give the impression that there is something abnormal about our winter weather in recent years.
Analysis of the data, along with historical observations, tell us that it is nothing of the sort.
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February 16, 2020 at 06:03AM
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