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Archives for October 2011

The winter forecast and media hype

Paul Hudson | 12:46 UK time, Thursday, 20 October 2011

The hype surrounding this year's winter forecast has been remarkable, unparalleled in my 20 years as a meteorologist.

Driven largely by sections of the tabloid press and several small private weather companies, the idea that this winter could be the worst ever recorded has already become firmly planted in many peoples' minds.

This is despite recent forecasting failures; the predicted heat-wave this summer by Netweather that never materialised; and the cold and snowy October blast, forecast by Exacta weather, that has turned out to be a total non-event - temporary chilly conditions in the last couple of days are perfectly normal for this time of year.

But both stories were lapped up by an ever eager media.

There are several reasons why we have seen a rise in sensationalist weather stories recently.

Firstly, weather sells newspapers. I remember when I worked for the Met Office they tried to tackle one national newspaper about their 'over the top' coverage of weather stories only to be told that weather sells newspapers (a rise in circulation of 10% was quoted by one newspaper editor each and every time there was a front page weather headline).

Secondly, a vacuum has been created by the Met Office, now they don't publish their seasonal forecasts anymore. This vacuum has been readily filled by small, private companies keen to get coverage.

But back to the subject of this winter. With the sun much more active than it was this time last year, there are no guarantees that this winter is going to be cold and snowy despite one forecaster's claim that this winter could be the 'coldest ever recorded' - which is, in my opinion, extremely unlikely.

Piers Corbyn of Weather Action, who analyses solar activity and how it impacts climate patterns, told me earlier in the week that this winters' forecast is not straight forward and 'a difficult call'. He will publish his winter forecast early next month.

Close inspection of the forecasts that are available suggests that on the balance of probabilities a colder than average winter is the most likely scenario. This would mean some disruption due to snow, but not as extreme or long lived as last year.

It's worth pointing out that this would mean 4 colder than average winters in succession, itself unusual for the UK, and we shouldn't altogether rule out an average, or even a mild winter.

Interestingly the latest seasonal forecast is now available from the European Centre for Medium Range Weather Forecasting (ECMWF).

It indicates close to average winter temperatures (averaged over Dec, Jan & Feb).

But perhaps more interestingly, as can be seen below, it suggests higher than average pressure - which means lower rainfall.



This would be bad news for drought affected eastern England, and could, if correct, lead to serious problems next year.

Met Office wakes up to solar influence on climate

Paul Hudson | 15:09 UK time, Wednesday, 12 October 2011

For as long as I have been a meteorologist, the mere suggestion that solar activity could influence climate patterns has been greeted with near derision.

Quite why this has been the case is difficult to fathom. But it's been clear for a long time that there must be a link of some kind, ever since decades ago Professor Lamb discovered an empirical relationship between low solar activity and higher pressure across higher latitudes such as Greenland.

Perhaps the art of weather forecasting has become so dominated by supercomputers, and climate research so dominated by the impact of man on global climate, that thoughts of how natural processes, such as solar variation, could influence our climate have been largely overlooked, until very recently.

In fact new research published this week & conducted by the Met Office and Imperial College London, showing how solar variability can help explain cold winters, will come as no surprise to readers of this blog.

Most studies in the past have largely focused on the sun's brightness, but this research has discovered that it's the variation in the sun's Ultra Violet (UV) output that's crucial.

According to the new paper, published in the journal Nature Geoscience, when UV output is low, colder air than normal forms over the tropics in the stratosphere. This is balanced by a more easterly flow of air over the mid-latitudes. The cold air in the stratosphere then makes its way to the surface - leading to bitterly cold easterly winds across the UK and parts of Europe.

When UV output is higher, the opposite is true, with warmer air making its way to the surface, and carried across the UK and Europe from the west.

Of course there are other factors involved in determining our weather, and this alone does not mean scientists have discovered the holy grail of long range forecasting.

Looking globally the research makes clear that the impact of the sun's changing UV output acts to redistribute heat, with cold European winters going hand in hand with milder winters in Canada and the Mediterranean, for example, with little impact on overall global temperatures.

The work is based on an 11 year solar cycle, with the regional temperature changes associated with the peaks and troughs of the UV cycle effectively cancelling each other out over that time.

But there are some scientists who believe that there are longer term cycles, such as the bi-centennial cycle and that on average over the coming decades solar activity will decline.

If so, not only will cold European winters become more common, but global temperatures could fall, too, although the general consensus amongst most scientists at the moment is that any solar-forced decline would be dwarfed by man-made global warming.

This is an exciting time for solar physics, and its role in climate. As one leading climate scientist told me last month, it's a subject that is now no longer taboo. And about time, too.

Latest global satellite temperatures for September

Paul Hudson | 17:24 UK time, Wednesday, 5 October 2011

The latest global temperature anomaly for September has been released and according to the UAH measure is +0.289C above the running 30 year mean, shown on the graph below.



Adjusted to the more standard time period, the anomaly is approximately +0.542C above the 1961-1990 time period used by the Met Office and WMO.

With the onset of La Nina widely expected, global temperatures are likely fall in the coming months.

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