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Met Office: We Don’t Know What We Don’t Know

Dr David Whitehouse

In the Met Office the UK has the best weather forecaster in the world. Predicting the ever changeable weather for these isles, on the western edge of a continent and the eastern shore of a great ocean, is one of the most challenging topics in science, a challenge that has to be faced every few hours as new forecasts are made. The upper time limit for such forecasts seems to be going back at about a day per decade. Now we can see 4 – 5 days into the future. Sometimes forecasters look upon a weather chart that shows fine weather and clear skies stretching all the way into the Atlantic. But they can read the fine print of the data and predict that a mighty storm will track across the UK in a few days, even though to the untrained eye there is no sign of it yet. According to some scientists looking into the weather much further probably cannot be done as we will come upon the forces of random fluctuations overcoming extrapolation from initial conditions, as well as computing power.

Looking at the longer term and on a global scale it was once said that forecasting decades ahead was relatively straightforward because many short-term factors will average out leaving only the CO2 driven upward trend. The problem is deciding at what point does this averaging out occur and the CO2 forcing exceed natural climate variability. It was thought that it would be here by now. Remember the Met Office predictions made a few years back that half of the years up to 2014 would be global temperature record breakers, or the prediction that 2013 would be 0.3 deg C warmer than 2003 (it wasn’t any warmer). In recent years, as a result of the ongoing global temperature standstill, estimates of warming have been scaled back. There is still no sign that we are emerging from the current period when natural fluctuations dominate the climate preventing it from warming.

The bit in-between, forecasting weeks, months and several years ahead, is the most difficult because of those natural variations. It can’t be done at the moment, and anyone who tries is bound to flounder at the barrier of chaos and known and unknown natural climatic variability. That’s why the advice to the UK government from the Met Office just a few months before the unusually cold winter of 2010 was something like a 40% chance of colder than average, a 30% chance of warmer than average and a 30% chance of average. Such predictions are an absurdity, even more so if it is claimed they were vindicated by the extreme cold weather that was to follow! These days, who would dare predict a BBQ summer?

Remember the advice given to us by those who tried to predict years ahead. In 2000 there was the now infamous prediction from a scientist at the University of East Anglia that our children would not know what snow was. Then there was advice from the Met Office that gardeners in the UK should consider drought-resistant plants and that in the future British gardens would have more in common with those in Italy with palms, olives and Mediterranean herbs. The traditional lawn, they said, would be a thing of the past.

Increasing Evidence?

What a difference a few years of ‘strange’ weather makes? We had a very unusual drought in 2012 followed by a very unusual wet period. Such droughts, whilst unusual, are not unprecedented. They occurred in 1975, 1963 and 1933, so perhaps we should have been prepared for another one in recent years. In addition to 2010’s winter the spring of 2013 was exceptionally cold. What is going on?

The much publicised Met Office meeting this week to discuss these issues concluded the answer was a big, “We don’t know.” What we do know is that a lot of it is down to the Jet Stream moving south of the UK, when it usually stays north of us. There are many suggestions why the Jet Stream might wiggle this way, and why it might be happening more often recently. Perhaps it’s due to natural cyclic variations in the temperature of the North Atlantic, or the melting of the Greenland Ice Cap, or the decline in Arctic summer sea ice, or La Ninas, or the Sun, or something else we don’t yet know about.

The decline of Arctic sea ice is being used by many these days as an explanation for almost everything climatological. There is no good evidence for this, as the Met Office scientists said at their meeting. This was one reason why the big “We don’t know,” was so refreshing from the assembled scientists, as it contrasts with the scientifically sloppy ponderings we have come to expect from some Met Office scientists and even the former government Chief Scientific Advisor. Dr Julia Slingo, the Met Office’s chief scientist said to the UK Parliament recently that there was “increasing evidence” that the depletion of ice can plausibly impact our winter weather. In another setting she later said it could cause heavier rainfall. She also told ITN that she would be “surprised” if the warming Arctic wasn’t playing a part in our strange weather.

The scientists at the Met Office’s meeting, attended by Julia Slingo, said they found no evidence that the melting Arctic summer ice had any effect, which is what Parliament should have been told as it is a more accurate scientific statement than what Dr Slingo said. It’s no wonder our politician frequently come away from such briefings confusing personal hopes with sound science.

It’s Cold Outside

Then there is the effort to attribute unusual events such as the cold 2010 UK winter with climate change. Sometimes I think that at our current stage of understanding such efforts mistake events that haven’t occurred before with events that are unexpected. The 2010 winter was unusual but within the bounds of natural variability and if you wait long enough it will happen. Saying that it was twice as likely to occur because of climate change is an absurdity. Two such winters in short order would be unusual, but still explainable, three or more would be suspicious. A recent event like 2010’s winter tells us nothing about climate change. It was the same with the severe Russian heat wave. When it happened climate change was said to be to blame. More detailed analysis conducted later said it was natural but rare, and well within natural climatic variations. Afterwards some journalists and scientists went on to say that the causes of the Russian heat wave was both natural and man-made!

That’s why it was good to see scientists saying “we don’t know,” to almost every question put to them at a press conference following the over-hyped routine meeting. A bit more “I don’t know,” in front of the press, and parliament, and not seeing anthropogenic climate change behind every corner would be a new and better approach to the communication of climate change. I think the public would appreciate it if some scientists did not make out they are cleverer than they are.