It’s mild out there at the moment. Temperatures are above normal for early November. Does this mean our autumns are getting milder? Well, in isolation, no. Although there may be a long-term trend, you don’t have to be a meteorologist to know that in a few weeks we may have a bitterly cold spell, which wouldn’t prove anything either. Short-term change is no proof of longer-term climate tendencies. Or is it?
Seeing the wood for the trees
Talking of longer term – the globe is warming at an unprecedented and accelerating rate. The need for collective action to mitigate the worst impacts has been highlighted in recent weeks by the latest IPCC Report. It explains that for temperature rise to stay below 1.5°C, the the world must embark on a wholesale transition away from fossil fuels.
…there are often ‘low-hanging fruit’ for denialists to pluck
One of the hardest tasks is to dispel the myth pedalled by many (particularly those with disproportionately loud voices) that the changes we are seeing are merely down to natural cycles. And because of the huge daily, annual, even decadal fluctuations that naturally occur in our weather patterns, there are often ‘low-hanging fruit’ for denialists to pluck.
Our memories are short. By ‘cherry-picking’ weather events, it’s very easy to build a smokescreen to block out the bigger picture. The ‘Beast from the East‘ which delivered the coldest March day on record to the UK is a classic case in point. “How on earth can all this talk of global warming be true when we see record cold?”
The answer is down to scale. Yes, the weather will fluctuate dramatically on small scales. It always has. However, when we look beyond this ‘noise’, the steadier underlying trends are more obvious.
Trusted scientific organisations, such as the Met Office, use 30-year periods, or longer, to see through the noise. It is these long-term trends that help us see the wood for the trees.
But the Met Office has just presented a report that compared the 30-year period of 1961-90 with a much shorter recent 10-year period (2008-2017) to demonstrate changes in our climate.
Amongst the findings from the last 10 years, some of the headlines were that, on average:
- Hot nights have increased in frequency
- Hot days have got hotter
- Freezing days have become rarer
- Wet days have become more extreme
There were many other findings, some of which showed significant change, some didn’t, and others the Met Office chose not to publicise.
Whilst the evidence they presented will add urgency to the worthy cause for political and lifestyle changes (from governments to individual households), it raises different alarm bells for me.
Comparing like with like?
My concern is this. Setting a 10-year period (2008-2017) against a 30-year period (1961-90) is not to compare like with like.
Let me draw a sporting analogy. A batsman may be performing really well this season, with his run-scoring average significantly higher than in previous years. However, it would be wrong to give these recent innings equal weight to his longer, lower, career average. He simply hasn’t played enough good innings lately. Beware the unknowns – he may have another dip in form.
Is the Met Office leaving itself ‘Hostage to Fortune’
So back to the Met Office report. Such are the quirks of our weather that it is entirely feasible that another 10-year period would show something very different.
For example, we are currently heading into a natural cyclical period of low sun-spot activity, which is now known to disrupt atmospheric circulation patterns. The giant storage heater of the oceans also behaves in its own cycles that are yet still poorly understood. Additionally and even less predictably, atmospheric particulates from volcanic eruptions could randomly help cool the planet for several years. Mt Pinatubo did just that in 1991. As a result, we could quite easily go through a cluster of cold years, resulting in a very different ‘trend’, especially on smaller regional scales. Would the Met Office deliver these findings with a similar fanfare to their recent report?
One thing’s for sure. Those on the other side of the argument surely would. So is the Met Office leaving itself ‘Hostage to Fortune’?
Scientific standards matter
And this is my worry. If scientists lower their benchmarks, even if they think it’s in the interest of the greater good, they could lay themselves open to the charge of ‘cherry-picking’ . The thin end of a very large wedge. From 30-year averages to 10-year averages. What’s next? 1-year averages to prove a trend?
Anyway, here in my corner of southern England, the outlook for the next few days is mild. But I don’t suggest that means we’ll have a mild winter. The weather doesn’t work that way.