By Paul Homewood
https://blog.metoffice.gov.uk/2017/01/24/looking-hard-at-the-accumulated-evidence-of-climate-change/
From the Met Office blog:
HRH, the Prince of Wales, who has co-written the forthcoming Ladybird Expert Series Climate Change book – wrote a guest editorial in the Mail on Sunday in which he suggested a ‘focus on looking hard at the accumulated evidence’ of climate change.
Professor Stephen Belcher is the Met Office Chief Scientist. He said: “Last week, climate scientists reported on the fact that during 2016, the world had marked yet another record-breaking year for global temperature, so the comments by HRH, the Prince of Wales on climate change are extremely timely.”
The natural variability of weather means that extreme weather events have always occurred. The challenge for climate scientists is to be able to attribute extreme weather events to a changing climate.
Climate scientists around the world, including colleagues at the Met Office are thus striving to understand the links between the natural variability of extreme weather events and climate change. This is a developing science and increasing understanding will be vital to decision makers when planning policies to avert the worst effects.
Professor Peter Stott is the Acting Director of the Met Office Hadley Centre, and is a world authority on attribution science – the study of ‘attributing’ weather events to climate change. He said: “The frequency of many weather extremes, such as heatwaves and heavy rainfall events, has been increasing worldwide. This is in line with predictions from climate models and well established understanding of how the climate responds to increasing greenhouse concentrations in the atmosphere.”
As temperatures rise the frequency of hotter temperatures increases and with more moisture in the air there is a greater chance of very intense rainfall.
“A wealth of evidence has now shown that increasing greenhouse gases from human emissions have caused the planet to warm. Global temperatures for 2015 and 2016 were over 1 degree Celsius warmer than late 19th century temperatures. The dominant contributor to the warming seen over the past century is from human activity through burning of fossil fuels.” But does that mean we can link recent extreme weather events – like Storm Desmond that brought flooding to Cumbria in December 2015 or like the heatwave over large parts of England in September 2016 – to human-induced climate change?
It can be all too easy to put the entire blame of weather-related disasters on anthropogenic climate change. Floods, droughts and heatwaves have happened many times in the past in our variable climate, but given that natural climate variability can also lead to extremes in our weather, misattribution can easily lead to bad policymaking about how to adapt to climate change.
Peter Stott added: “Now scientific research is showing that we can address the attribution of extreme events by calculating how the probability of particular types of events such as floods and heatwaves have changed as a result of human induced climate change. To do this we compare what actually happened with what might have happened in a world without climate change. Climate models are used to determine how the world could have evolved without greenhouse gas emissions and other human factors on climate.”
Such studies have shown that many heat-related events observed in recent years have been made much more likely by climate change. The chances of the record annual mean UK temperatures seen in 2014 have become about 10 ten mores likely as a result of climate change.
Peter Stott added: “But attributing extreme rainfall events such as occurred in Storm Desmond in December 2015 and which led to extensive flooding is much more difficult. This is because rainfall is much more variable than temperature and climate models can still struggle to simulate some of the fine details of how rain forms in weather systems. But as models improve new research is beginning to emerge showing that for some events at least anthropogenic climate change is playing a significant role.”
More research needs to be done before such attribution analyses become as routine as our familiar weather forecasts. But researchers at the Met Office are collaborating with international partners to develop an operational attribution system for extreme weather and climate events. Such a system would deliver regular updates putting recent extreme events into the context of climate variability and change. This would enable people to better understand how climate change has affected them and help them prepare better for the future.
https://blog.metoffice.gov.uk/2017/01/24/looking-hard-at-the-accumulated-evidence-of-climate-change/
Peter Stott is called “a world authority on attribution science, the study of ‘attributing’ weather events to climate change”. Now what could go wrong with that?
If he fails to blame weather events on climate change, he will end up out of a job!
And of course it is very easy to programme the computer models to assume that a warmer climate leads to more extreme weather. Then, Bob’s your uncle, the model says that climate change is to blame every time there is a bit of bad weather!
But let’s look at some of his specific claims:
1) “The frequency of many weather extremes, such as heatwaves and heavy rainfall events, has been increasing worldwide”
On the face of it, a slightly warmer climate will mean that heatwaves also get slightly hotter. But the whole concept of a heatwave is relative.
What someone living in Edinburgh might regard as a heatwave would be a cold day for a Bedouin Arab!
Indeed, heatwaves and temperature extremes can only be defined with regard to a typical, average temperature. As this average gradually rises in a warmer world, so too does the threshold that makes a heatwave.
But is there actually any evidence of record breaking summer temperatures or more frequent heatwaves?
Certainly not in the UK, where no summer since has come close to the scorcher of 1976.
http://www.metoffice.gov.uk/climate/uk/summaries/actualmonthly
http://www.metoffice.gov.uk/hadobs/hadcet/index.html
And certainly not in the US either:
https://www3.epa.gov/climatechange/science/indicatorsEPA-2-24-2016/weather-climate/high-low-temps.html
And not even in Australia:
http://www.bom.gov.au/climate/change/index.shtml#tabs=Tracker&tracker=extremes-timeseries&tQ=graph%3DHD40%26ave_yr%3D0
When we do see record temperatures quoted, they are often in the middle of large cities, or next to busy airport runways.
2) What about extreme rainfall?
“The frequency of many weather extremes, such as heatwaves and heavy rainfall events, has been increasing worldwide”
There is precious little evidence for this statement, although it is easy to cherry pick a few sites where it is true.
The UK Met Office don’t publish much in the way of daily rainfall data, but we know that monthly data shows no such trends.
https://notalotofpeopleknowthat.wordpress.com/2017/01/13/england-wales-precipitation-annual-stats-2016/
In the US, it is fair to say that a step up in extreme rainfall occurred in the 1990s, since then the trend is flat. (For the definition of the graph, see here.)
There is an argument, of course, that much of the 20thC was a period of severe drought.
https://www.ncdc.noaa.gov/extremes/cei/graph/us/4/01-12
And again, in Australia the facts don’t support Stott’s contention of a worldwide increase.
http://www.bom.gov.au/climate/change/index.shtml#tabs=Tracker&tracker=extremes-timeseries&tQ=graph%3DR99p%26ave_yr%3D0
And other scientists who have studied the issue in great detail state that :
In part because of large intrinsic variability, no evidence was found for changes in extreme precipitation attributable to climate change in the available observed record.
https://notalotofpeopleknowthat.wordpress.com/2016/09/10/new-study-finds-no-evidence-of-global-warming-increasing-extreme-rainfall/
3) The chances of the record annual mean UK temperatures seen in 2014 have become about 10 ten mores likely as a result of climate change.
To which I can only reply – “So what?”
We are also much less likely to see a really cold year like 1963.
This tells us nothing at all about extreme weather.
The Met Office blog begins by applauding Prince Charles’ ridiculous Ladybird book. It is a pity they did not use the opportunity to provide a few home truths.
But still, if they had, they might have missed out on a few gongs.