A headline in The Guardian, 27th April 2015:
Headlines like the one above have all been helping to convey a message that extreme weather events are both increasing, and attributable to human intervention. Note the picture chosen to accompany the article!
A little bit alarming, eh? But wait. A calmer mind has been looking at extreme weather events since 1900, and he finds that there were more extremes in the first half of the 20th century than in the second half. His recent paper on this raises many concerns, but perhaps the main one is that the policymakers are liable to have the view captured by the Guardian headline, rather than be informed about what the empirical data actually supports.
Professor Michael Kelly, a physicist at the University of Cambridge, is the author and his paper can be downloaded from here. (hat-tip: notalotofpeopleknowthat). Kelly has clearly been exercised by two reports on the increased frequency of extreme weather events being attributed to ‘man-made global warming’ and purporting to be providing sound advice to governments. He notes that the relevant IPCC working group claims that this warming ‘started in earnest in about 1960’, and also that they have low confidence in being able to attribute recent extreme weather events to this warming. A special IPCC report known as SREX supports this view. Kelly notes that SREX relies heavily on papers that use data beginning in 1950 or 1960, and that they use upper and lower deciles for their analyses rather than more widely used definitions of extremes which use ‘several standard deviations away from the average’ as their guide. Not withstanding this, Kelly has taken his own look at the 20th century data, and he finds ‘the weather in the first half of the 20th century was, if anything, more extreme than in the second half’.
But who else has noticed this? Kelly captures one crucial problem here: ‘The lack of public, political and policymaker appreciation of the disconnect between empirical data and theoretical constructs is profoundly worrying, especially in terms of policy advice being given.’ The ‘two reports’ mentioned above are from the Royal Society of London, the second of them being a joint work with the US National Academy of Science. Kelly notes that the first is ‘without empirical foundation and the second is misleading’.
————–An Aside to Look for Evidence—————————-
I found it easy to find supporting evidence of ‘The lack of public, political and policymaker appreciation of the disconnect’. Here are some triggered by flooding in England in December 2014:
PUBLIC, January 2015: ‘The results suggest that being hit by an extreme weather event makes climate change more prominent in people’s mind’ from a survey run by a group at Cardiff University
POLITICIAN, January 2014: ‘the prime minister said he suspected global warming could be responsible for an increase in extreme weather events ‘
POLICYMAKER, January 2016: Sir James Bevan, chief executive of the UK’s Environmental Agency ‘He added: “We face a very big challenge now in an era of more extreme weather, and the way to deal with the challenges is to deal with them together.”
—————-End of the Aside————————————-
Let us return to the Kelly paper. The data he refers to first are HADCRUT4 for global mean surface temperatures, followed by local data sets from the USA, the UK, and Australia. These are locations of some our best climate records, but he includes a sprinkling of reports (see his Table 1) about conditions elsewhere. He also notes with concern the data adjustments that have been taking place which purport to show ‘an increase in the overall rate of global warming’. He concludes that ‘the data integrity for claiming extreme events needs to be shown to be of the highest order, and that the results claimed do not depend on the data manipulation itself’. He gives an example of NASA adding a 0.35C shift, an adjustment which ‘represents about 40% of the century variation.’
The paper deserves more critical review than I give here, not least because of his stark conclusion: ‘Extreme events play an important role in deciding the safety margins and the point where extra protection is not worth it. The lack of clarity about future extreme weather, after 20 years of intensive analysis of future climates is deeply worrying. There is nothing that emerges from references (1,2) [these are the two Royal Society reports mentioned at the start of his paper – JS] that would require a significant refinement of the margins that have applied over the last half-century, and hyperbole is no substitute for hard facts in the engineering of the physical infrastructure. Over-adaptation that is not needed leaves clients free to sue advisors if the problems have been oversold and the costs of protection prove to have been excessive, even on a 20-year basis.’