Thursday, October 29, 2015

How do you tell if it is "extreme"?

There are constant claims that extreme events are becoming more frequent, but when you really dig down, you cannot see any trends even in long-term data.  Of course, the scaremongers claim that it hasn’t happened yet, but their models predict it is going to happen any day real soon now, just you wait! All agree it has been warming for at least the past 150 years.If there were any effect such as the models predict, surely we would have seen it by now? It surprises many, but there is no detectable trend in extreme events in the historical data sets. 

However, it is not quite straightforward.For instance, how do you define an extreme event, particularly with phenomena that are not normally distributed? Do you only have to consider the high extremes,or must you also consider the low extremes? And how many extreme events does it take to determine a baseline, let alone a trend? 

To illustrate the challenges, consider the longest rainfall record we possess, that of England and Wales, which has monthly data back to 1766. The annual totals are close to normally distributed, as shown in the figure. 
A multi-parameter distribution such as a Weibull would do a better job, but we can treat the distribution as normal for the purposes of this exercise. The average annual rainfall is 918mm with a standard deviation of 119mm. 

We would expect 12.5 extreme events in 250 years, if an extreme event is defined as one that exceeds the 95% confidence limits. The figure shows that there are seven such events above the upper limit and four below the lower, or 11 in total, where 12.5 had been expected.
Given the slight skewness of the data and the approximation of normality, the difference is not significant. What is significant, however, is that there is no detectable change in the frequency of the extreme events.Indeed, to detect such a change with any degree of confidence, you would need far more than eleven events or, in the present case, far longer than 250 years. So those who claim we are facing disaster from “climate change” need to reflect on the fact that even with a generous 95% measure of extremeness, it took 250 data points to approximate a baseline.How can we tell if an event is extreme if we have no baseline? 

Is 95% generous? I think it is.Engineers typically design for the 1:100 year event, not 5:100. For really critical structures, they may use the 1:1000 year event. By and large, the engineers have been successful in protecting us against all manner of natural forces.The Great Kanto earthquake of 1923 devastated Tokyo; it had a magnitude of 7.9. The Great Tohoku earthquake of 2011, which caused the tsunami that destroyed the nuclear reactors at Fukushima, had a magnitude of 9.0 and the rebuilt, earthquake-proofed Tokyo was virtually unscathed.

When you hear that the effects of climate change will fall more strongly on poor nations, realize that it is probably true.However, it actually has nothing to do with climate change, and everything to do with some poorly engineered infrastructure in those nations.

Monday, October 5, 2015

Those naughty engineers at VW

“How could they have been so stupid?” is a question I have heard numerous times over the past few days. “How could they not have seen the risks?” “Purposely defeating testing must surely be criminal?”

I think the problem may be deeper than it seems.  Perhaps those clever engineers were too clever.  Perhaps they recognized some things that we need to recognize.  Perhaps they have identified  underlying challenges that need to be faced.

One challenge is the use of language in American law that allows perfectly natural processes to be described as harmful.  For instance, we may think we know what a “pollutant” is, but US law defines carbon dioxide as a pollutant. I’m not certain how they manage to avoid arresting every citizen for breathing, or destroying every plant, but in 2007, the US Supreme Court held that the Clean Air Act gives the Environmental Protection Agency [EPA] the authority to regulate emissions of greenhouse gases. Two years later the EPA issued an endangerment finding that "greenhouse gases in the atmosphere may reasonably be anticipated both to endanger public health and to endanger public welfare.”

In the same vein, nitrogen oxides, which the VW diesel evidently emits at up to 40 times the legal limit when not being tested, are natural substances, produced whenever there is a wildfire.  Wildfires are part of nature – many fynbos species require fire to propagate. Lightning makes nitrogen oxides.  Many decay processes lead to release of ammonia, which is converted into nitrogen oxides.  And the nitrogen oxides are essential substances for the growth of most plants.  These days we use artificial nitrogenous fertilizers rather than night soil to fertilize our crops.

The perceived problem is that humans produce excessive nitrogen oxides.  So, for instance, nitrogen oxides were supposed to contribute to “acid rain”.  That is an environmental scare about which we do not hear very much these days, because it turned out to be another “sky-is-falling-on-our-heads” problem.  The Germans are particularly aware of the failure of “acid-rain”. They were suckered into spending billions uselessly to prevent Waldsterben – forest death.  They love their forests, and were horrified to think that the “acid rain” might be killing them.  It transpired that the forests were dying of old age, and that the “acid rain” was actually nurturing them. All rain is acid. What happens when rain reaches the ground determines whether the runoff is acidic or alkaline.

A real environmental impact of nitrogen oxides is the “eutrophication” of water. Nitrogen, being a nutrient, can stimulate growth of plants and algae in water systems to the point where the systems become unstable and the whole system dies.  The problem arises particularly from excessive use of artificial fertilizers.  So, for instance, the Mississippi river is a rich source of nutrients and there are frequently dead zones in the ocean at its mouth.

The impact of nitrogen oxides in the atmosphere is small.  Human-related emissions come largely from artificial fertilizers, sewerage works and animal feedlots, and to a lesser extent from the burning of fossil fuels. One of the oxides, nitrous oxide, is a potent greenhouse gas, but its concentration is very low, so that its impact is about one-ten thousandth that of the primary greenhouse gas, water vapour. It is also implicated in ozone destruction, but its effect is ameliorated by the fact that other nitrogen oxides help to form ozone at lower levels in the atmosphere.

How severe is the impact of vehicle emissions compared to all emissions, natural and anthropogenic? The EPA says about 40% of all emissions are anthropogenic, 75% of the anthropogenic emissions come from agriculture and only 5% from transport. So transport is responsible for 2% of the total emissions; aircraft, shipping, heavy construction and mining equipment, diesel-electric sets on trains and and the trucking industry are responsible for 80% of that.  So those awful VW diesels were making a small contribution to about 0.4% of the putative problem.

Perhaps the engineers at VW asked themselves some simple questions. How much is it worth spending to help reduce 0.4% of a putative problem? Are the limits set by a US regulator realistic?  Just because you can measure something, does it mean it is a problem? Is something which is predominantly natural a pollutant? Even if it is, when agriculture is the main source, isn’t that where it needs to be addressed?

American law is in danger of threatening all our lives, on the one hand by redefining our language and on the other by conferring power on Government agencies that in many cases have grown so powerful that they can no longer be controlled. These may well be behind the thinking that led the VW engineers to an economic solution to a non-problem.

Note well, I am NOT saying they were right to take the law into their own hands.  But I am saying that VW's reputation would have suffered far less if it and other car manufacturers had challenged the EPA in the court of law when the EPA first proposed its ridiculous limits.  The environment is not something to be protected at all costs. De minimis non curat lex.