Are Extreme Weather Events Increasing?
By Paul Homewood
Time for a closer look.
It must be emphasised at the outset that all of these case studies rely wholly on computer modelling to arrive at their conclusions. Essentially they attempt to model the probability density distributions of temperature, rainfall, or whatever it is they are measuring, using first natural forcing. They then do the same with all forcings, ie including AGW, and compare.
Needless to say, this is little more than Play Station stuff, and depends on the input to the models.
Having made this point, let’s look at some specifics.
Out of the 29 cases studied, the researchers claim to have found 17 where anthropogenic influence increased the strength or likelihood of the event.
It should also be pointed out here that any global or regional warming is deemed to be anthropogenic!
Out of these 17 cases, 10 involve hot weather and all use the same basic methodology. If we examine the Brisbane heatwave in Chapter 28, we can see how they arrive at their conclusion:
Effectively, all they are saying is that as average temperatures have gone up slightly, the temperature in those very hot days has also increased slightly.
Let us ignore, for a moment, the issue of UHI and historical temperature adjustments, and examine the principle. As the probability curve has moved to the right slightly, there is a greater likelihood of days exceeding, say, 38C.
This is then interpreted as an increasing likelihood of heatwaves. For instance, this is how the Met Office summed the paper up:
But heatwaves are never ABSOLUTE, they are RELATIVE. If they were not, we would never have one in the UK because the bar would be set much higher.
Indeed this is exactly how the Met Office themselves define it:
A heatwave is an extended period of hot weather relative to the expected conditions of the area at that time of year.
The likelihood of 38C days may have increased in Brisbane, but if average temperatures have also increased, then that is the new norm. It is irresponsible and misleading to claim human influence has increased the likelihood of heatwaves.
In any event, it is of course equally true that cold spells in winter won’t be quite as cold either.
The reality is that nothing has happened to alter the weather conditions which bring spells of hot weather. But this is not the message that the Met Office and AMS want you to hear, as they would rather you believe that “extreme weather” is on the increase.