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Are Extreme Weather Events Increasing?

November 11, 2015

By Paul Homewood    

 

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https://www2.ametsoc.org/ams/index.cfm/publications/bulletin-of-the-american-meteorological-society-bams/explaining-extreme-events-from-a-climate-perspective/

 

Time for a closer look.

 

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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:

 

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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.

 

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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:

 

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http://www.metoffice.gov.uk/news/release/archive/2015/BAMS-report

 

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.

http://www.metoffice.gov.uk/learning/learn-about-the-weather/weather-phenomena/heatwave

 

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.

6 Comments leave one →
  1. November 11, 2015 9:02 pm

    It is the other variables, particularly in cities like London, that help drive the warmer temperatures. But how warm can it get? And why has sunshine decreased in heatwaves?

    https://wansteadmeteo.wordpress.com/2015/06/10/hot-and-bothered-by-london-heat-escalator/

    https://wansteadmeteo.wordpress.com/2015/06/26/premier-league-of-heatwaves-1850-2015/

  2. November 11, 2015 9:13 pm

    The whole enterprise makes no basic sense. Weather extremes are by definition local/regional. Climate models do very poorly at regional downscaling. There is a large literature covering the various downscaling techniques and their many problems. A good primer is Pielke Sr. et. al. Regional Climate Downscaling: What’s the Point? EOS 93: 52-53 (2012). Climate models simply lack sufficent resolution owning to the computational intractability of suitably small grid cells for modelling weather phenomena. This is about a seven order of magnitude problem that won’t get solved any time soon by superer duperer computers. In laymens terms, climate model results are too ‘blurry’ to be regionally useful. BAMS should know this. More runup to Paris silly desperation.

  3. CheshireRed permalink
    November 11, 2015 11:17 pm

    ‘Extreme’ weather, ocean acidification, accelerated sea level rise etc: ALL designed as back-up to distract attention from the lack of observed warming. Simple as that.

  4. VTee permalink
    November 12, 2015 1:27 am

    Paul as a Brisbane resident I can tell you that the highest November Brisbane maximum temperature so far this month was on Saturday 7 November 2015. It reached 33.0 degrees. Nine days have been under 30 degrees, one day 30.5 and another at 31.0 degrees. No daily temperature this month has come close to the record temperature for that day.

  5. VTee permalink
    November 12, 2015 7:38 am

    Paul as a Brisbane resident I can assure you that during the November 2014 G20 there was one day only when Brisbane’s maximum temperature equalled the record high (40 degrees) for that date. However, during the last 12 months there has not been a single day where the maximum temperature has equalled or exceeded the record temperature for that date. Indeed, so far this month of November, we have experienced 9 days in the mid to high 20’s, one day at 31 another at 30.5 and on 7 November it reached 33.3 … the highest maximum for this month so far. Most daily maximums have been between 3 to 9 degrees below the record maximum for that date based on BOM records going back to the 1880’s. Clearly, the predicted likelihood of an increase in hot to very hot days has not occurred so far.

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