{"id":279576,"date":"2023-09-20T12:52:22","date_gmt":"2023-09-20T10:52:22","guid":{"rendered":"https:\/\/climatescience.press\/?p=279576"},"modified":"2023-09-20T12:54:40","modified_gmt":"2023-09-20T10:54:40","slug":"extremely-common-rarities","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=279576","title":{"rendered":"Extremely Common Rarities"},"content":{"rendered":"\n
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From Watts Up With That?<\/a><\/p>\n\n\n\n

Guest Post by Willis Eschenbach.<\/em><\/strong><\/p>\n\n\n\n

With all the recent interest in rare or extreme weather events, I got to wondering \u2026 what makes a weather event rare or extreme?<\/p>\n\n\n\n

With that in mind, here\u2019s a thought experiment whose relevance will be made clear shortly.<\/p>\n\n\n\n

Imagine some woman works in the Tennessee Valley plant of a big corporation. It\u2019s a 24\/7\/365 operation. The Regional Manager likes to visit each plant, spend a day or more there, and stir things up. So the woman decides to record the comings and goings of the Regional Manager. At the end of the year, she graphs it up and it looks like this:<\/p>\n\n\n\n

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Figure 1. Dates of visits of the Manager to the plant.<\/em><\/figcaption><\/figure>\n\n\n\n

When she runs the numbers, she finds out that the Regional Manager\u2019s been visiting the Tennessee Valley plant about one day in five.<\/p>\n\n\n\n

So here are two questions.<\/p>\n\n\n\n

In Figure 1, is a visit by the Regional Manager a \u201crare event\u201d?<\/p>\n\n\n\n

In Figure 1, are these visits \u201cextreme events\u201d?<\/p>\n\n\n\n

Obviously, no. Something that happens about one time out of five is neither rare nor extreme.<\/p>\n\n\n\n

Why is this a relevant thought experiment? Well, like I said, I was wondering what makes an event \u201crare\u201d or \u201cextreme\u201d. So I went to \u201cTHE SCIENCE\u201d, which in this case are the Glossaries of the two latest IPCC Assessment Reports. Here are the definitions from the Fifth (AR5) and Sixth (AR6) Assessment Reports.<\/p>\n\n\n\n

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Extreme weather event<\/strong><\/p>\n\n\n\n

An extreme weather event is an event that is rare at a particular place and time of year. Definitions of rare vary, but an extreme weather event would normally be as rare as or rarer than the 10th or 90th percentile of a probability density function estimated from observations.<\/p>\n<\/blockquote>\n\n\n\n

and<\/p>\n\n\n\n

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Extreme weather event <\/strong><\/p>\n\n\n\n

An event that is rare at a particular place and time of year. Definitions of \u2018rare\u2019 vary, but an extreme weather event would normally be as rare as or rarer than the 10th or 90th percentile of a probability density function estimated from observations. By definition, the characteristics of what is called extreme weather may vary from place to place in an absolute sense. <\/p>\n<\/blockquote>\n\n\n\n

I cracked up when I saw those definitions. <\/p>\n\n\n\n

Why? <\/p>\n\n\n\n

Well, because on average, one observation out of every five is \u201cas rare or rarer than the 10th or 90th percentile of a probability density function estimated from observations\u201d<\/em>.<\/p>\n\n\n\n

So the IPCC is claiming that one weather observation in five is \u201crare\u201d \u2026 here\u2019s how that plays out for a few years of daily Chicago Midway Airport temperatures. This shows the IPCC-defined \u201cextreme Chicago temperatures\u201d.<\/p>\n\n\n\n

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Figure 2. Daily average temperatures at Midway Airport, Chicago. Horizontal red lines show the 10th and 90th percentiles of the observed temperatures. Yellow area shows the one in five temperature records that exceed those percentiles. Middle white area encompasses the 80% of the data between the 10th and the 90th percentiles.<\/em><\/figcaption><\/figure>\n\n\n\n

I swear, the inmates are in charge of the IPCC asylum.<\/p>\n\n\n\n

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CODA: This post is about extreme weather events. About a month ago, in a post called \u201cThe IPCC Says No Climate Crisis<\/a>\u201d I highlighted that the IPCC agreed with a recent study pointing out how little change there\u2019s been in extreme weather events.<\/p>\n\n\n\n

The study was entitled \u201cA critical assessment of extreme events trends in times of global warming<\/a>\u201c, and the conclusion says:<\/p>\n\n\n\n

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In conclusion on the basis of observational data, the climate crisis that, according to many sources, we are experiencing today, is not evident yet.<\/em><\/strong><\/p>\n<\/blockquote>\n\n\n\n

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Can\u2019t say it any better than that. And the IPCC itself agrees. Here, shown as white squares in the first data column, are the areas of the weather where the IPCC says there is no significant change in frequency or strength.<\/p>\n\n\n\n

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Figure 3. IPCC AR6 Table 12.12. The column entitled \u201cAlready Emerged In Historical Period\u201d shows climate phenomena that the IPCC says have or haven\u2019t changed due to \u201cglobal warming\u201d.<\/em><\/figcaption><\/figure>\n\n\n\n

Let\u2019s be clear about this. The following are the areas where the IPCC itself, in the graphic above, says there is low scientific confidence in the existence of any visible \u201cglobal warming\u201d effects<\/em><\/strong> in the form of weather extremes:<\/p>\n\n\n\n