Friday, September 3, 2021

Climate is what you expect. Weather is what you get.

As Hurricane Ida peters out in New York and New Jersey, everywhere among politicians and TV pundits there are claims that this is one more piece of evidence for anthropogenic global warming (AGW), or marginally more credible, global climate change.  

What this ignores is that weather events are definitionally independent of climate change.  You have to measure the delta over time in order to begin to get a sense of whether it is even plausible that climate change is causing more storms.  This is difficult owing to the shortness of the time horizon, the paucity of data even a few decades back and the variability in the data.  

In the past several decades, since 1900, just for the eastern US, the average number of hurricanes per year has varied from 40 to 74.  It is a noisy system with difficulty establishing trend lines due to the issues of data comprehensiveness, data completeness, data accuracy, and definitional comparability.  

To the latter point about data and the definitions - Defining storms by the loss of life or by monetary damage is problematic.  For decades, via good sense and zoning, we have been making infrastructure in hurricane regions much more storm resistant.  Both in terms of loss of life and in terms of monetary damage, we are much better off than in the past.  Not because the storms are more or less numerous or more or less powerful, but because of human mitigation.

Which brings us back to the old saw that weather is what is happening now while climate change is what happens over time.  Weather events on their own are never evidence of weather trend lines.  The UN IPPC itself has backed away from the claim that climate change will be evidenced by an increasing number of hurricanes and an increasing number of the more powerful of such hurricanes.

Worldwide, the trend line for number and power is pretty flat within wide margins.  There are some changes by region.  In other words, it is not uncommon to see some multi-decadal changes in storm frequency and power in certain regions; up in some region and down in others but globally stable.

Politicians and media pundits opining that a single storm in the northeast is evidence of global climate change is definitionally, historically, empirically, and scientifically ignorant and unsupported by any data.  

Fake news, misinformation, call it what you want.  It is ignorant human chatter without empirical merit.  

One wag has noted 

Climate is what you expect. Weather is what you get.

Not strictly accurate but pertinent to the general debasement of politicians and TV pundits.


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