The Science of Doom

In the last set of articles we’ve looked at past trends in extreme weather, following the flow of chapter 11 from the 6th assessment report of the IPCC.

How do we know the cause of any changes?

In recent years in most of the media everything that changes is “climate change” which is implicitly or explicitly equated with burning fossil fuels, i.e., adding CO2 into the atmosphere. It’s a genius catchphrase from a marketing point of view, not so helpful for scientific understanding.

I used to prefer the term “anthropogenic global warming” but it has its flaws as well, as some recent trends are believed to be anthropogenic but not from adding CO2 into the atmosphere. An example is changes that result from reduced aerosols in the atmosphere as a result of burning less biomass.

I’ll generally try and stay with “anthropogenic” or “from more CO2”, but there’s no copy editor, so let’s see.

Lots of changes in past climate metrics are simply natural variability. Understanding and quantifying natural variability is a big topic and our knowledge is always going to be imperfect.

For example, there were multi-decadal megadroughts in North America and Europe in the past 1000 years. They were probably “unprecendented” for their time, but clearly weren’t caused by burning fossil fuels.

Here is a reconstruction of the drought index over 1000 years of western North America..

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