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Land use change and the climate

08 Mar 2023 | Science Notes

Over at Roger Pielke Jr’s Substack channel his father, Roger Pielke Sr, a highly accomplished atmospheric scientist, has written an essay discussing how changes in land cover have been found to affect the climate. It stands to reason that the big changes in land cover, such as deforestation and conversion to agriculture, have to have had a local effect. And it has, especially when such changes alter precipitation patterns and, in turn, change local temperature patterns. But Pielke Sr. notes that large-scale land use change can have climatic effects that reach thousands of miles away. And if land cover has changed everywhere, that means land use change is one of the big drivers of global climate change. Although good luck trying to convince the climate experts of that.

Pielke Sr. presents some compelling imagery of changes to the land surface, such as this comparison of South Florida between 1900 and 1992:

Of course you could pick just about anywhere on Earth and find such changes. Since both urbanization and agricultural cultivation cause local warming, that means some fraction of the measured warming over the post-1850 interval, and of whatever actual warming has in fact occurred, must be attributable to changes to the land surface. And Pielke Sr. lists many publications that have documented such changes in specific locations.

Since those changes are inherently local, it is customary for the IPCC to dismiss their role in global climate change. The fact that every location around the globe exhibits local land surface changes doesn’t suffice to convince them to take this seriously as a driver of global warming. It’s far simpler for the IPCC to blame everything on your carbon sins. But in doing so they are overlooking an obvious alternative possibility. Pielke Sr. notes:

“The complexities of the human influences on climate challenge simple assertions of attribution for observed changes and create significant obstacles to the skillful projection of how regional climates might change in the future.”

Next time you fly over a long distance and see out the airplane window how the land surface reflects human modifications compared to pre-settlement times, if you are wondering whether that might perchance have affected the climate. The answer is yes, locally, regionally and globally. Not to mention statistically.

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