Some old literature I was reading the other night carried shades of Roger Pielke Sr.’s argument that land use changes are important to climate change:
Notwithstanding the apparent uncertainty of the seasons, it is found that the mean temperature of particular localities is very constant, provided we compare observations made at different periods for a series of years. Yet, there must be exceptions to this rule, and even the labours of man have, by the drainage of lakes and marshes, and the felling of extensive forests, caused such changes in the atmosphere as raise our conception of the important influence of those forces to which even the existence in certain latitudes of land or water, hill or valley, lake or sea, must be ascribed.
That’s from Charles Lyell’s “Principles of Geology,” published from 1830-1833. Lyell was a leader in the community of geologists trying to make sense of why there were fossilized sea creatures on the tops of mountains, and why there was fossilized jungle flora and fauna in places were no jungles today exist. He therefore spent a lot of time trying to understand how climates could change. He ascribed the changes in climate to changes in physical geography – sea basins pushed up to form mountain ranges, for example. That, he assumed, drove climate change, and did so on vast time scales. (Lyell, like Darwin, was part of that first generation of scientists who realized they had “deep time” to play with, and busied themselves making the most of the opportunity.) Anthropogenic land use changes notwithstanding, Lyell didn’t expect climate to change very quickly:
(H)owever great, in the lapse of ages, may be the vicissitudes of temperature in every zone, it accords with our theory that the general climate should not experience any sensible change in the course of a few thousand years, because that period is insufficient to affect the leading features of the physical geography of the globe.
Actually, most of the change before 1900 was from land use changes, particularly clearing of land for farms in North America.
Hmmm – I wonder how much land use changes had to do with the temperature decrease from 1940 to 1970 – you know, the one that actually started climate change fear? (except the concern then was global *cooling*) Naw, that was the 30 years before the 30 years everybody talks about. CO2 couldn’t have changed from *no* influence to *total* influence instantly could it?
And back on that “clearing of American land for farming” What was that … 10% of America? That would make it … well, a lot less than 1% of Earth’s surface, right?
It’s rather more than 10%. Many states in the center of the country are something like 90% farmland. Add to that the land use changes relating to logging, vegetation shifts (e.g., native grasses replaced by non-natives in the southwest), the filling in of wetlands and urbanization, and we’re talking a lot of land.
Regarding the global cooling myth and the role of CO2, you’re just repeating stuff you know to be false or misleading.
The relation between changes in land use in New England and corresponding change in climate is described by William Cronon in Changes in the Land: Indians, Colonists and the Ecology of New England.
Hmmm – I wonder how much land use changes had to do with the temperature decrease from 1940 to 1970 – you know, the one that actually started climate change fear?
You could look it up instead of asking a misleading question.
Steve B –
Okay, let’s say 50% of the US. That’s still less than 1% of Earth’s surface (including Alaska).
I’m curious about this “global cooling myth” you’re talking about. Are you now saying Earth didn’t cool from 1940 to 1970, or are you claiming MBH98 is valid, or what?
Look what up, exactly? Are you insinuating that even as we are just now discovering the complexities of aerosols, we knew what they did before?
Do you have a very short synopsis?