The NT Slimes has a long article about how “Climate Change” is impacting Mexico City. Let me save you the bother of reading it because other than repeating the holy words “climate change” every third paragraph, nothing the article describes is caused by the fearmongering formerly known as “global warming”.

Let’s start with the basics. If you wanted to plan where to put a major city/urban area, this is not where you would put it. Mexico City is built half way up a volcano in a dry lake bed. It suffers from endemic subsidence (see “lake bed”) and has immense problems getting water. It’s only there because of the weight of history and tradition: it used to be the Aztec capital ~700 years ago. At that time most of the current city area was a marsh, the population was about 300,000 and, according to the NYT, all was sweetness and light, until the evil conquistadors showed up:

The whole city occupies what was once a network of lakes. In 1325, the Aztecs established their capital, Tenochtitlán, on an island. Over time, they expanded the city with landfill and planted crops on floating gardens called chinampas, plots of arable soil created from wattle and sediment. The lakes provided the Aztecs with a line of defense, the chinampas with sustenance. The idea: Live with nature.

Then the conquering Spaniards waged war against water, determined to subdue it. The Aztec system was foreign to them. They replaced the dikes and canals with streets and squares. They drained the lakes and cleared forestland, suffering flood after flood, including one that drowned the city for five straight years.

Aztecs – living with nature. What a slogan. Also what a lie. The “chinampas” were the first stage in what we modern people call “land fill” and the Aztec city needed landfill because it kept on expanding in the lake. In addition numerous places on the web (such as infogalactic or wikipedia) point out that the Aztecs also suffered flooding, and built various dikes and defences. The reason they didn’t drain the lake was because they wanted it for defense – for some reason the Aztec rulers were not universally beloved by their subjects and neighbors.

Mexico City Subsidence rates in recent years (via NY Times)

Back to the present. The problems of Mexico City today aren’t helped by the way the greater urban area has swelled to some 3000 sq miles up from 30 in the 1950s and the related massive increase in population to 21 million or so (~9 million in Mexico City the rest in various neighboring municipalities and slums). If doesn’t help that the climate appears to resemble California – i.e. a cycle of drought and flood, although the rainy period is June-September – and that, as with California, the aquifers beneath the city are getting depleted and not replenished because the surface is now impermeable concrete/tarmac and not earth. As a major hub of population in a relatively dry place, Mexico City is always going to have problems unless the climate changes so that it gets lots of regular rain all year round. Interestingly this UN study that also talks about the effect of “climate change” on Mexico City shows that rainfall there has gradually increased by about 50% in the time from 1870 to 2000

Mexico City annual precipitation 1877-1997 from the UN’s Global Report on Human Settlements 2011

When you combine all the environmental issues with governing bodies that are corrupt and incompetent and you have a recipe for problems, no matter what the global climate will do. Historically there was horrible air pollution (the city is surrounded by mountains so nothing blows the pollution away), a lack of sufficient water and the majority of the greater metropolitan area has grown up shanty town by shanty town. Although the air pollution is much improved, there are plenty of other issues. Most of its problems would be fixed by the sorts of large scale public engineering works that have let Los Angeles flourish – namely lots and lots of dams, pipelines and canals. One suspects that the people bleating abut climate change would bleat far worse about the mass environmental “degradation” that such projects would entail. Not to mention the undoubted impact on farmers, villagers, wildlife and so on in the places where the dams would be built.

In fact an objective reading of both the NYT article and the UN one realizes that while climate change is a problem in Mexico City, the climate change at issue is purely local and is caused 100% by humanity – specifically the massive growth in population and urbanization of the Mexico City area. Fixes to ameliorate this local climate change will solve any problems from more general global climate change because the local climate issues are far more pressing today and far greater in magnitude than any global ones.