It is not so hard to destroy cities and prevent food crops from growing. Merely control the level of sunlight that is allowed to reach particular parts of the Earth.
Consider, if you will, flocks of solar controllers — either orbiting in space, or floating in the upper atmosphere. The solar controllers can be tuned to block all sunlight, allow any portion of sunlight through, or focus any portion of the solar spectrum of radiation onto particular patches of Earth at very high levels of amplification.
Control over sunlight gives you the power to cut insolation to virtually nothing, or to magnify incoming radiation to unbearable levels. It is an ultimate control over a regions ability to feed itself, a chokehold on a people’s ability to survive. __ Who Can Help You Now, Pitiful Earthlings?
Using either of these methods of controlling sunlight — orbital or upper atmospheric — one could demand ransom or particular policy changes, under threat of destruction of either cities, crops, or both. And actually, such a method of solar control could be used far more destructively — on virtually any scale.
More from Josh Hall quoted by the original Al Fin blog:
Each aerostat contains a mirror, and also a control unit consisting of a radio receiver, computer, and GPS receiver. It has just barely enough power and fans or other actuators to tilt itself to a preferred orientation. That’s all it does—listens for commands on the radio, and tilts to an angle that is a function of its latitude and longitude. It’s not really a complicated machine.
… …the radiative forcing associated with CO2 as a greenhouse gas, as generally mentioned in the theory of global warming, is on the order of one watt per square meter. The weather machine would allow direct control of a substantial fraction of the total insolation, on the order of a kilowatt per square meter—1000 times as much. _Nanodot
More complex combined systems of orbital solar mirror/sunshades and upper atmospheric aerostats, could achieve even better control of solar insolation to the ground below.
It is easy to see that in a low-g atmosphere, tension-web-based (or inflatable) structures could be constructed to quite large sizes.
Of course, for purposes of blocking, focusing, or filtering sunlight to Earth, large flocks of much smaller structures would serve quite well — in a far more versatile manner.
Certain countries — such as Russia, England, Sweden, Norway, Iran, Saudi Arabia, Brasil, Indonesia, Malaysia, France, Argentina, Mexico, etc. place an inordinate amount of power, control, and resources within just one or two cities. The destruction of such over-centralised cities would likely spell doom for such nations.
It is certainly possible to make such overly-important cities uninhabitable for hundreds or thousands of years using nuclear dirty bombs, of course, but the wise global dictator will wish to spare as much productive capacity as possible — as long as he can control it. Dirty bombs may affect much wider areas for much longer periods of time than might be wished.
Large numbers of geoengineering schemes have been proposed, in order to “save the world from climate apocalypse.” Most of these would-be saviours appear oblivious to the possibility that they may actually tip Earth’s climate in a far more destructive direction than if they had simply done nothing. That would be one of many ways that “The Precautionary Principle” might go awry. 😉
Humans certainly need to learn to utilise the resources and advantages of outer space, the upper atmosphere, and other parts of the planet such as the deep oceans and the deep underground. But such things must be done wisely, using higher levels of thought than those that humans have typically used thus far.
Is it possible to create “fail-safe” methods of controlling incoming solar radiation in a way that would let us grow far more food crops, and control climate and weather in a completely benign manner? Perhaps. But humans had best learn to adapt to changing climates and changing weather, just in case things do not work out as planned.