I've gone ahead and contributed an essay to WorldChanging's "Earth Day" series, a brief set of scenarios based on the matrix shown above. It's very much a high-level view of potential Earth futures, and is meant more as a provocation to discussion than as a complete picture of Things To Come.

Here's a sample:

Geoengineering 101: Pass/Fail

2037: The Hephaestus 2 mission reported last week that it had managed to stabilize the wobble on the Mirror, but JustinNN.tv blurbed me a minute ago that New Tyndall Center is still showing temperature instabilities. According to Tyndall, that clinches it: we have another rogue at work. NATO ended the last one with extreme prejudice (as dramatized in last Summer's blockbuster, "Shutdown" -- I loved that Bruce Willis came out of retirement to play Gates), but this one's more subtle. My eyecrawl has some bluster from the SecGen now, saying that "this will not stand," blah blah blah. I just wish that these boy geniuses (and they're all guys, you ever notice that?) would put half as much time and effort into figuring out the Atlantic Seawall problem as they do these crazy-ass plans to fix the sky.

This is a world in which attempts to make the broad social and behavioral changes necessary to avoid climate disaster are generally too late and too limited, and the global environment starts to show early signs of collapse. The 2010s to early 2020s are characterized by millions of dead from extreme weather events, hundreds of millions of refugees, and a thousand or more coastal cities lost all over the globe. The continued trend of general technological acceleration gets diverted by 2020 into haphazard, massive projects to avert disaster. Few of these succeed -- serious climate problems hit too fast for the more responsible advocates of geoengineering to get beyond the "what if..." stage -- and the many that fail often do so in a spectacular (and legally actionable) fashion. Those that do work serve mainly to keep the Earth poised on the brink: bioengineered plants that consume enough extra CO2 and methane to keep the atmosphere stable; a very slow project to reduce the acidity of the oceans; and the Mirror, a thousands of miles in diameter solar shield at the Lagrange point between the Earth and the Sun, reducing incoming sunlight by 2% -- enough to start a gradual cooling trend.

I have to say, I really had to restrain myself from turning each of these into lengthy stories -- but the Earth Day essays all seemed relatively brief.