Not a week goes by where I don't learn something that suggests we're even more screwed than I already thought we were.
I found a new report yesterday via the BBC discussing that the latest climate models, which now take into account the deep impact of fossil fuel consumption, among other factors, on climate change, indicate that Earth's average temperature will likely increase by 4 degrees Celsius by 2070, possibly even as early as 2060. I have no reason to think that this is a liberal estimate. To the contrary - if the history of climate modelling has shown anything, it's that models frequently overestimate the stability of the environment and its capacity to keep rolling with the punches.
The only spot of light in all this is that these estimates are based on a "business as usual" forecast, the assumption that human civilization will continue burning fossil fuels along the same exponential trajectory as it does today. There is still a chance to avert the worst impacts of climate change, but realistically, unless China and India realize that the environmental system doesn't give a shit about per capita pollution, I don't believe we're going to see any kind of effective emissions cuts. World leaders are just too short-sighted, stupid, and chained to lobbyists' wallets for that sort of revolution.
I think geoengineering is the answer. Despite the risks inherent in it, I think an active guidance and maintenance of the planetary system is now absolutely necessary to our continuity and survival as a technological civilization in the long term. Really, we've been conducting geoengineering ever since we started pumping carbon dioxide into the atmosphere in a large scale, irresponsibly and with no oversight. The planetary system is sufficiently fragile that we can no longer rely on purely natural systems such as oceanic carbon dioxide absorption to mitigate our impact on the planet.
Still, geoengineering is a big tent. It doesn't all have to be along the lines of pumping sulfur dioxide into the atmosphere. What we can do through geoengineering, what I think we've got to do, is shore up natural systems that are being overwhelmed. What we need is a bandage for the world, so we can do the work while it heals.
The melting of the Arctic ice cap is a significant threat for greater climate change because of its simple nature; white ice is far more reflective than dark seawater, and light and heat that would stick around to increase Earth's temperature is instead bounced back into space by it. This was good enough when humanity wasn't futzing with the thermostat, but now it needs a hand. If we can increase the albedo (reflectivity) of the planet, even locally, that would provide us additional breathing room in which to make the difficult shifts.
What we might do - I don't know if this is feasible from an engineering standpoint, but I can't see anything that would break the deal about it myself - is build and launch constellations of solar-powered aerostats, high-altitude balloons with station-keeping capability, over the Arctic icecap. These groups of aerostats could support, between them, sheets of thin but intensely reflective material. Enough of these put in place could create a sort of "flying icecap," but one that won't melt, while leaving the true icecap in deeper shadow and cooler temperatures. This would allow the formation of thicker, more robust ice, and allow the icecap to endure through our harshness for a bit longer.
There's no such thing as a perfect geoengineering method. Considering that all humanity lives in the laboratory, I'm sure there are a great deal of radical geoengineering methods that will never be explored because of the danger in manipulating the planetary environment too much. Consider the present, though; we already *are* manipulating the planetary environment, dangerously so. I don't think it's too much to ask to weigh the geoengineering we might do against the geoengineering we're already doing.