Here's what leads me to that (seemingly obvious, but apparently not) observation.

We know these to be true:

Feedback effects ranging from methane released from melting permafrost to carbon emissions from decaying remnants of forests devoured by pine beetles will boost greenhouse gases faster than natural compensation mechanisms can handle.

The accumulation of non-linear drivers can lead to "tipping point" events causing functionally irreversible changes to geophysical systems (such as massive sea-level increases). Some of these can have feedback effects of their own, such as the elimination of ice caps reducing global albedo, thereby accelerating heating.

Because of the long, slow nature of carbon cycles, no matter what we do, we are committed to warming the planet for at least 2-3 decades beyond when we stop adding to greenhouse gases.

We also know these to be likely:

The economic, environmental and social benefits accruing to early adopters of cleaner infrastructure and behavior can serve as a catalyst for faster adoption by lagging actors. In short, the first ones in demonstrate that the water's fine.

Many of the cleaner technologies, infrastructure and behavior have ancillary benefits, from quality-of-life to political rebalancing, that can accelerate their adoption.

Continued technological innovations could allow for faster mitigation of greenhouse gases, even potentially allow for the uptake of atmospheric carbon, accelerating the natural cycle of carbon from the atmosphere.

So: we have a set of demoralizing forces at play, countered by a set of encouraging possibilities. What is the common element that would allow those possibilities to play out? Time.

Time is what we need. Time is what we may not have.

Climate and environmental sciences remain imperfect, but few of the improvements in our understanding have reduced the sense of urgency surrounding global climate disruption. On the contrary, much of the enhanced analysis has increased scientists' level of worry. Richard Clarke once famously described a subset of international security analysts running around Washington DC in 2000 and 2001 with their "hair on fire," trying to alert policy-makers to the potential for a terrorist attack in the US. Today, it's the geophysical scientists with their hair on fire, sounding increasingly desperate and shrill about delays in responding to climate meltdown. And they have good cause for alarm: even an enlightened transition away from business-as-usual energy, transportation and social systems may not happen fast enough to avoid catastrophe; certainly, the slow, mulish pattern we've seen up to the present won't.

If it all comes down to time, we have two choices: move faster, or get more time.

Moving faster is the approach preferred by nearly everyone making a study of climate and environmental changes. We know what we need to do, we know roughly what it will cost and how long it will take, and we know ways to make it happen to all of our benefit. Unfortunately, we apparently have bigger priorities at the moment, and will get to this climate thing when it really starts to make some noise (by which time, it will be far too late). It seems we're just not that good at thinking in terms of lagging cause-and-effect, and the need for long-term thinking.

We could get lucky; positive feedbacks and "the water's fine" demonstrations may allow us to move faster.

We could also get "lucky" in a not-so-lucky way: a clarity-inducing global disaster could trigger the necessary economic and political shifts without pushing us over the edge. Arguably, a series of even moderate natural disasters that could be convincingly tied to global warming (convincing at the political level, even if scientists remain cautious) might serve as a goad to get recalcitrant actors to move faster or suffer political harm (c.f., tobacco.) It wouldn't be so lucky for the thousands or millions of people suffering from these "clarity-inducing" disasters, of course, or for the thousands or millions who would suffer from subsequent disasters happening while we get ourselves in gear.

Getting more time means slowing down the greenhouse gas-heat-feedback cycle, and that means geoengineering. Let me be clear: we don't know enough about how the various geoengineering proposals would play out to make a persuasive case for trying any of them, and I -- along with most geoengineering proponents I've interacted with -- want to see far more study before making any even moderate-scale experimental effort. This is not something to try today. The most important task for current geoengineering research is to identify the approaches that might look attractive at first, but have devastating results -- we need to know what we should avoid even if desperate.

Make no mistake: I am not arguing that geoengineering, should it be tried, would be a replacement for making the economic, social, and technological changes needed to eliminate anthropogenic greenhouse gases. It would only be a way of giving us more time to make those changes. It's not an either-or situation; geo is a last-ditch prop for making sure that we can do what needs to be done.

Claims that we shouldn't even talk about geoengineering, or give it any kind of meaningful research funding, while we're trying to get people to move faster smacks of Condoleezza Rice's infamous statement regarding contingency planning and the Iraq war:

"It's bad policy to speculate on what you'll do if a plan fails when you're trying to make a plan work."

No. Wrong. Sorry. The only rational, resilient, ethical approach is to prepare to deal with failure of one's preferred strategy before that failure occurs. I don't want us to have to engage in geoengineering. I want us to stop being such idiots and start to make real changes to our societies, our infrastructure, our lives. But I also know that we're getting awfully close to the point of being too late for those changes to have a meaningful impact.

And if we're too late, millions, perhaps billions, of people will die. I will not accept the loss of so many lives as the only alternative to political leaders in the US and China getting their acts together. Depopulation is not a global warming strategy. It's a horrific, tragic result of the failure of strategy, the failure of imagination, and the failure of our capacity to fight to the last breath for our future.