The following is a guest essay from Jamais Cascio, a cross-disciplinary futurist specializing in the interplay between technology and society. He co-founded, and now blogs at


With the recent release of a detailed comparison between different geoengineering strategies and the launch of a German-Indian joint experiment in ocean-iron-fertilization, the debate over whether geoengineering will have any place in our efforts to combat global warming is one again churning. I’ve been writing about the geoengineering dilemma since 2005, and Grist’s David Roberts — no big fan of geoengineering — asked me to give my take on where the issue stands today. My top-line summary?

Geoengineering is risky, likely to provoke international tension, certain to have unanticipated consequences, and pretty much inevitable.

Just to be clear, here’s what I want to see happen over the next decade: An aggressive effort to reduce carbon emissions through the adoption of radical levels of energy efficiency, a revolution in how we design our cities and communities, a move away from auto-centered culture, greater localism in agriculture, expanded use of renewable energy systems, and myriad other measures, large and small, that reduce our footprints and improve how we live.

This plan, or something very much like it, is required for us to have the best chance of avoiding disastrous climate disruption. Could we make it happen within the next decade? Definitely. Are we likely to do so? I really want to say yes … but I can’t.

And that’s a real problem, because we’re not exactly overburdened with global warming response plans that have a solid chance of actually doing something about it in time. We all know that half-measures and denial masquerading as caution certainly won’t be enough to avoid disastrous warming; unfortunately, neither will the kinds of ideas still coming out of the world’s capitals. Although clearly better than nothing, they simply won’t get carbon emissions down far enough fast enough to avoid a catastrophic climate shift.

Here’s why: No matter what we do, even if we were to suddenly cut off all anthropogenic sources of carbon right this very second, we are committed to at least another two to three decades of warming, simply due to thermal inertia. Add to that the feedback effects from environmental changes that have already happened: ice cap losses increasing polar ocean temperatures, accelerating overall warming; melting permafrost in Siberia releasing methane, which can be up to 72 times more powerful a greenhouse gas than carbon dioxide; overloaded carbon sinks in oceans and soil losing their ability to absorb CO2. These factors combine in a way that could make even our best efforts too slow to avoid disaster.

So what would we do?

Now I know some of you are saying “stop right there — you’re giving up before we’ve even really tried.” I understand the sentiment, but I strongly disagree. In a complex environment, with myriad uncertainties (not about the science, but about how quickly and how thoroughly we can respond), thinking through the alternatives in case we aren’t successful is absolutely critical. Arguments that we shouldn’t even think about whether or not geoengineering will be necessary remind me of Condoleezza Rice’s argument for why there were no backup plans for Iraq: “It’s bad policy to speculate on what you’ll do if a plan fails when you’re trying to make a plan work.” I take the opposite view — the only ethical choice is to have alternative plans ready, because no plan ever works the way you intend.

No matter what, we would have to continue with emission reductions, even if we don’t work fast enough to escape serious problems. Carbon dioxide sticks around in the atmosphere for centuries; the more we add, even slowly, the longer the crisis will last. But we’d also have to decide on a more immediate strategy.

The conventional response would be to focus on mitigation, building the kinds of projects needed to lessen the very worst impacts of global warming. Even in the best scenario, we’d still see disastrous events, and many deaths; in time, however, we’d learn how to deal with the new climate. Hopefully, we’d be able to do so before too many people died from heat waves, drought, opportunistic diseases, storms, resource wars, forced migration, and the like. But make no mistake: the mitigation scenario would still be catastrophic for many around the world.

That’s why the geoengineering option appeals to many: systems that cool the planet a bit over the short run could suppress many of the more disastrous effects of warming temperatures, even as we continue with emissions reductions. Geoengineering projects are generally within our current technological and financial capabilities, and most emulate well-known natural processes. The goal would be to give us time to make the social, political, economic and technological changes needed to stop building up greenhouse gases.

Varieties of geoengineering

There are two chief forms of geoengineering under consideration: albedo management, which reduces heat in the short term by blocking or reflecting a small portion of the sunlight hitting the Earth; and carbon management, which uses a variety of techniques to gradually sequester large amounts of atmospheric carbon. Albedo management techniques include cloud brightening, stratospheric particle injection (mimicking the effects of large volcanic eruptions), and the infamous orbiting space mirrors. Carbon management techniques include biochar burial, trees and other plants engineered to absorb more CO2, and “air capture,” which uses a chemical process to remove CO2 from the atmosphere.

Of the two, albedo management would be most likely to be used to give the short-term “stay of execution” to allow carbon emission reductions to take hold. Enhanced carbon sequestration, while ultimately more effective, would be too slow to make a difference in a time scale measured in months and years rather than decades and centuries.

A variety of albedo management techniques have been suggested. Some, such as putting reflective sheets in the desert to launching thousands of square kilometers of mirror fabric into orbit, don’t pass the plausibility test, either due to cost or clear draw-backs. The two approaches that seem most likely to be considered are stratospheric injection of sulfates and cloud-brightening via seawater pumps.

The sulfate injection plan is explicitly modeled on the effects of massive volcanic eruptions, such as Mount Pinatubo; global temperatures dropped by half-a-degree celsius in the months after the 1991 eruption. The favorable aspects of this plan are reasonably solid: the cooling effect would start within weeks of the injection process; the technology is readily available;
and because of the historical record around volcanic eruptions, we actually have a decent idea of what kinds of impacts this kind of geoengineering would have. The less-favorable aspects are also fairly clear: likely damage to the ozone layer (as happened after Mt. Pinatubo); the potential for health and ecological damage should the sulfate injections fail to reach the stratosphere; and a temperature “spike” if sulfate injections are stopped abruptly.

Cloud-brightening has a similar temperature impact, but is less eco-mimetic. It appears to have fewer potential drawbacks and would be used over a smaller area than sulfate injection (which is necessarily global). Its likely problems include bigger uncertainties about the technologies required, questions about the potential for as-yet unknown consequences, and the same temperature bounce-back as sulfate injection if the process is halted suddenly.

Albedo management of any kind also faces the probability of altering rainfall patterns, with the potential for inducing droughts and triggering storms in places that wouldn’t necessarily have been hit in a no-geoengineering scenario. And, of course, moderating temperatures does nothing to stop ongoing ocean acidification.

Sociopolitical issues

Any kind of geoengineering would also face a variety of non-technical issues that at best add complexity to their use. Most prominent are the political concerns. With geoengineering being global in impact, who determines whether or not it’s used, which technologies to deploy, and what the target temperatures will be? Who decides which unexpected side-effects are bad enough to warrant ending the process? Given that the expense required for sulfate injection (and likely cloud-brightening) would be low enough for a single country to undertake, what happens when a desperate “rogue nation” attempts geoengineering against the wishes of other states?  And with the benefits and possible harm from geoengineering attempts being unevenly distributed around the planet, would it be possible to use this technology for strategic or military purposes? That last one may sound a bit paranoid, but it’s clear that any technology with the potential for strategic use will be at the very least considered by any rational international actor.

There are also more mundane questions of liability. If (for example) South Asia experiences an unusual drought during cyclone season after geoengineering begins, who gets blamed? Who gets sued? Would all “odd” weather patterns be ascribed to the geoengineering effort? If so, would the issue of what would have happened absent geoengineering be considered relevant?

The broad push-back against geoengineering from many environmentalists tends to focus upon other issues, however. Some people argue that geoengineering is at best a distraction from making the necessary cuts to carbon emissions, and at worst a temptation to delay or abandon those cuts entirely. Others argue that geoengineering is simply dangerous, as the Earth’s geophysical systems are far too complex to “engineer,” and any attempt to manipulate the climate in this way is bound to have enormous unanticipated consequences.

Both are possible. I’m less concerned about the first, as geoengineering would most likely be a controversial reaction to a desperate need to avoid catastrophe, and the inevitable loud debate over the value of geoengineering would drive home the point that carbon emissions have to continue. The question of complexity and unintended results can’t be so easily set aside, however. Frankly, I would go so far as to say that problems of complexity and dangerous surprises are close to certain in any geoengineering scenario.

The bottom line

But none of those concerns matter.

If we start to see faster-than-expected increases in temperature, deadly heat waves and storms, crop failures and drought, the pressure to do something will be enormous. Desperation is a powerful driver. Desperation plus a (relatively) low-cost response, coupled with quick (if not necessarily dependable) benefits, can become an unstoppable force.

If we don’t want to see geoengineering deployed, we have to get our carbon emissions down as rapidly and as widely as possible. If we don’t — if our best efforts aren’t enough against decades of carbon growth and temperature inertia — we will see efforts to do something, anything, to avoid global catastrophe.

The choice remains ours … but time is quickly running out.