The document states that “deliberately manipulating physical, chemical, or biological aspects of the Earth system” should be explored alongside the more conventional approaches to climate change. Conventional approaches means reducing emissions – “mitigation” in policy-speak – and adjusting to the unavoidable effect of climate change – known as “adaptation”.

The all too predictable reason is not so much that shooting sulfur into the sky or dumping iron filings into the ocean looks like a good way to address climate change, but rather that the more conventional options don’t look likely to be adequate:

The paper states that “even aggressive mitigation of future emissions cannot avoid dangerous climate changes resulting from past emissions.

Note that the paper will reportedly call for more research, and that it is not an out and out endorsement of geo-engineering. The association also wants that research to include the moral, legal and ethical aspects of  geo-engineering.

Stephen Holdren, the White House scientific advisor, raised eyebrows earlier this year when he made supportive comments about geo-engineering – although there was later some confusion about whether he was referring to his own personal views, or to White House policy.

The Atlantic’s current edition has a good piece explaining the most prevalent geo-engineering ideas, and highlights their crucial advantage is that they are not only potentially simpler than the myriad of efforts needed to avert the worst of climate change – they are also likely to be a lot cheaper.

The culprit is atmospheric carbon dioxide (CO2), which even in a cooler globe will continue to be absorbed by seawater, creating acidic conditions.
“There would be a slight reduction in this problem, because land plants would be expected to be able to grow more vigorously in a high CO2, but cool world,” said Ken Caldeira of the Carnegie Institution’s Department of Global Ecology.

Land plants and soils would hold onto more carbon in this scenario, so less would find its way into the oceans.

“However this expansion of the land biosphere, while it’s a slight help to ocean acidification is not enough to make a big difference,” said Calderia.

A widely-discussed proposal for countering warming with geoengineering involves injecting small, reflective particles into the upper atmosphere.

This would partially block incoming sunlight before it reached the Earth’s surface, lowering global temperatures just as volcanic ash from the Mount Pinatubo did following its eruption in 1991.

But, critics have warned that such a scheme might also alter rainfall patterns, damage the planet’s ozone layer,  or have other unexpected effects.

Until the current study, which used a computer model of the Earth’s climate system and biosphere to simulate the effect of geoengineering on climate and the ocean’s chemistry, the potential impact of such a scheme on ocean acidification had never been calculated.

In the simulations, reduced sunlight cooled the planet as expected, and it also slightly slowed the rise in atmospheric CO2, as natural sinks absorbed more carbon. But, this slight change was not enough to significantly mitigate ocean acidification.

Ocean acidification rivals global warming as a threat to marine ecosystems, especially coral reefs, which need to be surrounded with mineral-saturated water in order to grow.

Rising levels of carbon dioxide make seawater more acidic, leading to lower mineral saturation.

Recent research has indicated that continued CO2 emissions will cause coral reefs to begin dissolving within a few decades, putting the survival of these ecosystems at extreme risk.

“Geoengineering approaches come with all sorts of risks. It is important we learn about the full set of these risks and all of their implications,” said Caldiera.

Alarms of an imminent ice age have been raised from time to time, for example in the 1970s after a prolonged period of climatecooling, and even more recently as the climate cooled slightly in the past few years.  One needs to distinguish, however, between a Little Ice Age that may be part of a more-or-less regular 1,500-year cycle (and likely related to solar activity) and a true ice agethat relates to a change in solar irradiance brought about by changes in earth’s orbit, axis inclination and precession.
Not everyone agrees that such a Milankovich glaciation is imminent.  For example, Andre Berger et al believe it might be as much as 40,000 years away.  In any case, everyone agrees that a glaciation would bring about unprecedented hardship to the world, including crop failures, starvation – and wipe out much of the earth’s human population.

The accepted mechanism for the initiation for a glaciation is the survival of a snow field at high northern latitudes during the summer, with feedback (due to increased albedo and cooling) enlarging the snow and ice area gradually over the years to cover much of the Northern Hemisphere.  This effect may be the ‘Achilles heel’ of glaciation.  Can it be stopped before it spreads?

The geo-engineering task would consist of three phases:  (1) a more detailed studied of the Milankovich glaciation mechanism; (2) setting up a protocol for satellite search for surviving snowfields; (3) field experiments with soot dispersal to decrease the albedo and cause the disappearance of snowfields so they absorb solar radiation instead of reflecting it.

1.  A search of climate literature suggests that the sensitive region for initiation of an ice age is in the vicinity of 56 deg North latitude, which would place it into Canada, Scandinavia, or Siberia.  The coldest areas in these regions are likely to be at the higher altitudes, which narrows the search to particular locations.  Since the initiation mechanism depends on the survival of high-albedo snowfields throughout the whole summer, one can search existing data sources for such locations and define others where the duration of a high-albedo snowfield might extend well into the summer before melting.  It may turn out that the initiation mechanism is more complicated and depends on being “kicked-off” by a century or even a decades-long period (like a Little Ice Age)—or perhaps even by a major volcanic eruption like the one that led to the very cold summer of 1816 – that promotes the survival of the initiating snowfield.

2.  Once the likely locations are defined, one can set up a protocol whereby weather satellites can routinely observe and track the albedo in these regions, locate snow fields that survive during the summer and expand from year to year—and alert decision makers on the possibility of an ice-age initiation.  This task seems fairly routine and could be initiated with existing resources.

3.  Finally one would like to demonstrate the feasibility of artificially melting and removing a snowfield.  This task would investigate the technical resources needed and define the details and costs of such an operation.  One possibility that comes to mind will be to use “crop-duster” planes to distribute soot material over the snow field and observe the rate of melting, comparing it to what would be expected from theory.  Such field experiments could be usefully conducted while the other parts of the project are proceeding.

The end result would be to demonstrate a reliable means of overcoming the initiation of a future ice age.  The geo-engineering operation of removing the high-albedo snow fields might have to be done year after year until the astronomical conditions change sufficiently so that the sun itself could operate to remove the possibility of an ice age.

Mr. Victor, the director of Stanford University’s Energy and Sustainable Development Program, is a leading voice in the effort to get governments and policymakers to start thinking seriously about the possibility of technological tinkering with the atmosphere, as a weapon of last resort in the battle against global warming.

In the March/April edition of Foreign Affairs, Mr. Victor was the lead author of an article that candidly acknowledged the challenge. “Fiddling with the climate to fix the climate strikes most people as a shockingly bad idea,” he wrote.

I watched Mr. Victor make his case before a small group of mainly government policymakers from nine nations at a private gathering north of San Francisco earlier this month, organized by the Institute for Large Scale Innovation, a nonprofit group. He is an engaging, even cheerful bearer of bad news.

In his analysis, there are three ways of coping with climate change: controlling emissions, adapting to the altered climate and geoengineering, which he concedes, is the most drastic, even desperate. “It is Dr. Strangelove, but it is entirely doable,” said Mr. Victor, who is also a law professor at Stanford.

Geoengineering, he said, needs to be brought in from the mad-scientist fringe. Governments, he said, should finance research, weigh policy options and discuss geoengineering in international climate-change organizations. “It may be we never use this option, but is needs to be ready,” he said.

John Holdren, the chief science adviser in the Obama administration and an environmental policy specialist, recently suggested that geoengineering has to be taken seriously. “It’s got to be looked at,” he told The Associated Pressin April. “We don’t have the luxury of taking anything off the table.” Mr. Holdren later clarified that the White House was not strongly considering pursuing geoengineering as a policy.

At the California meeting, Mr. Victor’s pitch was greeted with polite skepticism, as he reviewed ideas like spraying tiny reflective particles into the upper atmosphere to help block the sun’s rays and cool the planet.

Francelino Grando, a senior government official from Brazil, worried that geoengineering might be seen as a solution instead of a stop-gap. “It may give people the impression that we don’t have to worry about climate change because we can solve it through engineering,” he said. “But the only real answer is that we have to fundamentally change the pattern of energy use.”

For his part, Mr. Victor declared himself optimistic that technologies to curb emissions — from alternative fuels to carbon capture — will be the long-term answer. But he worries about making it to the long term without environmental disaster, especially during transition years, he said, from 2050 to 2070 or so. “So I think we’ll need to have the geoengineering option,” he said.