(Carlos Garcia Rawlins/Reuters)

Here’s a word guaranteed to start an argument among scientists and environmental activists: geoengineering. The word covers a variety of hypothetical technological fixes for the problem of climate change.

For example, tiny particles of sulfur dioxide could be sprayed into the upper atmosphere. That would mimic the effects of a volcanic eruption. The thin haze would reflect sunlight, cooling Earth’s surface. Our planet would literally be shinier when seen from space.

Many environmentalists and scientists abhor the idea. Among their objections: It doesn’t address the rise of atmospheric carbon dioxide, which causes ocean acidification and kills coral reefs. It’s a short-term fix for a long-term problem, since carbon dioxide lingers for centuries and aerosol particles fall to the surface in just a couple of years. And critics say that even discussing this kind of geoengineering could sap momentum from efforts to cut carbon emissions.

But supporters of geoengineering research say that we’re already changing the planet in stupid ways and should at least consider doing it intelligently, using technology.

“A muffler is a technological fix for the fact that the internal combustion engine is very noisy, and people don’t have a problem with mufflers,” said David Keith, a Harvard University professor of applied physics.

Photographic documentation showing earth observations taken from the space shuttle Discovery. (NASA)

The debate will intensify this coming week when the National Research Council, part of the National Academy of Sciences, releases a massive report on geoengineering, one nearly two years in the making.

“It will come as no surprise that there were very, very vigorous discussions by people on the committee who had very different viewpoints,” said committee member and University of Chicago climate scientist Ray Pierrehumbert. “Once the report is out, it’ll be a free-for-all in figuring out what the report actually means.”

That an institution as lofty as the National Academy of Sciences would take seriously an idea as dramatic as geoengineering is a sign of how little progress has been achieved in efforts to mitigate climate change. The scientific consensus is that not enough is being done to offset the rate at which carbon is being dumped into the atmosphere. That has opened the conversation to this once-unthinkable notion of applying technology on a global scale to adjust the planet’s temperature or extract some of that carbon.

Environmental activists are generally skeptical that this kind of technology will save the day when it comes to climate change. They don’t think we should rely on technology to fix a problem that is rooted in human behavior.

“Geoengineering is pretty much a blind alley,” says Richard Heinberg, a senior fellow at the Post Carbon Institute in Santa Rosa, Calif. “We’re probably not going to be able to solve climate change with techno-fixes. We’re actually going to have to change our behavior and our expectations and our economy. Nobody likes to hear that.”

The report was funded in part by the U.S. intelligence community. Other sponsors include NASA, the Energy Department and the National Oceanic and Atmospheric Administration. The report being released in a relatively hushed atmosphere; committee members and reviewers are not supposed to talk about the specifics.

One fact is already public: The report will be in two volumes, separately addressing the two most commonly discussed geoengineering strategies — solar radiation management (SRM), which is designed to increase the reflectivity of the planet, and carbon dioxide removal (CDR), in which the carbon dioxide is directly extracted from the air and sequestered in some form.

The two-volume approach appears to be designed to keep the more radical idea of solar radiation management from being conflated with the less jarring proposals to subtract the carbon dioxide that we’re currently adding.

The main virtue of solar radiation management, known as albedo modification, is that it’s relatively cheap and would work quickly. The effort might use balloons or a high-altitude aircraft to spray small particles into the air. Because the aerosols eventually rain from the atmosphere, the program would have to be continuous.

Advocates concede that solar radiation management could have unintended consequences. The cooling of continental land masses could reduce the summer monsoon in some areas, with a dramatic effect on agriculture. And those tiny particles could lead to chemical reactions that reduce the amount of ozone, which serves as a radiation shield for the planet.

And there are subtler effects that could make people unhappy.

“You’d get whiter skies. People wouldn’t have blue skies anymore,” said Alan Robock, a Rutgers University climate scientist who was not on the academy committee. “Astronomers wouldn’t be happy, because you’d have a cloud up there permanently. It’d be hard to see the Milky Way anymore.”

Still, there are advocates who say that this kind of geoengineering, even if not implemented anytime soon, should receive research dollars as a potential element of humanity’s response to the spike in atmospheric carbon and the warming climate. Funding so far has been limited.

“Every single climate model that we’ve run, and basic theory, suggests that a world with high CO2 and a little bit less sunlight is less dangerous than a world with high CO2,” said Harvard’s Keith, who reviewed a draft of the new report but was not on the committee.

A couple of miles away, at MIT, senior research engineer Howard Herzog — also not on the academy committee — said the sunshine fix is too much like a Hail Mary pass at the end of a football game.

“You never want to rely on a Hail Mary pass, especially with the stakes that we’re talking about,” Herzog said.

Herzog and others are more open to carbon dioxide removal, the second type of geoengineering addressed by the academy committee. This would merely subtract what has already been added.

“You’re really controlling the actual knob that’s created the problem. CDR is a way of dialing that back down. With CDR, you are not risking putting the Earth in a completely different climate state,” Pierrehumbert said.

But Herzog, who has spent years working on carbon removal, says the technologies for doing this remain astronomically expensive. The CDR technologies, which typically use a liquid to create a chemical reaction that extracts carbon dioxide from the air, are already used on submarines and spacecraft.

But those vessels can simply dump or vent the extracted carbon dioxide, which is not an option for a geoengineer who wants to park it somewhere permanently. The best place to put the stuff appears to be porous rock formations, such as depleted oil and gas reservoirs, but this has been done only on a limited scale so far.

A basic problem with scrubbing carbon from the air is that there’s not much carbon to begin with. Atmospheric CO2 is extremely dilute. It makes more sense to scrub the CO2 at smokestacks, particularly at coal-fired power plants, where the CO2 is concentrated, but even there, the technology is expensive and not widely employed, Herzog said.

The new report presumably will discuss other techniques for pulling carbon from the atmosphere, including something as straightforward as reforestation.

Any effort, though, collides with the scale of the problem. Humans emit a lot of CO2. And there are challenging economic and political issues about who, exactly, will pay for these efforts. There is a vocal camp in Congress that denies that climate change is a serious problem and questions whether the scientific consensus can be trusted.

Thus the forecast for the geoengineering debate is clear: storms on the way.