A record loss of Arctic sea ice and faster-than-expected melting of Greenland's ice cap made worldwide headlines in 2012, but research published in major science journals in the fall suggest warming in the North doesn't have to continue.
We could refreeze the Arctic, proposed a paper in Nature Climate Change. It wouldn't even cost that much, said an affiliated study in Environmental Research Letters.
The question is should we?
"In terms of pure technical capacity, any significant nation in the world could do it," said David Keith, a Calgarian and professor of applied physics at Harvard University, one of the lead authors in both studies.
"The really hard questions here aren't mostly technical. They're questions about what kind of planet we want and who we are."
In a world that seems unable to come to grips with carbon dioxide emissions driving climate change, manipulating the Earth's climate to cool it down has some calling geoengineering a bad idea whose time has finally come.
Scientists have long theorized that injecting reflective particles of some kind into the high atmosphere could reduce the amount of sunlight reaching the Earth's surface and compensate for the greenhouse effect. High CO2 levels would continue to trap heat, but with less energy coming in to begin with, temperatures on the surface would go down.
Keith's paper used climate models to cautiously suggest that the method could be adapted to engineer regional effects. The right amount of aerosols in the right place at the right time could restore the Arctic's frozen glory.
"With an average solar reduction of only 0.5 per cent, it is possible to recover pre-industrial sea ice extent," the paper says. "Decisions involving (solar radiation management) do not need to be reduced to a single 'global thermostat.'"
A separate paper concluded that it could all be done with a few modified Gulfstream jets widely available on the used market. Annually, it could cost somewhat less than $8 billion — about the price of a major oil pipeline.
While Keith believes emissions should be cut, he doesn't advocate such a plan, at least not yet.
He suggested geoengineering may be a viable response to a "climate emergency" — a sudden collapse of ice sheets or a killing drought.
"If your primary view is pragmatic, and you want to reduce the risk to Asian farmers who might get hit by high temperatures that make their crops not germinate, then the answer is you should do whatever is actually safe and controllable and produces the outcomes."
Some environmentalists are starting to think there may be something to that.
"We all agree: mitigation, that's the thing you should do," said Steve Hamburg, chief scientist of the U.S.-based Environmental Defense Fund. "But everyone also recognizes that even if we did that, we may have climate surprises. We'd be irresponsible not to try and understand what our options are.
"It's easy to dismiss this as too radical a solution, but that does a disservice to what we don't know. We need to be prepared with information to understand what our options are or aren't depending on how things play out."
If we don't at least understand the risks, a desperate situation may lead to a disastrous decision, Hamburg said.
Keith Allott, head of climate change for the World Wildlife Fund UK, agrees that research is needed.
"We do see the need for a grown-up conversation about the type of research that may be acceptable at this stage," he said.
The United Nations, through its Convention on Biological Diversity, has ruled out open-air or large-scale geoengineering experiments.
Current research, including some that Environment Canada is involved in, is restricted to using models to better understand how the Earth's climate might respond to manipulation.
Hamburg said discussions on everything from how research is conducted to who gets to set the global thermostat are just beginning.
He's part of the Solar Radiation Management Governance Initiative, a partnership between his group and several scientific academies from around the world.
"Everybody has to feel like their interests are represented," he said.
"It can't be about North American and European voices. It has to be about global voices and global communities being aware of it so that there is some kind of consensus that ignorance is our enemy."
Peter Mooney of the Ottawa-based Etc Group, an environmental technology watchdog, is skeptical of anyone's ability to manage geoengineering.
"There's a marvellous naivete to it all," he said. "We need to prepare for this horrible thing of Plan B because governments have proved themselves incapable of addressing the real problem. Therefore, we need to have governments go ahead and do Plan B."
But that thinking is flawed, he suggested.
"The governments who screwed up in the first place can't be expected to take something like planetary systems management and do a better job of it."
Others hold that geoengineering is just more of the same kind of thinking that caused the problem — a reliance on technical fixes instead of looking at causes.
"They kind of like the fact the problem is hard to solve because it gives you a lever to say we have to make these deep reforms in consumer culture, which I personally would like to see," said Keith.
But really, he asks, what is society but one technical fix after another? Sanitation, for example, is a technical fix for cities producing sewage.
Mooney feels it's asking too much of governments to expect they'll make science-based unbiased decisions.
"It's naive to think that once Plan B becomes a political option that governments won't just take it on and interpret it as they wish. They will always find scientists who will give them the spin that they want.
"(We shouldn't be) opening up the back door for politicians to creep out of, claiming that, 'Don't worry folks. We don't need to do anything because we have technological fixes that we can deploy on short notice.'"
Allott, too, is concerned that geoengineering could become a way to excuse the continued consumption of CO2-causing fossil fuels.
"There are some unfortunate overlaps between parts of the geoengineering community and parts of the fossil fuel lobby," he said. "That's not OK."
He also points out that no plan to manage solar radiation does anything to address ocean acidification, another byproduct of CO2 emissions. The best way forward, he said, is to reduce the emissions in the first place.
"People talk about this as if (geoengineering) is an easy option. That ain't true."
Geoengineering isn't likely to become a reality any time soon. There are no aerosol-laden planes on a tarmac waiting for clearance to take off.
But the debate is coming, predicted Hamburg.
"We're not going to put the genie back in the bottle ... (We need) a robust and broad conversation about how to govern research in this area with widely agreed-upon rules of the road."
Even then, said Keith, we need to cut CO2 emissions.
"If we do this and we do not cut emissions, we just walk further and further off the cliff, like Wile E. Coyote."
We could refreeze the Arctic, proposed a paper in Nature Climate Change. It wouldn't even cost that much, said an affiliated study in Environmental Research Letters.
The question is should we?
"In terms of pure technical capacity, any significant nation in the world could do it," said David Keith, a Calgarian and professor of applied physics at Harvard University, one of the lead authors in both studies.
"The really hard questions here aren't mostly technical. They're questions about what kind of planet we want and who we are."
In a world that seems unable to come to grips with carbon dioxide emissions driving climate change, manipulating the Earth's climate to cool it down has some calling geoengineering a bad idea whose time has finally come.
Scientists have long theorized that injecting reflective particles of some kind into the high atmosphere could reduce the amount of sunlight reaching the Earth's surface and compensate for the greenhouse effect. High CO2 levels would continue to trap heat, but with less energy coming in to begin with, temperatures on the surface would go down.
Keith's paper used climate models to cautiously suggest that the method could be adapted to engineer regional effects. The right amount of aerosols in the right place at the right time could restore the Arctic's frozen glory.
"With an average solar reduction of only 0.5 per cent, it is possible to recover pre-industrial sea ice extent," the paper says. "Decisions involving (solar radiation management) do not need to be reduced to a single 'global thermostat.'"
A separate paper concluded that it could all be done with a few modified Gulfstream jets widely available on the used market. Annually, it could cost somewhat less than $8 billion — about the price of a major oil pipeline.
While Keith believes emissions should be cut, he doesn't advocate such a plan, at least not yet.
He suggested geoengineering may be a viable response to a "climate emergency" — a sudden collapse of ice sheets or a killing drought.
"If your primary view is pragmatic, and you want to reduce the risk to Asian farmers who might get hit by high temperatures that make their crops not germinate, then the answer is you should do whatever is actually safe and controllable and produces the outcomes."
Some environmentalists are starting to think there may be something to that.
"We all agree: mitigation, that's the thing you should do," said Steve Hamburg, chief scientist of the U.S.-based Environmental Defense Fund. "But everyone also recognizes that even if we did that, we may have climate surprises. We'd be irresponsible not to try and understand what our options are.
"It's easy to dismiss this as too radical a solution, but that does a disservice to what we don't know. We need to be prepared with information to understand what our options are or aren't depending on how things play out."
If we don't at least understand the risks, a desperate situation may lead to a disastrous decision, Hamburg said.
Keith Allott, head of climate change for the World Wildlife Fund UK, agrees that research is needed.
"We do see the need for a grown-up conversation about the type of research that may be acceptable at this stage," he said.
The United Nations, through its Convention on Biological Diversity, has ruled out open-air or large-scale geoengineering experiments.
Current research, including some that Environment Canada is involved in, is restricted to using models to better understand how the Earth's climate might respond to manipulation.
Hamburg said discussions on everything from how research is conducted to who gets to set the global thermostat are just beginning.
He's part of the Solar Radiation Management Governance Initiative, a partnership between his group and several scientific academies from around the world.
"Everybody has to feel like their interests are represented," he said.
"It can't be about North American and European voices. It has to be about global voices and global communities being aware of it so that there is some kind of consensus that ignorance is our enemy."
Peter Mooney of the Ottawa-based Etc Group, an environmental technology watchdog, is skeptical of anyone's ability to manage geoengineering.
"There's a marvellous naivete to it all," he said. "We need to prepare for this horrible thing of Plan B because governments have proved themselves incapable of addressing the real problem. Therefore, we need to have governments go ahead and do Plan B."
But that thinking is flawed, he suggested.
"The governments who screwed up in the first place can't be expected to take something like planetary systems management and do a better job of it."
Others hold that geoengineering is just more of the same kind of thinking that caused the problem — a reliance on technical fixes instead of looking at causes.
"They kind of like the fact the problem is hard to solve because it gives you a lever to say we have to make these deep reforms in consumer culture, which I personally would like to see," said Keith.
But really, he asks, what is society but one technical fix after another? Sanitation, for example, is a technical fix for cities producing sewage.
Mooney feels it's asking too much of governments to expect they'll make science-based unbiased decisions.
"It's naive to think that once Plan B becomes a political option that governments won't just take it on and interpret it as they wish. They will always find scientists who will give them the spin that they want.
"(We shouldn't be) opening up the back door for politicians to creep out of, claiming that, 'Don't worry folks. We don't need to do anything because we have technological fixes that we can deploy on short notice.'"
Allott, too, is concerned that geoengineering could become a way to excuse the continued consumption of CO2-causing fossil fuels.
"There are some unfortunate overlaps between parts of the geoengineering community and parts of the fossil fuel lobby," he said. "That's not OK."
He also points out that no plan to manage solar radiation does anything to address ocean acidification, another byproduct of CO2 emissions. The best way forward, he said, is to reduce the emissions in the first place.
"People talk about this as if (geoengineering) is an easy option. That ain't true."
Geoengineering isn't likely to become a reality any time soon. There are no aerosol-laden planes on a tarmac waiting for clearance to take off.
But the debate is coming, predicted Hamburg.
"We're not going to put the genie back in the bottle ... (We need) a robust and broad conversation about how to govern research in this area with widely agreed-upon rules of the road."
Even then, said Keith, we need to cut CO2 emissions.
"If we do this and we do not cut emissions, we just walk further and further off the cliff, like Wile E. Coyote."
