Earth's temperatures are on track to blow past the objectives set in the Paris climate agreement. Last year was the fourth warmest on record for surface temperatures and the hottest ever for oceans.

A recent report from the United Nations' Intergovernmental Panel on Climate Change (IPCC) found that nations around the globe must implement "rapid and far-reaching" changes in energy sources, infrastructure, industry, and transportation to avoid catastrophic consequences of climate change.

But some researchers are looking into another way to address dangerous warming: hacking the climate.

The technical term for this is geoengineering, and the technology generally involves either capturing carbon dioxide from the air and storing it, or manipulating the atmosphere to help cool Earth.

The risk is that the effects of geoengineering in one corner of the world could lead to unintended consequences in another.

"The atmosphere has no walls," Andrea Flossmann, a weather-modification expert with the World Meteorological Organisation, said in a bulletin.

"What you add may not have the desired effect in your vicinity, but by being transported along might have undesired effects elsewhere."

So if a rogue nation were to start a geoengineering project without international oversight or buy-in, some experts worry the unintended consequences could lead to war.

Geoengineering might be necessary, but it comes with geopolitical risks

To limit Earth's temperature rise to 1.5 degrees Celsius above pre-industrial levels – the Paris climate agreement's most ambitious goal – emissions of heat-trapping gas like carbon dioxide have to drop by 45 percent from 2010 levels in the next decade or so, according to the IPCC.

If that doesn't happen, dry regions would be much more likely to experience severe drought, and areas prone to heat waves or hurricanes would get more of those disasters, too. Most coral reefs would die, and melting Arctic ice would cause sea levels to rise dramatically.

These changes could trigger huge migrations of people and mass extinctions of animals.

But so far, the required emissions reductions are not happening. Worldwide carbon emissions from fossil fuels rose by 1.6 percent in 2017 and 2.7 percent last year, according to the World Resources Institute.

"Climate change is getting worse," Ted Parson, an environmental law professor at the University of California, Los Angeles, told Business Insider, "which is why it's necessary to talk about geoengineering right now."

Geoengineering can take many forms, some of which exist already. Climeworks, a company that sucks carbon dioxide out of the air, opened its first commercial plant in Switzerland in 2017.

A New York-based start-up, Global Thermostat, uses carbon sponges to absorb CO2 directly from the atmosphere or smokestacks.

A more ambitious and untested option, though, is solar geoengineering, which would involve scattering sulphur particles as aerosols in the sky in order to reflect more sunlight back into space.

This approach has yet to be tested, but Harvard University's solar geoengineering research program is currently researching how to disperse clouds of sulphur particles via small, steerable balloons.

Most models predict that the effects of a project like this would be felt differently around the globe, and consequences could arise even in spots far from the rollout location.

That means that if a country tries out this kind of geoengineering, its neighbours would almost certainly feel the effects – as could nations on the far side of the world.

"[Solar geoengineering] has geopolitical ramifications, unlike carbon capture," Juan Moreno-Cruz, an associate professor at the University of Waterloo who studies geoengineering, told Business Insider.

For example, aerosol injections deployed in the southern hemisphere could impact ocean temperatures and wind speeds, leading to more hurricanes in the northern hemisphere.

In a worst-case scenario, this kind of geoengineering could leave Earth's atmospheric chemistry irreversibly altered.

"The side effects may be almost as bad as the disease you're trying to cure," author and environmental activist Bill McKibben previously told Business Insider.

A 'rogue nation' could hack the climate single-handedly

Alan Robock, an environmental science professor at Rutgers and an expert on geoengineering, previously told Business Insider that he's "got a list of 27 reasons" we shouldn't attempt any large-scale planet hacking.

One major risk is that a reprobate country or even a private company could pull the trigger on an atmospheric-transformation project that affects the entire world.

"There's always first movers, certain countries driving things," David Keith, a professor of engineering and applied sciences at Harvard University, told Business Insider.

This is already happening on a smaller scale: Chinese, Russian, and US governments employ a form of atmospheric manipulation called cloud seeding, in which silver ions are scattered into the atmosphere to make it rain.

Beijing spent millions on such technology ahead of the 2008 Olympics. But this technology only triggers regional weather impacts, according to Parson.

In a recent debate about geoengineering hosted by Intelligence Squared, Keith said he expects bigger geoengineering initiatives to be very much be on the table for some nations in the future.

"Some government – maybe China after a monsoon causes the crops to fail, maybe Indonesia after a heat wave kills 100,000 people, maybe the United States after a category 5 hurricane hits [New York City] head-on – will consider it," he said.

If there aren't international rules governing the geoengineering process and its consequences, some experts say, conflict could easily emerge.

"The threat of war never is out of the question," Moreno-Cruz said.

He added that the nations most likely to attempt geoengineering projects are also nuclear powers, which further complicates the picture.

But is geoengineering really that scary?

Some scientists like Keith think the threat of war, nuclear or otherwise, is overblown, since independent geoengineering would go against a country like India's self interest.

"They would want to be able to continue reducing their climate risks, and the best way to do that would be to collaborate with others, not go extremely rogue and then get shut down," he said.

Plus, he noted, any project that injects particles into atmosphere is finite unless the efforts are continuous – for solar geoengineering to work, planes would need to constantly spread aerosols.

"There aren't single interventions that change things forever," Parson said. "This isn't like Doctor Evil pulling great big handle in his island lair and that's it."

Parson is confident that if a single individual or company attempted a geoengineering project, it could easily be brought to a halt.

"Any megalomaniac, individual entrepreneur is a citizen of some country and their enterprises operate under the legal jurisdiction of that country," he said during the Intelligence Squared debate.

But although Parson thinks geoengineering might be the only way for the world to meet the Paris agreement goals, he emphasised that it should never be an alternative to cutting emissions.

"Managing climate change requires multiple strategies. Geoengineering in no way replaces or undoes the urgency of cutting emissions," he said.

Still, the once-fantastical idea of geoengineering seems to be entering the mainstream. Presidential candidate Andrew Yang is advocating for the technology, and 5,000 academic papers about the methods and ramifications of solar geoengineering technology have been published since 2015.

"Regular people, the policy elite, and environmental groups are taking this topic more seriously than 10 years ago," Keith said. "Let's examine it seriously, not put it in the crazy corner and forget about it."

This article was originally published by Business Insider.

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