When it comes to climate change, the consensus is clear: The planet is heating up and we’re in big trouble. So we’re going to need big solutions.

And there are no solutions bigger than geoengineering, the emerging term for the study of planetwide climate-change initiatives that are experimental, drastic, and possibly deranged. These proposals call for large-scale manipulation of the environmental systems that influence Earth’s climate. Artificial forests, orbital umbrellas, glacial doorstops — that sort of thing.

The proposals may seem extreme, but maybe there are no bad ideas in apocalyptic brainstorming! Here are seven provocative climate change remedies proposed by scientists, industry leaders, and government agencies. Hold onto your hats, earthlings.

Planetary whitening!

When the first geoengineering proposals popped up in the 1990s, they were dismissed as alarmist, extreme fringe science. However, the oil industry itself was already considering radical geoengineering solutions to climate change, even as it spent millions trying to sow doubt about climate science in public.

In 1997, two Exxon climate scientists contributed to a book, Engineering Response to Global Climate Change. Among the proposals they outlined: Whiten the planet’s surface to reflect more sunlight back into space. To achieve this, the researchers suggested dispersing millions of tons of white-painted chips or foam throughout the world’s oceans. By putting a reflective film over the oceans, we would reduce solar heat in the air. They also considered the option of towing glaciers around to maximize their reflectivity.

The Exxon team conceded that the proposal might have a few downsides. Towing icebergs, they wrote, would “require moving roughly the entire Arctic ice sheet each year to have a significant effect.” Still, the basic idea has persisted. Recently, scientific groups have focused on more sustainable methods to increase the Earth’s reflective properties, such as painting houses white or planting crops with shiny leaves.

Space umbrellas!

In the late 1990s, a remarkable geoengineering idea for cooling the planet gained traction among scientific groups. It was big, bold, two-fisted space science: Deploy a giant orbital space umbrella to shade the Earth from solar heat.

Putting such a massive object into space would require one slight tweak: building the shield on the Moon, using lunar rocks.

Mathematically, it’s entirely feasible. Studies suggest that we would only need to block about one to four percent of the Sun’s rays to offset the warming effect of industrialization. Logistically, it gets a little trickier. One of the earliest plans proposed putting a solar shield into space and anchoring it at a Lagrange point — an area in space between the Earth and the Sun where their gravitational pull evens out. Putting such a massive object into space would require one slight tweak: building the shield on the Moon, using lunar rocks. So, yeah, we’ll need to work that out.

More recent proposals suggest seeding the Earth’s outer orbit with millions of small sunshades, rather than one big umbrella.

Robotic cloud boats!

Space umbrellas and “whitening” techniques fall into the category of solar radiation management — and there are several other variations on the theme.

Marine cloud brightening would artificially manipulate the Earth’s cloud cover to reflect more sunlight back into space. One approach involves deploying a massive fleet of robotic boats across the world’s oceans. The boats would suck up seawater, then spray it hundreds of feet into the sky. The resulting atmospheric condensation should create more reflective cloud cover.

Robot boats are exciting in a sci-fi kind of way, but scientists are also looking at land-based facilities and aircraft to increase the atmosphere’s reflectivity. One of the many drawbacks to marine cloud brightening: We’d have to keep the system running, uninterrupted and worldwide, more or less forever.

Synthetic trees!

Carbon dioxide removal is the other major geoengineering category in play these days. To tamp down atmospheric warming, the idea goes, we need to do more than reduce greenhouse gas output. We need to remove the stuff that’s already there.

Mother Earth, in her infinite wisdom, is already doing this, turning carbon dioxide into oxygen with plants and trees. In the spirit of biomimetic progress, some scientists have suggested using artificial trees for more carbon-scrubbing.

A few years back, researchers at Columbia University Earth Institute unveiled a synthetic tree that could potentially absorb CO2 thousands of times faster than natural trees. The idea has since evolved in multiple directions, including systems designed to directly remove existing CO2 from the air. Newer proposals combine green energy systems with techniques that contain all CO2 at the source. One technique, known as “bioenergy with carbon capture and storage,” involves extracting future energy from biomass (trees, for instance), capturing the emitted CO2, and pumping it underground. It’s a busy area of research right now, although some scientists argue that it would do more harm than good.

Algae madness!

Trees are good carbon scrubbers, but since oceans cover 70 percent of the Earth, maybe water is a better place to start. That’s the idea behind an audacious 2007 proposal to scrub CO2 from the atmosphere using wave energy, massive pipes, and giant algae blooms floating on the ocean surface.

The proposal made waves, as it were, due in part to the primary author: James Lovelock, the famed environmentalist and originator of the Gaia theory, which argues that Earth is essentially a vast self-regulating organism. Lovelock’s initial plan, radically simplified, was to install a network of tethered vertical pipes in the world’s oceans. The pipes — 10 meters in diameter, 200 meters long — would deliver nutrient-rich waters from near the seafloor to the ocean surface. These nutrients would, in turn, fertilize massive algae blooms that would absorb CO2 from the air.

It gets a lot more complicated than that, but the basic idea has since sparked parallel paths of inquiry. Broadly referred to as ocean fertilization, these proposals involve leveraging the ocean’s phytoplankton and other algae to help out with planetary cooling efforts. The downside to such colossal geoengineering? Tinkering with the ocean’s ecosystem is a dangerous business, and algae blooms can release harmful gases and toxins of their own.

Glacial doorstops!

Impending doom has encouraged geoengineering proponents to think big. But there’s a growing movement afoot to consider more tightly focused plans. The idea is to buy some time so that future generations might succeed where we have failed.

A team of Princeton University researchers hope to target two related symptoms of global warming: melting glaciers and rising sea levels. The proposal involves building underwater walls around unstable glaciers using colossal piles of sand and stones. The plan could dramatically slow glaciers’ collapse and migration.

Computer simulations suggest that these glacial doorstops could indeed buy us some time. In addition to slowing sea level rise, keeping the world’s glaciers intact would also help reflect more of the Sun’s energy back into space.

Scooting the Earth!

Finally, we have the ultimate geoengineering solution to a warming planet, one that tends to occur to fourth-graders. If the planet’s getting too hot, why not scoot it back a little ways from the Sun?

To be clear, no one is seriously proposing this remedy for global warming. Yet. But science-fiction circles have bounced the idea around for decades, and it doesn’t take a rocket scientist to work out the feasibility.

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Well, actually it does. And he did. Last summer, University of Glasgow space engineering professor Matteo Ceriotti crunched the numbers on ways we might gently nudge the planet away from the Sun. Among the possibilities for scooting the Earth: Ion drives, electric thrusters, solar sails, and asteroid slingshots. Among the dangers of scooting the Earth: floods, earthquakes, atmospheric superstorms, and perhaps a violent end to all life on the planet.

This is why monkeying around with the planetary systems has traditionally been the jurisdiction of alien invaders, angry gods, and James Bond villains. The ethical issues alone are mind-boggling. As a recent article in the journal Global Sustainability asks, what foundation-funded person or interdisciplinary panel, deploying a radical climate experiment, could possibly have the right to risk all people, all species, our entire planet?

Still, these radical proposals — weirder and more extreme than current mainstream thinking — can at least help us grasp the colossal scope of the problem. And who knows? Maybe a space umbrella would come in handy.