The Environmental Minister of the Marshall Islands, David Paul, left the low-lying tropical islands last week and flew to London. He journeyed all that way to stand in front of a packed room at the United Nations International Marine Organization (IMO) and emphasize that Marshallese children may have to one day desert their ancestral islands and "set sail across the oceans to an uncertain future."

The reason, Paul noted, is the "scientific fact" that rising sea levels stoked by human-caused global warming could put the Marshall Islands underwater sometime later this century.

Many of the inhabited Marshall Islands don't even reach 6 feet above the ocean. The airport sits 6 feet above sea level; the highest point in the capital is 10 feet above the water.

After a week of negotiations, the IMO decided Friday on a plan to significantly slash the amount of carbon dioxide — a potent greenhouse gas — emitted from the world's shipping sector. Most large ships burn a notoriously thick, dirty fuel, known as "heavy fuel oil." In fact, if the shipping sector was its own country, it would be the sixth largest carbon emitter in the world — contributing around the same amount of emissions into the atmosphere as industrial Germany.

The broad plan is to slash carbon emissions from ships to at least 50 percent of 2008 levels by the year 2050. The carbon-reduction strategy will be truly finalized by the IMO in 2023. Of the plans on the table, this was considered one of the more ambitious options, though Minister Paul had been pushing for even more aggressive cuts.

Satellite imagery of Mili Atoll in the Marshall Islands, taken in 2016. Image: DigitalGlobe/Getty Images

"We must leave here in no doubt. History has been made in the IMO," Paul said in a statement Friday. Though, he noted that the "job is far from over," as nothing has yet to actually be implemented.

“IMO took a big step this week by agreeing to a mid-century emissions cap,” Dan Rutherford, the International Council on Clean Transportation's (ICCT) program director for marine and aviation, said via email.

How will dirty shipping emissions be cleaned up?

The IMO's lofty emissions targets might be three decades away, but achieving these ambitious cuts requires prompt action.

“Next up is to start decarbonizing shipping by tightening energy efficiency requirements for ships this fall," said Rutherford.

There are a few ways to begin slashing the carbon emitted from massive shipping vessels. A quick solution that doesn't require new technology is requiring all ships to slow down as they voyage across the oceans.

"Speed factor has a strong influence on how much fuel burns and how much carbon ships emit," said Rutherford.

A concrete dome, called 'The Tomb' by locals, caps radioactive waste from 1940s nuclear testing on low-lying Renit Island in the Marshall Islands. Image: GIFF JOHNSON/AFP/Getty Images



Other solutions, which could be implemented on ships by around 2025, involve adding innovative technologies to newly built vessels. This includes "wind assists" aboard ships, which essentially act as modern sails. Another option is "air lubrication," which involves blowing air bubbles below ships to reduce friction, lessening the amount of dirty fuel needed for cross-world voyages.

Longer-term efficiency changes mean completely decarbonizing ships, so they're not running on oil at all, but fuels of the future, like hydrogen.

Previously, 196 nations met in Paris in 2015 and agreed to a global effort to combat climate change, agreeing to cap future warming at 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial temperatures. But global leaders did not include the marine, or shipping, sector in these climate plans.

"Marine is the last group that doesn’t have a climate framework," said Rutherford, before the IMO's Friday agreement.

How big of a threat is sea-level rise to the Marshall Islands?

Right now, sea levels are rising by between three and 3.5 centimeters (over an inch) per decade, Josh Willis, an oceanographer at NASA's Jet Propulsion Laboratory, said in an interview.

"We also know that this rate is accelerating," said Willis.

Depending on how emissions are limited and how the world's massive ice sheets melt, this could mean 2 or 3 feet by century's end, said Willis. Or it could mean a devastating 6 feet.

The Thwaites Glacier, a rapidly melting portion of the West Antarctic ice sheet. Image: nasa

"That’s a difference between existing as a nation and evacuating to go live somewhere else," said Willis.

He noted that the science here is indisputable.

"We know it's caused by global warming and human emissions of these greenhouse gases. The basic physics of the warming planet have been known for over a century," said Willis.

But precisely estimating how much the world's ice sheets will melt into the ocean — specifically those on Greenland and Antarctica — is difficult to precisely predict.

"We’re watching them melt for the first time in scientific history," said Willis. "We’ve never watched something like this happen before.

NASA is already seeing a rapid melting of Antarctic ice at its precarious edges. Here, ocean water beneath glaciers, like the Thwaites and Pine Island glaciers, can amplify melting.

"They're melting like gangbusters," said Willis. "These are massive rivers of ice that are dumping just huge amounts of ice into the oceans."

Big ships mean big emissions. Image: AFP/Getty Images

Low-lying Pacific Island nations are especially vulnerable to this added water. The Marshall Islands are relatively thin rings of coral reef that once surrounded volcanic mounts — mounts that have long since eroded away. It's not hard to see why Paul pushed for such ambitious emission targets.

"Climate change is an existential threat for them, and they have been pressing the case strongly," said Rutherford.

Sea level rise itself isn't yet drowning the islands in water — though this may very well be the case on many islands by the century's end. However, the rising seas cause damaging floods during recurrent storms and high tides.

"The storms are getting more intensive, we’re getting more cyclones," Jimmy Nuake, the Under Secretary Technical of the Solomon Islands' Ministry of Infrastructure Development, said in a statement at the IMO.

"We’re going to lose more islands," he said, citing the fact that almost five Solomon Islands have been lost since 1980.

If global emissions aren't controlled, Willis said low-lying Pacific Islands will no longer be safe from storms that once weren't a threat. The impact to the islands won't be gradual, he said. It will come suddenly, when the right merging of sea level rise and storm whop the islands.

"Eventually, they’re going to get you," said Willis.