Climate change might seem like a far off thing, a vague concept — until it doesn't. Even if you've only ever really connected climate change with fewer white Christmases, a new NASA tool can now predict how melting glaciers will affect various coastal cities as global warming intensifies and sea levels continue to rise. Scientists at NASA's Jet Propulsion Laboratory at Caltech carried out a study that looks at how meltwater flowing off of various ice sheets around the world will contribute to sea level rise in different places. Given the seriousness that rising sea levels pose to humanity, this study and the tool that it produced could have a great effect.
"I think the new NASA tool has the potential to make coastal planners more aware about the uncertainties and risks of future sea level rise and the contributions from land ice," says Dr.-Ing. Sönke Dangendorf, a researcher at the University of Siegen in Germany who studies sea levels. "It allows us to identify individual melt areas which are most important for our area. It further breaks down the complex processes related to ice-melt on a level accessible for everyone, which I think is a major step."
The way that melting ice affects global sea levels doesn't quite work the way you might expect it to, though.
When water flows into the ocean from, for example, the ice sheet covering Greenland, it doesn't raise the sea level everywhere in the world equally. The polar ice caps and huge ice sheets like the one that covers Greenland are massive objects, and when they gain and lose mass with the seasons, they actually affect the Earth's movement through space. Furthermore, Dangendorf explains, it's actually these large ice sheets that are contributing to the current, accelerating rise in sea levels more than melting glaciers are.
The Earth wobbles as it moves, and when mass shifts from one place on the globe to another, it affects that wobble. So when an ice sheet like Greenland's, which isn't normally affected by seasonal changes, loses a lot of mass that the ocean then gains, the Earth's wobble changes. This sends the water in particular directions to compensate for that altered wobble, which doesn't affect different coastal cities evenly.
What this also means, then, is that the uneven redistribution of water actually happens counterintuitively. You might expect that the glaciers closest to coastal cities would create the greatest effect, but it's actually glacial melt from more distant ice sheets that contributes to sea level rise in any given coastal city. Think of the way a see-saw works, for a more comprehensible example.
In explaining their research, the scientists used the example of the melting Greenland ice sheet, and the two major coastal cities on either side of the Atlantic: London and New York. As it turns out, the sea level around London will rise the most when the ice sheet covering the northwest corner of the island melts. This, of course, is the corner of Greenland farthest from Buckingham Palace and Trafalgar Square, but that melting ice will redistribute water to the shores of the Thames thanks to the Earth's wobble and the ensuing gravitational changes. Much more of the Greenland ice sheet has the potential to affect New York, but again, it's not the southwest corner; instead, it's entire northern and eastern chunks of the island. If we head to the opposite side of the globe, the ice sheets whose runoff will lead to higher sea levels in Sydney are the ones on the opposite side of the Antarctic continent from Australia.
Since scientists can now pinpoint which ice sheets are likely to affect which cities, coastal city planners and developers can now use that information to their advantage — if they want to.
"Coastal planners need to take into account the large uncertainties of futures sea level rise and built coastal structures in a way that they are easy to adjust in the future with minimal monetary effort," Dangendorf says.
This tool gives the world valuable information about exactly where climate change could have the greatest detrimental effects caused by rising sea levels, but of course what it all comes down to now is what we decide to do to limit it.
"Whether or not humans will be able to limit the sea level acceleration over the coming century and beyond strongly depends on the societies' (and politicians') willingness to reduce CO2 emissions and keep global mean temperature below the Paris targets," Dangendorf tells Bustle.
The ice sheets currently covering Greenland and Antarctica — the same ice sheets that could threaten New York, London, and Sydney with rising sea levels — are the ones that offer the most uncertainty, he explains.
"Whether we (humans) will be able to reach the Paris goals and limit the corresponding sea level rise is open, I think," Dangendorf says, "Which also means that we need to be prepared that our society will not reach the goal."