Sea Level in the Year 3000: Why We Should Care

Sometimes a new scientific result is so clearly important that the bottom line needs no explaining — a report showing how ocean acidification threatens food security around the world, for example, or one that ties melting ice in the Arctic to the threat of colder, snowier winters for the U.S.

But it’s tougher to see why anyone should care about the fact that sea level could rise by 3 and a half feet or higher . . . by the year 3000. Nevertheless, that’s what a study published on Tuesday in Environmental Research Letters says — and it is, believe it or not, an important result.

Here’s why: climate scientists have known for a long time that once you pump heat-trapping carbon dioxide into atmosphere by burning coal and oil, it stays there for a thousand years or more. Even if we reduced emissions to zero as of today, Earth would continue warming, and it would stay warm for many centuries to come.

Figure 3. Committed evolution of global sea-level and its components for the constant composition scenarios explained in the report .
Credit: H Goelzer et al 2012 Environ. Res. Lett.

This obviously isn’t going to happen, which makes the paper purely theoretical. Even so, it’s still a useful exercise to ask what the result would be, since it tells us how much climate disruption we’ve already committed to so far. Any greenhouse-gas emissions we create tomorrow, or next week, or over the next 10 years will be on top of that.

Some climate change is already visible in the form of higher seas, rising temperatures and an increase in droughts, heat waves and torrential rainstorms; more is already guaranteed by the emissions we’ve already created; and more still will come from inevitable future emissions.

And in fact, the scientists also ran simulations showing what future sea level rise will look like if we keep emitting gases over the rest of the century: if we don’t cut back at all, the ocean will eventually rise by about 20 feet, and if we cut back moderately, the number comes in at between 6 and a half and 13 feet.

The other thing that makes this study significant is that it’s the first (the researchers believe, anyway), to take all possible sources of sea level rise into account, including the expansion of ocean water as it warms and the melting of land ice from some 200,000 mountain glaciers as well as the ice caps that cover Greenland and Antarctica., a sea level rise analysis by Climate Central that allows you to navigate an interactive map tool and see areas below different amounts of sea level rise and flooding, down to neighborhood. 

The one drawback, however: ice can get into the sea two ways: by melting or by sliding. The computer model the scientists used in this case doesn’t factor in sliding. Over a thousand years, that makes no difference, since even if the ice didn’t slide at all, it would melt dramatically. Over the short term, however, sliding ice could drive sea level up relatively fast over the next century, even if the ultimate level would eventually end up the same.

With a millennium of lead time, it wouldn’t be such a big deal to rebuild cities further inland and get Earth’s population out of the way of rising seas. If the oceans rise 3 feet by the end of this century, as many scientists now expect, the job is drastically tougher.

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