Either we reverse President Trump’s climate policies and embrace the Paris Climate Accord quickly or all of America’s coastal cities will be inundated in decades.

That’s the unprecedented conclusion from top scientists in a special new issue of the journal Nature dedicated to Antarctica. They warn that if the Paris Accord fails to reverse emission trends, we will see “economic losses from the flooding of coastal cities [that] exceed US$1 trillion per year” within decades.

What happens to Antarctic is of existential concern to our coastal cities because it contains enough landlocked ice to ultimately raise sea levels more than 100 feet — and we are near a point of no return beyond which collapse of large parts of the Antarctic ice sheet will be unstoppable.

The Nature article that has been getting the most media attention is a detailed analysis of ice loss using three different methods that lead to one grim conclusion: Antarctica lost more than a trillion tons of ice from 2012-2017 — five times the rate of ice loss in the 1990s.


But in another equally important article, “Choosing the future of Antarctica,” a global group of scientists — all winners of the Tinker-Muse Prize for Science and Policy in Antarctica — have taken the unusual step of laying out two specific futures for the world in 2070.

In the low-emissions scenario, the nations of the world work together to continuously slash emissions and achieve the Paris Accord goal of keeping warming “well below 2°C” (3.6°F). That scenario is a relatively benign one where, “Antarctica looks much like it does today.” Sea level rise is a serious problem, but it is both steady and manageable.

In the high emissions scenario, the Paris Accord fails and the world continues with business-as-usual emissions, which results in catastrophic rates of sea level rise. In such a world, “collapse of the West Antarctic Ice Sheet is now irreversible” with “runaway retreat” of key land-based glaciers.

Humanity's choice: In the high emissions scenario, the Antarctic ice sheet destabilizes irreversibly, leading to runaway sea level rise. In the low emissions scenario, sea levels rise modestly, and the rate of rise remains steady. CREDIT: Nature.

The situation in 2070 — roughly 50 years away — is a calamity. Sea levels will have risen nearly half a meter (20 inches, or 1.6 feet) since 2000. Flooding of coastal cities will be costing the world more than $1 trillion a year.

But, even worse, sea level at that time will be rising at an unimaginable rate — and still speeding up. The researchers explain that under this scenario “the total rate of sea level rise is similar to rates during the last deglaciation,” 20,000 years ago, and is averaging 4 to 6 inches (10 to 15 cm) each decade.


How do you adapt to seas rising that rapidly? The simple answer is that by that time the world would already have started abandoning many, if not most, coastal cities.

And this is not even the worst case scenario, which was spelled out last fall in the massive climate report released by the Trump administration, the National Climate Assessment (NCA). In the NCA’s higher scenarios, we would see the impacts Nature imagines for 2070 a full two decades earlier (in 2050).

The central point of both reports is that if we want a high probability of preserving a livable climate and coastal cities for our children and grandchildren, we will have to adopt policies that are considerably more ambitious than Paris — and we need to do that as soon as possible.

With the policies President Trump has embraced — where we don’t even meet the initial Paris targets and we return to promoting fossil fuels — then we face the very realistic prospect that total warming will be 3.5°C (6°F) or higher. And that, as the journal Nature and the rest of the scientific literature makes clear, would be the end of modern civilization as we know it.

It should not be a hard choice.