As Hurricane Sandy moved into New York City in 2012, I walked out to the Hudson River and watched the water churn. It was more gray-green than usual, and frothy, and high. Really high. On the Jersey City side, it seemed to be just a foot or two below the retaining walls running along the riverside walk. Later in the day, the Hudson would break above those walls and flood into the streets. Like downtown Manhattan, much of downtown Jersey City was inundated. Parts of Hoboken, just up the river, would stay submerged for days.
Over the next days and weeks, climate change became local for many of us. Global mean projections rattled off in media reports turned into block-by-block discussions of who got flooded and where you could get heat and power. Opinions changed and hardened, and took politicians along with them.
It is that power of the local that Ben Strauss wants to capture. He is CEO of the non-profit organization Climate Central, which has produced a remarkable collection of flood maps that have captivated me ever since I came across them shortly after Sandy. They let you dial in some amount of sea level or global temperature rise, and then view the effect on most any city in the world.
At 1.5 degrees of global temperature rise, which Strauss figures is all but inevitable, downtown Jersey City is a five-block-square island in the middle of a sea. New York City is mostly OK, but Boston and Cambridge look like swimming pools. Miami is reduced to a skeletal-looking set of dry islands just inland from the Atlantic coast.
The maps are compelling, dystopic, and genius. You can walk future shorelines past your your college, your office, and the corner deli. And as Strauss tells me in conversation, what you see is just a conservative estimate of what we’re all in for.
This interview has been edited and condensed for clarity.
Medium: Why build maps of predicted sea level rise?
Ben Strauss: Climate change is often discussed in terms that make it distant in time and place, and abstract and statistical. And that makes it hard for people to engage or grasp the issue. My goal in developing our online maps and tools has been to share climate change as a local issue that matters for specific homes and families.
What’s been the most surprising or notable reaction to the maps?
A lot of artists have used the maps for public art projects or modifying images in ways that are really interesting. We’ve also made presentations to a lot of local officials and coastal stakeholders. Many times, we saw the scales lift from their eyes. They can’t believe what the maps show. I’ve heard stories of diplomats who saw maps of their countries like this for the first time and were profoundly moved and understood the stakes of climate change for their countries in an entirely new way.
Many of the people to whom I’ve shown your maps simply don’t believe them.
This change is unprecedented in human history. None of our institutions or beliefs are conditioned on dealing with any problem like this one, so it’s not surprising that it’s hard for people to digest. We don’t have a near or useful precedent, so it is a big challenge to get through to people.
There is an academically established tendency for climate scientists to understate danger.
How do we know how much sea level rise to expect?
One of the ways we know is by examining the deep geologic record. Over the last couple million years, the planet has cycled through ice ages and warm intervals between them. There are a variety of ways we can estimate how warm those past warm periods were, and how high the sea level got. And when we do that, we see that sea level is extremely sensitive to temperature. That science is continually under further development, so like with any true science there’s never a final word. But one paper two years ago found on the order of seven or eight feet of sea level rise per degree Celsius warming. Other research suggests much greater sensitivity, maybe 10, 15, or 20 feet of sea level rise per degree Celsius warming.
And how do we match CO2 levels to temperature?
Past regional and global temperatures can be inferred from different isotope ratios in ancient microfossils and a range of other substrates. CO2 concentrations are measured in air bubbles trapped in ancient ice samples. Multiple independent methods have been checked against each other, providing a reasonable degree of confidence.
Where is the greatest uncertainty in the models?
I’d say the maximum uncertainty is in the timing. If I were to dump a freezer full of ice out in the middle of Miami, anyone on the planet could tell you in an instant how much of that ice is going to melt. All of it. But it would take a great deal of measurement and scientific expertise to tell you how many ounces of ice would melt each minute and exactly when the ice would finish melting. That is the task facing scientists trying to give projections over the coming decades. Every ton of carbon we put into the atmosphere is like unplugging another freezer full of ice. It doesn’t instantly melt. But the number of freezers we’ve already unplugged is enough to wreck many important coastal cities in the world.
Do climate scientists tend to be conservative in their estimates?
There is an academically established tendency for climate scientists to understate danger. The scientific community tends to be reluctant to be drawn into public argument, or be accused of alarmism. The tragedy of this field is that it’s become so politicized in the United States. I think climate scientists in general really want to share their information and want to be heard by the public, but sometimes the messenger gets shot.
What’s an example of the community being conservative?
The IPCC [Intergovernmental Panel on Climate Change], which is the consensus voice of the global climate science community, historically has ignored most contributions from Antarctica because we didn’t have the science to make a reasonable forecast from Antarctica. Therefore it was just left out, or there was a small footnote that said, “By the way, true sea level rise might be greater because we’re basically not counting Antarctica.” Now, Antarctica holds more than three-quarters of the sea level rise potential in the world. The last IPCC report did more explicitly include Antarctica but we’re just beginning to understand Antarctica a little bit better. We’re going from thick ignorance to early understanding.
What is the most common misconception that you’ve encountered about climate change?
I think the most common misconception about climate change is that scientists disagree whether it’s happening and if humans are causing it. There is extreme consensus on this issue. Like there is for gravity. Now we don’t know everything about gravity. We are still learning. And the same is true for climate change, but it really is not the subject of scientific debate around its fundamentals, or whether it’s happening, or whether it’s us, or whether it’s dangerous.
The tragedy of this field is that it’s become so politicized in the United States.
Why focus on maps of sea level rise, and not drought or other effects of climate change?
I chose to focus on sea level rise because you can localize in advance where the problem is going to be. I think it is uniquely suited for communicating around climate change more broadly. But, other problems can also be localized in different degrees. The increase in weather extremes is different in different places. Risk of drought or inland flood is different in different places. Same for wildfires. And sometimes you might be able to localize a problem by, for example, making a forecast for increased wildfire risk over a broad region and then intersecting that with data on the location and the characteristics of forests within that region in proximity to development. Then you might be able to say something much more local.
Sounds like you have another map cooking.
What do you think is the most dangerous consequence of climate change?
In the near term, the most dangerous threat of climate change is drought and disruption of agriculture, diminishment of food security and political instability and conflict.
What global temperature rise have we irreversibly locked in right now, assuming we never pull CO2 out of the atmosphere?
If we could get to zero emissions tomorrow, I bet we’d end up with maybe a touch less than 1.5 degrees Celsius. We’ve already warmed by more than 1 degree Celsius from a pre-industrial baseline and some amount of warming is being masked by aerosols that are the result of fossil fuel combustion. And that number is probably a few tenths of a degree Celsius. I don’t think it’s well established.
How does that masking work?
It’s a tragic secret about climate change. When you burn coal you actually are producing more cooling power than warming power. Burning a ton of coal cools the earth more than it warms the earth but only for two weeks. The cooling power then rains down out of the atmosphere and the warming power lasts for centuries and millennia. If we were to stop burning all fossil fuel tomorrow, within a few weeks we would lose the shade from all of those dirty particulates and aerosols in the atmosphere that are helping to shade us and we would see a spike in global temperature.
When you say that we’ve locked in 1.5 degrees Celsius, you’re saying that we’ve locked in something like nine feet of sea level rise?
In our fairly conservative analysis, yes.
One of your recent paper abstracts includes the claim that “Without protective measures, revised median relative sea-level projections would by 2100 submerge land currently home to 153 million people.” What kind of rise does that correspond to?
That corresponds to around five feet of sea level rise and that’s using data that grossly overestimate elevation and therefore underestimate the threat. You can probably double or triple the number of affected people. A lot of people live on really low coastal land around the world, especially in Asia. Also, this forecast is of land that would be permanently inundated, not just temporarily flooded.
So we’re talking a displacement of maybe a half a billion people by the end of this century?
Possibly. I should add that a really important paper came out a few weeks ago that showed that the rate of ice loss from Antarctica has tripled over the last couple of decades. We do seem to be waking this sleeping giant. If that kind of acceleration were to continue then we would be talking about on the order of 10 feet of sea level rise by the end of this century.
If we neglect the tripling of the Antarctic melting speed, when is a conservative estimate for when we’ll get our 9 feet of sea level rise from the 1.5 Celsius we’ve already locked in?
I’d say 400 years. That would be quite conservative. It’s very easy to imagine it happening at the end of the next century.
How irreversible is this sea level rise?
There’s some amount of sea level rise that we wouldn’t be able to avoid even by somehow cooling down the planet, because you have these giant ice sheets on Greenland and Antarctica flowing out into the ocean through outlet glaciers, and right now the ice dams and plugs that are blocking those outflow glaciers are disintegrating. Once you destroy those plugs the ice is going to flow out into the ocean even if we cool things down again. It’s just gravity. And we don’t know exactly what the point of no return is for different ice sheets and glaciers.
I’m partial to Boston, and it seems to be in particular danger.
Yes, I think Boston is in more danger from sea level rise than almost any other city in the country. South Florida gets all the press, and it deserves a lot of press, but we overlook the threat to Boston.
How does the threat in Boston compare to that in Miami?
In Miami and south Florida, the bedrock is porous like a sponge so you can’t build effective flood control structures in the long run. In Boston, that’s not the case. The Charles River Dam and another structure are already providing important protection. It’s easy to imagine that there are engineering solutions that will be able to help good chunks of Boston in ways that they won’t be able to help Miami in the long run. But the challenge with a place like Boston is that you can’t just build dikes along the Charles River and have that be the end of the solution, because the river runs through the city.
Would you buy a house in Boston today?
Yes, but I’d look carefully at where and I would think closely about it.
You’d use your own maps.
I certainly would use my own maps. I actually would not buy a house in Boston less than six feet above the local high tide line. And I’d probably go a good deal higher from that.
Is there a U.S. city that will be especially resilient to climate change?
It’s hard to know. I think I would stay out of the Southwest because of water problems. In general, look north. I wouldn’t rule out the coast because there are some places, Seattle, for example, where the hills come down to the water. So the sea level rise will be a problem, but it won’t be an existential problem.
Are we seeing any effects today on the economics of American cities from climate change?
In Miami there’s evidence that sea level rise is already depressing home values in the lowest lying areas. There’s a study by Jesse Keenan, and also a working paper by Asaf Bernstein and colleagues, which doesn’t focus on south Florida specifically. It’s a national analysis that finds a 7% discount in home values nationally that are less than six feet above local high tide line.
What are low-lying coastal property buyers thinking?
I think we tend to expect that eventually when the problem gets bad enough the authorities will do something about it. And that will probably be the case in dense and economically important areas. It probably won’t be the case in a lot of other areas. I don’t think localities can depend on bailouts from state governments or the federal government because essentially this is a problem that’s going to be afflicting everyone on the coasts at the same time. So there aren’t likely to be enough centralized resources to help all those people. Most communities will most likely have to pay their own way out.
That means there’s going to be greater city-to-city inequality.
Absolutely. The classic example that I see is between Miami Beach and Atlantic City. Both are barrier islands with a similar size and similar sea level rise and flooding problems today. Miami Beach is investing almost half a billion dollars from self-taxation to raise roads and put in pumps and Atlantic City is bankrupt and doing almost nothing and there are working-class families whose home values have essentially gone to zero because they flood multiple times a year. But you don’t read about that in the press, usually because it’s a poorer community and it doesn’t have the kind of microphone or cultural cache that a Miami Beach or a New York City does.
Will new technology save us?
I don’t think we need big new technology. I think we basically have the renewable energy technology that we need. To the extent that there’s a missing piece, that’s energy storage through batteries or other means that can help us move the grid to near-100 percent renewable. Carbon removal from the atmosphere would help as well. But I’m skeptical that that will ever be developed with enough efficiency to be utilized at the scale it would need to be.
What do you say to a city whose fate is sealed?
There are cities in this country and in this world which are doomed by sea level rise. But that doesn’t mean that they can’t have productive existences today. Just as all of us can live our own lives productively even knowing that eventually we will die. We are mortal, right? Just because in the long run Miami will not be able to exist doesn’t mean there can’t be a vital Miami today.
Pessimism is an occupational hazard for climate scientists today.
The idea of winding down an entire city is hard to wrap your mind around.
It is. But a lot of other cities in the world are facing the same problem. So that presents an economic and service opportunity. If you can figure out how to do it well, that’s something you can export and help other cities with. Over time I could imagine doing things like transitioning ownership of homes from individuals to corporations or public institutions, larger entities that can distribute risk. But ultimately there would be a wind down in a place like Miami. Other cities may find the means to defend themselves over the long-term.
Do you yourself think about where you or your children or grandchildren should live as the climate changes?
Yeah, sure, to some degree. I don’t like weather that’s too hot and sticky so I expect I’ll be moving north or up someday. But the northeast is alright for now. We just have to look out for cloudbursts. Downpours and flooding are going to be the main climate hazard in most of the northeast. And of course sea level rise if you live in the wrong place near the coast.
What have you learned about how to communicate with the public about climate change?
It’s easy to become focused on the people who strongly deny the existence of climate change. And I don’t focus there. I’m much more interested in people who are in the middle, who are uncertain, who are open to information. That’s where we’re going to make progress over time. I think we can waste a lot of energy trying to fight people who are dug in for ideological or tribal reasons. Also, our approach of focusing on the local dimensions of climate impacts is tuned to reach broader audiences. Because when a serious credible source tells you that your business may be threatened by climate change, or the value of your home may be threatened, then I believe in the quiet and privacy of your own study, you have to take it seriously.
Are you optimistic or pessimistic?
Pessimism is an occupational hazard for climate scientists today. There are things that give me optimism though. I feel that just as there are frightening climate impacts that could occur much more quickly than we expect, there are also climate solutions that can develop much more rapidly than we expect. Things like conversion to a renewable energy economy and the electrification of our transportation through electric vehicles, and other means. The way that the price of solar and wind power has come down recently is promising and I think we could be living with clean energy much more quickly than anyone would have anticipated.
I don’t think we need big new technology. I think we basically have the renewable energy technology that we need.
You trained as an evolutionary biologist. How does that affect your view of our reaction to climate change?
I see human beings as animals as well as people, and animals look out for their self interest. We don’t expect that evolution would produce a species who could forecast the future and change its behavior in a deep way because of that forecast. We expect evolution to produce a species that would eat all of its food if it could and thereby starve its whole population. I don’t therefore on some level expect that we will solve this climate problem as a human species. But I do think we have a chance, and if we do do it it would arguably be the greatest achievement of human civilization and the greatest distinction between humankind and other species.
In other words you expect that a solution will not be found but you would like to be surprised.
Yes. What else can we do but try? What else can we do but put one foot in front of the other and try and walk in a positive and helpful direction? I don’t know when it will reach the destination that we’ve set, but I would lose the meaning in my life if I weren’t trying to make a difference on this issue.
Correction: A previous version of this story misstated the location of Miami. It is on the Atlantic coast.