I don't have a ton to add to the retrospectives and analyses prompted by the 10th anniversary of Hurricane Katrina. I just want to make one small point, something that struck me about Katrina at the time and has been on my mind ever since.

Why not just adapt to climate change?

There is a certain line of thinking that goes like this: Climate change may well be happening, but disrupting the world's economic and energy systems to reduce carbon emissions is too expensive and difficult. Why launch some crazy, probably doomed effort to control the weather? We'll just do what people have always done, which is adapt to the changes.

Here's Rep. Joe Barton (R-TX):

When it rains we find shelter. When it’s hot, we get shade. When it’s cold, we find a warm place to stay. Adaptation is the practical, affordable, utterly natural reflex response to nature when the planet is heating or cooling, as it always is.

I suspect this view is fairly widespread, even among people who might not be able to fully articulate it. Trying to prevent (the worst of) climate change by rapidly reducing global carbon emissions is a huge and politically fraught task with uncertain success. On the other hand, humans have always shown immense resourcefulness in adapting to what nature throws at us. We live in all sorts of places with extreme heat or cold; we live in swamps, on mountains, in deserts, atop tundra; we live in places beset by monsoons and tornadoes and droughts. We've shown that we can adapt to just about anything. Why wouldn't we be able to adapt to whatever climate change brings?

Adapting to the old climate isn't the same as adapting to the new one

The "let's just adapt" view has two key problems.

First is the fact that people are extremely bad at envisioning inclement circumstances they haven't experienced or witnessed. We are generally familiar with natural disasters as rare and extraordinary one-offs. This leads people intuitively to underplay both the severity of the damages climate change threatens and the effort and expense required to prepare for them.

In fact, if climate change remains unchecked, there will be multiple simultaneous disasters: heat waves, droughts in key agricultural areas, rising sea levels and more frequent floods, food shortages, resource conflicts, and mass migrations. Even if we think it's better to adapt to those things, we are certainly nowhere near prepared at present. Getting prepared will be extremely expensive — much more expensive than reducing carbon emissions up front — and just as politically difficult.

But the second problem with the adaptation view is the one Katrina always makes me think about. People often imagine mitigation and adaptation as substitutes, different ways of preventing the same amount of suffering. In fact, mitigation and adaptation are not equivalent. One key way they differ is morally. (I once wrote a longer post about this if you want to dig in.)

Mitigation is altruistic and universalist; adaptation is tribal and local

Put simply, every unit of mitigation (preventing CO2 emissions or pulling CO2 out of the air) helps everyone.

Carbon dioxide is not a local pollutant like smog. Its only negative effects are global; it holds heat in the atmosphere, thus tweaking the entire planet's climate systems.

Similarly, the effects of preventing CO2 emissions are not local but global. Any little bit of climate change that is forestalled helps everyone on the planet and everyone in future generations. (For simplicity's sake, I'm putting aside the "co-benefits" of reducing carbon for now.)

In other words, mitigation is an altruistic, universalist undertaking. Jesus would dig it.

Adaptation is very different. It is not global but local, not universal in impact but highly targeted. A billion dollars of mitigation helps everyone a little bit; a billion dollars of adaptation helps a few people a lot. Specifically, adaptation helps people who have the luck to live in areas that can afford it.

Mitigation slows the spread of inequality; adaptation speeds it up

Among its other ill effects, climate change threatens to exacerbate global inequality; it will hit first and hardest in countries that are already poor, setting back decades of development efforts aimed at raising them to a decent standard of living.

Mitigation helps prevent that acceleration of inequality. Adaptation does not. Adaptation, in fact, is likely to further exacerbate it.

One's ability to adapt is tied directly to one's wealth. Rich countries will be able to do more of it than poor countries; within rich countries, wealthier cities will be able to do more of it than poorer cities and rural areas; and even within wealthy cities, it will be the more affluent residents who have access to the most adaptation and the poor who have access to the least.

It's not just that money can buy more sea walls, drought-tolerant agriculture equipment, private water supplies, and other material aids to adaptation. It's that money also tends to come along with social capital, and one of the most important findings in research on resilience is that social cohesion is just as important as technology. It is the places with strong social networks that tend to have plans, civic institutions, early warning systems, and systems of aid and support that help communities through crisis.

It is socially cohesive communities, in which people are "in it together," that survive disaster and rebuild afterward. Places without those social networks fragment; their suffering becomes a self-reinforcing cycle.

Unfortunately, economic inequality also tends to reduce social cohesion, leading to lack of trust and fewer shared resources. So if the people who support adaptation were being honest, they would acknowledge that perhaps the first and most effective form of adaptation is to reduce economic inequality, to create more cohesive communities defined by fellow-feeling rather than mutual suspicion and resentment. That's true on the local level and also on the national and international level, as resource transfers between and within countries will need to rise markedly to prepare the most vulnerable places for what's to come.

Spoiler alert: That won't happen. The people most likely to be pushing the never-mind-mitigation-we'll-adapt line also tend to be the people most hostile to attempts to reduce inequality.

Katrina shows what adaptation looks like for a segregated city

Which brings us back to Katrina.

The debate over whether the hurricane was strengthened by climate change — which tends to be the focus of any attempt to link the two — is utterly beside the point. We know events like Katrina are going to become more common in coming decades. And what Katrina reveals is that adaptation, in this world at least, is a cruel joke.

The failure of New Orleans to properly prepare for a foreseeable hurricane has been written about a great deal and there's no need to rehash it. One key factor in that tale is the role played by the extraordinary inequality and segregation within the city, which made lawmakers and taxpayers loath to spend money on shared resources.

So when disaster struck, all of New Orleans's submerged dysfunctions rose to the surface. There was shockingly little solidarity. Wealthier white people fled; poorer black people were trapped. The authorities were grotesquely racist in every stage of their response, nowhere more unforgivably than in the way police treated dislocated black residents. It was a nightmare in slow motion and an uncomfortable experience for everyone who watched it unfold on television. This was a wealthy city in the wealthiest country in the world. And this is what happens?

What's it going to look like when climate change brings storms, droughts, and floods to more and more places, more and more often?

Perhaps New Orleans isn't a fair example. It's unique in many ways, not all of them good. New York seemed to handle Hurricane Sandy at least somewhat better. But even there, residents in lower Manhattan made out a whole lot better than residents of Rockaway, Queens. And what city in the world has more social and economic capital than New York?

Real adaptation begins with reducing inequality

US policymakers face two trends, proceeding in tandem. One is accelerating climate change. The other is accelerating economic inequality and racial and class-based segregation.

The trends are not unrelated. Climate impacts will put communities under greater stress even as economic and racial inequality make them more brittle and vulnerable.

Those who oppose climate mitigation in favor of adaptation need explain how they are going to reduce inequality and segregation, not only within US cities but between them, and between nations. Otherwise, their talk of adaptation is little more than a veneer for selfishness: "We'll be fine; everyone else is on their own."

As things stand now, Katrina shows exactly what adaptation looks like: The wealthy escape while the poor suffer.