President Trump announced Thursday afternoon that he is withdrawing from the Paris Climate Accord, satisfying a campaign promise while placing the United States on the other side of a nearly unanimous international consensus aimed at minimizing the effects of global warming. The decision immediately set off alarm bells, sparking uproar and uncertainty from the scientific community, corporate executives, the United Nations and even some members of Trump's own party.

Hours after the decision, we spoke with Ben Orlove, a senior research scientist at the International Research Institute for Climate and Society and a professor at the Columbia School of International Public Affairs. He's also the co-director at the Center for Research in Environmental Decisions, and has spent decades studying climate change adaptations and glacier retreat, with additional focuses on urban sustainability, natural hazards and disaster risk, and the loss of iconic landscapes. Still, Orlove tells me that he's "not a doom and gloom kind of guy."

Below, he offers a measured analysis of what the Paris withdrawal means for the Earth, for the country, and for the everyday lives of millions of New Yorkers.

As someone who has dedicated their life to advancing climate science, how painful was this decision for you? The word painful is correct. You have to remember that Trump is isolated in a bubble, and it certainly seems like Bannon and Pruitt won out over other voices from Europe and major corporations and the Department of State and the armed forces. It's quite incredible. It's either that or he's playing to his base. And I guess he's playing the long story of environment verse economy, that we have to pay attention more to the short term employment concerns, and there are so many reasons why that's wrong.

Among the people I've seen and spoken to online, it's clear that some people are discouraged, some people are angry. But there's also a sense of the importance of taking action. This is unfolding in the context of an unprecedented crisis of governance in the United States. And it does seem to me that this has a geopolitical importance. I was struck that the French, German, and Italian response was a single one—they clearly have something prepared. So there's an international reaction that even Trump is going to have trouble ignoring. In terms of the concrete environmental climate questions around energy policy, around preparedness and adaptation, I think there's going to be more action in this country going forward. Personally I wonder whether this is yet another short term strategy of Trump retreating to his shrinking base.

But really I'm not a doom and gloom kind of guy. The Paris Agreement, while never perfect, is a remarkable achievement. You could also say we're going from 195 to 194 countries that signed this agreement. In a way, Trump may not appreciate how powerfully he's marginalized the United States in the international climate arena. He may not understand how important the international climate arena is among all other international negotiations. He may not understand the consequences to the international position of the United States.

Is it possible to measure how significant the US withdrawal will be for the global effort to fight climate change? So the global climate agreements have sought to limit warming to 2 degrees centigrade. The commitments that countries made in Paris would have limited that warming to 3 degrees, which would still be too much, but it also signaled a movement for a periodic review of these commitments that different countries would make to reduce their emissions.

If the US says we're not going to reduce at all, well that's in fact not the case because we're moving heavily from coal to natural gas, as solar and wind are increasing. You could just say: What's going to be the effect of the amount of greenhouse gases in the atmosphere that would have followed if we would have remained in the agreement. That's maybe half a degree centigrade, which is a lot. Still, the rest of the world is advancing on its commitment. They're improving systems of monitoring their greenhouse gas emissions and they're moving toward a system where it's going to become increasingly embarrassing not to participate.

The big question here is: If the United States can be outrageous, who else can be outrageous? Putin has said he's not going to be outrageous. China certainly is not going to be. No European countries are going to be. Japan isn't. Developing countries aren't, with the possible exception of India, which has its own dynamic—though if Trump were to give license to India to return to its heavy dependence on coal, that would also be really bad news. But still those would be just two rogue players in the international climate. I don't see any others weakening. Maybe Australia.

So, yes this is a huge loss, but I think the Paris Agreement was such an impressive accomplishment that most of those 194 countries are going to stick with it. And we're already seeing some mobilization here in the United States—Cuomo's climate alliance with the three governors, de Blasio has said that New York City will also do its part. I think we're going to see more of that going forward.

When de Blasio says that the city will uphold its end of the Paris Agreement, is that something that's actually meaningful? What sort of power do cities have when the federal government refuses to act on climate change? City officials can, in some ways, make decisions that have stronger impacts on emissions than national leaders can. Cities invest in transportation systems. Cities manage a large chunk of real estate and can seek to retrofit their buildings. The other thing is that cities have a long time horizon. There's something about old public buildings that remind people in cities about the long term. New Yorkers know that the city has been here centuries and can look ahead to centuries, when our national government doesn't seem to have that awareness of deep time. The branch of the federal government that has a strong sense of deep time, surprisingly, is the military. They remember early wars, plus the Navy sure knows that all its bases are affected by sea level rise.

There's quite a bit that cities can do to be highly visible as voices, and it's particularly important in North-South alliances. If the mayor of New York talks to the mayor in Durban, South Africa or the mayor of Ho Chi Minh City in Vietnam, there's an immediacy of that connection. There's the sense that urban dwellers face common threats. And really, cities have really been leading climate action for more than a decade now, since the C40 Cities Climate Leadership Group was founded in 2005. They've continually shown easier paths to agreement than the national leaders.

One of the big surprises is that cities are not just acting on adaptation, but on mitigation, on reducing emissions. So you might think that cities would only care about the sea level rise and the heat waves and the droughts in the areas that supply food to them. Because of course no city in the world is a major player in emissions—the United States and China together each account for perhaps 20 percent of the world's emissions. No city accounts for even a tenth of that. And yet, cities are seeking to reduce their own emissions, I think because they recognize the importance of action in this area.

What are New Yorkers doing to push our city to be a leader in fighting climate change? What more should we be doing? New York is striking in two areas. It's already a leader in thinking about climate change because of PlaNYC under Bloomberg—reworked as OneNYC under de Blasio. And it has also been striking in terms of implementation. While many cities gather data, New York has actually moved forward with that data.

For example, New York City is vulnerable to these heavy rain events—we had those heavy rains a few weeks ago—which are growing more frequent because of climate change. Those lead to flooding. They overwhelm our single system that manages both storm drains and sewers. If too much water is treated through that, that means that untreated sewage is going into our rivers. So the city has taken many steps to promote green infrastructure, from expanding parks to larger tree pits to incentives for green roofs to these things called bioswale, which are just kind of planted areas on the sides of streets where there used to be asphalt. Those improve the permeability and mean that more of the water that falls during these heavy storms is going to enter the soil slowly rather than running down into the sewer. And it also helps with heat in the summer, because all of this vegetation cools the city. It's something dispersed so it's not a highly visible project—no one cuts the ribbon for a tree pit, but those million trees that Bloomberg promoted make a difference.

Some of the most polluted air in New York is in the Bronx and the planting of trees actually absorbs some of the particulate matter that all the cars driving up the highways through the Bronx put into the air, which helps address the great unevenness of asthma among children in our city. When people thinks of city parks, they're aware that parks in the most favored neighborhoods seem to attract the most resources—Central Park obviously has deep pockets, or Brooklyn Bridge Park in a gentrified neighborhood. But in terms of this green infrastructure, there's also a lot of it out in Queens and the Bronx. This is reaching out across the Bronx River, where these projects are being helped by local engagement. People often take care of the tree pit on that block, which leads to a local engagement and a local awareness. So, cities end up being one of the key ways of bringing together climate change adaptations and environmental justice.

Another piece of the green infrastructure project is school gardens, which have been shown to help the food patterns in poor neighborhoods. Children who grow up with school gardens are more likely to eat vegetables, to encourage their parents to seek out vegetables and to help address the food desert problem, which is a product of real estate markets really affecting our city. That's another way the green infrastructure projects can directly bring health benefits, and how we're seeing the city move forward with implementation.

This is all unfolding so quickly, and certainly it'll unfold over many time frames. But in the short term there's already some agreement between Cuomo and de Blasio, which we should salute them for, while making sure they follow through. And while they're at it, if they really care about low emission forms of transportation, could they please get together and figure out how fix the subway.