Todd Stern was U.S. special envoy for climate change from 2009 to 2016.

President Trump is reportedly considering whether to pull the United States out of the Paris climate agreement. That would be a huge mistake, and you don’t have to be a softhearted environmentalist to understand why. Hardheaded analysis based on the interests of national security and U.S. business leads to the inescapable conclusion that remaining in the agreement is in America’s best interest.

Start with national security, and listen to what the Pentagon said in its most recent (2014) Quadrennial Defense Review. After noting that climate change will increase sea levels, temperature and severe weather patterns, the review described “the pressures caused by climate change” as “threat multipliers that will aggravate stressors abroad such as poverty, environmental degradation, political instability, and social tensions — conditions that can enable terrorist activity and other forms of violence.”

Could the Pentagon reason that climate change is important but the Paris agreement is not? No. Climate change is a global threat that can be countered only by global action, so an international regime is essential. After more than 20 years of trying, world leaders, with U.S. leadership, finally established that regime in Paris — strong, flexible, durable and fair. It would be an act of careless disregard for national security to walk away.

As a matter of diplomacy, withdrawing from the Paris agreement would be a stain on the legacies of both the president and Secretary of State Rex Tillerson, an act of diplomatic malpractice. Countries large and small, rich and poor, are deeply invested in Paris because they understand the peril of climate change and know the Paris agreement cannot be truly effective without U.S. engagement. They would see withdrawal as a slap in the face, disrespecting their fundamental interests and, in turn, eroding the United States’ diplomatic capital.

(Daron Taylor/The Washington Post)

This matters. In diplomacy, as in life, if you tell someone, “to hell with what you care about,” don’t expect open arms when you come calling with your own needs. Finally, if any one country stands to profit from the diplomatic capital the United Sates would waste from withdrawal, it’s China, which would depict itself as the hero willing to lead while the United States goes AWOL.

It is unclear whether Tillerson, Defense Secretary Jim Mattis and national security adviser H.R. McMaster have been full-throated, aggressive participants in this debate, but they should be, considering the fateful stakes and their own equities. Now should be a look-in-the-mirror moment for them. They should go to the mat to prevent withdrawal.

As for big business, the corporate community, from oil giants to tech firms to industrial behemoths, is strongly in favor of continued U.S. participation. Business support reads like a who’s who of major players, including DuPont, Hewlett-Packard, Apple, BP, General Mills, Google, PG&E, The Hartford, GE, ExxonMobil, ConocoPhillips, Microsoft, Johnson & Johnson, Cargill, General Motors, Bank of America, Intel, American Express, AT&T, Monsanto, Procter & Gamble, Nike, Coca-Cola, Pepsi, Walmart and NRG Energy.

The reasons for this support are clear. Business leaders are fact-based. There is no room for ideological nonsense in the “C-suite.” Whatever their political party, corporate executives get that climate change is real and most are actively planning business strategy to manage its consequences and limit their own emissions. They see Paris as a balanced agreement they can work with. Recognizing that negotiations on guidelines and rules will continue and that their interests on matters such as intellectual property, trade and transparency could be affected, business leaders care — a lot — about having U.S. negotiators at the table to protect those interests. They also value predictability and hate the political gamesmanship of pulling out of Paris.

Finally, corporate leaders understand that the transition to clean energy presents one of the biggest economic opportunities of this century, that climate change is a major driver of this transition and that the United States is perfectly positioned to lead it with our unmatched culture of innovation. They also know, conversely, that opting out on climate change will undermine this chance to create jobs and wealth.

So my advice to the president is: Listen carefully to the views of your national-security and diplomatic team as well as top business executives. Reach a decision soon, but don’t let anyone tell you that a final decision must be made before the G7 Summit later this month. There is no such deadline; the right decision is better than a hasty one. And keep in mind that — as much as I would be sorry to see any retrenchment — countries can adjust their emissions targets downward. The agreement permits it, and I know because I helped negotiate that flexibility. So don’t pull out — it’s a decision you’d live to regret.