In a recent speech to the United Nations, President Barack Obama said that climate change is a more serious threat than terrorism.

So, why aren’t more Americans terrified?

Parades of panicked politicians talk about the Islamic State as if it were a combination of Hitler’s Germany and Stalin’s Soviet Union, faulting the president for not taking drastic action sooner. But climate change? What’s the hurry?

A majority of Americans (67 percent, in an August Pew/USA Today poll) believe the Islamic State is, like al-Qaida, a “major threat” to our national security. Yet, fewer than half (48 percent) see climate change the same way.

An evaluation of the actual danger posed by the Islamic State is a subject for a later time, but right now the group, while it is vicious and barbaric and wants to hurt us, has limited capability to make that happen on American soil.

Yet, climate change already has invaded the homeland, reducing to ruins the homes of thousands of Americans, turning them into refugees of a sort. In his U.N. speech, Obama listed just a few of the terrors we already have experienced, “Along our eastern coast, the city of Miami now floods at high tide. In our west, wildfire season now stretches most of the year. In our heartland, farms have been parched by the worst drought in generations, and drenched by the wettest spring in our history. A hurricane left parts of this great city (New York) dark and underwater.”

Earth’s rising temperature represents a greater menace than any terrorist “sleeper cell.”

Extreme weather events are not the only danger: As food and water shortages increase and already vulnerable people suffer dislocation and loss, the stability of governments and even civil societies are jeopardized.

In an ironic twist, climate change could have been a factor in the rise of the Islamic State. To be sure, the repressive regime of Bashar Assad, in Syria, is the major reason for the civil war that has fed the group’s rise. However, some experts point also to the social upheaval tied to a widespread drought caused by climate change, the worst since the beginning of agricultural civilization, according to an expert quoted by the Center for Climate and Security, a think tank advised by retired senior military and security officials.