Cambridge, Mass. — For a week in November, people across the United States were complaining bitterly about the cold. Record low temperatures were experienced in 43 states; in some northern regions, residents had to dig tunnels to get out of houses engulfed by as much as seven feet of snow.

The freakish cold snap hardly rates in comparison with the devastating floods, fires and droughts that have recently afflicted other parts of the world. But it is another example of how extreme weather has become a global reality, one that is putting the contentious issue of climate change squarely in the middle of everyday conversations.

“Everybody is starting to understand that weather is doing something strange,” said Marilyn Weiner, director of “Extreme Realities,” a documentary produced by her husband, Hal Weiner. The film is making the rounds of American universities and civic groups ahead of its television premiere in December.

The film, narrated by the actor Matt Damon, argues that climate change has geopolitical consequences, which in turn have implications for American national security. Natural catastrophes have stoked wars, political instability, a surge in refugees, even terrorism.