The people of El Salvador lived in fear of gangs for decades. Then President Nayib Bukele decided enough was enough. What happened next was a miracle, and all it took was la mano dura: an iron fist.

Let’s start with a quick look at what an El Niño is. El Niño and its opposite, La Niña, are climate patterns that influence weather around the world. El Niño tends to raise global temperatures, as we ...