New Delhi, April 22 -- Years ago, after taking an Earth science class, I found myself looking at the world differently. It was the 1990s, and lakes in Wisconsin where I lived at the time were beginning to freeze later in winter and thaw earlier in spring, and flowers seemed to bloom a bit earlier.

That geology class helped me understand the gradual warming that was underway, warming that has accelerated since then.

People are more likely to believe an explanation when they see direct evidence of it. In the US, the percentage of people who recognise that global warming is happening is higher in counties that experienced record high temperatures in the previous decade. But understanding what's happening and why also matters. That's becaus...