Steven Landsburg writes in Slate:

Why parking your car is more environmentally destructive than driving it....It's crazy to feel guilty about dirtying the atmosphere without feeling even guiltier about clogging city streets. You might argue that global warming is a bigger problem than urban congestion, and you might be right. But that's not the issue. The issue is your contribution to global warming versus your contribution to urban congestion. And if you're a typical urban driver, the latter probably dwarfs the former.

Even if you never drive into the city, you're (at least indirectly) still part of the problem. Suburban shopping malls almost everywhere are required to have vastly oversized parking lots that are never close to full.

So, lets get this straight. Your contribution to congestion is greater than your contribution global warming, and this is true whether you are a "typical urban driver" or whether "you never drive into the city." And yet as a whole the problem of congestion is less serious than the problem of global warming.

Landsburg is aware that if you add up bigger numbers, your result will be bigger? I could put it in terms an economist like him can understand by saying that addition is a monotonically increasing function of its arguments.