Seth Godin, a marketing guru, passes along this nugget:

One mistake marketers make is a little like the goldfish that never notices the water in his tank. Our environment is changing. Always. Incrementally. Too slowly to notice, sometimes. But it changes. What we care about and talk about and react to changes every day. Starbucks couldn’t have launched in 1970. We weren’t ready.

Of course, sometimes the reason that our perspective on an issue changes is because the thing itself has changed, perhaps imperceptibly. In other cases, it’s because our perceptive apparatus has been modified in some way.

It is a case of the latter, an improvement in scientific precision, which now seemingly shows that diesel-powered otives aren’t as clean as we thought they were. In a piece in today’s WaPo, Juliet Eilperin writes, “For years, government scientists who measure air pollution assumed that diesel otive engines were relatively clean and emitted far less health-threatening emissions than diesel trucks or other vehicles.”

She continues, “But not long ago, those scientists made a startling discovery: Because they had used faulty estimates of the amount of fuel consumed by diesel trains, they grossly understated the amount of pollution generated annually. After revising their calculations, they concluded that the annual emissions of nitrogen oxide, a key ingredient in smog, and fine particulate matter, or soot, would be by 2030 nearly twice what they originally assumed.”

(Note: Washington Post environment writer Juliet Eilperin will host an online discussion today at 11 a.m. ET about the environmental effects of smog and air pollution here. You can submit a question ment ahead of time here.)