David Travis' work featured on April 18 NOVA
News & Publications, April 10, 2006

In spring 2002, UW-Whitewater climatologist David Travis' research on the impact of jet contrails on Earth's climate received worldwide attention. His research, done following Sept. 11, 2001, when commercial flights were grounded for three days, found that jet contrails are leveling off "diurnal temperature ranges" in certain parts of North America, essentially making average days cooler and nights warmer than normal.

That research, along with contrails' limiting affect on sunlight reaching Earth, will be highlighted in an upcoming NOVA special called "Dimming Sun." The show aired on April 18 on PBS.

The idea behind global dimming is that pollution - particles in the air - are blocking sunlight and causing cooling. The documentary, originally produced for the British Broadcasting Company's well-regarded "Horizons" specials, points out that there are scientists who believe that global warming may be slowed by global dimming.

"It is possible that the solar dimming resulting from buildup of particulate pollutants has partially offset the rate of warming attributed to greenhouse gas increases," Travis said. "This might lead some to speculate that this is a 'good' thing but clearly it's never a good idea to try and reduce one problem through creation of a new one. The numerous respiratory health risks from buildup of particulate pollutants alone justify the need to deal with this problem as soon as possible."

WGBH in Boston said about the upcoming NOVA special: In a stunning investigation, Nova reports on the discovery that the sunlight reaching Earth has been growing dimmer, a big surprise given all the international concern over global warming. At first glance, less sunlight might hardly seem to matter when our planet is stewing in greenhouse gases. But the discovery of global dimming has led scientists to realize that they've miscalculated their models of the climate and how fast it's changing. And if their models are wrong, it means the worst-case warming scenario could be a lot worse than anyone has predicted. To find out what global dimming means for the fate of the planet, "Dimming Sun" reveals the findings of the world's top climate detectives, including an American scientist (David Travis) who found a grim but crucial opportunity on Sept. 11, 2001, when the entire US airline fleet was grounded. Nova unravels this baffling climate conundrum and the implications for Earth's future.

 - Sara Kuhl