If the city seems a shade smarter this week, it may be because more than 7,000 physicists are in town for a convention.
Members of the American Physical Society are here not so much to calculate the density of the fries within a Primanti Brothers sandwich, though one hopes a few find time to approach that meaty topic. The brains are here, at least in part, to hear and give talks on alternative energy and green buildings.
The David L. Lawrence Convention Center, its six acres of exhibit space flooded with natural light, was the perfect setting. So I took in an early morning session detailing how Pittsburgh went from a smoky, polluted place to one that hosts bass tournaments.
Joel A. Tarr, 74, the Carnegie Mellon University professor with expertise in urban environmental history and an enduring love of his adopted city, began with a slide show: There was a 19th-century woman dumping wastewater beside a well, part of the reason Pittsburgh led the country in typhoid fever in the latter half of the 19th century; there was one of those classic photos of what looked like a night-time scene of Downtown, but only newcomers were surprised to hear that the dark vista was actually a mid-day photograph from 1946.
The building of thousands of miles of sewers in the first part of the 20th century was followed by the strict enforcement of local anti-smoke laws after World War II, "the first major attempt to redo an industrial city," Dr. Tarr said.
What we've done since, and what we do next, might not be as dramatic as the past century's transformation, but could be as important. On the same morning that Dr. Tarr and other speakers outlined Pittsburgh's long makeover, speakers in another part of the city were urging folks to make more modest changes to stop, or at least slow, global warming.
It's suggested that we all replace inefficient incandescent light bulbs with compact fluorescents. They cost more but use less electricity and last longer. If every household in Pittsburgh changes just one bulb, the coal-burning utilities will put 24 million fewer pounds of heat-trapping gases into the atmosphere each year.
That's a huge and incomprehensible figure, and I have no idea how that would compare to the dramatic change in the skies when households shifted from coal heat to natural gas in the late 1940s, but it worries me that we're unlikely to see any difference if we cut back.
So if changing the bulbs and adjusting the hot water heater down to 120 degrees doesn't result in visible savings for consumers, it may be hard to make much headway. Moving the numbers on the Pittsburgh Climate Initiative Web site does not a mass movement make.
On the other hand, if the environmental history of Pittsburgh tells us anything, it's that this town is capable of making visible improvements relatively quickly -- once we get serious about it. We can, for instance, dump slag in a corner of the city for 50 years, have that mountain of waste rise 20 stories tall, and still come back and make it all into something beautiful.
Dr. Tarr's talk ended with the story of Nine Mile Run, the little stream in the valley beneath Squirrel Hill. Frederick Law Olmstead Jr., son of the creator of New York's Central Park, once saw the secluded brook with high wooded banks as a great place for a park. But the Duquesne Slag Products Co. bought 94 acres there in 1922 and proceeded to dump 17 million cubic yards of waste until 1972.
Fortunately, the story didn't end there.
I met Dr. Tarr yesterday morning at the head of the Nine Mile Run Trail. I'd already driven through Summerset at Frick Park, just up the old slag hill from the stream. It's a beautiful, walk-friendly neighborhood with more than 225 porched homes and still growing. Seven years ago, townhouse prices started at $198,000 but the lowest-priced home is now $309,900. Construction continues apace.
Walking the stream that was once an open sewer and is now a seamless extension of Frick Park, we saw a pair of ducks gliding in the water and a perched red-tailed hawk entirely unimpressed by the two humans walking the trail beneath him. The only evidence that we were in a city of more than 300,000 people were the occasional dog walkers and the Department of Public Works earth-mover dredging a bit of the stream for better flow.
"I'm really a city lover," Dr. Tarr said, "but I don't think 'nature' and 'city' have to be separate."
When you consider how far Pittsburgh has come, reducing greenhouse gases 20 percent by 2023 looks like a relative snap.
Brian O'Neill can be reached at firstname.lastname@example.org or 412-263-1947.