One of the hottest spots during the just-concluded Global Climate Action Summit was the private runway at San Francisco International Airport, where SFO spokesman Doug Yakel reports corporate jet traffic was up 30 percent over normal.

Airport sources told us that the carbon-spewing corporate jets nearly filled the landing area’s parking slots and that many had flown in for the conference.

The three-day climate confab drew more than 4,000 elected officials, business executives and environmentalists from around the globe and was aimed at addressing how to lower the carbon emissions responsible for global warming.

The summit was organized by Gov. Jerry Brown, who has been known to fly private.

In 2015, Brown flew with real estate mega-millionaire and major Democratic Party donor George Marcus via private jet to a climate change conference at the Vatican. The next year, the go-green governor jetted off with Marcus for a two-week trip that included stops in Italy, Bulgaria, Romania and Ukraine.

This time, the governor and his wife, Anne Gust Brown, stayed grounded and carpooled in from Sacramento with his security detail.

BART rising: With nary a word of opposition, BART has green-lighted a high-rise housing, office and retail development at its Lake Merritt Station that will probably completely transform the area around Oakland’s Laney College.

“I’m on cloud nine,” BART Board President Robert Raburn said after the board voted 8-0 to enter into an exclusive negotiating agreement with the East Bay Asian Local Development Corp. and Strada Investment Group.

The goal is a transit-oriented development that includes a plaza and a pair of apartment and office high-rises — one 27 stories and the other 21 stories. One tower would be located on the old Metropolitan Transportation Commission headquarters site and the other on what is now the BART station’s parking lot.

In all, the plan calls for 519 units of housing, with 44 percent to be rented out at below market rate. About a fifth of the office space will go to local nonprofits.

The combination of affordable housing, space for nonprofits and a local minority partner in the deal is a veritable trifecta of political correctness.

Plus it supports regional and state climate goals, Raburn said.

One thing the development will not have is parking. The station’s 177 spaces are doomed to extinction, with no significant replacement parking included in the plan.

Oakland Mayor Libby Schaff is already on board, saying the use of a local project partner with a history of lifting up “rather than push out our longtime vulnerable communities” was a winner all around.

Councilman Abel Guillén, whose district includes the station, said that in addition to creating housing, the three-block-project would bring “commercial vibrancy to an area that is need of more businesses.”

The Lake Merritt project is the latest in a series of high-density housing and office developments springing up on BART parking lots throughout the system and changing the face of the Bay Area.

Developments have gone up at the Pleasant Hill, MacArthur and Fruitvale stations, with North Concord next in line.

Tunnel trouble: The big $41 million overhaul of San Francisco’s Twin Peaks Tunnel appears to have been hit with the Muni curse.

The project drew the ire of Mayor London Breed when Muni underestimated the number of buses needed to ferry commuters around the tunnel and track rebuild.

Then a private contractor was struck and killed by a steel beam in early August as work wrapped up inside the tunnel. And after the job was finally completed in late August, there were a couple of glitches with the signals that caused the trains to stop as they entered the tunnel.

“But we cleared them up pretty quickly,” Muni spokesman Paul Rose said.

All was fine until last week, when a contractor’s crew doing “routine work” damaged parts of the tunnel’s automatic control system. The damaged controls meant operators had to move trains through at significantly lower speeds, which in turn slowed down the entire citywide Muni Metro system.

The Municipal Transportation Agency replaced the damaged components, but the problem has continued.

More parts are on order from the manufacturer in Germany.

Commanding presence: The attempt to clean up San Francisco’s U.N. Plaza has almost become an annual event.

It usually starts with the closing down of the plaza’s fountain for cleaning, coupled with an increase in police patrols.

The fountain is being cleaned again, but this time the police have upped the ante by bringing in one of the department’s bus-size mobile command centers and parking it at the Market Street end of the plaza — where it will stay 24/7 for the foreseeable future.

“We are just trying to restore some order to an area where there has been a lot of criminal activity,” Deputy Chief Michael Redmond said.

And it’s not just the command center that’s been brought in: On Friday morning, there were four bicycle cops patrolling the block-long plaza, plus a police sport utility vehicle parked on the City Hall side.

The plaza and its underground Civic Center BART Station have become ground zero for the open drug dealing and drug use in the city. As of Sept. 3, police clocked 588 criminal or quality-of-life incidents within 500 feet of U.N. Plaza this year, resulting in 637 police bookings and citations.

Eric Wong, who has been selling sunglasses at the plaza for 10 years, said he welcomed the rolling substation.

“There used to be booths up and down the plaza, now maybe there are half as many,” Wong said. “People are scared to come here.”

Another park denizen, sitting on nearby steps, declined to give his name, but said he was fine with the increased presence as well.

“It’s cool,” he said, as he took another hit from his morning spliff.

San Francisco Chronicle columnists Phillip Matier and Andrew Ross appear Sundays, Mondays and Wednesdays. Matier can be seen on the KPIX-TV morning and evening news. He can also be heard on KCBS radio Monday through Friday at 7:50 a.m. and 5:50 p.m. Got a tip? Call 415- 777-8815, or email matierandross@sfchronicle.com. Twitter: @matierandross