Despite the addition of West Campus, the University is still on track to meet its greenhouse gas emissions reduction goals for 2020.

Over the past four years, Yale has reduced its greenhouse gas emissions by 7 percent despite a 5.5 percent increase in the size of the main campus, the Office of Sustainability announced Thursday.

“We worked hard to find ways to achieve those reductions,” University President Richard Levin said in a phone interview.

Main campus emissions dropped to 242,000 metric tons of carbon dioxide equivalents in 2009, down from 260,700 metric tons in 2005, according to the Office of Sustainability.

In 2005, the University announced a goal to reduce its greenhouse gas emissions to 10 percent below 1990 levels by 2020, equivalent to 43 percent below 2005 levels. The University’s original plan targeted emissions produced by its two on-campus power plants and for electricity purchased for the central and medical campuses. Since then, Yale has added reduction goals for emissions from West Campus and for fuel and electricity purchased for buildings not connected to the power plants.

Emissions from the University’s vehicle fleet, employee commuting and employee air travel emissions are being considered for inclusion in the reduction goals.

Levin said he expects Yale to meet its emissions reduction goals by 2020. But plans to expand the University’s size by 10 percent from its current 13.5 million gross square feet will make the process more difficult.

“We have to get down 43 percent by 2020,” Levin said. “It’s harder because the West Campus added so much more territory, but I think we can still make it.”

Keri Enright-Kato, the project manager at the Office of Sustainability, said primary energy efficiency projects, which include lowering heating and cooling costs for buildings, were responsible for most of the decrease in emissions.

A 2005 inventory report of Yale’s emissions revealed that Yale buildings — described as “energy dinosaurs” — use up to 18 times the energy of a comparable educational buildings in Europe and twice the energy of Stanford’s buildings. In recent years, the University has invested in occupancy sensors for many buildings, senior energy engineer Tom Downing said in September.

In addition to reducing heating and cooling costs, Yale has also invested in geothermal and wind energy projects, Downing added.

The recession should not affect the emissions reduction goals, Downing said. While there are initial costs to energy conservation projects, he said, there are significant savings in the long run.

The cost of these projects, Downing added, should still amount to less than one percent of Yale’s annual operating budget over the next 11 years.

Downing also cautioned that the University has a long way to go.

“So far, so good,” Downing said. “[But] we can’t rest on our laurels one bit.”

By 2020, the University plans to reduce its greenhouse gas emissions to 147,000 metric tons of carbon dioxide equivalents.