Following national trends, greenhouse gas emissions linked to climate change continue dropping locally, a government report shows.
The region’s weak economy clearly is playing a role in the decline, a University of Arizona expert said. But it’s not just dollars and cents.
Recent signs of a shift to solar energy and to natural gas from coal burning for electricity also have made a difference, said the UA expert, Derek Lemoine, an assistant professor who specializes in energy and environmental economics.
Some numbers:
- Emissions of carbon dioxide, methane and nitrous oxide, all known to heat up the atmosphere, declined in the Tucson metro area by 3 percent from 2010 to 2012, says the latest greenhouse gas inventory from the regional Pima Association of Governments.
- That follows a 3 percent decline from 2008 to 2010 that the association chronicled in an earlier report.
- Emissions started dropping here in 2007, by 1 percent from 2006, the association said. That’s the year that most economists believe the Great Recession kicked in.
- Nationally, greenhouse gas emissions increased 5 percent from 1990 to 2012, but dropped 5 percent in the 2010-12 period, the PAG report said, quoting Environmental Protection Agency figures. But people in Pima County generated nearly three tons per person fewer emissions annually in 2012 than did the entire U.S. population per person, the PAG report said.
The association releases such reports every two years, based on computer modeling based on data from two years earlier. The report covers emissions from household, business and local government energy use; public and private transportation; and waste disposal.
The 2010-12 emissions decline occurred across many sectors of the local economy: home and industrial energy use, transportation and landfill waste disposal, the report showed. Commercial business was one of the only sectors to show an increase: about 2 percent.
At the same time, the longer-term trend in greenhouse gas emissions in the Tucson area still shows an increase. Emissions in the metro area were 32 percent more in 2012 than in 1990, due to rapid population growth, the PAG report said.
But because of the recent dropoff in emissions, the long-term increase since 1990 is now significantly less than the 46 percent increase recorded in urbanized eastern Pima County from 1990 through 2006.
The local decline in greenhouse gas emissions and the forces underlying it are in sync with four national trends, UA’s Lemoine said:
- The recession made people feel poorer, which decreased energy use.
- High gasoline prices during this period reduced driving. At the same time, those gas prices and federal auto fuel efficiency requirements caused people to buy less gas-guzzling cars, a trend that is now starting to go in reverse due to the recent crash in gas prices.
- The rise of renewable energy sources, especially solar, due mainly to declines in the costs of producing solar panels and to state and federal policies such as tax credits for installation of solar equipment.
- A gradual shift to natural gas from coal-burning to produce electricity, because the production of shale gas through fracking has driven down natural gas prices. Natural gas doesn’t produce nearly as many greenhouse gas emissions as does coal, although the methane that gas generates is considered more potent than coal as a greenhouse gas.
Sorting out how much each of these factors contributed to the decline would be difficult, Lemoine said. But it’s possible to see evidence of each one when looking at various local trends in the economy, energy use and driving habits, he said.
Since not all the trends reducing greenhouse gases stem from the economy, it’s reasonable to conclude that some of these trends could continue or accelerate as the economy recovers, Lemoine added.
“The recession is probably an important piece of the puzzle, but it is unlikely to be the whole puzzle,” he said.
