Geoscience Reference
In-Depth Information
for any source; the Senate did not follow suit. The President's climate
change initiative is likely to stir renewed interest in this subject.
I
NTRODUCTION
Over the past four years, the Environmental Protection Agency (EPA) has
begun to address emissions of greenhouse gases (GHGs)
1
from both mobile
and stationary sources, using broad regulatory authority provided by Congress
decades ago in the Clean Air Act. Although Congress has never specifically
directed EPA to regulate emissions of GHGs, the Clean Air Act as enacted in
1970 and as amended in 1977 and 1990 gave the agency authority to identify
air pollutants and promulgate regulations to limit their emission.
From the late 1990s until 2007, EPA and various interested parties
debated whether that authority covered greenhouse gases. This debate was
settled by the Supreme Court in April 2007, in
Massachusetts v. EPA
. In a 5-4
decision, the Court found that greenhouse gases are unambiguously air
pollutants:
The Clean Air Act‗s sweeping definition of ‗air pollutant' includes
‗any air pollution agent or combination of such agents, including any
physical, chemical ... substance or matter which is emitted into or
otherwise enters the ambient air.... ‗... Carbon dioxide, methane, nitrous
oxide, and hydrofluorocarbons are without a doubt ‗physical [and]
chemical ... substances[s] which [are] emitted into ... the ambient air.'
The statute is unambiguous.
2
Since the Court's
Massachusetts
decision, EPA has addressed GHG
emissions in a number of steps, among them:
In December 2009, the agency laid the groundwork for regulations by
finding that emissions of greenhouse gases endanger public health and
welfare, and that GHGs from motor vehicles cause or contribute to
that endangerment.
In May 2010, the agency promulgated GHG emission standards for
model year 2012-2016 cars and light trucks.
In January 2011, the agency began requiring permits and the
imposition of Best Available Control Technology on new stationary
