You can read the whole brief, attached (which we highly recommend), but the following will give you a sense of where the case is going:
“As practicing scientists who study the earth’s climate
system, we and many in our profession have long
understood that continued human-caused emission of
greenhouse gases—primarily carbon dioxide (CO2), but
also methane (CH4), nitrous oxide (N2O), and
fluorocarbons—would eventually warm the earth's
surface. Most were skeptical that we would see strong
signs of human-induced climate change in our lifetimes.
But by the beginning of this decade, we observed that
global temperatures are rising, plant and animal ranges
are shifting, glaciers are in retreat globally, and arctic sea
ice is retreating. Sea levels are rising and the oceans are
becoming more acidic. To the extent that these changes
result from human alteration of the atmosphere, we know
that they are just the first small increment of climate
change yet to come if human societies do not curb
emissions of greenhouse gases.
The evidence of these changes, though attended by the
uncertainty or caveats that appropriately accompany
scientific knowledge, is nonetheless so compelling that it
has crystallized a remarkable consensus within the
scientific community: climate warming is happening, and
human activities are very likely a significant causal factor.
The nature of this consensus may be obscured in a public
debate that sometimes equates consensus with unanimity
or complete certainty. We are profoundly troubled by the
misunderstanding or misrepresentation of the current
state of knowledge of climate change evident in the United
States Environmental Protection Agency’s (“EPA’s”)
denial of the petition for rulemaking to regulate emissions
of greenhouse gases from mobile sources, Pet. App. A59-
A93, Control of Emissions From New Highway Vehicles
and Engines, 68 Fed. Reg. 52,922, (Sept. 8, 2003), and the
subsequent court of appeals review of that action, Pet.
App. 1-58, Massachusetts v. EPA, 415 F.3d 50 (D.C. Cir.