As students, scientists, and faculty at Harvard work to decrease the University’s contributions to global climate change and environmental pollution, the Supreme Court recently called into question part of the Environmental Protection Agency’s regulation of greenhouse gases.

The Supreme Court agreed Tuesday to hear challenges to the EPA’s regulations of greenhouse gas emissions from stationary sources, specifically questioning whether the agency “permissibly determined that its regulation of greenhouse gas emissions from new motor vehicles triggered permitting requirements under the Clean Air Act for stationary sources that emit greenhouses gases.”

In 2007, the Supreme Court heard the case, “Massachusetts v. Environmental Protection Agency,” in which it ruled that the EPA was required by law to regulate greenhouse gas emissions from new motor vehicles if they were found to endanger public health or welfare.

After publishing findings that high concentrations of greenhouse gases in the atmosphere were indeed harmful for the public health and welfare, the EPA set limits on greenhouse gas emissions from both new motor vehicles and stationary sources, such as power plants.

State and industry groups challenged the EPA’s regulations, alleging that there was not sufficient evidence to prove greenhouse gases’ harmful effects, that the agency was overstepping its legal authority by regulating stationary sources, and that the regulations themselves were ineffective.

The District of Columbia Circuit of the US Court of Appeals unanimously rejected these challenges, and the Supreme Court has agreed to review this rejection, but only the specific question of whether the EPA is required to regulate, according to Law School Professor Richard J. Lazarus.

“EPA’s ultimate authority here is not truly at stake in this case,” Lazarus said. “The pathway may be a little bit harder. It might take a little bit longer, but the court denied review of issues that could have blocked that pathway, and it granted review of an issue which doesn’t.”

Daniel J. Jacob, a professor of atmospheric chemistry and environmental engineering, added that the greenhouse gases that are emitted from a motor vehicle’s tailpipe are the same as those from the smokestacks of a stationary source.

“I’ve seen the EPA be more aggressive about going after power plants than going after cars, and the reason for that is that power plants are more easily controlled,” Jacob said. “They are very large sources with very large budgets. You know exactly what is burned and how efficiently they burn. You can monitor the exhaust gases coming out of the stack. You have a whole lot more control.”

While the societal costs of greenhouse gas emissions are difficult to quantify, Jacob said that the scientific community does not doubt that they increase the frequency of damaging weather disasters.

“You can think of climate change as a deck of cards. You pick a card at random and if it’s the ace of spades you get a hurricane,” Jacob said. “Well, take your deck of cards and remove the deuces and play again. Now you have a greater chance of getting a hurricane.”