Canada must have the latitude to address the national and international concerns posed by climate change, according to a lawyer for the federal government.

"Despite Saskatchewan's view to the contrary, the rapidly increasing accumulation of CO2 in the atmosphere, the grave risks posed by climate change… to do our part to achieve significant reductions that are necessary, as early as possible, are relevant and fundamental to this case," Sharlene Telles-Langdon told court Thursday.

"Failing to address these cumulative dimensions are potentially catastrophic."

Watch Power & Politics' primer on the court challenge

The federal government is presenting its case in support of carbon pricing in Saskatchewan's Court of Appeal, in response to Saskatchewan's legal arguments Wednesday that a carbon tax is unfair, uneven, illegal and violates provincial jurisdiction.

Telles-Langdon told court that the federal government makes laws for peace, order and good government, addressing matters that provinces cannot on their own.

She said Canada is falling short of its international targets to reduce greenhouse gas emissions, and that it must use the peace, order and good government clause in order to try and meet these targets.

When asked by one of the five justices why the federal government does not set its own carbon price and plan across the board, Telles-Langdon said this would be less respectful of provincial jurisdiction.

Lawyer Sharlene Telles-Langdon is representing the federal government of Canada in the Saskatchewan Court of Appeal on Thursday. (CBC News)

More pollution in Saskatchewan per capita, says lawyer

Intervenors such as The Canadian Public Health Association and environmental groups like the David Suzuki Foundation will also argue today in favour of the federal government's plan to put a national price on carbon.

"There's more pollution per person in Saskatchewan than any other part of Canada," Amir Attaran, a professor with the Ecojustice Environmental Law Clinic, told reporters outside of court on Wednesday.

"When the Saskatchewan government says they're doing a lot, they're only doing a lot if last place counts."

Amir Attaran, a professor with the University of Ottawa’s eco-justice environmental law clinic, is counsel for the Athabasca Chipewyan First Nation, one of 16 intervenors in the legal case. (CBC News)

Attaran is counsel for Athabasca Chipewyan First Nation, which is among the intervenors that support the federal government's position.

On Wednesday, lawyers representing the Government of Saskatchewan argued the federal government is violating provincial jurisdiction with its price on pollution.

CBC Saskatchewan reporter Adam Hunter is in court to cover the legal challenge. Follow what's happening through his tweets below. For those on mobile, click here.

However, lawyers for the federal government are expected to argue national carbon pricing should be allowed because climate change is a matter of national concern, and falls under the peace, order and good government clause of the Constitution.

We just don't feel confidence that it's going to help the environment. - Todd MacKay , Canadian Taxpayers Federation

Groups ranging from the Canadian Taxpayers Federation (CTF) to the Agricultural Producers Association of Saskatchewan made submissions on Wednesday against the tax.

"This is going to take so much money from taxpayers," said CTF executive director Todd MacKay. "We just don't feel confidence that it's going to help the environment."

In court, one of the lawyers representing Saskatchewan said the province is not arguing that climate change is real.

"The government of Saskatchewan is not made up of a bunch of climate change deniers," lawyer Mitch McAdam said in his opening remarks to the Saskatchewan Court of Appeal in Regina on Wednesday morning.

"The government recognizes that climate change is a serious issue that has to be addressed and that effective measures are required to deal with greenhouse gas emissions. None of that is in dispute."

The province argues the carbon levy is an unfair, uneven, illegal tax and that it violates provincial jurisdiction.

Thursday