Despite politicians in his own party, like House Speaker Paul Ryan (R-Wis.), calling on him to ditch his plan to impose tariffs on steel and aluminum, President Trump said Monday he's "not backing down."

Last week, Trump surprised everyone by announcing he planned on implementing a 25 percent tax on steel imports and a 10 percent tax on aluminum imports. On Monday, Ryan released a statement saying he was "extremely worried about the consequences" of such a move, and his spokeswoman said there were concerns this would launch a "trade war," with Ryan "urging the White House to not advance with this plan."

A Canadian government official told Reuters that Prime Minister Justin Trudeau called Trump on Monday, letting him know that if he imposed tariffs, it would be a roadblock in ongoing talks on updating NAFTA. Canada is the largest supplier of aluminum and steel to the U.S., and the official said during the call, Trudeau "forcefully defended" his country's workers and industries. Trump was not swayed by Ryan's concern or his conversation with Trudeau; in a meeting at the White House with Israeli Prime Minister Benjamin Netanyahu, Trump said, "We're not backing down. I don't think you're going to have a trade war." Catherine Garcia

President Trump's attempt to block a subpoena from House Democrats has been overruled.

Washington, D.C. District Court Judge Amit Mehta ruled Monday that Trump could not block the House Oversight Committee's subpoena of his financial records from his accounting firm. Mehta also denied Trump's lawyers' request to stay the ruling, meaning the firm is now supposed to hand over eight years' worth of Trump's records, Politico reports.

House Oversight Chair Elijah Cummings (D-Md.) subpoenaed Trump's accounting firm last month as part of Democrats' ongoing attempts to access the president's tax returns. He asked for the records first, but officially subpoenaed them after Trump's former lawyer Michael Cohen testified that the president had inflated his wealth on past financial statements. Trump quickly sued Cummings in return.

Trump's lawyers' argument revolved around claiming Congress' records requests were made for "a law-enforcement purpose" rather than "to work on legislation." Yet in the process, those lawyers implied the Whitewater and Watergate investigations were invalid, leaving Mehta visibily skeptical.

In his Monday ruling, Mehta said "it is not for the court to question whether the committee's actions are truly motivated by political considerations" and ruled in the committee's favor. Trump's lawyers are expected to appeal the decision immediately, setting it up for a decision in a circuit court.

In another subpoena-blocking move, Trump also sued a few banks to stop them from handing over his financial records as well. That suit is still ongoing in a Manhattan court. The Week Staff

President Trump doesn't want former White House Counsel Don McGahn in front of Congress.

The West Winger turned fascinating Mueller report witness was subpoenaed by the House Judiciary Committee for testimony last week, though Trump has publicly said he wouldn't let McGahn attend. McGahn isn't in the administration anymore, but that didn't stop the Department of Justice from issuing a 15-page letter spelling out why McGahn could not legally be called to testify, and it didn't stop Trump from publicly directing him not to testify on Monday.

In the Monday letter to current White House Counsel Pat Cipollone, Assistant Attorney General Steven Engel wrote that "Congress cannot constitutionally compel the president's senior advisers to testify about their official duties." He specifically cited an opinion from former President Bill Clinton's Attorney General Janet Reno, along with precedents from throughout presidential administrations. White House Press Secretary summed up this "bipartisan and constitutional precedent" in a statement, and affirmed that Trump had directed McGahn not to testify.

McGahn still hasn't said if he'll comply with Trump's order, but he faces a pitfall either way. If McGahn ignores Trump and testifies, he'll likely "damage his own career in Republican politics, but also put his law firm" at risk because Trump could tell its GOP clients to "withhold their business," The New York Times explains. But if McGahn steps out on Congress, he could face a contempt charge. Judging by Attorney General William Barr's jokes in the past few days, though, that doesn't seem to matter much. The Week Staff

A group of scientists from Stanford University have proposed a rather unconventional plan to fight climate change.

Their research, published on Monday in Nature Sustainability, concluded that converting methane into carbon dioxide could actually help reduce the warming of the Earth. Methane and carbon dioxide are both so-called "greenhouse gases" — in fact, carbon dioxide is largely responsible for the climate predicament we find ourselves in, the Los Angeles Times explained. But as it turns out, more carbon dioxide might not be as disastrous as we think.

Methane traps much more heat than carbon dioxide, "on a molecule-for-molecule basis." So by converting much of our atmospheric methane into carbon dioxide, we could dramatically reduce the impact of climate change. This process would eliminate about one-sixth of human-caused global warming, while only adding a few months' worth of carbon dioxide to the atmosphere, researchers found.

Of course, the best case scenario would be to stop greenhouse gas emissions entirely, as many scientists have been saying for years. But since that hasn't been a very popular plan, this could be the next best thing. Converting methane into carbon dioxide "would not be a deal-breaker," said Rob Jackson, the study's lead author.

Further research will be required in order to determine whether this plan would be realistic to achieve, but the study's authors are "cautiously optimistic." Learn more at the Los Angeles Times. Shivani Ishwar

Game of Thrones just went out on top by breaking another viewership record.

The series' final episode, "The Iron Throne," drew 19.3 million viewers on Sunday, The Hollywood Reporter writes. This includes 13.6 million people who tuned into the initial 9:00 p.m. airing, as well as those who tuned in for replays and those who streamed the episode online.

This breaks Game of Thrones' previous ratings record — 18.4 million people tuned in last Sunday night to the season's fifth episode, "The Bells." It also sets a new record for HBO itself. The season 4 premiere of The Sopranos previously held the HBO record for biggest linear audience with 13.4 million viewers in 2002, although this was before the rise of streaming.

These impressive viewership numbers Game of Thrones has been drawing each week don't factor in those who watch the episode beyond Sunday night. When including those who watch later, HBO says the eighth season has been averaging 44.2 million viewers, Deadline reports.

Now, the network can only hope to retain these tens of millions of viewers for the forthcoming Game of Thrones spinoffs and that fans' watch hasn't ended quite yet. Brendan Morrow

Of the many mysteries of the beloved former planet Pluto, the likely presence of a liquid ocean under its icy surface is one of the biggest. Now, a new study is offering up a theory on how its ocean has avoided freezing along with the rest of the dwarf planet.

The new research, published on Monday in Nature Geoscience, used data from NASA's New Horizon spacecraft, which collected data from Pluto and its moon Charon back in 2015. That data, combined with computer simulations, determined that Pluto's ocean is probably insulated from the well-below-freezing temperatures of its surface and atmosphere by a layer of gas, CNN reported.

Methane, which would likely be released from Pluto's core back while it was still forming, "would be thick and have low thermal conductivity," which would allow it to act as an insulator between the large amounts of ice on the dwarf planet's surface and the liquid water underneath.

It's possible that similar insulating layers of gas exist elsewhere in our galaxy and beyond, hiding similar oceans from the extreme cold of outer space. This would make "the existence of extraterrestrial life more plausible," said Shunichi Kamata, the study's lead author. Read more at CNN. Shivani Ishwar

Rep. Justin Amash (R-Mich.) is back with another scorching Twitter thread.

On Saturday, Amash, a common critic of Trump, became the first sitting Republican congressmember to call for the president's impeachment. His GOP colleagues predictably had a big problem with that, but Amash still spelled out why he thinks Trump's impeachment defenders "are resting their argument on several falsehoods" in a series of Monday tweets.

According to Amash's reasoning, Trump's defenders "say there were no underlying crimes," "say obstruction of justice requires an underlying crime," claim Trump should be able to end a "frivolous investigation," and attempt to redefine "high crimes and misdemeanors." But there were "many" crimes — not that obstruction of justice charges require them, Amash continues in his thread. The "high crimes and misdemeanors" portion of impeachment proceedings aren't even "defined in the constitution," Amash also said, adding that a president just has to commit "conduct that violates the public trust."

Amash's Saturday tweetstorm has already led Michigan state Rep. Jim Lower (R) to announce he'll primary Amash next year. House Minority Leader Kevin McCarthy (R-Calif.) told Fox News that Amash "just want to have attention," though as CNN's Haley Byrd said in a tweet, that doesn't usually seem to be Amash's top priority. Kathryn Krawczyk