A brewing carbon trade war with Europe threatens to scuttle President Joe Biden’s hopes for cross-Atlantic harmony in the fight against climate change. The European Union’s leadership is set to unveil a proposal on Wednesday to tax imports from countries — including the U.S. — that lack aggressive carbon-reducing policies. That move has sparked fears that protectionism will derail hopes for a new era of international climate change cooperation ushered in by Biden’s presidency. The Biden administration is wrestling with how to respond to the new tariff threats, even as it works with the EU to remove trade barriers that former President Donald Trump had slapped onto European goods like steel and aluminum.