April 19, 2021 7:01 AM By Zachary Sherwood President Joe Biden aims to prove to the world this week that the U.S. has rejoined the international fight against climate change by vowing cuts in greenhouse gas emissions that are both ambitious and achievable. Whether those cuts will be either ambitious enough to reassure skeptical allies or achievable given myriad domestic obstacles is far from a sure thing. The Biden administration is expected to unveil the countryâs new pledge under the Paris climate agreement, known as a nationally determined contribution, before the international climate summit set to begin this Thursday. Heâll have to overcome the major trust deficit run up by former President Donald Trump, who withdrew from the Paris agreement and dismantled domestic policies key to driving the countryâs promised emissions cuts. The past four years revealed how tenuous pledges of U.S government action can be.