For a second time, the United States has abandoned its promise to fight climate change by reducing greenhouse gas emissions. The reversal comes a year after President Trump signed an executive order to begin the process for U.S. withdrawal from the Paris Climate Agreement. Critics argue that the goals of the Paris Accords, like achieving net-zero emissions, are unrealistic and place an unnecessary financial burden on wealthy nations. The U.S. bears responsibility for more historical greenhouse gas emissions than any other country and accounts for 13% of global emissions each year. Twenty-three wealthy, developed nations have contributed to half of all greenhouse gas emissions over the past 175 years, despite comprising only 12% of the world's population.