“Standing by is not an option," Theresa May said.,The UK could become the first major economy in the world to legally require itself to emit net zero greenhouse gas emissions by 2050, according to a new plan unveiled Tuesday which would introduce legislation to amend the country’s 2008 climate change act and include the new midcentury target. The change will go before Parliament on Wednesday and, if enacted, would make the U.K. the first G7 country to take such a step. Environmental groups have expressed some disappointment with May’s plan, which would allow the U.K. to purchase international carbon credits. Doug Parr, chief scientists for Greenpeace UK, told The Guardian the provision amounted to a “loophole” that would shift the burden of full adaptation in part to developing nations."