WASHINGTON (Reuters) - President Barack Obama announced his nominees to lead a new U.S. push to tackle climate change on Monday, choosing an air quality expert to run the Environmental Protection Agency and a nuclear physicist to head the Department of Energy. In a widely expected move, Obama selected agency veteran Gina McCarthy to replace Lisa Jackson as EPA administrator and scientist Ernest Moniz from the Massachusetts Institute of Technology to take over for Steven Chu as Energy secretary. Obama also announced his choice to lead the White House budget office - Sylvia Mathews Burwell, president of the Walmart Foundation,...