The debate about sustainable diets has focused on meat production, which requires lots of land and water to grow grain to feed livestock. It also contributes to methane emissions. But the cabinet secretaries with final authority say the 2015 dietary guidelines won't include sustainability goals. David McNew/Getty Images hide caption

itoggle caption David McNew/Getty Images

India's capital is among the most polluted cities in the world, thanks in large part to the growing number of vehicles on its roads. In its just-announced climate change plan, India does not commit to an absolute reduction of its emissions. Instead, it will slow the release of greenhouse gases. DIBYANGSHU SARKAR/AFP/Getty Images hide caption

itoggle caption DIBYANGSHU SARKAR/AFP/Getty Images

Using an instrument they've named the HOLODEC, for Holographic Detector for Clouds, scientists can now see in fine detail the way air and water droplets mix at a cloud's wispiest edge. iStockphoto hide caption

itoggle caption iStockphoto

David Whitcomb of Waynesboro, Va., says he paid a premium for the diesel engine on his 2015 Passat TDI because he thought it would mean fewer emissions. Courtesy of David Whitcomb hide caption

itoggle caption Courtesy of David Whitcomb

Residents of Flint, Mich. (shown here in January), have been protesting the quality and cost of the city's tap water for more than a year. Steve Carmody/Michigan Radio hide caption

itoggle caption Steve Carmody/Michigan Radio