Another year of extreme weather brought the Philippines a super typhoon and the United States the widest tornado ever observed, deadly wildfires, severe drought and killer floods. President Obama released his plan to battle climate change and its impact on people and wildlife, but the warming planet passed another troubling milestone as heat-trapping greenhouse gases continued to accumulate. Here is a look back at some of the most significant events to affect the environment in 2013. — Lenny Bernstein and Darryl Fears
Carbon dioxideRecorded carbon dioxide levels in the atmosphere reached the unsettling milestone of 400 parts per million on May 10, a level of the heat-trapping gas unseen for 3 million to 5 million years. The burning of fossil fuels is primarily responsible for the increase. In 1958, when scientists began monitoring the carbon dioxide level in the air atop Mauna Loa volcano in Hawaii, it was at 316 parts per million. Other scientists reported, however, that the rate of increase in emissions slowed. Pictured: An electronic screen projects through heavy smog in Shenyang in China’s Liaoning province.Sheng Li/Reuters
Battling wildfires in Portugal and California, Ironman World Championship triathlon, the front line in Raqqa, Syria, record for most people dressed as Rosie the Riveter and more images from around the world.
The contest is accepting entries in one or all of four categories: wildlife, landscapes, underwater and aerials. The grand-prize winner will receive $10,000, publication in National Geographic Magazine and a feature on National Geographic’s Instagram account.