Agence France-Presse: US President Barack Obama said Saturday that climate change poses the world's biggest single threat.
"Today, there's no greater threat to our planet than climate change," Obama said in his weekly address, which had an environmental theme to mark Earth Day on April 22.
"Climate change can no longer be denied, or ignored," he added, noting that 2014 was the hottest year on record.
The United States is the second largest greenhouse gas emitter after China, and Obama has pledged to reduce US...