The world is starting to get serious about climate change. This is happening for one major reason: leadership.

U.S. President Barack Obama's announcement this week of a broad set of actions to reduce the greenhouse gas emissions that are changing our climate was very welcome.

His plan, largely based on executive orders, will cut carbon pollution in the United States, prepare the country for the rising number of extreme weather events such as hurricanes and droughts, invest more in clean-energy sources and help lead international efforts to combat climate change and manage its effects.