The U.S. decision not to ratify the Kyoto Protocol in 2001 led to a lack of global leadership in addressing climate change. This was a big blow because the U.S. is a major emitter of greenhouse gases and has the power and resources to make a difference. Without the U.S. on board, other countries may also hesitate to take action. The failure of the Kyoto Protocol was not a surprise to experts, who knew it was hard to agree on emission reduction targets. But the U.S. was seen as the main reason for the Protocol's downfall.