The global march toward solving the climate crisis received a major boost from this week's joint announcement by President Barack Obama and Chinese President Xi Jinping that they would commit to unprecedented reductions in their countries’ carbon emissions. This historic announcement from the world’s two largest emitters sets an important precedent for other nations to follow - and follow they must when leaders gather in Paris in 2015 to craft a new agreement on climate action. An agreement in which all countries make internally binding, unconditional emission reduction commitments is absolutely necessary to avoid the grave costs of carbon pollution and create a healthy and sustainable future for all of us. The United States and China have demonstrated that solutions to climate change are at hand and that they have the will to pursue them. It’s time for other global leaders to embrace this notion and make serious commitments to reducing their emissions as well.