Rajendra K. Pachauri is chair of the Intergovernmental Panel on Climate Change (IPCC) and director-general of the Energy and Resources Institute of New Delhi, India. Mr. President: You will assume office at a critical period in human history. A series of recent developments has led to a decline in the prestige of the United States globally. To repair this will require a strong commitment to address global problems. The United States has, unfortunately, lost a position of leadership in tackling the challenge of climate change, which, with the release of the IPCC's fourth assessment report and extensive dissemination of its findings, is now seen by the public in most countries as one of the biggest challenges facing human society. The president of the United States, however, has to see this challenge not merely as a burden to be carried in coming up with far-reaching actions to mitigate emissions of greenhouse gases, but also as a unique economic opportunity, irrespective of what the United States does in the next few years to reduce its carbon footprint. The world as a whole is bound to move toward a much lower carbon economy. Those nations and businesses that move toward low-carbon intensity in the technologies, processes, and products they develop will be the leaders in the new low-carbon market that will evolve globally as early as within the next decade. If the United States wants to maintain political and economic leadership, it has to anticipate the development of these market conditions and seize the full benefits of being a leader rather than a laggard. You should announce an enlightened and responsible policy within a week of becoming president. The stakes are so high that nothing short of a bold approach will restore the leadership of the United States in this critical area of human endeavor and global action.