What Science Is Telling Us About The Climate-Change Challenge

TUESDAY, SEPTEMBER 29TH, 2009 AT 10:25 AM
What Science Is Telling Us About The Climate-Change Challenge
Posted by John P. Holdren
Climate is changing all across the globe. The air and the oceans are warming, mountain glaciers are disappearing, sea ice is shrinking, the great ice sheets on Greenland and Antarctica are slipping, and sea level is rising. And the consequences for human well-being are already being felt: more heat waves, floods, droughts, and wildfires; tropical diseases reaching into the temperate zones; and coastal property increasingly at risk from the surging seas.

All this is happening faster than was expected. Sea level is rising at twice the average rate for the 20th century. The coverage and thickness of the sea ice in the Arctic at its summer minimum have been shrinking at a pace far faster than the projections of just a few years ago. The average area burned by wildfires in the Western United States annually has increased four-fold in the past 30 years.

We know the primary cause of these perils – it is the emission of carbon dioxide and other heat-trapping pollutants from our factories, our vehicles, and our power plants, and from land clearing. We also know that failure to curb these emissions will bring far bigger impacts in the future than those experienced so far.

But we also know what we can and must do to avoid the worst. We must work together – East and West, North and South– to transform our energy technologies from polluting and wasteful to clean and efficient. We must create new incentives and agreements to accelerate this transformation and to reduce deforestation and other destructive land-use change around the world. And we must invest in adaptation, to reduce our vulnerability to the degree of climate change that can no longer be avoided.

We can do this together. And when we do, we will benefit not only by avoiding the worst damages from climate change, but also by reducing our dangerous overdependence on petroleum, alleviating the air pollution that afflicts our cities, preserving our forests as havens for biodiversity and sources of sustainable livelihoods, and unleashing a new wave of technological innovation – generating new businesses, new jobs, and new growth in the course of creating the clean and efficient energy systems of the future.

How aggressive must these efforts be? The science is increasingly clear that holding the global average temperature increase to no more than 2 degrees Celsius is likely to be essential for keeping climate change to a manageable level. It is likewise clear that having a good chance of meeting this goal requires that global emissions of carbon dioxide and other heat-trapping pollutants should level off by about 2020 and shrink thereafter to something like 50 percent of the current levels by 2050, with continuing declines after that. Economic and political realities, including recognition that emissions from the industrialized countries have caused the largest part of the problem up until now, suggest that the United States and other industrial nations should take the lead in this effort, reducing our emissions to well below current levels by 2020.

President Obama understands this challenge with crystal clarity, and under his leadership the United States is moving rapidly to do what is required to meet it. The Recovery Act has provided the largest boost in history in Federal support for research, development, demonstration, and deployment of clean and efficient energy technologies. New cooperative efforts to help developing countries move in this direction have been launched. And, most importantly, the Administration is working with Congress to get comprehensive energy-climate legislation that, by rewarding energy options that don't harm the climate, will unleash American ingenuity to tackle this challenge in ways that will create jobs and help drive economic recovery while showing the whole world the way toward a climate we can live with.


John P. Holdren is Assistant to the President for Science and Technology and Director of the Office of Science and Technology Policy