Global Warming: The Threat to the Planet
James E. Hansen
Remarks at press conference for American Solar Energy Society
Washington, DC
January 31, 2007
Climate change is happening. Animals know it. Many are beginning to migrate to stay within their climate zones. But some will run out of real estate. They are in danger of being pushed off the planet, exterminated.
Humans are starting to notice climate change. Yet the public is not fully aware of some basic scientific facts that define an urgency for action. Within a decade we must be on a fundamentally different energy path, if we want to preserve a planet resembling the one on which civilization developed. Actions to achieve those changes must start now, within the next few years.
One quarter of the carbon dioxide (CO2) put in the air by burning fossil fuels will stay there “forever”, more than 500 years. So it is imperative to develop technologies that reduce CO2 emissions. That task seems to be staggering, at first glance.
Judging from the history of the Earth, if we want to keep global temperature from exceeding the warmest periods in the past million years, so that we can avoid creating “a different planet”, we must keep atmospheric CO2 from exceeding about 450 parts per million (ppm). Already humans have caused CO2 to increase from 280 to 380 ppm.
The limit on CO2 may be larger if we reduce non-CO2 pollutants, such as methane, black soot and carbon monoxide. There are other reasons to reduce those pollutants, so it is important to do so. But that will only moderately increase the limit on CO2 emissions.
If we fail to keep CO2 within reasonable limits, the most devastating impact, in my opinion, will be future sea level rise. You will hear disagreement among scientists about how much sea level will rise this century if we stay on “business-as-usual”. But the only disagreement is how long it will take the ice sheets to melt.
If we follow “business-as-usual” CO2 emissions, that will cause summer melt on the West Antarctica and Greenland ice sheets. In turn, in my opinion, as a physicist, we would surely get sea level rise this century measured in meters, causing devastation to millions of people. I am very confident of that assessment.
The good news is what you are going to hear today. There is no reason that we must follow business-as-usual. There is tremendous potential in energy efficiency and renewable energies, including solar power, wind energy, biofuels and geothermal energy.
These technologies can put our emissions on a downward path, an alternative scenario, which keeps climate within the range of the past million years. I am sure that more R&D in these technologies, and in next generation safe nuclear power, would be helpful to improve cost, performance, and future options. But technologies ready now, especially energy efficiency, can put us on the needed path.
If anything that I say relates to policy, I am speaking for myself, not as a government employee.
It is important that we move promptly, so that we can avoid the tipping point at which changes such as ice sheet disintegration begin to run out of our control. Prompt action will allow us to be a world-leader in these developing technologies, and thus bolster our economy and provide good high-tech high-pay jobs. Benefits of making carbon emission reduction a top national priority would be widespread, especially for energy independence and national security.
Most people want to exercise responsible stewardship with the planet, but individual actions, in the absence of standards and policies, cannot solve the problem. In my personal opinion, it is time for the public to demand effective leadership from Washington in these energy and climate matters. We owe that to our children and grandchildren, so that they can enjoy the full wonders of creation.
The report is available as a free download. High-quality graphics showing the various emissions reductions and deployment locations are available on the press resources page >>. |
