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Source: heatisonline.org

Hansen: "Time's Up!"


NASA Goddard Institute for Space Studies, May 27, 2007

NASA and Columbia University Earth Institute research finds that human-made greenhouse gases have brought the Earth's climate close to critical tipping points, with potentially dangerous consequences for the planet.

From a combination of climate models, satellite data, and paleoclimate records the scientists conclude that the West Antarctic ice sheet, Arctic ice cover, and regions providing fresh water sources and species habitat are under threat from continued global warming. The research appears in the current issue of Atmospheric Chemistry and Physics.

Tipping points can occur during climate change when the climate reaches a state such that strong amplifying feedbacks are activated by only moderate additional warming. This study finds that global warming of 0.6 degrees centigrade in the past 30 years has been driven mainly by increasing greenhouse gases, and only moderate additional climate forcing is likely to set in motion disintegration of the West Antarctic ice sheet and Arctic sea ice. Amplifying feedbacks include increased absorption of sunlight as melting exposes darker surfaces and speedup of iceberg discharge as the warming ocean melts ice shelves that otherwise inhibit ice flow.

The researchers used data on earlier warm periods in Earth's history to estimate climate impacts as a function of global temperature, climate models to simulate global warming, and satellite data to verify ongoing changes. Lead author James Hansen, NASA Goddard Institute for Space Studies, New York, concludes: "If global emissions of carbon dioxide continue to rise at the rate of the past decade, this research shows that there will be disastrous effects, including increasingly rapid sea level rise, increased frequency of droughts and floods, and increased stress on wildlife and plants due to rapidly shifting climate zones."

The researchers also investigate what would be needed to avert large climate change, thus helping define practical implications of the United Nations Framework Convention on Climate Change. That treaty, signed in 1992 by the United States and almost all nations of the world, has the goal to stabilize atmospheric greenhouse gases "at a level that prevents dangerous human-made interference with the climate system."

Based on climate model studies and the history of the Earth the authors conclude that additional global warming of about 1 degree centigrade (1.8 degrees fahrenheit) or more, above global temperature in 2000, is likely to be dangerous. In turn, the temperature limit has implications for atmospheric carbon dioxide (CO2), which has already increased from the pre-industrial level of 280 parts per million (ppm) to 383 ppm today and is rising by about 2 ppm per year. According to study co-author Makiko Sato of Columbia's Earth Institute, "the temperature limit implies that CO2 exceeding 450 ppm is almost surely dangerous, and the ceiling may be even lower."

The study also shows that the reduction of non-carbon dioxide forcings such as methane and black soot can offset some CO2 increase, but only to a limited extent. Hansen notes that "we probably need a full court press on both CO2 emission rates and non-CO2 forcings, to avoid tipping points and save Arctic sea ice and the West Antarctic ice sheet."

A computer model developed by the Goddard Institute was used to simulate climate from 1880 through today. The model included a more comprehensive set of natural and human-made climate forcings than previous studies, including changes in solar radiation, volcanic particles, human-made greenhouse gases, fine particles such as soot, the effect of the particles on clouds and land use. Extensive evaluation of the model's ability to simulate climate change is contained in a companion paper to be published in Climate Dynamics.

The authors use the model for climate simulations of the 21st century using both "business-as-usual" growth of greenhouse gas emissions and an "alternative scenario" in which emissions decrease slowly in the next few decades and then rapidly to achieve stabilization of atmospheric CO2 amount by the end of the century. Climate changes are so large with "business-as-usual", with additional global warming of 2-3 degrees centigrade (3.6-5.4 degrees fahrenheit) that Hansen concludes " 'business-as-usual' would be a guarantee of global and regional disasters."

However, the study finds much less severe climate change -- one-quarter to one-third that of the "business-as-usual" scenario -- when greenhouse gas emissions follow the alternative scenario. "Climate effects may still be substantial in the 'alternative scenario', but there is a better chance to adapt to the changes and find other ways to further reduce the climate change," said Sato.

While the researchers say it is still possible to achieve the 'alternative scenario,' they note that significant actions will be required to do so. Emissions must begin to slow soon. "With another decade of 'business-as-usual' it becomes impractical to achieve the 'alternative scenario' because of the energy infrastructure that would be in place," says Hansen.


By James Hansen, The Nation, May 7, 2007

(This is an adaptation of a talk delivered February 26 at the National Press Club. Comments relating to policy are Dr. Hansen's personal opinion and do not represent a NASA position).

There's a huge gap between what is understood about global warming by the relevant scientific community and what is known about global warming by those who need to know: the public and policy-makers. We've had, in the past thirty years, one degree Fahrenheit of global warming. But there's another one degree Fahrenheit in the pipeline due to gases that are already in the atmosphere. And there's another one degree Fahrenheit in the pipeline because of the energy infrastructure now in place--for example, power plants and vehicles that we're not going to take off the road even if we decide that we're going to address this problem.

The Energy Department says that we're going to continue to put more and more CO2 in the atmosphere each year--not just additional CO2 but more than we put in the year before. If we do follow that path, even for another ten years, it guarantees that we will have dramatic climate changes that produce what I would call a different planet--one without sea ice in the Arctic; with worldwide, repeated coastal tragedies associated with storms and a continuously rising sea level; and with regional disruptions due to freshwater shortages and shifting climatic zones.

I've arrived at five recommendations for what should be done to address the problem. If Congress were to follow these recommendations, we could solve the problem. Interestingly, this is not a gloom-and-doom story. In fact, the things we need to do have many other benefits in terms of our economy, our national security, our energy independence and preserving the environment--preserving creation.

First, there should be a moratorium on building any more coal-fired power plants until we have the technology to capture and sequester the CO2. That technology is probably five or ten years away. It will become clear over the next ten years that coal-fired power plants that do not capture and sequester CO2 are going to have to be bulldozed. That's the only way we can keep CO2 from getting well into the dangerous level, because our consumption of oil and gas alone will take us close to the dangerous level. And oil and gas are such convenient fuels (and located in countries where we can't tell people not to mine them) that they surely will be used. So why build old-technology power plants if you're not going to be able to operate them over their lifetime, which is fifty or seventy-five years? It doesn't make sense. Besides, there's so much potential in efficiency, we don't need new power plants if we take advantage of that.

Second, and this is the hard recommendation that no politician seems willing to stand up and say is necessary: The only way we are going to prevent having an amount of CO2 that is far beyond the dangerous level is by putting a price on emissions. In order to avoid economic problems, it had better be a gradually rising price so that the consumer has the option to seek energy sources that reduce his requirement for how much fuel he needs. And that means we should be investing in energy efficiency and renewable energy technologies at the same time. The result would be high-tech, high-paid jobs. And it would be very good for our energy independence, our national security and our balance of payments.

But a price on carbon emissions is not enough, which brings us to the third recommendation: We need energy-efficiency standards. That's been proven time and again. The biggest use of energy is in buildings, and the engineers and architects have said that they can readily reduce the energy requirement of new buildings by 50 percent. That goal has been endorsed by the US Conference of Mayors, but you can't do it on a city-by-city basis. You need national standards. The same goes for vehicle efficiency. We haven't had an improvement in vehicle efficiency in twenty-five or thirty years. And our national government is standing in court alongside the automobile manufacturers resisting what the National Research Council has said is readily achievable--a 30 percent improvement in vehicle efficiency, which California and other states want to adopt.

The fourth recommendation--and this is probably the easiest one--involves the question of ice-sheet stability. The old assumption that it takes thousands or tens of thousands of years for ice sheets to change is clearly wrong. The concern is that it's a very nonlinear process that could accelerate. The west Antarctic ice sheet in particular is very vulnerable. If it collapses, that could yield a sea-level rise of sixteen to nineteen feet, possibly on a time scale as short as a century or two.

The information on ice-sheet stability is so recent that the Intergovernmental Panel on Climate Change report does not adequately address it. The IPCC process is necessarily long and drawn out. But this problem with the stability of ice sheets is so critical that it really should be looked at by a panel of our best scientists. Congress should ask the National Academy of Sciences to do a study on this and report its conclusions in very plain language.

The National Academy of Sciences was established by Abraham Lincoln for just this sort of purpose, and there's no reason we shouldn't use it that way.

The final recommendation concerns how we have gotten into this situation in which there is a gap between what the relevant scientific community understands and what the public and policy-makers know. A fundamental premise of democracy is that the public is informed and that they're honestly informed. There are at least two major ways in which this is not happening. One of them is that the public affairs offices of the science agencies are staffed at the headquarters level by political appointees. While the public affairs workers at the centers are professionals who feel that their job is to translate the science into words the public can understand, unfortunately this doesn't seem to be the case for the political appointees at the highest levels. Another matter is Congressional testimony. I don't think the Framers of the Constitution expected that when a government employee--a technical government employee--reports to Congress, his testimony would have to be approved and edited by the White House first. But that is the way it works now. And frankly, I'm afraid it works that way whether it's a Democratic administration or a Republican one.

These problems are worse now than I've seen in my thirty years in government. But they're not new. I don't know anything in our Constitution that says that the executive branch should filter scientific information going to Congressional committees. Reform of communication practices is needed if our government is to function the way our Founders intended it to work.

The global warming problem has brought into focus an overall problem: the pervasive influence of special interests on the functioning of our government and on communications with the public. It seems to me that it will be difficult to solve the global warming problem until we have effective campaign finance reform, so that special interests no longer have such a big influence on policy-makers.

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