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Can We Still Avoid Dangerous Human-Made Climate Change? (PDF 3.7 Mb; 42 pp)
James E. Hansen
Summary:
The Earth’s temperature, with rapid global warming over the past 30 years, is now passing through the peak level of the Holocene, a period of relatively stable climate that has existed for more than 10,000 years. Further warming of more than 1ºC will make the Earth warmer than it has been in a million years.
“Business-as-Usual” scenarios, with fossil fuel CO2 emissions continuing to increase ~2%/year as in the past decade, yield additional warming of 2-3°C this century and imply changes that constitute practically a different planet. Multiple lines of evidence indicate that the Earth’s climate is nearing, but has not passed, a point or no return beyond which it will be impossible to avoid climate change with far ranging undesirable consequences.
The changes include not only loss of the Arctic as we know it, with all that implies for wildlife and indigenous peoples, but losses on a much vaster scale due to worldwide rising seas. Sea level will increase slowly at first, as losses at the fringes of Greenland and Antarctica due to accelerating ice streams are partly balanced by increased snowfall and ice sheet thickening in the ice sheet interiors. But as Greenland and West Antarctic ice is softened and lubricated by melt-water, and as buttressing ice shelves disappear due to a warming ocean, the balance will tip to rapid ice loss, bringing multiple positive feedbacks into play and causing cataclysmic ice sheet disintegration.
The Earth’s history suggests that with warming of 2-3°C the new equilibrium sea level will include not only most of the ice from Greenland and West Antarctica, but a portion of East Antarctica, raising sea level of the order of 25 meters (80 feet). Contrary to lethargic ice sheet models, real world data suggest substantial ice sheet and sea level change in centuries, not millennia. The century time scale offers little consolation to coastal dwellers, because they will be faced with irregular incursions associated with storms and with continually rebuilding above a transient water level.
The grim “Business-as-Usual” climate change is avoided in an Alternative Scenario in which growth of greenhouse gas emissions is slowed in the first quarter of this century, primarily via concerted improvements in energy efficiency and a parallel reduction of non-CO2 climate forcings, and then reduced via advanced energy technologies that yield a cleaner atmosphere as well as a stable climate.
The required actions make practical sense and have other benefits, but they will not happen without strong policy leadership and international cooperation. Action must be prompt, otherwise CO2-producing infrastructure that may be built within a decade will make it impractical to keep further global warming under 1°C.
There is little merit in casting blame for inaction, unless it helps point toward a solution. It seems to me that special interests have been a roadblock wielding undue influence over policymakers. The special interests seek to maintain short-term profits with little regard to either the long-term impact on the planet that will be inherited by our children and grandchildren or the long-term economic well-being of our country. The public, if well-informed, has the ability to override the influence of special interests, and the public has shown that they feel a stewardship toward the Earth and all of its inhabitants. Scientists can play a useful role
(10 February 2006)
Recommended by Elizabeth Heij in the latest CSIRO (Australia) newsletter:
James E. Hansen, one of the most senior climate scientists in the USA has recently posted this comprehensive presentation made on 10 February 2006 to the New School University, NY, and earlier to the American Geophysical Union.
Nobel Prize winner on global warming: Wake up while you can still smell the roses
Peter Doherty, Sydney Morning Herald
The proof of climate change is convincing, writes Peter Doherty. Now we owe it to ourselves to learn more, and do more, about it.
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…The lesson is that no matter how pervasive the global-warming argument, no matter how good the evidence, the only thing that will persuade many human beings to moderate their behaviour is to make environmentally damaging practices either expensive or illegal.
I’m not an authority on climate change and, though I’m a working experimental biologist, this is too complex an area for me to claim any authoritative position. My professional obsession is with understanding, and hopefully enhancing, immunity to the influenza A viruses.
This has assumed much greater significance as we sit and watch the extremely dangerous H5N1 bird flu spreading throughout the world. Of course, if the H5N1 viruses did jump the species barrier and kill off 30 to 50 per cent of the human population, they would, at least for a time, diminish the population pressure that most consider a primary driver of global warming. The number of people on the planet has increased at least fourfold in the past 100 years, and sixfold from the beginning of the industrial revolution.
…Science is all about measurement, and numbers matter a great deal. What numbers should we look for? The fact atmospheric carbon dioxide levels have been rising rapidly since we started burning large quantities of fossil fuels at the beginning of the industrial revolution seems incontrovertible. Much of the “back information” has come from the measurement of gas levels in, for example, air bubbles trapped in ice formations. Everyone is aware of this, and we should expect to continue seeing such numbers published.
The evidence that mean water and air temperatures around the world are increasing also seems valid, but this can be a confusing area, even for the experts. My naive perception is that cloud effects can cause confounding, and unpredicted, consequences.
…Again, as a society, we must ensure this information is freely available and, as individuals, we need to keep these numbers in our consciousness. If you are a young person reading this, I would like to persuade you that one of the best things you can do is to spend at least a little of your time learning biology and some of the chemistry and physics that affect the environment. It’s your future, and the future of the children who come after you, that we are talking about. Strength comes through knowledge and insight.
Edited extract from Griffith Review 12: Hot Air – How nigh’s the end? (ABC Books, $16.95). www.griffith.edu.au/griffithreview.
Professor Peter Doherty, awarded a Nobel Prize for medicine in 1996…
(6 May 2006)
Al Revere
An interview with accidental movie star Al Gore
David Roberts, Grist
Al Gore is on the campaign trail again, and he actually seems to be enjoying it.
For those who remember his ponderous, consultant-driven bid for president, the idea of Gore enjoying anything about campaigning may seem far-fetched. But this time, the campaign’s not about him; it’s about the issue that has been his consuming intellectual passion for nearly a quarter century: what he calls the “climate crisis.” It’s a perfect union of dedicated wonk and intractable problem.
In the years since his dramatic “loss” in 2000, he has, largely under the media radar, been practicing a form of retail politics: traveling the globe with a computer slideshow on global warming, educating small crowds, trying to boost the public profile of the problem through sheer force of door-to-door persistence.
… Q: There’s a lot of debate right now over the best way to communicate about global warming and get people motivated. Do you scare people or give them hope? What’s the right mix?
AL I think the answer to that depends on where your audience’s head is. In the United States of America, unfortunately we still live in a bubble of unreality. And the Category 5 denial is an enormous obstacle to any discussion of solutions. Nobody is interested in solutions if they don’t think there’s a problem. Given that starting point, I believe it is appropriate to have an over-representation of factual presentations on how dangerous it is, as a predicate for opening up the audience to listen to what the solutions are, and how hopeful it is that we are going to solve this crisis.
Over time that mix will change. As the country comes to more accept the reality of the crisis, there’s going to be much more receptivity to a full-blown discussion of the solutions.
Q: Let’s turn briefly to some proposed solutions. Nuclear power is making a big resurgence now, rebranded as a solution to climate change. What do you think?
A: I doubt nuclear power will play a much larger role than it does now.
Q: Won’t, or shouldn’t?
A: Won’t. There are serious problems that have to be solved, and they are not limited to the long-term waste-storage issue and the vulnerability-to-terrorist-attack issue. Let’s assume for the sake of argument that both of those problems can be solved.
We still have other issues. For eight years in the White House, every weapons-proliferation problem we dealt with was connected to a civilian reactor program. And if we ever got to the point where we wanted to use nuclear reactors to back out a lot of coal — which is the real issue: coal — then we’d have to put them in so many places we’d run that proliferation risk right off the reasonability scale. And we’d run short of uranium, unless they went to a breeder cycle or something like it, which would increase the risk of weapons-grade material being available.
When energy prices go up, the difficulty of projecting demand also goes up — uncertainty goes up. So utility executives naturally want to place their bets for future generating capacity on smaller increments that are available more quickly, to give themselves flexibility. Nuclear reactors are the biggest increments, that cost the most money, and take the most time to build.
(9 May 2006)
