By Matt Owens April 17, 2013
Many people are familiar with James Hansen as the prominent climate scientist who has been consistently arguing for climate action for decades now. He's also well-known as the author of "Storms of my Grandchildren" - some will be very familiar with the boiling oceans story from this book. It comes at the end where he uses a fictional story about an interstellar family sent by their own overheating home planet to Earth (before they realized we had our own greenhouse issues). When the family arrive at Earth's atmosphere however, they don't see the blue and green of water and life - instead they see a yellow haze of dust and clouds. All human life is gone. All life is gone it seems! And surface temperatures are at 100 °C, the boiling point of water - with no oceans in sight.
This shocking illustration of the potential threat of climate change has shaped many people's view on the subject. Now, Hansen says his next edition of the book will rework that closing story so the ocean's haven't boiled off. Other researchers (Goldblatt and Watson) had challenged Hansen's implication about the oceans, concluding that it was probably impossible because of a number of factors. And now Hansen agrees.
Going a step further, he even studied the issue himself, concluding that it is not possible on this planet. Boiling the oceans: no longer a worry! Unfortunately, the point of Hansen's scifi short-story is that “continued - unfettered burning of all fossil fuels will cause the climate system to pass tipping points, such that we hand our children and grandchildren a dynamic situation that is out of their control” -from “Storms of my Grandchildren.”
Hansen made the retraction in a paper released Tuesday night. He's released several similar papers for general public consumption, although they tend to be a bit heavy into the science - even though he tries not to be. The rest of this latest paper, titled “Making Things Clearer: Exaggeration, Jumping the Gun, and The Venus Syndrome” is exceptionally frank and lays out the key uncertainties and unknowns about climate change.
Besides clarifying the point about boiled oceans, Hansen explains the significance of runaway feedbacks. To make the situation easier to understand, he distinguishes between feedbacks that accelerate and those that decelerate. It's the accelerating kind of "positive" climate feedback that we need to worry about because they push warming ahead faster, which causes even more feedback and thus a terrible spiraling warming ensues. These include permafrost and methane hydrate feedbacks. But these are what he calls “mini-runaways” and don't lead to a full-fledged runaway greenhouse effect which technically would include a boiled-off ocean.
These mini-runaways are “mini” for another reason too - because they run out of fuel at some point. Hansen says they could release about 5 GtC (18.35 GtCO2) per year (which essentially is the fuel), comparable to what the current human emissions are now each year (now, about 10 GtC, just a few years ago, we were at 5 GtC). He says that about 5 GtC per year has been released in past times, and led to extreme warming. One such period is known as the PETM (Paleocene–Eocene Thermal Maximum), a period about 20,000 years long when global temperatures rose by 6 °C. If we let our climate reach a warming of 6 °C above pre-industrial conditions, we will certainly trigger at least the permafrost feedback, and probably the Arctic methane hydrates too.
To counteract such runaways, Hansen says we'd need to sequester carbon dioxide out of the air - pull it right out. He cites a study by the American Physical Society that shows this can in fact be done. But, assuming that every country paid for the sequestration in proportion to their share of emissions, the USA would incur a bill equal to about 17% of its GDP. And that expense would go on for decades at least, possibly centuries.
Hansen says that reducing the costs of such an operation would be possible once the process got going, but because of the amount of energy involved, cost reductions would not be significant. What he doesn't say, is that in a world where energy is increasingly valuable, the cost might actually rise - and there could be major sacrifices required to afford such an endeavor. Besides, 17% of GDP is a staggering figure. To add to that, our own carbon emissions will constitute far more than a mini-runaway warming if we just keep letting them go.
Back to the science, Hansen also says that part of his endeavor to evaluate the potential for a complete-runaway warming actually confirmed one possibility about climate sensitivity that we'd been unsure of - what would climate do under extreme warming? The GCM (general circulation models) had shown an increased climate sensitivity at extreme forcing, that is - an accelerated warming per unit increase in greenhouse gases as the extreme levels were reached (e.g. around 1,000 ppm CO2, which we'll hit by the end of this century if we keep this up). This is bad news and yet another reason to act fast.
Finally, Hansen says that if we do let climate change go, parts of the Earth will become so hot, that being outside of an air-conditioned space would be lethal. The human body wouldn't be able to cool itself through any amount of sweating, rest, shade, or breeze. As of today, there are almost no places on Earth that ever get this way. The recent heat wave in Australia indicates such events might not be far off however. And while he doesn't go into the details, he mentions species extinction, which he's examined before, as have others who've essentially reached the unsurprising conclusion that with global climate change of 6 °C per century, a large portion of all species would go extinct. The ramifications of such a rapid mass-extinction are very uncertain, but could be quite lethal for humans as well (to put it bluntly). None of what's in this latest paper is controversial, or really new - except for the bit about increased sensitivity. And there's a full research paper on that topic planned to hit the presses this summer.
What was nice to read, was the explicit confirmation that we're not yet beyond tipping the scales and triggering a runaway in Hansen's opinion, either from the permafrost or the methane hydrates. And yes, we will see some emissions grow from both these sources and others no matter what, but as my synthesis of the research indicates, those emissions probably won't get going full-tilt and would wind down next century - if we do act. This view apparently is also shared by Hansen, although he doesn't go into details.
Yet, the narrow time frame to act is not at all reassuring and serious doubts remain. Namely, will we convince our fellow citizens and policy makers to act with us? We must bring our greenhouse gas emissions to a halt and we must start this process within 10 years and bring global emissions close to zero by about 2040. If we don't, we absolutely will have mini-runaways on top of the other warming. Or, as I've pointed out elsewhere, someone or some agency may take the initiative, and reduce our emissions for us.
Bottom line: we're only partly screwed - it looks promising that we can still “unscrew” ourselves and save most of the planet from extinction - and God help us - most of the people now living on it from starvation. But we've really got to start now. It would be better if we started earlier rather than later to make real policy change really happen - and that's what it's going to take - policy - we can make it real, but it takes time to convince people - so we need to start now - and if you care, you need to act - now (and try to pull in those people you know still on the fence).
Hansen closes his paper by listing his favorite activist groups: 350.org, Our Children's Trust, and CitizensClimateLobby.org. You can sign up with 350.org to get their emails about upcoming events and action - they took the lead organizing the excellent climate-rally in DC earlier this year. You can also sign up for the Fairfax Climate Watch Newsletter (on the right hand column of this page), and we'll keep you in the loop about climate developments and climate action.