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For those who follow climate news, James Hansen is working on a paper, called “Global warming in the pipeline,” that examines long-term effects of human-caused climate change, slow feedbacks that, when they are triggered, cause sudden change.
Ice-free earth is one of them, since when that occurs, all the white that reflects solar energy back to space will be gone, all of it being converted into heat, not just some of it. Another “slow feedback” is change in ocean currents, like the Gulf Stream. These changes may be slow to occur (or not), but the results, once present, will be fast — in this case, a sudden drop in European temperatures, making Paris in winter like Montreal.
The paper is in draft at the moment and available for comment. The latest version is here.
Hansen and Sea Level Rise
Hansen announced this version of his paper to his mailing list, where he writes, among other things, that:
The present greenhouse gas forcing is 70% of the forcing that made Earth’s temperature in the Early Eocene Climatic Optimum at least +13°C relative to preindustrial temperature.
and:
There are 60 m of sea level in the Greenland and Antarctic ice sheets between today and an ice-free planet.
In other words, 70 percent of the planet-wide energy imbalance that drove Earth temperature to 13 C [23.4 F] higher than today, is present today.
About sea level rise: For Americans, 60 meters is about 200 feet. (For most of the rest of the world, it’s 60 meters.) Philip Bump, writing in the Atlantic, concurs, by the way; those sea level rise calculations are not in doubt.
The So-Called ‘Asian Century’
The map at the top shows the southeastern US after all ice melts. This is not a local phenomenon; it will happen all around the world. Consider Asia, and in particular, China:
Needless to say, there won’t be an Asian Century.
https://twitter.com/ThomasNeuburger/status/1660036579077881857
Paleoclimate Data
But back to Hansen and his latest paper. It’s a fascinating read, especially if you’re interested in what paleoclimate events tell us about where we’re headed and understand the basic language of these papers, terms like “climate sensitivity.”
I’d like to parse just a few of the main points. From the Abstract:
Improved knowledge of glacial-to-interglacial global temperature change implies that fast feedback equilibrium climate sensitivity (ECS) is 1.2 ± 0.3°C (2σ) per W/m2. Consistent analysis of temperature over the full Cenozoic era — including “slow” feedbacks by ice sheets and trace gases — supports this ECS and implies that CO2 was about 300 ppm in the Pliocene and 400 ppm at transition to a nearly ice-free planet.
Translation: Looking at the full Cenozoic Era — the period from the death of the dinosaurs to today — global temperatures were very high at the start, preventing the formation of ice, much less permanent glaciers. According to Hansen’s latest calculations, the crossing point between an ice-free earth and one where glaciers could form is at roughly 400 ppm CO2.
I’ve marked the graph below with a blue oval to show when this change occurred. Note that the graph’s atmospheric CO2 number, though calculated from earlier data, is in line with Hansen’s current one.
Today’s atmospheric CO2 at Mauna Loa is above 420 ppm, with CO2 rising at a little under 1 percent per year. You don’t have to do the math to do the math.
Back to the Hansen’s Abstract (emphasis added):
Equilibrium global warming including slow feedbacks for today’s human-made greenhouse gas (GHG) climate forcing (4.1 W/m2 ) is 10°C, reduced to 8°C by today’s aerosols.
He explains this later in the paper (Section 6.6):
The human-made climate forcing exceeds the forcing at transition from a largely ice-free planet to glaciated Antarctica, even with inclusion of a large, negative, aerosol climate forcing [“aerosols,” i.e., air pollution, are a climate cooling agent; without them, earth would be hotter by several degrees]. Equilibrium global warming for today’s GHG level is 10°C for our central estimate … including the amplifications from disappearing ice sheets and non-CO2 GHGs (Sec. 4.4). Aerosols reduce equilibrium warming to about 8°C. Equilibrium sea level change is + 60 m (about 200 feet).
In other words, the long-term earth will probably be ice-free, all ice will enter the sea, and all those maps above will describe our world, whatever “our” means by then.
IPCC: Corrupt and Comfortable
Why doesn’t the IPCC worry about this issue?
Discussions between the first author (JEH) and field glaciologists 20 years ago revealed a frustration of the glaciologists with the conservative tone of IPCC’s assessment of ice sheets and sea level. One of the glaciologists said — regarding a photo of a moulin (a vertical shaft that carries meltwater to the base of the ice sheet) on Greenland — “the whole ice sheet is going down that damned hole!” Their concern was based on observed ice sheet changes and paleoclimate evidence of sea level rise by several meters in a century, which imply that ice sheet collapse is an exponential process. Thus, as an alternative to the IPCC approach that relies on ice sheet models coupled to atmosphere-ocean GCMs (global climate models), we made a study that avoided use of an ice sheet model, as described in the paper “Ice Melt.”
I’ll come back to the passages I’ve bolded in the paragraph above.
About the IPCC and the paper “Ice Melt,” Hansen writes:
Ice Melt was blackballed from IPCC’s AR6 report in a form of censorship, as alternative views normally are acknowledged in science. Science grants ultimate authority to nature, not to a body of scientists. In the opinion of JEH [Hansen], IPCC is comfortable with gradualism and does not want its authority challenged. Caution has merits, but with a climate system characterized by a delayed response and amplifying feedbacks, excessive reticence is a danger, especially for young people. Concern about locking in nonlinearly growing sea level rise is amplified in our present paper by the revelation that the equilibrium response to current atmospheric composition is a nearly ice free Antarctica.
The IPCC is indeed “comfortable with gradualism” if judged by what they do, not what they say.
But there’s more. Hansen’s too polite to add, perhaps, that the IPCC is funded by fossil fuel-controlling nations like Saudi Arabia and fossil fuel-controlled nations like the US. This leads them to a kind of censorship that comforts the wealthy at the expense of the victimized poor. (For a look at some of this censorship, see “How Fossil Fuel Governments Control the IPCC,” by yours truly.)
What About the Timing?
What about the timing, you ask? When will this occur? Hansen is unspecific in this paper, but he does mention exponential growth of “ice sheet changes and paleoclimate evidence of sea level rise by several meters in a century” (my emphasis).
It’s true that the rate of increase in CO2 emissions is unprecedented in earth history. It’s also true that very rapid increases in global temperature in the run-up to previous interglacial periods (periods like the one we’re living in now, but earlier) have been steep. Here’s a look at temperatures in the previous interglacial, called the Eemian, compared to the present interglacial, the Holocene. (Note that this graph, past to present, reads from right to left.)
The steepness of the Eemian temperature rise is striking. In addition, at its peak, global temperatures were roughly 3 C [5.4 F] above the Holocene average.
How Much Should We Worry?
So, should we worry about sea level rise of “several meters in a century”? I would answer this way:
1. Everything in the climate prediction world is wrong to the slow side. Things are happening sooner than anyone thought they would. For example, in a paper titled “Deep Adaptation,” professor Jem Bendell writes:
For instance, the IPCC previously assigned a probability of 17% for crossing the 1.5 °C global ambient warming mark by 2030, which underestimated a few key factors, which “bring forward the estimated date of 1.5 °C of warming to around 2030, with the 2 °C boundary reached by 2045” (Xu, et al. 2018). The natural fluctuations in the Pacific “raises the odds of blasting through 1.5 °C by 2025 to at least 10%.”
The latest prediction is a 66 percent chance of crossing at least once above +1.5°C [2.7 F] before 2027. I discussed the tendency to be wrong to the slow side here: “Erring on the Side of Least Drama.”
2. Sea level rise of “several meters in a century” places the problem of relocating coastal cities like New York in this generation. If the estimate is wrong and we do act anyway, it’s undeniably good. If it’s right and we don’t act at all, the country collapses before us as we watch.
3. Even if it takes a century or longer for these predictions to come true, they will come true. No one with power is slowing climate change. They’re offering excuses instead, or appealing to the manly virtues of “energy independence” — meaning, more fracked oil to sell; more money for the rich who control it; more warming for everyone else as the price of that wealth. The day will come when children of earth will scramble like mice from a burning barn, which they set on fire themselves — into a burning world they also lit up. Disbelieve that prediction when our betters act differently.
4. Even if this generation escapes and successfully passes the whole disaster on to its children, how is that not a world-historical act of shame? What does it say of us, if we condemn our kin to chaos and slavery so our own ability to eat more than we need, drive more than we should, consume the goods of the earth just to throw them away, can be preserved till we ourselves are dead?
Nero on his couch of gold deserves more honor than a generation that sells out its own to save a life of excess for those who have it.
But frankly and ultimately, I don’t blame the many — the billions who struggle to walk the earth each day — for the state of our world. I blame the few — the thousands who live to control — for blocking the rest of us from fixing it.
We live to serve the few in so many ways. We’ll serve them in this as well, till we decide to stop.
Published with the permission of Thomas Neuburger. A version of this piece originally appeared in his newsletter God’s Spies.
