Unfortunately, I can not embed The Newsroom video in which Aaron Sorkin tackles climate change (episode 3, season 3). I suggest you watch it and then return here for the analysis. Here's the relevant part of the transcript. McAvoy (Jeff Daniels) is the anchor of the fictional news network. Westbrook (Paul Lieberstein) is the climate expert being interviewed (emphasis added).
McAVOY: Okay. Tell us about the findings in the report that was just released.
WESTBROOK: The latest measurements taken at Mauna Loa in Hawaii indicate a CO2 level of 400 parts per million.
McAVOY: Just so we know what we're talking about, if you were a doctor and we were the patient, what's your prognosis? 1000 years? 2000 years?
WESTBROOK: A person has already been born who will die due to catastrophic failure of the planet.
McAVOY: Okay, can you expand on that?
WESTBROOK: Sure. The last time there was this much CO2 in the air, the oceans were 80 feet higher than they are now. Two things you should know Half the world's population lives within 120 miles of an ocean.
McAVOY: And the other?
WESTBROOK: Humans can't breathe under water.
McAVOY: You're saying the situation's dire?
WESTBROOK: Not exactly. Your house is burning to the ground, the situation's dire. Your house has already burned to the ground, the situation's over.
McAVOY: So what can we do to reverse this?
WESTBROOK: There's a lot we could do.
McAVOY: Good.
WESTBROOK: If it were 20 years ago or even 10 years ago. But now, no.
The obvious idea here is that Westbrook is telling McAvoy and the world that it's all over, that humans are already fucked and actions taken now will be mostly futile. And the equally obvious question is whether Westbrook's supporting evidence is true—the last time there was this much CO2 in the air the oceans were 80 feet higher than they are now.
You will recall that CO2 in the atmosphere reached 400 ppmv (parts-per-million by volume) last year. At that time, a handful of people did indeed think to ask when carbon dioxide last reached that level. Based on current paleoclimate studies, Robert Monroe laid out what is known in general terms.
The Pliocene is the geologic era between five million and three million years ago. Scientists have come to regard it as the most recent period in history when the atmosphere’s heat-trapping ability was as it is now and thus as our guide for things to come.
Recent estimates suggest CO2 levels reached as much as 415 parts per million (ppm) during the Pliocene. With that came global average temperatures that eventually reached 3 or 4 degrees C (5.4-7.2 degrees F) higher than today’s and as much as 10 degrees C (18 degrees F) warmer at the poles. Sea level ranged between five and 40 meters (16 to 131 feet) higher than today.
Estimates covering the entire Pliocene (~5.3 to 2.6 million years ago) are not particularly useful, so let us turn to the relevant part of the AR5, which is one chapter in the latest IPCC report (pdf, see Figure 5.2). Fortunately, we have two very useful slides in a presentation of the relevant paleoclimate results. These slides include what is known as the mid-pliocene warm period (MPWP).
Figure 1 (click to enlarge)
Figure 2 (click to enlarge)
Based on paleoclimate proxy data, Figure 1 shows that carbon dioxide levels in the atmosphere were last at current levels in the mid-to-early Pliocene, approximately 3.3 to 2.6 million years ago. This is a medium confidence result according to the IPCC.
Based on paleoclimate proxy data, Figure 2 shows that sea level was 15 to 20 meters above current levels during the same period. The range is 49-66 feet. There is high confidence that sea level rise did not exceed 66 feet. Many studies have gotten similar results.
Thus we are entitled to conclude that Aaron Sorkin did exaggerate the sea level rise we are committed to. But it is not an exaggeration which makes a difference. 49-66 feet? 80 feet? Who cares?
And now consider the following relevant points:
-
Based on Pliocene proxy data, our best science says that long-run (centuries, millennia) climate sensitivity is higher than that captured by so-called "fast feedbacks" alone.
Climate sensitivity—the mean global temperature response to a doubling of atmospheric CO2 concentrations through radiative forcing and associated feedbacks—is estimated at 1.5–4.5°C. However, this value incorporates only relatively rapid feedbacks such as changes in atmospheric water vapour concentrations, and the distributions of sea ice, clouds and aerosols. Earth-system climate sensitivity, by contrast, additionally includes the effects of long-term feedbacks such as changes in continental ice-sheet extent, terrestrial ecosystems and the production of greenhouse gases other than CO2.
Here we reconstruct atmospheric carbon dioxide concentrations for the early and middle Pliocene, when temperatures were about 3–4°C warmer than preindustrial values to estimate Earth-system climate sensitivity from a fully equilibrated state of the planet. We demonstrate that only a relatively small rise in atmospheric CO2 levels was associated with substantial global warming about 4.5 million years ago, and that CO2 levels at peak temperatures were between about 365 and 415 ppm. We conclude that the Earth-system climate sensitivity has been significantly higher over the past five million years than estimated from fast feedbacks alone. -
Other paleoclimate studies have found the same thing.
"One of our major findings is that the Arctic was very warm in the middle Pliocene and Early Pleistocene [~ 3.6 to 2.2 million years ago] when others have suggested atmospheric CO2 was not much higher than levels we see today. This could tell us where we are going in the near future. In other words, the Earth system response to small changes in carbon dioxide is bigger than suggested by earlier climate models," the authors state.
-
Humans are not nearly done dumping CO2 into the atmosphere. It seems almost certain that we will get to 450 ppmv in the coming decades, which is 35 ppmv higher than the highest estimated value in the Pliocene.
Therefore, if current climate sensitivity is comparable to Pliocene climate sensitivity, we can be confident that over the longer-term we will indeed reach Aaron Sorkin's 80 feet of sea level rise.
I did finally manage to track down the number Sorkin probably used. It comes from Hansen and Sato via the always confused Joe Romm.
Right now, we’re headed towards an ice-free planet. That takes us through the Eemian interglacial period of about 130,000 years ago when sea levels were 15 to 20 feet higher, when temperatures had been thought to be about 1°C warmer than today. Then we go back to the “early Pliocene, when sea level was about 25 m [82 feet] higher than today,” as NASA’s James Hansen and Makiko Sato explain in a new draft paper, “Paleoclimate Implications for Human-Made Climate Change.”
And Hansen and Sato took that number (82 feet) from a 1994 study by Harry Dowsett, et. al. (Science Direct). Dowsett seems to be the only source of that number (e.g., see Pliocene Role in Assessing Future Climate Impacts).
So! We went from one man's estimate of Pliocene sea level directly to The Newsroom on HBO.
And that's all there is to say about that.
My favourite part of this clip is when MacAvoy asks Westwood if 'This is your administration's position on this (issue) or yours, and Westwood replies that 'There isn't a 'position' on this any more than there's a ''position' on the temperature at which water boils....'-
Posted by: Jim Bowron | 11/25/2014 at 12:43 PM