Before I get to the classic disingenuous conservative argument that is the cornerstone of Goklany’s essay, I must first deal with one of the most astonishing statements ever seen in a serious climate debate. Goklany says:
… there is no guarantee that stabilizing CO2 at 450 ppm would optimize human or environmental well-being. For all we know, stabilizing at 750 may be more optimal.
Wow. The IPCC’s Fourth Assessment says, “As global average temperature increase exceeds about 3.5°C [relative to 1980 to 1999], model projections suggest significant extinctions (40-70% of species assessed) around the globe.” But really, who needs half the current species anyway? After all, Goklany says we should ignore the model projections of the hundreds of leading climate scientists in the world, and the inclusions that every member government signed off on word for word, and instead trust him and a handful of other non-experts that everything will be hunky-dory.
In fact, we know three things with very high certainty:
1. Modern human civilization has developed and thrived in the last 10,000 years during a very narrow window of temperature and CO2 concentrations, a very small fluctuation around 280 ppm.
2. Stabilizing at 750 ppm, even if that were possible, would bring the Earth to temperatures last seen when the planet was virtually ice-free, ultimately leading to sea levels 80 meters higher and the loss of all inland glaciers.
3. A 750-ppm world may be “optimal” in some alternative universe, but would ultimately lead to several billion environmental refugees here on Earth and unimaginable misery for the rest of humanity.
I dare say that Goklany is one of the few climate analysts in the world who has ever posited that 750 ppm of CO2 might be “more optimal” for human or environmental well-being — given that we have been very close to one-third that level for 10,000 years.
Here is a figure from Bob Correll, former head of the Arctic Climate Impact Assessment:
[Click image for larger version]
So I think we do in fact know what the “optimum” temperature window is for modern human civilization — and we are about to find out the unpleasant consequences of breaking through that window.
In the figure, the IPCC (2007) forecast of 2°C to 3°C warming by 2100 is based on stabilizing atmospheric concentrations of CO2 around 550 ppm (a doubling from pre-industrial levels of 280), up from 385 today. The “band of uncertainty” involves the uncertainty about the climate sensitivity to a doubling of CO2 (absent the slow feedbacks). But the longer-term climate sensitivity to a doubling is probably much higher (see here).
In any case, the IPCC makes clear that 750 ppm would result in total warming from preindustrial levels of 4°C by 2100. Now, as an important aside, it is quite doubtful one could actually stabilize at 750 ppm, since work by the National Center for Atmospheric Research and the Hadley Center suggest that carbon cycle feedbacks, like the defrosting of the tundra or the die-back of the Amazon rain forest, would release greenhouse gas emissions that would take the planet to much higher levels. This was a key point that I made in my first post, which neither Manzi nor Goklany refuted.
The last time the earth was 4°C warmer, it was essentially ice-free. Being ice-free would have two rather “nonoptimal” outcomes for humans and the other surviving species. First, long before the two great ice sheets, Greenland and Antarctica, disappeared, we would lose all of the inland glaciers that currently provide most of the water for about a billion people. I’m guessing those folks would probably see that as nonoptimal.
As for sea-level rise, I defy Manzi or Goklany to find a single serious climate expert who thinks the ice sheets would survive 4°C warming. I will address this point in a separate response to Manzi, but Goklany makes the classic mistake of thinking that stabilizing concentrations at 750 ppm means the climate shifts to a new, static state.
In fact, the latest scientific research suggests that what would almost certainly happen at those concentrations of CO2 is that, in the second half of this century, sea levels would start rising several inches a decade, which would quickly become 6 to 12 inches a decade. Ultimately, we would probably hit 20 inches a decade, the rate at which sea levels rose during the last deglaciation. (The rate of warming Goklany thinks could be a new optimum for the planet is comparable to the rate of warming that we had at the end of the last Ice Age.) This rate of sea level rise would continue for centuries, although it would probably be marked periodically by large surges in sea levels as various large chunks of the ice sheets disintegrated.
The point is not whether 450 ppm would optimize human or environmental well-being. The point is to stay as close as is possible to the conditions under which modern civilization developed.
Goklany asks what is the basis for the claim that 450 ppm — or a maximum of 2°C warming or a 50% cut in global greenhouse gas emissions by midcentury — is the “correct target” for humanity. The answer is the entire body of work of the IPCC, along with the statement of the National Academies of Sciences of the leading countries in the world, the American Geophysical Union, the Bali Declaration from more than 200 of the world’s leading climate scientists, and on and on.
Let me end by addressing Goklany’s core point: the classic disingenuous conservative argument that there are better things to spend money on than climate mitigation. This argument assumes 1) there isn’t enough money to do everything whose benefits exceed their cost and 2) conservatives would actually support things like government-funded efforts to deal with “hunger, malaria, unsafe water, and other poverty related problems.”
I worry a lot about those problems and think we should be spending a lot more money on them. I have no doubt we would be spending a lot more money on poverty-related problems if it weren’t for conservatives and libertarians in Congress and the White House who consistently oppose such efforts and cut funding for such programs.
Goklany’s position that there are better things to spend our money on than mitigating climate change is almost identical to the position of Danish statistician Bjørn Lomborg based on the Copenhagen Consensus project. But as one of the authors of the Copenhagen Consensus Project’s principal climate paper, Gary Yohe, very recently wrote, “I can say with certainty that Lomborg is misrepresenting our findings thanks to a highly selective memory”:
The IPCC’s message is clear: climate change is real, compelling and urgent — and we need a concerted, comprehensive and immediate effort to confront it….
Lomborg claims that our “bottom line is that benefits from global warming right now outweigh the costs” and that “[g]lobal warming will continue to be a net benefit until about 2070.” This is a deliberate distortion of our conclusions.
We did find that climate change will result in some benefits for developed countries, but only for modest climate change (up to global temperature increases of 2C — not the 4 degrees that Lomborg is discussing in his piece). But developed countries are relatively prepared to handle climate change’s effects — they tend to be in colder areas, and they have the infrastructure to mitigate severe depletion of resources like fresh water and arable land.
That is precisely why our analysis concluded — and Lomborg ignores — that climate change will cause immediate losses for developing countries and the planet’s most vulnerable, millions of whom are already facing challenges that climate change will exacerbate.
So again, contrary to what Goklany asserts, if we can limit total warming to 2°C — the basis of the 450 ppm target — we could avert the worst outcomes.
As I made clear in my first post, failing to stabilize near or below 450 ppm risks crossing carbon cycle tipping points that will take us to 750 to 1000 ppm and warming of 4°C to 6°C. Notwithstanding a few papers that Goklany has dug up, the overwhelming majority of climate scientists recognize such warming as an unmitigated disaster for humanity — and indeed for all species — for generations to come.