[I am retroactively inserting this entry in the series for the sake of completeness. Much of the content has been previously posted.]
What happens if we fail to take the following actions to reverse emissions trends starting in 2009?
- Start a cap-and-trade system that sets a serious price for CO2.
- Launch most of the 14 to 16 major mitigation strategies (wedges) described here.
- Begin a global effort to ban new coal plants that do not capture and store their carbon, an effort that quickly brings in China and other developing countries.
Failing to do that, we are headed to 800 to 1000 parts per million (ppm) of atmospheric carbon dioxide.
The idea of stabilizing at, say, 550 or 650 ppm, widely held a decade ago, is becoming increasingly implausible given the likelihood that major carbon cycle feedbacks would go into overdrive, swiftly taking the planet to 800 ppm or more. In particular, the top 11 feet of the tundra would probably not survive 550 ppm (a point I will be blogging about soon) and two other key carbon sinks — land-based vegetation and the oceans — already appear to be saturating. That said, even if stabilizing at 550 ppm were possible, it would probably bring catastrophic impacts and in any case requires implementing some 10 wedges starting now.
At 800 to 1000 ppm, the world faces multiple miseries, including:
- Sea level rise of 80 feet to 250 feet at a rate of 6 inches a decade (or more).
- Desertification of one third the planet and drought over half the planet, plus the loss of all inland glaciers.
- More than 70% of all species going extinct, plus extreme ocean acidification.
LIVING/SUFFERING IN A 1000 PPM WORLD
I listed only three catastrophes that would probably occur at 800 to 1000 ppm because I think those are the most serious and most inevitable. Climate scientists don’t spend a lot of time studying 800 to 1000 ppm, in part because they can’t believe humanity would be so self-destructive as to ignore their increasingly dire warnings and fail to stabilize at well below 550 ppm.
The IPCC notes that if equilibrium CO2-equivalent concentrations hit 1000 ppm, the “best estimate” for temperature increase is 5.5°C (10°F), which means that over much of the inland United States, temperatures would be about 15°F higher.
This increase would be the end of life as we know it on this planet. Interestingly, 5.5°C is just about the temperature difference between now and the end of the last ice age, the difference between a livable climate for human civilization that is well suited to agriculture and massive glaciers from the North Pole down to Indiana.
Is it 100% certain that 1000 ppm would result in the three major impacts above? Of course not. Such certainty is not possible for a climate transition that is completely unprecedented in the history of the human species. That said, the impacts are probably more likely to be worse than not. The catastrophes we can’t foresee may be just as serious, given that, for instance, no one foresaw that at a mere 385 ppm, warming would help spur an infestation is wiping out essentially every major pine tree in British Columbia (see here).
Importantly, even a 3% chance of a warming this great is enough to render useless all traditional cost-benefit analyses that argue for delay or only modest action, as Harvard economist Martin Weitzman has shown. Yet, absent immediate and strong action, the chances of such warming and such effects are not small, they are large — greater than 50%. These impacts seem especially likely in an 800 to 1000 ppm world given that the climate appears to be changing much faster than the IPCC had projected.
The Greenland and Antarctic ice sheets already appear to be shrinking “100 years ahead of schedule” as Penn State climatologist Richard Alley put it in March 2006. Indeed, a number of peer-reviewed articles have appeared in the scientific literature in the past 18 months supporting the real possibility of a 6-inch-a-decade sea level rise.
As for desertification, “The unexpectedly rapid expansion of the tropical belt constitutes yet another signal that climate change is occurring sooner than expected,” noted one climate researcher in December. As a recent study led by NOAA noted, “A poleward expansion of the tropics is likely to bring even drier conditions to” the U.S. Southwest, Mexico, Australia and parts of Africa and South America.”
In 2007, the IPCC warned that 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. That is a temperature rise over pre-industrial levels significantly exceeding 4.0°C. So a 5.5°C rise would likely put extinctions beyond the high end of that range.
And these horrific impacts are certainly not the worst-case scenario. As NASA’s James Hansen explained in a 2004 Scientific American article:
Imagine sea level rise of nearly 20 inches a decade lasting centuries — a trend perhaps interrupted occasionally by large chunks of the West Antarctic ice sheet disintegrating, causing huge sea level jumps in a span of a few years. And imagine that by 2100, we lose all the inland glaciers, which Are currently the primary water supply for more than a billion people. Now imagine what future generations will think of us if we let it happen.
A year ago Science (subs. req’d) published research that “predicted a permanent drought by 2050 throughout the Southwest” — levels of aridity comparable to the 1930s Dust Bowl would stretch from Kansas to California. And they were only looking at a 720 ppm case! The Dust Bowl was a sustained decrease in soil moisture of about 15% (“which is calculated by subtracting evaporation from precipitation”).
Even the one-third desertification of the planet by 2100 scenario by the Hadley Center is only based on 850 ppm (in 2100). Princeton has done an analysis on “Century-scale change in water availability: CO2-quadrupling experiment,” which is to say 1100 ppm. The grim result: Most of the South and Southwest ultimately sees a 20% to 50% (!) decline in soil moisture.
You may be interested in how fast we can hit 1000 ppm. The Hadley Center has one of the few models that incorporates many of the major carbon cycle feedbacks. In a 2003 Geophysical Research Letters (subs. req’d) paper, “Strong carbon cycle feedbacks in a climate model with interactive CO2 and sulphate aerosols,” the Hadley Center, the U.K.’s official center for climate change research, finds that the world would hit 1000 ppm in 2100 even in a scenario that, absent those feedbacks, we would only have hit 700 ppm in 2100. I would note that the Hadley Center, though more inclusive of carbon cycle feedbacks than most other models, still does not model any feedbacks from the melting of the tundra even though it is probably the most serious of those amplifying feedbacks.
Clearly, 800 to 1000 ppm would be ruinous to the nation and the world, creating unimaginable suffering and misery for billions and billions of people for centuries to come. No one who believes in science and cares about humanity can possibly believe that adaptation is a more rational or moral policy than focusing 99% of our climate efforts on staying far, far below 800 ppm and far away from the tipping points in the carbon cycle.
And that means current CO2 levels are already too high. And that means immediate action is required. So our choice is really to stay below 450 ppm or risk self-destruction. That’s why climate scientists are so damn desperate these days. That’s why a non-alarmist guy like Rajendra Pachauri — specifically chosen as IPCC chair in 2002 after the Bush administration waged a successful campaign to have him replace the outspoken Dr. Robert Watson — said in November: “If there’s no action before 2012, that’s too late. What we do in the next two to three years will determine our future. This is the defining moment.” That’s why more than 200 scientists took the remarkable step of issuing a plea at the United Nations climate change conference in Bali. Global greenhouse gas emissions, they declared, “must peak and decline in the next 10 to 15 years, so there is no time to lose.” The AP headline on the statement was “Scientists Beg for Climate Action.”
That is the position of the true “scientific realists.” If the scientific realists (and others) convince the political realists it should be their position, too, then humanity has a chance. If the political realists remain stuck in the past, then we do not.
In Part 1, I explore the immense scale of energy challenges involved in stabilizing at 450 ppm or lower.