| Climate change is a monumental problem. I characterize it by saying that it is our species' greatest confirmed threat. Nuclear war? Possible but unlikely in any given decade. An asteroid/comet collision with Earth resulting in an extinction level event? Possible but unlikely in any given decade. I would, however, rate the asteroid/comet threat above nuclear war. One day, the former will happen, we just don't know when; the latter can be held off and eliminated based on our own decision making. In a way, climate change combines aspects of both of these threats. Climate change (at a level that will challenge our civilizations) is both possible and likely in a given decade; it is currently happening and its magnitude will only increase each decade during the rest of this century unless and until we decide to do something about it.
It should not be surprising then that, given the sheer magnitude of catastrophic climate change, solutions addressing it are also monumental in scale. That's the root of why so many climate change activists have been calling for a "climate-Manhattan Project" or a "climate Apollo Project". My view on climate change actions has shifted somewhat from thinking a bunch of personal actions will eventually accumulate enough inertia to reduce our climate forcing to recognizing that the number of actions will require large-scale policy shifts - something that requires governments to act. That's why the U.S. Senate's recent failure to seriously address this developing crisis is so maddening. The status quo approach to policy will not work with climate change, mostly because we're dealing with physical systems that respond to forcing, not people's tender egos and greed.
|Within the past 10 years, one of the viable proposals for addressing climate change was put forth by Stephen Pacala and Robert Socolow in the journal Science back in 2004: "Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies". An early paragraph of that paper reads:
Humanity already possesses the fundamental scientific, technical, and industrial know-how to solve the carbon and climate problem for the next half-century. A portfolio of technologies now exists to meet the world's energy needs over the next 50 years and limit atmospheric CO2 to a trajectory that avoids a doubling of the preindustrial concentration. Every element in this portfolio has passed beyond the laboratory bench and demonstration project; many are already implemented somewhere at full industrial scale. Although no element is a credible candidate for doing the entire job (or even half the job) by itself, the portfolio as a whole is large enough that not every element has to be used.
<!--more-->Their proposal therefore looks at avoiding a doubling of CO2 concentrations in the atmosphere from ~280ppm to 500 ± 50ppm. For reference, 2009's average atmospheric CO2 concentration was 387.35ppm. We would easily pass 500ppm before the end of this century if we adhered to the IPCC's B1 and A1T emission scenarios. As I've written before, however, we're on the "bad side" of the IPCC's range of scenarios: we were closer to the A1B and A1F1 scenarios in the past decade (with the exception of 2009, which is projected to be lower due to the 2009 Great Recession) than the B1 and A1T scenarios. All that said, 500ppm isn't a viable target to aim for anyway. NASA's James Hansen described why 325-355ppm is the range that humanity should be striving for if we want to maintain our civilization(s) in a recognizable fashion. So my discussion will start with Pacala and Socolow's initial proposal in an attempt to demonstrate how difficult it will be to target 500ppm while keeping in mind that 500ppm target is inadequate. In a future post, I will leverage other writings to illustrate how much more needs to be done to get back down to 350ppm as quickly as possible.
Let's start with some basic definitions. Stabilization is used to describe the flat trajectory of fossil fuel emissions: 7GtC/year. Business-as-usual (BAU) conditions are represented by a linear increase in emissions until 2054. A stabilization wedge, also commonly referred to as a stabilization triangle, "represents an activity that reduces emissions to the atmosphere that starts at zero today and increases linearly until it accounts for 1 GtC/year of reduced carbon emissions in 50 years." So it's emissions that we actively prevent from going into the atmosphere. To get from the BAU case to the stabilization case then requires a cumulative total of 25GtC over the 2004-2054 period. In order to get to 500ppm concentration at the end of 100 years, emissions would have to be held constant for 50 years, then slashed by 2/3 for the following 50 years! But there are critical problems with this preliminary approach. 500ppm isn't the goal we should be shooting for and emissions have only increased since 2004, which means it will take even more effort to get back down to 7GtC/year, then even more effort to slash emissions in that last 50-year time period!!
With definitions in mind, we can move onto specific wedge proposals. Pacala and Socolow identify 15 (see below) that are already present at an industrial scale and could be further deployed to account for at least 1 wedge worth of emissions. They take care to point out that "most readers will reject at least one of the wedges listed here, believing that the corresponding deployment is certain to occur in BAU, but readers will disagree about which to reject on such grounds." Keep that in mind as you peruse the following list:
- Increase fuel economy for 2 billion cars from 30 to 60 mpg
- Decrease car travel for 2 billion 30-mpg cars from 10,000 to 5,000 miles per year
- Cut carbon emissions by one-fourth in buildings and appliances projected for 2054
- Produce twice today's coal power output at 60% instead of 40% efficiency (compared with 32% today)
- Replace 1400 GW 50%-efficient coal plants with gas plants (four times the current production of gas-based power)
- Introduce CCS (Carbon Capture & Sequestration) at 800 GW coal or 1600 GW natural gas (compared with 1060 GW coal in 1999)
- Introduce CCS at plants producing 250 MtH2/year from coal or 500 MtH2/year from natural gas (compared with 40 MtH2/year today from all sources)
- Introduce CCS at synfuels plants producing 30 million barrels a day from coal (200 times Sasol), if half of feedstock carbon is available for capture
- Add 700 GW nuclear fission energy (twice the current capacity)
- Add 2 million 1-MW-peak windmills (50 times the current capacity) "occupying" 30 x106 ha, on land or offshore
- Add 2000 GW-peak PV (700 times the current capacity) on 2x106 ha
- Add 4 million 1-MW-peak windmills (100 times the current capacity)
- Add 100 times the current Brazil or U.S. ethanol production, with the use of 250x106 ha (one-sixth of world cropland)
- Decrease tropical deforestation to zero instead of 0.5 GtC/year, and establish 300 Mha of new tree plantations (twice the current rate)
- Apply conservation tillage to all cropland (10 times the current usage)
That's quite the list, isn't it? 2 billion cars, ..., 4 million windmills, ..., all to stabilize to just 500ppm. Pacala and Socolow do point out that carbon saved from 1 wedge often means carbon cannot be similarly saved by another wedge due to interactions between the wedges. "The more the electricity system becomes decarbonized, for example, the less the available savings from greater efficiency of electricity use, and vice versa."
I personally see big problems with numbers 6, 7, 8, 9 and 13. Even though this article was published in 2004, large-scale CCS still isn't viable today. Part of that is technological; perhaps a larger part is ambiguous market forces. The costs of not deploying large-scale CCS technologies are currently externalized. Once that status quo shifts, the extent of CCS deployment will change. Adding twice the current nuclear capacity, and replacing the current capacity by 2054, would cost enormous sums of money, to say nothing of any other problem related to nuclear power. There is a large amount of risk involved with planning, building and operating nuclear fission plants, especially in the U.S. Nuclear isn't carbon-free power, either. Energy from renewable sources have lower life-cycle carbon costs associated with them. As long as we're working toward stabilizing CO2 concentrations, we should probably emphasize solutions that produce fewer overall problems.
With a basic premise of climate stabilization established, I hope the takeaway from this piece is stabilizing global CO2 concentrations by ~2100 at 500ppm is very challenging, but also technically doable. I'll follow with a discussion about another stabilization proposal using more recent information and outlooks since the 2004 Pacala and Socolow paper. The situation has worsened since then, which means the solutions have become harder to implement.
Cross-posted at WeatherDem - the blog.