James Hansen: Doubling Down on Our Faustian Bargain

by James Hansen, Pushker Kharecha and Makiko Sato, Huffington Post, March 31, 2013

Humanity's Faustian climate bargain is well known. Humans have been pumping both greenhouse gases (mainly CO2) and aerosols (fine particles) into the atmosphere for more than a century. The CO2 accumulates steadily, staying in the climate system for millennia, with a continuously increasing warming effect. Aerosols have a cooling effect (by reducing solar heating of the ground) that depends on the rate that we pump aerosols into the air, because they fall out after about five days.

Aerosol cooling probably reduced global warming by about half over the past century, but the amount is uncertain because global aerosols and their effect on clouds are not measured accurately. Aerosols increased rapidly after World War II as fossil fuel use increased ~5%/year with little pollution control (Fig. 1). Aerosol growth slowed in the 1970s with pollution controls in the U.S. and Europe, but accelerated again after ~2000.

Fig. 1. CO2 annual emissions from fossil fuel use and cement manufacture, update of a figure using recent data.
Fig. 2. Annual increase of CO2 at Mauna Loa. The 12-month running mean reduces the double noise in the 12-month change. Blue asterisks show the end-of-year 12-month change often reported in the media.

The rapid growth of fossil fuel CO2 emissions in the past decade is mainly from increased coal use (Fig. 1), mostly in China with little control of aerosol emissions. It is thus likely that there has been an increase in the negative (cooling) climate forcing by aerosols in the past decade, as suggested by regional aerosols measurements in the Far East, but until proper global aerosol monitoring is initiated, as discussed below, the aerosol portion of the amplified Faustian bargain remains largely unquantified.

In our current paper we describe another component to the fossil fuel Faustian bargain, which is suggested by a careful look at observed atmospheric CO2 change (Fig. 2). The orange curve in Fig. 2 is the 12-month change of CO2 at Mauna Loa. This curve is quite "noisy," in part because it has double noise, being affected by short-term variability at both the start-point and end-point in taking the 12-month difference in CO2 amount. A more meaningful measure of the CO2 growth is provided by the 12-month running mean (red curve in Fig. 2). The temporal variability of the red curve has physical significance, most of the variability being accounted for by the Southern (El Nino-La Nina) Oscillation and the Pinatubo volcanic eruption in the early 1990s, as discussed in our paper.

NOAA recently reported the second largest annual CO2 increase in their Mauna Loa record. What they report is the end-of-year change in the noisy orange curve, the end-of-year values being indicated by blue asterisks in Fig. 2. It is practically certain that still larger CO2 increases will soon be reported, because of the huge increase of the rate of fossil fuel CO2 emissions in the past decade (black curve in Fig. 1), indeed we must expect reports of annual CO2 increases exceeding 3 ppm CO2.

An interesting point, however, is the failure of the observed increases in atmospheric CO2 to increase as rapidly as the fossil fuel source has increased. This fact is contrary to suggestions that terrestrial and ocean carbon sinks are tending to saturate as CO2 emissions continue.

An informative presentation of CO2 observations is the ratio of annual CO2 increase in the air divided by annual fossil fuel CO2 emissions, the "airborne fraction" (Fig. 3, right scale). This airborne fraction, clearly, is not increasing. Thus the net ocean plus terrestrial sink for carbon emissions has increased by a factor of 3 to 4 since 1958, accommodating the emissions increase by that factor.

Fig. 3. Fossil fuel CO2 emissions (left scale) and airborne fraction, i.e., the ratio of observed atmospheric CO2 increase to fossil fuel CO2 emissions. Final three values are 5-, 3- and 1-year means.

Remarkably, the airborne fraction has declined since 2000. The seven-year running mean had remained close to 60% up to 2000, except for the period affected by Pinatubo. The airborne fraction is affected by factors other than the efficiency of carbon sinks, most notably by changes in the rate of fossil fuel emissions. However, the change of emission rate in 2000 from 1.5%/year to 3.1%/year (Fig. 1), other things being equal, would have caused a sharp increase of the airborne fraction (because a rapid source increase provides less time for carbon to be moved downward out of the ocean's upper layers). A decrease in land use emissions during the past decade might contribute a partial explanation for the decrease of the airborne fraction, but something more than land use change seems to be occurring.

We suggest that the surge of fossil fuel use, mainly coal, since 2000 is a basic cause of the large increase of carbon uptake by the combined terrestrial and ocean carbon sinks. One mechanism by which fossil fuel emissions increase carbon uptake is by fertilizing the biosphere via provision of nutrients essential for tissue building, especially nitrogen, which plays a critical role in controlling net primary productivity and is limited in many ecosystems. Modeling and field studies confirm a major role of nitrogen deposition, working in concert with CO2 fertilization, in causing a large increase in net primary productivity of temperate and boreal forests. A plausible addition of 5 TgN/year from fossil fuels and net ecosystem productivity of 200 kgC per kgN16 yields an annual carbon drawdown of 1 GtC/year, which is of the order of what is needed to explain the post-2000 anomaly in airborne CO2.

Independent of a possible aerosol effect on the carbon cycle, it is known that aerosols are an
important climate forcing. IPCC17 concludes that aerosols are a negative (cooling) forcing, probably between -0.5 and -2.5 W/m². Hansen et al., based mainly on analysis of Earth's energy imbalance, derive an aerosol forcing -1.6 ± 0.3 W/m², consistent with an analysis of Murphy et al. that suggests an aerosol forcing about -1.5 W/m². This large negative aerosol forcing reduces the net climate forcing of the past century by about half.

Reduction of the net human-made climate forcing by aerosols has been described as a "Faustian bargain," because the aerosols constitute deleterious particulate air pollution. Reduction of the net climate forcing by half will continue only if we allow air pollution to build up to greater and greater amounts. More likely, humanity will demand and achieve a reduction of particulate air pollution, whereupon, because the CO2 from fossil fuel burning remains in the surface climate system for millennia, the "devil's payment" will be extracted from humanity via increased global warming.

So is the new data we present here good news or bad news, and how does it alter the "Faustian bargain"? At first glance there seems to be some good news. First, if our interpretation of the data is correct, the surge of fossil fuel emissions, especially from coal burning, along with the increasing atmospheric CO2 level is "fertilizing" the biosphere, and thus limiting the growth of atmospheric CO2. Also, despite the absence of accurate global aerosol measurements, it seems that the aerosol cooling effect is probably increasing based on evidence of aerosol increases in the Far East.

Both effects work to limit global warming and thus help explain why the rate of global warming seems to be less this decade than it has been during the prior quarter century. This data interpretation also helps explain why multiple warnings that some carbon sinks are "drying up" and could even become carbon sources, e.g., boreal forests infested by pine bark beetles and the Amazon rain forest suffering from drought, have not produced an obvious impact on atmospheric CO2.

However, increased CO2 uptake does not necessarily mean that the biosphere is healthier or that the increased carbon uptake will continue indefinitely. Nor does it change the basic facts about the potential magnitude of the fossil fuel carbon source and the long lifetime of fossil fuel CO2 in the surface carbon reservoirs (atmosphere, ocean, soil, biosphere) once the fossil fuels are burned. Fertilization of the biosphere affects the distribution of the fossil fuel carbon among these reservoirs, at least on the short run, but it does not alter the fact that the fossil carbon will remain in these reservoirs for millennia.

The principal implication of our present analysis relates to the Faustian bargain. Increased short-term masking of greenhouse gas warming by fossil fuel particulate and nitrogen pollution is a "doubling down" of the Faustian bargain, an increase in the stakes. The more we allow the Faustian debt to build, the more unmanageable the eventual consequences will be. Yet globally there are plans to build more than 1,000 coal-fired power plants and plans to develop some of the dirtiest oil sources on the planet. These plans should be vigorously resisted. We are already in a deep hole -- it is time to stop digging.

The tragedy of this science story is that the great uncertainty in interpretations of the climate forcings did not have to be. Global aerosol properties should be monitored to high precision, similar to the way CO2 is monitored. The capability of measuring detailed aerosol properties has long existed, as demonstrated by observations of Venus. The requirement is measurement of the polarization of reflected sunlight to an accuracy of 0.1%, with measurements covering the spectral range from near ultraviolet to the near-infrared at a range of scattering angles, as is possible from an orbiting satellite. Unfortunately, the satellite mission designed for that purpose failed to achieve orbit, suffering precisely the same launch failure as the Orbiting Carbon Observatory (OCO). Although a replacement OCO mission is in preparation, no replacement aerosol mission is scheduled.

http://www.huffingtonpost.com/dr-james-hansen/doubling-down-on-our-faustian-bargain_b_2989535.html

Andrew Glikson: No alternative to atmospheric CO2 draw-down

by Andrew Glikson, Skeptical Science, February 14, 2013

This article suggests that the current atmospheric CO₂ level is already triggering amplifying feedbacks from the Earth system and therefore, in themselves, efforts at reduction in atmospheric CO₂-emission are no longer sufficient to prevent further global warming. For this reason, along with sharp reductions in carbon emissions, efforts need to be undertaken in an attempt to reduce atmospheric CO₂ levels from their current level of nearly 400 ppm to well below 350 ppm. NASA-applied, outer space–shade technology may buy time for such a planetary defence effort.

The scale and rate of modern climate change have been greatly underestimated. The release to date of a total of over 560 billion ton of carbon through emissions from industrial and transport sources, land clearing and fires, has raised CO₂ levels from about 280 parts per million (ppm) in pre-industrial periods to 397–400 ppm and near 470 ppm CO₂-equivalent (a value which includes the CO₂-equivalent effect of methane), reaching a current CO₂ growth rate of about 2 ppm per year.

Figure 1. Part A. Mean CO₂ level from ice cores, Mouna Loa observatory and marine sites; Part B (inset). Climate forcing 1880–2003. Aerosol forcing includes all aerosol effects, including indirect effects on clouds and snow albedo. GHGs include ozone (O₃) and stratospheric H₂O, in addition to well-mixed greenhouse gases.

Figure 2: Relations between CO₂ rise rates and mean global temperature rise rates during warming periods, including the Paleocene–Eocene Thermal Maximum, Oligocene, Miocene, glacial terminations, Dansgaard–Oeschger cycles and the post-1750 period.

These developments are shifting the Earth’s climate toward Pliocene-like (5.2–2.6 million years ago; mean global temperatures of +2–3 ^oC above pre-industrial temperatures) and possibly toward mid-Miocene-like (approximately 16 million years ago; mean global temperatures +4 ^oC above pre-industrial temperatures) conditions within a few centuries ― a geological blink of an eye.

The current CO₂ level generates amplifying feedbacks, including the reduced capacity of warming water to absorb CO₂ from the atmosphere, CO₂ released from fires, droughts, loss of vegetation cover, disintegration of methane released from bogs, permafrost and methane-bearing ice particles and methane-water molecules.

With CO₂ atmospheric residence times in the order of thousands to tens of thousands years, protracted reduction in emissions, either flowing from human decision or due to reduced economic activity in an environmentally stressed world, may no longer be sufficient to arrest the feedbacks.

Four of the large mass extinction of species events in the history of Earth (end-Devonian, Permian–Triassic, end-Triassic, K–T boundary) have been associated with rapid perturbations of the carbon, oxygen and sulphur cycles, on which the biosphere depends, at rates to which species could not adapt.

Since the 18th century, and in particular since about 1975, the Earth system has been shifting away from Holocene (approximately 10,000 years to the pre-industrial time) conditions, which allowed agriculture, previously hindered by instabilities in the climate and by extreme weather events. The shift is most clearly manifested by the loss of polar ice. Sea level rises have been accelerating, with a total of more than 20 cm since 1880 and about 6 cm since 1990.

For a temperature rise of 2.3 ^oC, to which the climate is committed if sulphur aerosol emission discontinues (see Figure 1), sea levels would reach Pliocene-like levels of 25 meters plus or minus 12 meters, with lag effects due to ice sheet hysteresis (system inertia).

With global atmospheric CO₂-equivalents (a value which includes the effect of methane) above 470 ppm (just under the upper stability limit of the Antarctic ice sheet, with the current rate of CO₂ emissions from fossil fuel combustion, cement production, land clearing and fires of ~9.7 billion ton of carbon in 2010), global civilization faces the following alternatives:

1. With carbon reserves sufficient to raise atmospheric CO₂ levels to above 1,000 ppm, continuing business-as-usual emissions can only result in advanced melting of the polar ice sheets, a corresponding rise of sea levels on the scale of meters to tens of meters, on a time scale of decades to centuries, and high-to-extreme continental temperatures rendering agriculture and human habitat over large regions unlikely.
2. With atmospheric CO₂ at about 400 ppm, an abrupt decrease in carbon emissions may no longer be sufficient to prevent current feedbacks (melting of ice, methane release from permafrost, fires). Attempts to stabilize the climate require global efforts at CO₂ draw-down, using a range of methods, including global reforestation, extensive biochar application, chemical CO₂ sequestration (using sodium hydroxide, serpentine and new innovations), as well as burial of CO₂.

As indicated in Table 1, the use of short-term solar radiation shields such as sulphur aerosols cannot be regarded as more than a band aid, with severe deleterious consequences in terms of ocean acidification and retardation of the monsoon and of precipitation over large parts of the Earth.

In contrast, retardation of solar radiation through space sunshade technology may allow time for CO₂ draw-down. Unlike sulphur dioxide injections, this will not have ocean acidification effects – an effort requiring a planetary defense project by NASA.

Dissemination of ocean iron filings aimed at increasing fertilization by plankton and algal blooms, or temperature exchange through vertical ocean pipe systems, are unlikely to constitute effective means of transporting CO₂ to relatively safe water depths.

In contrast to these methods, CO₂ sequestration through fast-track reforestation, soil carbon, biochar and possible chemical methods such as “sodium trees” and serpentine (combining Ca and Mg with CO2) may be effective, provided these are applied on a global scale.

Such efforts will require an effective planetary defense effort on the scale currently expended on military spending (totaling more than $20 trillion since WWII).

It is likely that a species which decoded the basic laws of nature, split the atom, placed a man on the moon and ventured into outer space should also be able to develop the methodology for fast sequestration of atmospheric CO₂. The alternative, in terms of global heating, sea level rise, extreme weather events, and the destruction of the world’s food sources is unthinkable.

Good planets are hard to come by.

http://www.skepticalscience.com/No-alternative-atmospheric-CO2-draw-down.html