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| A break in the clouds on October 29, 2014, allowed scientists the opportunity to fly over Pine Island Glacier—one of Antarctica’s most rapidly changing areas. The flight was part of NASA’s Operation IceBridge, a mission that makes annual surveys of Greenland and Antarctica with instrumented research aircraft. Photo Michael Studinger |
Is Earth headed towards warming of two degrees Celsius this century? If yes, can it be reversed? Should it be? How would it be done?
Two recent publications offer some startling insights. The first by hockey-stick author Michael Mann estimates when the Earth can be expected to reach a level of 2°C warming (3.5°F) of the atmosphere. The answer it seems is very soon. Mann assumes business as usual in carbon emissions, which are increasing in amount every year, and the effect of the carbon dioxide (CO2) already in the atmosphere. These numbers are easy to come by, but he has to come up with a climate sensitivity model to translate the increase of CO2 in the atmosphere into warming. He determines that an equilibrium climate sensitivity about midway between estimates of the IPCC best-fit recent climate data. From this he projects forward and estimates the year Earth’s atmosphere reaches 2°C warming is 2036, twenty-one years from now. This is much sooner than estimates by the IPCC.
Before we get mentally adjusted to accepting two degrees of warming we might ask ourselves why this number? It is arbitrary and chosen under the hopeful assumption that we would control emissions and limit them to around 400 ppm – where it is now. Even at two degrees of warming the consequences could be dire. Why, because of imperfect knowledge about tipping points in the climate system. Will two degrees destabilize the West Antarctic Ice Sheet and give humanity the task to deal with sea level rise of ten feet? My past entries (May 20, 2014; June 9, 2014) have described that the ice sheet is nearly out of balance now, so any increase in warming sure won’t help it re-stabilize.
In the climate change conundrum a few things are well known. First, that society is not in any rush to curtail CO2 emissions. In fact should Republicans take over the U.S. presidency in 2016 it is virtually guaranteed that gains in carbon control in the U.S. will be erased and no progress will occur for four to eight years. The second thing that is known is that there is so much carbon in the atmosphere that even cutting emissions to 90% it would take hundreds of years to have a cooling effect. A lot of momentum is in the system. This leaves the world with the inevitable chore of adaptation to warming – how, is unknown at this point.
This brings up the second important report just published, this by the National Research Council. It deals with Climate Intervention more popularly called geoengineering . The idea is because we refuse to stop burning all these fossil fuels, why don’t we engineer the climate and reverse global warming? Two routes are known for Climate Intervention, carbon sequestration (burial of CO2 now in the atmosphere) and albedo modification (reflecting sunlight) to shade the Earth. Sequestration would include sucking CO2 directly out of the atmosphere then pumping it underground, or burning crops and byproducts in power plants, capturing the CO2 produced and burying it. The crops have already sucked carbon out of the atmosphere to grow so this process shunts that carbon underground. An offshoot in sequestration would use CO2 injected underground to enhance oil recovery, the idea being that burning the oil becomes carbon neutral or carbon negative – if more CO2 is buried than released in using fossil fuels.
Although sequestration has a few things going for it, like we know how to do it pretty much, it would require a massive scale-up of effort and would be very slow in yielding results in terms of global cooling. In fact the report notes that sequestration might have an impact on the same timescale as controlling and decreasing carbon emissions by alternative energy routes. A plus side is that it could allow humanity to avoid addressing oil addiction, an unmanageable problem not likely to be solved this century.
Albedo modification by injection of aerosols into the atmosphere is the wild child of geoengineering. Aerosols are dust and chemicals similar to those erupted into the sky by volcanoes. Think of Mount Pinatubo, which erupted in the Philippines in 1991. Global temperatures dropped 0.6°C (~1.0°F) as a result of the dust and sulfur dioxide (SO2) aerosols this one volcano shot into the sky. This effect lasted three years. However the increase in SO2 also decreased the amount of ozone in atmosphere to the lowest in recorded levels.
In a scenario of Climate Intervention albedo modification would inject aerosols into the atmosphere by aircraft and rockets. The volcano example shows the effects could be immediate.
The NRC report raises significant issues that they believe require utmost caution in pursuing the albedo approach. Foremost is that the role of aerosols and clouds in the climate system are not well understood. This raises the chance of unintended environmental consequences. The fact that this method has immediate effect has a flip side – if it is stopped the effects will be immediate also. Global warming will resume where it left off. Along with this, cooling of the atmosphere by increased albedo will do nothing to decrease ocean acidification (global warming’s evil twin) caused by dissolved CO2.
The albedo approach also will require international coordination even if it is fully understood. A world-governing agency will be needed to administer it. That of course brings up the inevitable, what’s good for some is bad for others. The political issues might be intractable.
The NRC study concludes:
Climate change is a global challenge, and addressing it will require a portfolio of responses with varying degrees of risk and efficacy. There is no substitute for dramatic reductions in greenhouse gas emissions to mitigate the negative consequences of climate change, together with adaptation of human and natural systems to make them more resilient to changing climate. However, if society ultimately decides to intervene in Earth’s climate, the Committee most strongly recommends any such actions be informed by a far more substantive body of scientific research—encompassing climate science and economic, political, ethical, and other dimensions—than is available at present.