Tuesday, June 2, 2015

Climate Change Part 19: Geoengineering

Note: This program first aired on March 21, 2015.
The last thing to think about as we wind down our climate change series is the big question: What do we do now? We’re in quite a pickle, but the good news is we have lots of options, the bad news is not all of them are easy, or likely to occur.

We are a technology obsessed society, and there is a faction out there who, while fully accepting climate change as a reality, believes that we should be able to engineer our way out it, an option known as geoengineering. And most climate scientists concur that at least some attempt at geoengineering needs to be part of immediate climate change mitigation.  Broadly defined, geoengineering specifically pursues mechanisms to mitigate climate change and as climate change is a planetary phenomenon, the scale of most of these geoengineering projects must also be planetary.

Most geoengineering proposals follow one of two paths, to either remove carbon dioxide from the atmosphere using enhanced biological or abiotic processes, or to increase the reflectivity of the Earth or its atmosphere, thereby decreasing the amount of energy entering the climate system. There are many variations on the first theme, removing carbon dioxide from the atmosphere. They start with strategies as simple as reforestation. Strategically replanting deforested areas can result in large amounts of carbon being taken out of the atmosphere and fixed away in the biomass (aka wood) of the trees as they grow. For this to be considered truly long term carbon sequestration however, the trees that grow can’t be then burned or even allowed to rot. Healthy forests do tend to be net carbon sinks, or places where carbon accumulates, but at the same time, they will slowly release carbon dioxide as organic matter breaks down. “Normally” this is a good thing, carbon dioxide is a critical nutrient for photosynthetic plants, so the carbon in/carbon out cycling in forests supports that. At this point though there is enough excess carbon in the atmosphere that we need strong measures, we need carbon to come out of the atmosphere and stay out. That has lead to various schemes in which natural processes are enhanced. For example, land plants are often limited by a lack of available nitrogen. One carbon sequestration  plan is to fertilize trees with nitrogen—if they aren’t limited by nitrogen, they can grow even faster! Another scheme that has gotten some press in the last few years is that of ocean fertilization. The idea with this is that in many parts of the ocean, iron is the limiting nutrient for phytoplankton, the base of the oceanic food web. If low productivity areas of the ocean are seeded with iron, primary productivity would increase, drawing large amounts of carbon out of the atmosphere. And unlike the forest systems, when the plankton die (if they die without being eaten by zooplankton or fish), they sink to the bottom of the ocean, taking that carbon with them. The bottom of the ocean then becomes a pretty good carbon sink (and this is in fact the mechanism by which some fossil fuels are created, which got us into this mess in the first place). Dumping a bunch of iron sulfate into the ocean violates a couple of different UN conventions, but that didn’t stop some folks from trying it in the Pacific northwest a few years ago. The research on whether or not a significant amount of carbon was sequestered has been mixed, but what is clear is that the experiment resulted in an increase is salmon runs two to three years later. Increased primary productivity means a burst of extra energy into the ecosystem; these results show that least some of the carbon didn’t in fact sink to the bottom of the Pacific, but instead was metabolized in the oceanic food web.

Other carbon sequestration plans are more industrial, and involve installing mechanical “scrubbers” on the smoke stacks of power plants, pulling the carbon dioxide out of the exhaust and piping it away to be sequestered under ground into rock formations. Lastly related to this is the plan to create what are essentially artificial plants, machines that can pull carbon dioxide directly from the atmosphere, and put it into the same system of underground sequestration as used for power plants.

The other and far more controversial strategy is to inject sulfates into the upper atmosphere in an attempt to increase the reflectivity of the atmosphere. If more light is reflected, less comes to Earth, and it is light that gets absorbed by the atmosphere and Earth surface that turns into the heat that gets trapped by green house gasses. Less light equals less heat in this scenario. This is exactly what happens with certain types of large volcanic eruptions, which have resulted in things like the infamous year “1800 and froze to death” other wise known as 1816 when world wide temperatures dropped as a result of the explosion of Mount Tambora in Indonesia. Cloud generating technology goes for a similar effect. Increasing reflectivity doesn’t do anything to mitigate the amount of carbon dioxide in the atmosphere or more significantly the oceans however.

Google geoengineering and you will find a plethora of information, advocates and critics. A recent National Academy of Sciences report went so far as to strongly endorse carbon capture efforts, and while at the same time raise significant concerns about reflectivity schemes. I think what is clear is that carbon capture programs may at this point in the game need to play a part in climate change mitigation, but we should not, and can not rely on them entirely. Other mitigation efforts are needed as well, we’ll talk about those next week.


 New York Times article about a recent National Academy of Sciences report on geoengineering: http://www.nytimes.com/2015/02/11/science/panel-urges-more-research-on-geoengineering-as-a-tool-against-climate-change.html

Where do we put all this captured carbon? http://www.epa.gov/climatechange/ccs/

Wikipedia, actually a good overview of the different carbon sequestration ideas: http://en.wikipedia.org/wiki/Carbon_sequestration

DIY Geoengineering:

Here’s a guy in Peru trying to keep alpine glaciers from melting by increasing the albedo of the Andes: http://www.popsci.com/science/article/2010-06/peruvian-inventor-whitewashes-andes-hoping-slow-glacier-melt