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.
References:
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
National Geographic’s take on the same report: http://news.nationalgeographic.com/news/2015/02/150210-national-academy-geoengineering-report-climate-change-environment/
A few more specific proposals outlined by TreeHugger: http://www.treehugger.com/natural-sciences/7-geoengineering-solutions-that-promise-to-save-humans-from-climate-change.html
Iron fertilization and impact on salmon (instead of climate)
http://www.scientificamerican.com/article/fertilizing-ocean-with-iron-to-save-salmon-and-earn-money/
More on this, with lots of references: http://geoengineeringourclimate.com/2014/01/14/village-science-meets-global-discourse-case-study/
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
Russ George dumps iron into the ocean: http://www.popsci.com/science/article/2012-10/rogue-geoengineer-dumps-100-tons-iron-canadas-west-coast
