Water scarcity is only one of the issues associated with rising global temperatures... photo: Mark N via flickr
In case you missed the past years of debate, here's global climate change in a nutshell: Since human's began burning fossil fuels some 150 or so years ago atmospheric carbon dioxide levels have increased precipitously. As it stands now, unless these levels are kept at about where they are today (at a maximum) or decreased, by the end of the 21st century global temperatures could rise to levels that would make vast areas of the planet far less habitable for life (human, other animal, and plant alike) than they are today.
Enter geoengineering. In a worst case scenario it may be required, proponents of geoengineering say, for humans to intervene. Forget simply stopping or reversing deforestation and rehabilitating other natural carbon sinks. Here are some of the more interventionist proposals currently on the table:
Spray Sulfate Aerosols Into The Atmosphere
Though cited by a number of reports as being rather risky due to potential unintended consequences, the idea behind spraying sulfur particles into the atmosphere goes something like this: By using large balloons or aircraft to put more sulfur particles into the stratosphere, you could reduce the Earth's absorption of of sunlight and prompt planetary cooling. Similar to what happens when volcanoes erupt and put ash and sulfur into the air.
The downside? According to an article in Science doing this could trigger chemical reactions which would lead to destruction of the ozone layer.
Trap CO2 in Carbon ScrubbersPerhaps two years from being manufactured, researchers at Columbia University say that soon they may have a working carbon scrubber which could take one ton of CO2 out of the air per day. Small than a standard shipping container in size, and about $200,000 in price, these carbon scrubbers trap CO2 entering them on an ion exchange resin. The CO2 then can be either buried or used in other ways. Sounds like an interesting idea? It is, but as the device's developers point out, hundreds of millions of these would have to be deployed to suck up all the excess carbon emissions so this would only be part of any planetary medicine we'd be practicing.
Fertilizing Trees With Nitrogen
The idea here is said easily enough: Fertilize trees with nitrogen to stimulate their ability to absorb more carbon dioxide and, by increasing their albedo, reflect more solar radiation back into space. Voila! You've begun cooling the planet. Not so fast...
Fellow TreeHugger Jeremy Elton Jacquet :
For one thing, little is still known about the relationship between albedo and nitrogen; even if the nutrient does act as a switch that changes the leaves' structure to increase their albedo, only certain species would be able to take advantage of this property. As a result, if we wanted to apply this method on a sufficiently large scale to effect carbon emissions, we would have to plant entire forests made just out of those few species.
And then there are all the environmental downsides associated with high nitrogen concentrations: nitrous oxide emissions (a far more potent greenhouse gas), groundwater contamination and drying (trees that consume larger amounts of nitrogen need more water), just to name a few.
photo: Discovery Channel
Planting new trees in areas deforested by natural disaster or human action could increase the carbon sink potential of a given area of land, but given how much previously forested land has been cleared of trees in recent years, to complete the job quickly enough some scientists have proposed using airplanes to drop tree seedlings over wide areas of land.
Tested on an episode of Discovery Project Earth, tree seedlings were encased in a variety of biodegradable containers (to test which cradled the tree best for its journey back to Earth) and dropped from slow moving airplanes. As the episode shows, bringing an idea like this from concept to fruition is easier said than done. Without entirely giving away the show's ending, we all better grab the nearest spade and get planting trees. At least until better delivery methods are developed.
Dump Limestone into the Oceans
This one's a bit of a ringer in the group, in that rather than combatting global warming directly, plans for dumping powdered limestone in the ocean would mainly address anticipated increasing ocean acidity. Due to these changes in pH levels in the world's oceans brought about by climate change, most of the planet's coral reefs could be wiped out, with devastating consequences for marine life and the humans which depend on it. But, by adding large amounts of powdered limestone to the sea these changes in water acidity could be checked--with the added bonus of increasing carbon sequestration as well.
If you're wondering about side effects, you're not alone. At this point the whole procedure is very much theoretical, add even if everything went exactly as planned it could take decades and billions of tons of limestone for the plan to work.
Ocean Iron Fertilization
Essentially mimicking natural processes, ocean iron fertilization hopes to stimulate the rate of photosynthesis in phyto plankton, increasing the amount of carbon dioxide which is absorbed, and creating essentially an artificial algae bloom. The thing is that the CO2 absorbed has to sink to sufficient depth (a couple of miles) so that it won't simply be circulated back up into the atmosphere.
How effectively this works is a debate that swings both ways: A recent study published in Nature says that at least in one experiment in the Crozet Islands the results were less than stellar. The carbon sequestered was far less than theoretically predicted. That said, not everyone agrees with the conclusion drawn by both the researchers or journalists (predictions of ocean iron fertilization's death are greatly exaggerated...) on the effectiveness of this procedure.
However, new tests in the South Atlantic have recently begin given permission to proceed which will study the role of iron in the global climate system. The organizers of the study, the Alfred Wegener Institut, specifically say that they are not study ocean iron fertilization, but nevertheless, the results of their research will be of interest to both proponents and opponents of this geoengineering procedure.
Enrich Soils With Biochar
Sometimes called a modern version of the ancient Amazonian agricultural practice of Terra Preta, biochar promises to both enrich soils and soak up excess carbon dioxide. How it works is this:
Biochar is a fine-grained charcoal high in organic carbon and largely resistant to decomposition.Â It is produced from pyrolysis of plant and waste feedstocks.Â As a soil amendment, biochar creates a recalcitrant soil carbon pool that is carbon-negative, serving as a net withdrawal of atmospheric carbon dioxide stored in highly recalcitrant soil carbon stocks.Â The enhanced nutrient retention capacity of biochar-amended soil not only reduces the total fertilizer requirements but also the climate and environmental impact of croplands.Â Char-amended soils have shown 50 - 80 percent reductions in nitrous oxide emissions and reduced runoff of phosphorus into surface waters and leaching of nitrogen into groundwater.Â As a soil amendment, biochar significantly increases the efficiency of and reduces the need for traditional chemical fertilizers, while greatly enhancing crop yields.Â Renewable oils and gases co-produced in the pyrolysis process can be used as fuel or fuel feedstocks.Â Biochar thus offers promise for its soil productivity and climate benefits.Â (International Biochar Initiative)
Sounds easy, but will it actually do any good? A recent study on different geoengineering methods said that, combined with reforestation, biochar has greater short term cooling potential than ocean fertilization, and that it was a "win-win for soil fertility as well as the climate." What's more, James Lovelock calls biochar our one last chance to save ourselves from devastating temperature increases.
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