Noted environmental advocate Jim Hansen, in his testimony before the US House of Representatives this year, said that the "dangerous level of CO2 is at most 450ppm [parts per million], and it is probably less." Hansen added: "Note that I do not specify an exact fraction by which CO2 emissions must be reduced by 2050 or any other date, but we can say that emissions must be reduced to a fraction of their current values."
The current carbon dioxide level in the atmosphere is about 383ppm, having risen 2.6ppm last year. Human carbon dioxide emissions now rise by approximately 3.5 percent per year.
While nature soaks up about half of human carbon dioxide emissions now, that is expected to drop to 30 percent by 2030. In other words, a growing and developing world population has less than 20 years before the carbon dioxide level reaches 450 ppm.
However, using a more accurate measurement of carbon dioxide equivalent will show that the total of all greenhouse gases (GHG) in the air is 459ppm -- meaning, we've already passed the 450ppm mark.
To lower the chance of global warming by half, global GHG emissions must be cut 80 percent by 2050.
As developing nations continue to increase their GHG emissions per capita, it's only fair that they have to cut their emissions by more than 90 percent per capita. In other words, by 2050 Americans will have to cut their GHG emissions by more than 90 percent from this year's levels.
To lower the carbon dioxide level in the atmosphere, we either have to decrease our carbon dioxide emissions dramatically, or find a solution to improve nature's ability to lower carbon dioxide levels in the air.
Since worldwide demand for electricity is expected to double by around 2030 and coal-fired power plants account for about 30 percent of the supply, it is hard to see how carbon dioxide emissions can be reduced in a short time.
These carbon dioxide emission figures do not even include other factors, like increased natural emissions from carbon sinks that become carbon emitters when the earth continues to warm, increased growth of fossil fuel powered transportation, increased agricultural GHG emissions, or even decreased global dimming if emissions decrease.
Nature partially takes carbon dioxide out of the environment with plants that convert it into carbohydrates, and animals that convert it into tissue, bone and shell. Both are examples of autotrophs, which produce their own organic compounds using carbon dioxide from the air or water in which they live.
To do this they require an external source of energy, and almost all autotrophs use solar radiation to provide this.
The GHG can re-enter the atmosphere through decay or combustion. In fact, the carbon dioxide level in the air naturally fluctuates by about 6ppm per year as biomass grows and then shrinks with the seasons.
Because of a bias against releasing genetically engineered organisms into the environment, removing carbon dioxide from the air with naturally evolved autotrophs would be best.
The autotrophs that remove the most carbon dioxide from the environment are trees on land and phytoplankton in the ocean. Yet, neither removes the carbon dioxide for long before they die and release carbon dioxide back into the air through decay.
An expanding human population also places land use for reforestation at a premium, while decaying phytoplankton depletes oxygen in the ocean, leading to dead zones and the production of hydrogen sulfide by bacteria.
The Earth's biosphere evolved to regulate the carbon cycle in an equilibrium that is conducive to life. This cycle has gone out of equilibrium many times in the past, causing carbon sinks to turn into carbon emitters. Mankind's transfer of carbon from the geosphere to the atmosphere by burning fossil fuels has drastically upset the equilibrium of the carbon cycle.
As Hansen has said, "Humans are now in control of the global climate, for better or worse."
Engineering a biological solution to remove carbon dioxide in the air is quite simple.
We start with a biological template, modify it to fill an environmental niche and to remove the carbon from the atmosphere back into the biosphere long term.
Using recombinant DNA technology, we can add new traits by the modification of an organism's genes.
This is like cross breeding, but faster and more precise.
For instance, choosing a jellyfish as a biological template (because the ocean has a large niche and the jellyfish is tolerant of acidic water), we could insert a gene that stimulates the jellyfish tissue remove both oxygen molecules from carbon dioxide, and the grain of carbon will drift to the bottom of the ocean.
In other words, since mankind probably won't be able to cut its greenhouse gas emissions fast enough to prevent global warming, removing carbon dioxide from the air is the only solution.
There are several methods of mechanically extracting and separating carbon dioxide, but they all require a large amount of energy and are problematic to produce on a large scale.
On the other hand, there are several biological methods nature uses to extract carbon dioxide from the air, and separate it.
Howver, our Industrial Revolution mindset is biased against biological solutions because of a fear of unintended consequences.
One last factor that isn't being properly considered is abrupt climate change. The current climate models are programmed to predict gradual linear climate change with an increase in GHG.
Instead, paleoclimate data suggests abrupt climate change is common. Frankly, I think assuming only gradual linear climate change by 2050 is wishful thinking.
Generally, when a complex system is forced, it resists change, then abruptly switches to another stable state.
Our climate is currently in a sweetspot called the Holocene, where it is warm enough to prevent the formation of ice sheets on North America or Eurasia, but cool enough to keep ice sheets on Greenland and Antarctica.
The Holocene has seen the rise of human civilization, because favorable agricultural conditions have led to the formation of cities, technology and larger populations.
In the next few decades, the jet streams are expected to go further poleward, and the resultant droughts, higher high temperatures and heatwaves will send eco-systems into death spirals.
That will return our climate to a hotter dryer state that has seen massive extinctions many times in the past.
Asking developed countries to cut their carbon dioxide emissions by more than 90 percent by 2050 is an unrealistic goal, but any non-linear abrupt global warming event would make it impossible.
Furthermore, any planned resource intensive geo-engineering projects to mitigate global warming would have to be abandoned for lack of resources.
Brad Arnold
Saint Louis Park, Minnesota
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