Key words :
climate change,
carbon cycle
,emissions
,carbon dioxide
,climate change; global warming
,atmosphère
,ecology
Stabilizing the Climate Requires Near-Zero Carbon Emissions
28 Feb, 2008 11:30 am
 and Ken Caldeira (Carnegie Institution, Stanford, USA) in a study titled )
What warming is produced by an individual release of carbon dioxide to the atmosphere? This question was addressed by Damon Matthews (Concordia University, Montreal, Canada) and Ken Caldeira (Carnegie Institution, Stanford, USA) in a study titled "Stabilizing climate requires near-zero carbon emissions", scheduled to be published in Geophysical Research Letters on 7 March 2008.
Each increment of carbon dioxide emission contributes another increment to global warming. Therefore, to a close approximation, if we want to reduce emissions enough to stop global warming, we would need to eliminate all carbon dioxide emissions.
If the earth had no capacity to store heat, a puff of CO2 would very rapidly warm the Earth, and then the Earth would cool as the CO2 was absorbed by the oceans and land biosphere. But that is not what happens in the real world or in climate models.
The ocean is a huge reservoir of heat, although in this case it is better to think of it as a huge reservoir of cold. So, soon after the puff of CO2 is released, it is trapping a lot of heat radiation in the atmosphere, but most of this energy initially goes into heating the ocean and not the atmosphere. It takes a few decades before the upper ocean warms substantially, and it takes centuries to warm the entire ocean volume. Once the entire ocean is warm, it can take thousands of years to cool back down. So, after a release of CO2, most of the energy trapping initially goes into heating the ocean. Later, when CO2 concentrations diminish, the warm ocean helps keep the atmosphere warm. As a result, the climate signal from a CO2 emission does not look like the amount of CO2 in the atmosphere.
A puff of CO2 released to the atmosphere results in increasing global temperatures for a few decades as the ocean warms up, but then the climate remains warm for many centuries. Our simulations went out to 500 years, and there was very little reduction from peak temperatures even 500 years after the CO2 emission. It would take thousands of years for most of the peak warming to go away.
This study simplifies how we can think about climate effects of CO2 emission. Each CO2 emission results in increasing temperatures for a few decades, and then the Earth remains warm for many centuries. Thus, if we do not want the Earth to warm further and remain warm for many centuries, we would need to eliminate CO2 emissions.
Reference:
Matthews, H. D., and K. Caldeira (2008), Stabilizing climate requires near-zero emissions, Geophysical Research Letters, doi:10.1029/2007GL032388, in press.
Key words :
What is the amount of carbone released to the the atmosphere that cannot be reduced ?
The relaxation time is very long even in the 200 gtC curve. Do you have an exemple in the climate history which could be compared to your results ?
Welcome to the Anthropocene! The Holocene is now over...
One might paraphrase their findings with respect to carbon dioxide in the atmophsere, by saying that, in effect, "whatever carbon goes there, stays there", at least for a very, very long time.
That being the case, I think it is imperative to not only consider carbon-free technologies that provide electricity that will be needed in any case, but also those that can mitigate the warming by changing the net forcing equation. For example, by increasing the earth's albedo, the effects of increased carbon forcing can be counteracted to some degree.
One technology that could be deployed on a scale large enough to accomplish both of the above objectives is the Atmospheric Vortex Engine. By using warm surface currents, or seasonable warm lake or bay water, the device is capable of evaporating large amounts of water and sending humidity high into the troposphere where clouds would form to reflect more sunlight.
There are large areas of clear sky over ocean masses where the increased cloudiness would not affect agriculture and only effect ocean productivity to a minor extent.
There are cloudy areas over many shipping lanes that already accomplish this to some degree. By adding the AVE into the equation, cloudiness could be created in areas where it would not naturally exist, and, of course, radiation emitted to outer space above the "greenhouse blanket" would further tend to cool the planet.
The AVE is not a technology that requires any breakthroughs. It just needs to be built and its effects quantified, at a cost that is negligible compared to what's at stake.
[Response] Jerry Toman perhaps oversimplifies our results with respect to carbon, but his formulation is correct to a first approximation with respect to temperature change: "whatever warming we get, we will need to live with for a very, very long time." (Unless, of course, we are willing to attempt risky direct interventions in our climate system.) -- Ken Caldeira
Please confirm that, in the final parenthetical phrase of your response to my comment ,that you were not suggesting that somehow, the mere development and testing of the capabilities of one or several versions of the AVE somehow constitutes significant "risky direct intervention" in our climate system.
It was not clear from the short response.
Besides, I thought the whole point of the article was that we need to stop conducting "business as ususal", and quickly find alternatives. The AVE, due to its low cost, is one that has the shortest implementation times.
If you do have suggestions for the best pathway forward, I think they need to be stated. Just having a "Chicken-Little moment" will simply leave the Scitizen readers scratching their heads.
[Response] I meant to refer to "risky direct interventions" such as placing sulfate aerosols in the stratosphere. There was no intent to make any comment about AVE, either positive or negative. -- Ken Caldeira
The model is available at: http://climate.uvic.ca/model/
However, the correlation between the temperature and a straight line since 1850 is 0.93 ... which means that carbon emissions is a rather poor fit to the temperature. It does not do as well at predicting temperature as a straight line ...
For this we should get excited?