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Do negative feedback loops mostly cushion the effect of atmospheric CO2 increases?

The earth's climate is a system that contains feedback loops. If an input variable changes in a feedback loop, it effects the system in a way that changes the input variable itself. These changes cumulatively increase in a positive feedback loop, but progressively dampen in a negative feedback loop. The concern with increasing CO2, is that more CO2 in the atmosphere will warm the earth, in turn causing more CO2 to be released due to effects such as warmer oceans, i.e. a positive feedback loop.

Implications to Other Questions

Does atmospheric CO2 cause significant global warming?
Do negative feedback loops mostly cushion the effect of atmospheric CO2 increases?

Experts and Influencers

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Agree
Experts In Climatology


Richard Lindzen    Meteorology Professor
Agree
The notion that the earth's climate is dominated by positive feedbacks is intuitively implausible, and the history of the earth's climate offers some guidance on this matter. About 2.5 billion years ago, the sun was 20%-30% less bright than now (compare this with the 2% perturbation that a doubling of CO2 would produce), and yet the evidence is that the oceans were unfrozen at the time, and that temperatures might not have been very different from today's.
30 Nov 2009    Source


Roy Spencer    Meteorologist
Mostly Agree
The real climate system appears to be dominated by “negative feedbacks” -- instead of the “positive feedbacks” which are displayed by all twenty computerized climate models utilized by the IPCC.
22 Jul 2008    Source


Experts In Science


Tom Segalstad    Geology Professor
Agree
CO2 in the atmosphere and in the ocean reach a stable balance when the oceans contain 50 times as much CO2 as the atmosphere. The IPCC postulates an atmospheric doubling of CO2, meaning that the oceans would need to receive 50 times more CO2 to obtain chemical equilibrium. This total of 51 times the present amount of carbon in atmospheric CO2 exceeds the known reserves of fossil carbon- it represents more carbon than exists in all the coal, gas, and oil that we can exploit anywhere in the world.
07 Jul 2007    Source


Experts In Mathematics


David Evans    Mathematician
Agree
There are now several independent pieces of evidence showing that the earth responds to the warming due to extra carbon dioxide by dampening the warming. Every long-lived natural system behaves this way, counteracting any disturbance. Otherwise the system would be unstable. The climate system is no exception, and now we can prove it.
07 Apr 2011    Source


Miscellaneous Experts


Monte Hieb    Mining Engineer
Agree
The Late Ordovician Period [approximately 450 million years ago] was also an Ice Age while at the same time CO2 concentrations then were nearly 12 times higher than today-- 4400 ppm. According to greenhouse theory, Earth should have been exceedingly hot. Instead, global temperatures were no warmer than today. Clearly, other factors besides atmospheric carbon influence earth temperatures and global warming.
19 Dec 2006    Source


Disagree
Experts In Climatology


Intergovernmental Panel on Climate Change    (IPCC) Scientific Body formed by U.N.
Disagree
Human activities cause significant changes in long-lived gases, ozone, water vapour, surface albedo, aerosols and contrails. ... Positive forcings lead to warming of climate and negative forcings lead to a cooling. ... [The net effect is positive].
25 Mar 2008    Source


Andrew Dessler    Climatology Professor
Disagree
The small number of credible skeptics out there (e.g., Spencer, Lindzen) have spent much of the last decade searching for a negative feedback in our climate system. ... Most climate scientists, however, are reasonably certain that a negative feedback big enough to overwhelm the well-known positive feedbacks in the climate system [...] does not exist. ... it is extremely difficult to reconcile the existence of a big negative feedback with our past observations of climate variability.
21 Jan 2009    Source


Experts In Media


Time Magazine    Popular Magazine
Disagree
Pump enough CO2 into the sky, and that last part per million of greenhouse gas behaves like the 212th degree Fahrenheit that turns a pot of hot water into a plume of billowing steam.
03 Apr 2006    Source


Experts In Business


Bill Gates    Microsoft Cofounder, Philanthropist
Disagree
The [skeptics] who make scientific arguments are very few. [They say things such as] there are negative feedbacks effect to do with clouds that offset things... there are very few things that they can even say there's a chance in a million [of being true].
01 Feb 2010    Source


Neutral
Experts In Science


Nathan Paldor    Meteorology Professor
Neutral
It is quite possible that after an ‘adjustment time' the ocean (which contains far more CO2 than the atmosphere) will simply increase its biological activity and absorb the CO2 from the atmosphere.
04 Dec 2007    Source



Comments

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0 Points      Benja      22 Jun 2010      Stance on Question: Mostly Disagree
The easiest way to explain the mainstream position here is that you can't explain the rapid shifts in and out of ice ages without a positive feedback loop between CO2 and temperature. If the climate system is dominated by negative feedbacks, you would expect to see much slower shifts - if any shift at all. When trying to simulate paleoclimates, the models don't retrodict correctly unless a positive feedback is used.

An inherent contradiction in the skeptical position, is that nearly all skeptics claim that the climate is too complex for us to fully understand. Some claim that we can't understand the climate system at all, while others won't go that far, but still maintain how challenging it is to predict. Yet when it comes to the most complex aspect of climate altogether - modeling the feedback caused by clouds - suddenly the skeptics such as Roy Spencer become very confident in their position. That doesn't make sense.


0 Points      Jim Rennison      13 Jul 2009      Stance on Question: Agree
The FIRST 100 ppm of CO2 is highly effective as a greenhouse agent, but CO2 over and above this amount is logarithmically less effective. When we reach 200 ppm, we have saturation, wherein additional CO2 concentration has only a negligible effect on the atmosphere's heat budget.


0 Points      Steve      13 Jul 2009      General Comment
I respectfully dispute your facts here. Can you site a peer reviewed journal where that is demonstrated? It's hard to believe that all the scientists in the IPCC would miss something that simple.

Furthermore, even Roy Spencer, a leading skeptic and respected climatologist, would disagree with you that the effect of CO2 above 200 ppm is negligible. He says here that "Obviously, knowing the strength of feedbacks in the climate system is critical; this is the subject of most of my research":

Why would knowing the strength of the feedback be critical if the forcing effect of CO2 at today's levels was negligible?


0 Points      Jim Rennison      14 Jul 2009      Stance on Question: Agree
Even the IPCC does not dispute the FACT of logarithmically decreasing spectral absorption of CO2 with increasing concentration. In the AR4 report, the Beer-Lambert equation is invoked during the calculations of the direct 'greenhouse effect' of CO2 from first principles. This is how they arrive at the 1.7 watts per M^2 which is cited as the amount of heat energy attributable to the direct effect of the 380 ppm of CO2.

Of course the IPCC says that the effect of CO2 is not limited to its direct effect. They assert that there exists a strongly positive feedback between CO2 concentration and water vapor concentration through a simple thermal perturbation which leads to increased oceanic evaporation. Note that ANY GH agent or ANY OTHER thermal perturbation would also awaken this same feedback, if it exists. Note also that the IPCC has very little peer-reviewed support for this claim and most of the support comes from the output of computer models rather than from direct observations of the atmosphere.

The strength and sign of the feedbacks is therefore crucial to knowing whether increases in CO2 concentration are capable of changing climate in a meaningful rather than a negligible way.

If we look at past climates, its a wonder that we worry at all about such tiny changes in CO2 concentration such as we witnessed during the 20th century, as the atmosphere had in the past many times the current levels, over 2000ppm, yet there was never a climate 'runaway' event, wherein the oceans overheated and major species groups became extinct.

Nevertheless, this notion of 'strongly positive feedback' is fortunately a testable hypothesis. Christy, Spencer and Lindzen have done just that and the result of direct observation is that there does indeed exist a feedback between CO2 (or other thermal perturbations) and water vapor but the sign of that feedback is negative and works through the simple and elegant mechanisms of cloud formation and precipitation.


0 Points      Benja      14 Jul 2009      General Comment
Hi Jim,

I just what to chime in and say I really appreciate the fact that you've brought up the importance of a testable hypothesis. I think this is an inherent weakness in climatology. Andrew Dessler does try to head on talk about that problem here.

Just to clarify your statements:

1. CO2 becomes less effective at increasing concentrations.
2. CO2 saturates at 200 ppm, becoming negligible in effect.

The IPCC agrees (roughly) with 1, but would dispute 2.

Regarding paleoclimates, the IPCC does more than wonder about the high concentrations of CO2 in these times: they study it. These climates were so radically different to today's one (even the sun was once far less hot) that intuitive apples to apples comparisons are perhaps interesting in terms of turning a hunch into a formal hypothesis, but no conclusions can be drawn from them.

Also, to avoid confusion for anyone reading this - the overall role of clouds in the climate system is not simple. In fact, the IPCC acknowledges that this is the biggest source of uncertainty in their models. As a bystander in a scientific debate, it can seem ironic that the skeptics Christy, Spencer, and Lindzen present such a sure footed understanding of the most complex aspect of climate, while simultaneously criticizing the IPCC for being too sure of what they know.


0 Points      jack gabel      09 Aug 2013      General Comment
Christy, Linzen and Spencer have all contributed to IPCC assessments, have sat on the panels, in the conferences, etc. - have literally been in the game for decades - and what is the game? funding, grants, publishing credits - Lindzen is on record stating that the general, institutional bias toward AGW is so strong that by including an AGW angle in virtually any scientific grant research funding proposal, the proposal's chance of being approved is literally double - AGW hysteria is now the most politically correct position for any professional academician






0 Points      DGwartney      08 May 2009      Stance on Question: Neutral
The oceans and rain forests are primary carbon sinks in the world. Without them, and at the rate excess CO2 is pumped into the atmosphere via anthropogenic and biologic processes, the planet would likely see far more extreme temperatures than it currently does. The oceans are great sources for absorbing CO2 from the atmosphere which is beneficial to cooling the atmosphere. However, as air temperature increases (possibly from excess CO2 emissions) oceans will increase in temperature and will be less dense, thus losing their ability to absorb excess CO2 from the atmosphere. Due to this, increasing CO2 in the atmosphere will continue to increase air temperature, which in turn increases ocean surface temperature.


0 Points      Will Haas      02 Jul 2013      General Comment
There is no evidence in the paleoclimate record that CO2 has any effect on climate. Higher temperatures cause more CO2 to appear but there is no evidence that more CO2 causes higher temperatures.

CO2 is a passive element and does not itself produce heat. As greenhouseue gas CO2 acts as a radiant thermal insulator which restricting the flow of heat, causes higher temperatures in the lower troposphere and cooler temperatures in the mid to upper troposphere. The higher temperatures in the lowetropospherere causes more H2O to enter the atmosphere. H2O is also a greenhouse gas which causes aincreasese in radiant insulation but H2O is also a major heat transfer agent through the heat ovaporisationon. H20 moves heat energy from the surface to the clouds where it condenses through the heat ovaporisationon. More H2O causes more clouds that reflect incoming solar radiation and that provide a more efficient LWIR radiator to space than atmosphere without clouds. The net effect is that H2O provides a negative feedback to the addition of CO2 in the lower troposphere. In the mid to upper troposphere, adding CO2 causes cooling. The cooling reduces H2O which counteracts the addition of CO2. So in the mid to upper troposphere H2O also provides a negative feedback to the addition of CO2. The negative feedback says that the atmosphere is relatively stable in terms of the addition of greenhouse gasses so that is why we have not experienced a runaway greenhouse effect during the last 500 million years and as a result man has been able to evolve. We are here.