GW temperature lag?

Question

So, temperature increases precede co2 increases by as much as 800 years, and co2 fuels these temperature increases via the greenhouse effect. Why doesn't this "feedback loop" keep going out of control? In other words, what is the catalyst that brings temperature down? Also, why does co2 keep going up after temperature has already started going down again? Also, if it really is a "feedback loop", then why are the slopes of temperature and co2 identical?

Answer 1

Good discussion.

What is missing in all of this discussion is the main theme which is: "is man the cause of global warming?"

From the evidence presented, CO2 may or may be associated with global warming as a cause or an effect.  I doesn't explain why we should be so alarmed about mans CO2 GW impact over the last 100 years?

There are no experimental data to support the hypothesis that increases in human hydrocarbon use or in atmospheric carbon dioxide and other greenhouse gases are causing or can be expected to cause unfavorable changes in global temperatures, weather, or landscape. There is no reason to limit human production of CO2, CH4, and other minor greenhouse gases as has been proposed.

We also need not worry about environmental calamities even if the current natural warming trend continues. The Earth has been much warmer during the past 3,000 years without catastrophic effects. Warmer weather extends growing seasons and generally improves the habitability of colder regions.

As coal, oil, and natural gas are used to feed and lift from poverty vast numbers of people across the globe, more CO2 will be released into the atmosphere. This will help to maintain and improve the health, longevity, prosperity, and productivity of all people.

The United States and other countries need to produce more energy, not less. The most practical, economical, and environmentally sound methods available are hydrocarbon and nuclear technologies.

Human use of coal, oil, and natural gas has not harmfully warmed the Earth, and the extrapolation of current trends shows that it will not do so in the foreseeable future. The CO2 produced does, however, accelerate the growth rates of plants and also permits plants to grow in drier regions. Animal life, which depends upon plants, also flourishes, and the diversity of plant and animal life is increased.

Human activities are producing part of the rise in CO2 in the atmosphere. Mankind is moving the carbon in coal, oil, and natural gas from below ground to the atmosphere, where it is available for conversion into living things. We are living in an increasingly lush environment of plants and animals as a result of this CO2 increase. Our children will therefore enjoy an Earth with far more plant and animal life than that with which we now are blessed.

Answer 2

Keith has provided good information on the albedo impact on cooling and the effect of ice loss in additional warming. As for CO2 the reason it has never led to uncontrollable warming is not difficult to understand. It blocks three narrow bandwidths of the infrared spectrum. Sunlight hits the Earth and some is re-emitted as infrared radiation, some of which is then blocked before it escapes into space and instead stays inside the atmosphere, causing warming. But is there an unlimited amount of infrared radiation? No. There is a finite amount and each incremental increase in CO2 has less effect until finally that bandwidth is already being completely blocked and no further warming results.

It's a complex equation that can fairly be called chaotic, the relationship between atmospheric CO2 (a tiny amount), the vast reservoirs of CO2 in the oceans, CO2 on land and in growing things, it has thus far evaded any successful modeling. If the oceans warm and release CO2 there might be 10 times as much in the atmosphere as now, but with no additional infrared radiation to block, that would have no impact on global temp.

All you need to do is see that in the past, CO2 levels were 20 times higher than they are today and temp was only 7C warmer. The circumstances were very different back then which is why total additional warming even if we raise CO2 to that level is more likely to be limited to under 3c. The chart linked below illustrated no linkage at all between CO2 levels and temp, except that as a rule 800 years after a temp peak, CO2 levels rise. Since the Medieval Warm Period ended about 800 years prior to the current upward move in CO2, that may explain some of the extra CO2 as well. But since it comprises a total of .04% of our atmosphere, it's unlikely that increasing that to .05% would lead to the dramatic temp increases some are predicting.

Answer 3

The obvious explanation is that CO2 doesn't effect the climate much but climate effects CO2 concentration a lot.    

The theory popular amonst global warming believers is that even though CO2 suposedly significantly effects the climate, Milankovitch cycles (changes in the Earths orbital ecentricity) are even more significant.  The Milankovitch theory was not popular among scientists before the current AGW campaign.  

The idea that a very small change in the Earth's orbit can cause the Earth to freeze over then thaw out when the small change is reversed, is not supported by comprehensive mathematical modelling.  If the ice albedo effect was significant enough to start an ice age, the Earth would stay frozen and never revert back.

I think AGW believers like the Milankovic theory for so many reasons like it suggests that solar variability is insignificant, very small changes can produce very dramatic results and we really do have a comprehensive understanding of the climate.

Answer 4

This is definitely one of the better questions around here in a while. And you've already got some excellent answers.

Just to add a point to what Keith and Jazzfan have said, understanding the concept of climate sensitivity is important. Climate sensitivity is basically how much the global surface temperature (once equilibrium is reached) will warm in response to a doubling of the atmospheric CO2 level. Estimates range from about 1.5 to 4.5 C.

A doubling of CO2 (270 ppm to 540 ppm) will thus raise the temperature by 1.5 - 4.5C.  It then requires another doubling (540 ppm to 1080 ppm) to raise it again by that much (total warming = 3.0 - 9.0C).  And then another doubling (1080 ppm to 2160 ppm) to achieve a total warming of 4.5 - 13.5C, etc.

Answer 5

CO2 is a feedback loop for ice ages, but it's not the major feedback loop. The most important feedback loop is the ice-albedo feedback: when snow falls on the continents, the earth reflects more light and therefore gets cooler.

What stops the ice-albedo feedback is that eventually snow falls just about everywhere in the Northern Temperate zone, and further cooling no longer results in more areas covered in snow. So the ice-albedo feedback cooling stops. After a few hundred years more, the oceans are finally cooled too, and when they get cool enough they stop absorbing more CO2, and the level of CO2 in the air stablizes at a low level, maybe 190 ppm. At that point, we're at the bottom of an ice age, low temps and low CO2.

Then 10,000 years go by and the Earth's orbit changes again, and once more winter in the Northern Hemisphere becomes shorter than summer, and that kicks off a little bit of warming, which results in a little bit of melting, which results in a little more warming. After a few hundred years of that, the oceans begin warming too, and as they warm they release some of their dissolved CO2. Which causes more warming.

At the top of the loop, once the glaciers are gone, the ice-albedo feedback loop stops, and the warming continues at a much slower pace until the deep ocean CO2 reservoirs have given up all they can; then that feedback loop stops too, although the exact mechanism for stopping the loop at the top end is not well understood.

Overall, the ice-albedo feedback represents about 2/3 of the total feedback mechanism, while the CO2 feedback is the other 1/3.

The slopes of the graph aren't identical, and can't be, since the y-axes are not the same measurements. You can therefore scale the y-axes any way you want, including ways that emphasize the match between the two.

Answer 6

Keith has it nailed here. This is what the planet has been doing for millions of years. That is why in my opinion, we should let nature take it's course and stop polluting just because it is wrong. Not just because we think it'll save us one day. We owe everything to this planet and it has the ability to destroy us and make another one just like us. Cool question man.

Answer 7

Good question and some great and informative answers for a change.