[thedoc (OP)]

David Jones asked the Naked Scientists:
   Dear Chris, I have watched a youtube video called The Great Global Warming Swindle which puts forward convincing evidence that there is no correlation between CO2 levels and rising temperatures. Featured on the programme are Nigel Lawson, Nigel Calder (ex New Scientist Editor), Patrick Moore (founder of GreenPeace). They actually show graphs that say that over long periods of time, temperatures rise and THEN, 800 years later CO2 levels rise. They also show eveidence that states in the 1940s to 1970s when CO2 levels rose significantly, temps dropped. They also show a direct correlation between temperature rises and sun spot activity. How can climate change scientists refute these facts? Please explain. Thanks Hywel Jones
What do you think?

[chris]

Have you got the references / copies of the graphs to which you are referring? It would be helpful to see the material that was presented and attempt to establish whether the correct conclusions were being drawn.

As a general rule, temperature follows CO2. Draw-down of CO2 by mountain weathering causes global cooling; rising CO2, from a range of sources, is associated with rising global temperatures consistent with heat trapping.

[alancalverd]

The best historic data comes from the Vostok ice cores, which clearly show the 800-year lag (I estimated it at 500 years, but it's a lag, anyway) between the very sharp rises in T and the somewhat slower increases in CO2. The cooling lag is less spectacular but of similar magnitude.

You need a positive feedback mechanism to produce a sharp temperature rise, and the water cycle provides exactly that, whereas CO2 does not. You also need to postulate a mechanism for the subsequent cooling, which again makes sense if H2O is the driver, but not CO2.   

Moving from million-year to annual measurements, the Mauna Loa data shows a cyclic annual fluctuation of CO2 in addition to a slow general trend. The peak CO2 level occurs in summer, whereas peak anthropogenic emission is obviously in winter. The obvious (to me anyway, but I'm only a scientist, not a priest* or a politician**) explanation is that insects and other coldblooded creatures are more active in summer, converting plant material to CO2. Thus temperature controls CO2, not the other way around.

I could mither on about the physics of infrared absorption and reflection, but the subject was clearly beyond the comprehension of the Intergovernmental Panel on Climate Change, who admitted in their first report that water was obviously the overwhelming greenhouse gas but as they couldn't model its very complex physics, they would ignore it. Probably the most important footnote in history.


*priest - someone who makes a living by telling you it's all your fault
**politician - someone who makes a living by taxing you


PS apropos mountain weathering, where did all that chalk come from? Once upon a time there must have been a hell of a lot more CO2 in the atmosphere, and far from disaster, it produced the South Downs, Dover, East Anglia....

[chiralSPO]

Moving from million-year to annual measurements, the Mauna Loa data shows a cyclic annual fluctuation of CO2 in addition to a slow general trend. The peak CO2 level occurs in summer, whereas peak anthropogenic emission is obviously in winter. The obvious (to me anyway, but I'm only a scientist, not a priest or a politician) explanation is that insects and other coldblooded creatures are more active in summer, converting plant material to CO2. Thus temperature controls CO2, not the other way around.

The annual fluctuation is easily explained by natural phenomena. Anthropogenic CO₂ emissions are a very small component of the overall CO₂ cycle (but by no means negligible).

Deciduous forests are the cause of the annual cycle. There are many more deciduous trees in the northern hemisphere than in the southern, and they absorb huge amounts of CO₂ in the summer months. Then the leaves fall during autumn and decompose, releasing much of the CO₂ back into the atmosphere.

As far as OP's question goes--it would be false to say that there is no link between atmospheric CO₂ and global temperature. There are many links, including the greenhouse effect, whereby CO₂ absorbs IR radiation and re-radiates back to the surface, as well as the solubility of CO₂ in water (oceans) which is related to temperature.

The key here is that it is a very complex relationship. I am a chemist, not a climatologist, so I will stop my analysis there.

[alancalverd]

There are many more deciduous trees in the northern hemisphere than in the southern, and they absorb huge amounts of CO2 in the summer months.

So why does the Mauna Loa data show exactly the opposite?

[chiralSPO]

There are many more deciduous trees in the northern hemisphere than in the southern, and they absorb huge amounts of CO2 in the summer months.

So why does the Mauna Loa data show exactly the opposite?

It does not say the opposite. See the attached image, which shows the greatest decline (rate) in CO₂ concentration during the July and August, and the greatest increase (rate) during December and January.

[alancalverd]

You need to remove the underlying upward trend to see the seasonal cycle more clearly.

The question in my mind is why the concentration of CO2 rises during the period of most rapid growth of vegetation (Jan-June) when anthropogenic emission is decreasing, and declines throughout the fall/harvest/winter period with a minimum in October/November when deciduous trees are dormant and anthropogenic emission is increasing. Surely that is counterintuitive and suggests that there must be a third mechanism involved? Or are farmers so completely deluded that they harvest in August/September when the plants are actually growing most rapidly?

[Tim the Plumber]

David Jones asked the Naked Scientists:
   Dear Chris, I have watched a youtube video called The Great Global Warming Swindle which puts forward convincing evidence that there is no correlation between CO2 levels and rising temperatures. Featured on the programme are Nigel Lawson, Nigel Calder (ex New Scientist Editor), Patrick Moore (founder of GreenPeace). They actually show graphs that say that over long periods of time, temperatures rise and THEN, 800 years later CO2 levels rise. They also show eveidence that states in the 1940s to 1970s when CO2 levels rose significantly, temps dropped. They also show a direct correlation between temperature rises and sun spot activity. How can climate change scientists refute these facts? Please explain. Thanks Hywel Jones
What do you think?

I think the link between CO2 and temperature is 97% drivel.

3% true.

There seems to be some slight temperature increase due to increased CO2. Nothing at all to worry about though.

[Craig W. Thomson]

David Jones asked the Naked Scientists:
   Dear Chris, I have watched a youtube video called The Great Global Warming Swindle which puts forward convincing evidence that there is no correlation between CO2 levels and rising temperatures. Featured on the programme are Nigel Lawson, Nigel Calder (ex New Scientist Editor), Patrick Moore (founder of GreenPeace). They actually show graphs that say that over long periods of time, temperatures rise and THEN, 800 years later CO2 levels rise. They also show eveidence that states in the 1940s to 1970s when CO2 levels rose significantly, temps dropped. They also show a direct correlation between temperature rises and sun spot activity. How can climate change scientists refute these facts? Please explain. Thanks Hywel Jones
What do you think?

They might actually be right about long term changes and those time periods, but they are conveniently overlooking one simple fact: We've applied combustion to tens or hundreds of millions of years worth of fossil fuels in just 150 years to power the Industrial Revolution, so "long periods of time" and "800 years" don't apply to current changes. This sort of environmental change is unprecedented. It produces both heat AND carbon dioxide. Even the rise of the first photosynthetic organisms didn't change the atmosphere this fast. In fact, the atmosphere's carbon dioxide content and temperature move in lockstep, and have for at least 800,000 years.

https://robertscribbler.files.wordpress.com/2014/04/ice-core-co2-record-800000-years.jpg

That's enough to refute the skeptics' arguments. If the range from 320 parts per million to 400 parts per million was part of the natural range of carbon dioxide, we wouldn't be seeing levels this high for the first time in 800,000 years. There would be other readings like that.

[Craig W. Thomson]

I think the link between CO2 and temperature is 97% drivel.

3% true.

There seems to be some slight temperature increase due to increased CO2. Nothing at all to worry about though.

The only science plumbers have to know is that crap flows downhill. Politicians don't even have to know that much. Talk about the blind leading the blind.

Take a look at the periodic table of elements. Different atoms have different properties, lining them up in nice, neat columns. Put those atoms together into molecules, and those molecules have specific properties too. One of the things that makes a carbon dioxide molecule special is that it is particularly good at absorbing long-wave radiation, or heat energy, then re-releasing it. That has a tendency to keep heat from escaping into space, trapping enough to make the planet habitable. Without carbon dioxide in the atmosphere, the planet would be too cool for life. Too much carbon dioxide, and the planet gets too hot for life.

Shrugging that off as nothing to worry about is 100% drivel.

[Craig W. Thomson]

You need to remove the underlying upward trend to see the seasonal cycle more clearly.

The question in my mind is why the concentration of CO2 rises during the period of most rapid growth of vegetation (Jan-June) when anthropogenic emission is decreasing, and declines throughout the fall/harvest/winter period with a minimum in October/November when deciduous trees are dormant and anthropogenic emission is increasing. Surely that is counterintuitive and suggests that there must be a third mechanism involved? Or are farmers so completely deluded that they harvest in August/September when the plants are actually growing most rapidly?

Interesting, I have never really thought about it that way. I'd like to take a stab at guessing the cause. Temperature of the ocean. I don't like watering my house plants with tap water because of the chlorine and chemicals, but I'm too cheap to buy them bottled water. My alternative is to run hot water into a vessel, then leave it sitting around for a while until it's cool. The high temperature makes the chlorine and gases evaporate faster, leaving you with something closer to natural water. It even tastes better. Similarly, I would assume that when the ocean is cooler, it is better at absorbing carbon dioxide, less efficient when it is warm.

One more guess: It might have something to do with the distribution of agriculture and population. I'm pretty sure the vast majority of agriculture takes place in the Northern hemisphere. Circulation in the two hemispheres is somewhat independent. The equator is not a "hard" atmospheric boundary, but it is a boundary nonetheless. Coupled with uneven distribution of both land masses and water surface in the Northern and Southern hemispheres, that could explain a lot. Remember, the ozone hole was something that recurred on a yearly basis, but only at the South pole, and there aren't any people or hair spray in Antarctica.

One more guess, and this is a pretty wild one: Some human populations still rely on inefficient sources of heat when it is cold, like burning wood. So, depending on what population in which hemisphere is experiencing winter, you might have a higher or lower percentage of people releasing more or less carbon dioxide per capita, and natural absorption processes then either start to catch up or fall behind.

[alancalverd]

One more guess, and this is a pretty wild one: Some human populations still rely on inefficient sources of heat when it is cold, like burning wood. So, depending on what population in which hemisphere is experiencing winter, you might have a higher or lower percentage of people releasing more or less carbon dioxide per capita, and natural absorption processes then either start to catch up or fall behind.

Exactly my point. Mauna Loa is in the northern hemisphere, so we'd expect the greatest concentration of anthropogenic CO2 to be in the northern winter. But the maximum is in the warmest, not the coldest months. So it's pretty clear that temperature is driving some nonhuman source of CO2 that is more significant than the anthropogenic one.

[wolfekeeper]

The question in my mind is why the concentration of CO2 rises during the period of most rapid growth of vegetation (Jan-June) when anthropogenic emission is decreasing, and declines throughout the fall/harvest/winter period with a minimum in October/November when deciduous trees are dormant and anthropogenic emission is increasing. Surely that is counterintuitive and suggests that there must be a third mechanism involved? Or are farmers so completely deluded that they harvest in August/September when the plants are actually growing most rapidly?

There's going to be a lag relative to the growing season; the material that grows in the peak growing season is going to take a while to break down, and will still be breakng down while new growth is happening.

For example leaves fall off the trees and goes into the soil and then a lot of it gets oxidised by bacteria; it's going to take months and months.

[chiralSPO]

are farmers so completely deluded that they harvest in August/September when the plants are actually growing most rapidly?

Farmers aren't looking to maximize total accumulated biomass, they are looking to maximize edibility of their crop. Therefore, I think farmers harvest whenever the fruits (or veggies) are ready. Peaches in the summertime, apples in the fall... For annuals like corn, it makes sense to me that the best yield would be found at the time of year when growth is fastest--why sit around waiting for every last drop of sunshine when the bugs won't?

But let's not get distracted by a non-issue.

Yes, there are multiple mechanisms that are crucial to the carbon cycle, and anthropogenic emissions are one of the least significant in terms of magnitude (the rates of change in CO₂ concentration within the annual cycle totally dwarfs the overall slope of the multi-year trend-line). But if we look at cumulative contributions over years, suddenly the slow and steady anthropogenic emissions start to have more of an effect than the nearly perfectly balanced ebb and flow of the dynamic equilibrium that was established millennia before the first coal mine opened, and has remained mostly stable until we perturbed it.

Obviously there are also long-term variations in global climate, and the composition of the atmosphere has changed dramatically many times over the last 4 billion years. But, as I understand it, each time there was a rapid change in the composition, there was an associated mass-extinction. For instance, the "oxygen holocaust" https://en.wikipedia.org/wiki/Great_Oxygenation_Event, which was precipitated by photosynthetic organisms converting CO₂ into O₂ and biomass. Oxygen was quite toxic to most life at the time, but the major issue (as I understand it) was that the global temperature dropped precipitously because of the sudden decrease in atmospheric CO₂ and CH₄. You might be able to imagine why some of us view the exact opposite process with some trepidation...

[alancalverd]

Here, on the other hand, is a recent finding that may explain a lot:

http://goo.gl/93BWOD

shows that melting of Antarctic ice releases huge quantities of CO2. There's no reason why this shouldn't also apply to seasonal melting of Arctic ice, so once again we would expect to find a positive correlation between temperature and CO2, but with temperature being the driver.

This is fortunate as it brings chemistry, geology and climatology into line with the known physics of water and carbon dioxide.

Fixed a hyperlink - mod

[evan_au]

For a somewhat humorous take on the debate, listen to the Infinite Monkey Cage, with Brian Cox (30 minutes).

They discuss the impact that the somewhat erratic El Nino Southern Oscillation has on global temperatures.

One of their panel points out that CO₂ levels are the highest that they have been in recent human history (mostly due to burning fossil fuels). Also, 14 of the hottest 15 years in human history have occurred since the year 2000. They suggest that this is not a coincidence, but there is a causal link.

[alancalverd]

Usual response here:

1. Please define global mean temperature and explain how it has been measured throughout human history, or state what parameter has actually been used.

2. Explain the seasonal variation in Mauna Loa CO2 concentration if anthropgenic CO2 is a signficant contributor.

3. Remember that a causal relationship demands (a) a lag between cause and effect and (b) a concomitant reduction in effect with a simiilar lag  characteristic when the cause is reduced.

4. Never mind human history, ice core data suggests CO2 lags 100 - 500 years behind temperature so it can't be a driver.

All of which suggests that the most honest explanation of the status quo, based purely on evidence, is coincidence, not causality.

[Craig W. Thomson]

So it's pretty clear that temperature is driving some nonhuman source of CO2 that is more significant than the anthropogenic one.

Not quoting any sources here, just regurgitating a bunch of stuff I already know, so I'm not posting any links. There are a lot of feedback loops driving this phenomenon. One good example is the melting of permafrost. The more CO2 we release, the hotter it gets, permafrost melts and glaciers recede, exposing dead and decomposing matter, which releases CO2. If it gets hot enough to wither and destroy trees (I saw this happen to a lot of oak trees in Texas several years back), they release CO2, or they start to get eaten by termites, which releases CO2, etc. A hotter ocean is less likely to absorb CO2. Then you have things like the albedo effect, so the less ice there is to reflect heat back into space, the more stays here to make it hot, releasing even more CO2.

I am also aware that CO2 emissions can come from volcanic activity. I have read online many times before that the amount of CO2 added by all the world's volcanoes is smaller than our economic contributions, but having said that, I am a firm believer that shifting the mass of thousands of cubic miles of melting ice from land masses to the ocean can change the pressure on tectonic plates enough to trigger earthquakes and volcanoes. Perhaps this could be adding some CO2 as well, but in that case, I'm more worried about FUTURE contributions than present ones.

[Craig W. Thomson]

3. Remember that a causal relationship demands (a) a lag between cause and effect and (b) a concomitant reduction in effect with a simiilar lag  characteristic when the cause is reduced.

4. Never mind human history, ice core data suggests CO2 lags 100 - 500 years behind temperature so it can't be a driver.

All of which suggests that the most honest explanation of the status quo, based purely on evidence, is coincidence, not causality.

After 800,000 years of not rising above about 320 parts per million, in the 150 years since the start of the Industrial Revolution, CO2 content has risen above 400 ppm, a full 20% higher than it was in any of those ice core samples.

I've said this a bazillion times before, and I almost always get somebody who want to argue about it, but the simple fact is, when you apply combustion to 100 million years worth of fossil fuels, that produces a lot of HEAT, not just CO2 to trap the heat. That's the source of your "temperature driven CO2 release." Nothing in the history of the planet has ever led to the mass/energy conversion of 100 million years worth of fossil fuels in 150 years. This is clearly causality, not coincidence.

The "lag" you spoke of means nothing here. The exponential growth rate of our population and resource consumption has overwhelmed the natural balance mechanisms and normal lag times. The Earth has a fever, and we are the organism causing it.

[Craig W. Thomson]

Farmers aren't looking to maximize total accumulated biomass, they are looking to maximize edibility of their crop. Therefore, I think farmers harvest whenever the fruits (or veggies) are ready. Peaches in the summertime, apples in the fall... For annuals like corn, it makes sense to me that the best yield would be found at the time of year when growth is fastest--why sit around waiting for every last drop of sunshine when the bugs won't?

But let's not get distracted by a non-issue.

Your response made me think of something I think has been overlooked. When we harvest things like wheat and corn, we don't eat the whole plant. We take the edible grain and throw away the rest. Same with crops like tomatoes or green beans, we pick the edible fruit, the rest of the plant withers and decays. It's not the grain and fruit that contains the most greenhouse gases, but rather the green parts of the plant, like the grass that cows eat. I'm not a farmer or agriculturist, but it seems like "crop waste" of this sort could contribute a fairly large amount of CO2.