Arguments
Empirical evidence that humans are causing global warming
What the science says...
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Less energy is escaping to space: Carbon dioxide (CO2) acts like a blanket; adding more CO2 makes the 'blanket' thicker, and humans are adding more CO2 all the time. |
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Climate Myth...
There's no empirical evidence
"There is no actual evidence that carbon dioxide emissions are causing global warming. Note that computer models are just concatenations of calculations you could do on a hand-held calculator, so they are theoretical and cannot be part of any evidence." (David Evans)
At a glance
Empirical evidence? None? That's a big bold statement to make, so let's take a look. 'Empirical' is defined as something that may be actually measured and presented as a finding. Let's treat the topic as a criminal prosecution. The accused is CO2 and the accusation is that its increased levels through our emissions are warming the planet. As with all court cases, it's important to present an accurate account of events. So firstly, we'll examine the background to this particular case.
It all started in the 1820s, when French physicist Joseph Fourier had worked out that, at its distance from the Sun, Earth should be very cold. He proposed that Earth's atmosphere must contain something that kept the planet warm, like some invisible blanket. His ideas were, it turned out, correct albeit incomplete.
Some decades passed before the nature of Fourier's blanket was discovered. This was done through a series of experiments involving various gases. Interestingly, two investigators worked on it independently, John Tyndall, in the UK and Eunice Foote in the USA. Impressively, their results were virtually identical.
Foote, writing in 1856, was the first scientist to state that carbon dioxide can trap energy. She predicted that if there had been more CO2 in the atmosphere at times past, an increased temperature would have prevailed. That was something the geologists already knew. Tyndall went on to write, in 1861, that on top of carbon dioxide, hydrocarbons - such as methane - would have even greater effects at very low concentrations. The greenhouse effect and its key players had been identified.
The landmark paper, "The Carbon Dioxide Theory of Climatic Change", was published just under a hundred years later. Essentially, it stated what we know now. Without the atmosphere and its greenhouse gases, Earth would be an uninhabitable iceball. As Fourier started to reason all that time ago, greenhouse gases act like a blanket. They keep Earth warm by inhibiting the escape of energy back into space. Humans are adding CO2 to the atmosphere, mainly by burning fossil fuels, thereby intensifying the effect.
That's the background. As we emit more greenhouse gases, the effect is like wrapping yourself in a thicker blanket. Even less heat is lost. So how can we tell that? How can we find hard evidence, like good CCTV footage of our suspect up to their mischief?
How about measuring it?
Satellites orbiting our planet carry sensitive instruments on board. Through them we can measure how much energy is arriving from the Sun. We can measure how much energy is leaving the Earth, out into space. So right there we have two things to compare.
What do the measurements tell us? Over the last few decades since satellites became available, there has been a gradual decrease in the energy heading from Earth's surface back into space. Yet in the same period, the amount of energy arriving from the Sun has hardly changed at all. Something is hanging onto that energy and that something is getting stronger. That something is carbon dioxide - doing exactly as Foote and Tyndall said it would 160 plus years ago.
Verdict: guilty on all counts.
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Further details
The well-established theory that man-made CO2 is causing global warming is supported as well as any chain of evidence in a rock-solid court case. CO2 keeps the Earth warmer than it would be without it. It has done so for most of geological time. Humans are adding substantial amounts of CO2 to the atmosphere, mainly by burning fossil fuels. Empirical evidence abounds to support the contention that the rising temperatures are being caused by that increasing CO2.
The Earth is wrapped in an invisible blanket
It is the Earth’s atmosphere that makes most life possible. To understand this, we can look at the moon. On the surface, the moon’s temperature during daytime can reach 100°C (212°F). At night, it can plunge to minus 173°C, or -279.4°F. In comparison, the coldest temperature on Earth was recorded in Antarctica: −89.2°C (−128.6°F). According to the WMO, the hottest was 56.7°C (134°F), measured on 10 July 1913 at Greenland Ranch (Death Valley).
Man could not survive in the temperatures on the moon, even if there was air to breathe. Humans, plants and animals can’t tolerate the extremes of temperature on Earth unless they evolve special ways to deal with the heat or the cold. Nearly all life on Earth lives in areas that are more hospitable, where temperatures are far less extreme.
Yet the Earth and the moon are virtually the same distance from the sun, so why do we experience much less heat and cold than the moon? The answer is because of our atmosphere. The moon doesn’t have one, so it is exposed to the full strength of energy coming from the sun. At night, temperatures plunge because there is no atmosphere to keep the heat in, as there is on Earth.
Without the atmospheric greenhouse effect, Earth would be approximately 33°C (59.4°F) cooler than it actually is. That would make most of the surface uninhabitable for humans. Agriculture as we know it would be more or less impossible if the average temperature was −18 °C.
Greenhouse gases act like a blanket, keeping the Earth warm by preventing some of the sun’s energy being re-radiated from Earth's warmed surface, back out into space. If we add more greenhouse gases to the atmosphere, the effect is like wrapping yourself in a thicker blanket: even less heat is lost. So how can we tell what effect CO2 is having on temperatures, and if the increase in atmospheric CO2 is really making the planet warmer?
The heat-trapping effects of CO2 and other greenhouse gases were discovered in the mid-19th century but we can do more sophisticated stuff these days. We can measure the heat energy going into Earth's climate system and that coming back out.
In 1970, NASA launched the IRIS satellite measuring infrared spectra. In 1996, the Japanese Space Agency launched the IMG satellite which recorded similar observations. Both sets of data were compared to discern any changes in outgoing radiation over the 26 year period (Harries et al. 2001). What they consistently found was a drop in outgoing radiation.
This change in outgoing radiation was consistent with theoretical expectations. Thus the Harries paper found "direct experimental evidence for a significant increase in the Earth's greenhouse effect". This result has been confirmed by subsequent papers using data from later satellites (Griggs & Harries 2004, Chen et al. 2007). In the same period, the amount of energy arriving from the sun has hardly changed at all.
When there is more energy coming in from the Sun than there is escaping back out to space, it should come as no surprise to learn that our climate is accumulating heat. The planet's total heat build up can be derived by adding up the heat content from the ocean, atmosphere, land and ice (Murphy et al. 2009). Just since 1998, the planet has accumulated heat energy equivalent to the yield of 3,260,000,000 Hiroshima-sized atomic bombs.
The primary greenhouse gases responsible for the trapping of heat – carbon dioxide (CO2), methane (CH4), water vapour, nitrous oxide and ozone – comprise around 1% of the air. The main components of the atmosphere – nitrogen and oxygen – are not greenhouse gases, because they are virtually transparent to long-wave or infrared radiation.
For our next piece of evidence, we must look at the amount of CO2 in the air. We know from bubbles of air trapped in ice cores that before the industrial revolution the amount of CO2 in the air was approximately 280 parts per million (ppm). In June 2013, the NOAA Earth System Research Laboratory in Hawaii announced that, for the first time in millions of years, the amount of CO2 in the air had gone above 400 ppm. It's now getting on for 420 ppm. That information gives us the next piece of evidence; CO2 has increased by 50% in the last 150 years.
The Smoking Gun
The final piece of evidence is ‘the smoking gun’, the proof that CO2 is causing the increase in temperature. CO2 traps energy at very specific wavelengths, while other greenhouse gases trap different wavelengths. In physics, these wavelengths can be measured using a technique called spectroscopy. Here’s an example:
Fig. 1. Spectrum of the greenhouse radiation measured at the surface. Greenhouse effect from water vapour is filtered out, showing the contributions of other greenhouse gases (Evans et al. 2006).
The graph shows different wavelengths of energy, measured at the Earth’s surface. Among the spikes you can see energy being radiated back to Earth by ozone (O3), methane (CH4), and nitrous oxide (N20). But the spike for CO2 on the left dwarfs all the other greenhouse gases, and tells us something very important: most of the energy being trapped in the atmosphere corresponds exactly to the wavelength of energy captured by CO2.
Summing Up
Like a detective story, first you need a victim, in this case the planet Earth: more energy is remaining in the atmosphere.
Then you need a method, and ask how the energy could be made to remain. For that, you need a demonstrable mechanism by which energy can be trapped in the atmosphere, and greenhouse gases provide that mechanism.
Next, you need a ‘motive’. Why has this happened? Because CO2 has increased by nearly 50% in the last 150 years and the increase is mostly from burning fossil fuels.
And finally, the smoking gun, the evidence that proves ‘whodunit’: energy being trapped in the atmosphere corresponds exactly to the wavelengths of energy captured by CO2.
The last point is what places CO2 at the scene of the crime. The investigation by science builds up empirical evidence that proves, step by step, that man-made carbon dioxide is causing the Earth to warm up.
Finally, the myth-creator refers to climate models as "concatenations of calculations you could do on a hand-held calculator". That statement demonstrates nothing more than a limited grasp of what models are and do and is rebutted at this post in our series.
Last updated on 9 July 2023 by John Mason. View Archives
Read a little further into the IPCC report. FF has zero C14. The continued dilution of C14 in atmospheric CO2 since nuclear testing is consistant with the calculation of relative proportions of FF v LUC. You claim IPCC has not considered changes in agricultural management affecting soil carbon. However the IPCC source for LUC using fig 6.8 is Houghton et al 2012. This uses and compares a number of different studies all producing similar results. Your point is explicitly discussed in section 4.2. From the studies discussed, it concludes "Globally,
the current flux from agricultural management is uncertain
but probably not far from zero". If you have papers that can challenge those studies, then please cite. However, as Tom points out, if LUC contribution is higher than current estimates, then given known FF emissions, you then need to account for an unknown sink to get our measured concentrations (and the C14 dilution).
I see scaddenp has beat to the punch on Houghton et al. Here is the full quote:
The IPCC in turn indicated that it's estimates of emissions from LUC were:
So, the flux that RedBaron says the IPCC ignores is explicitly taken into account by the IPCC's primary source. Further, while he estimates that flux to dominate the flux from Fossil Fuel emissions without evidence or reading of the primary literature, Houghton et al (2012) looked at the primary literature and found that while in some cases the flux is positive, increasing atmospheric CO2, in others it is negative and that the net global effect is close to zero.
Think about it Tom. You said, "Houghton et al (2012) looked at the primary literature and found that while in some cases the flux is positive, increasing atmospheric CO2, in others it is negative and that the net global effect is close to zero." And the IPCC report that I quoted said, "Since 1750, anthropogenic land use change have resulted into about 50 million km2 being used for cropland and pasture, corresponding to about 38% of the total ice-free land area (Foley et al., 2007, 2011)" Meanwhile about 1/2 fossil fuel emissions are being sequestered (although not all of that is in terrestrial sinks)
Add up what all those independant sources mean. It means just what I said in my first post here. Agriculture has broken the natural buffering capability (ecosystem service of sequesting carbon and moderating climate) of the terrestrial biosphere roughly by about 1/2 +/- and the current biosphere is falling short of sequestering CO2 from fossil fuel emissions roughly by about 1/2. There is your primary problem confirmed in yet another way.
The reason this is important IMHO is that it points to many potential mitigation solutions that are biology based. Agricultural land is already intensively managed. It doesn't take huge budgets of new research and development that the energy technology fixes require to simply change the management. It's simply an educational solution. Farmers only need educated in the already developed management techniques that restore the ecosystem services to the land they manage. Very small costs, and big returns in both carbon sequestration and actually instead of costing society huge sums, turns out to be a net profit!
But what Houghton does is add up all those changes. That is where the numbers come from. Your original post was "Sure emissions also help somewhat," whereas the evidence from all those sources with all the maths, calculated by multiple methods, would suggest that the phrase should be "Sure human agriculture also help somewhat" - to the tune about 8% what FF does. There is strong evidence to support a number around that magnitude and so far you havent cited a source which would suggest otherwise.
@Scaddenp: You said, "But what Houghton does is add up all those changes. That is where the numbers come from. Your original post was "Sure emissions also help somewhat," whereas the evidence from all those sources with all the maths, calculated by multiple methods, would suggest that the phrase should be "Sure human agriculture also help somewhat" - to the tune about 8% what FF does..." Actually I have seen figures around 10% but either way 8-10% is close enough. That's emissions. The ecosystem service of carbon sequestration is on the opposite side of the carbon cycle. So we have emissions of 8-10% but what is missing from your analysis is that we have degraded the terrestrial biosphere's capability to sequester carbon by roughly ~50%+/- by degrading the terrestrail ecosystems world wide. Even in their highly degraded state, the ecosystems manage to sequester about ~ 50% of all emissions. Restoring the ecosystems to full function with regard to carbon sequestration should potentially be able to eliminate the other 1/2. Restore them to higher functionality than wilderness ecosystems should actually potentially begin drawdown.
Okay, RedBaron, it looks like we are in more agreement. What is the basis for your statement "we have degraded the terrestrial biosphere's capability to sequester carbon by roughly ~50%+/- by degrading the terrestrail ecosystems world wide." I havent seen data published on this (which is not to say that it doesnt exist). I admit to being skeptical because some sequestration mechanism are sensitive to CO2 concentration so the maths doesnt fit.
RedBaron @228 and 230:
1) The argument that we have degraded the terrestial biosphere's ability to sequester fossil fuels is different from your initial claim that:
Specifically, your current argument relies on fossil fuels providing the excess CO2, with the implication that has we equally degraded the biosphere, but not emitted the fossil fuels, there would have been a much reduced increase in CO2 emissions.
2) Degrading 50% of the terrestial biosphere's ability to sequester CO2 is not the same as degrading the terrestial biosphere's ability to sequester CO2 by 50%. For them to be the same, we would need to, not degrade, but eliminate 50% of the terrestial biosphere's ability to sequester CO2, that 50% would have to account for half of natural sequestration, and there would have to be no compensating increases in the ability to sequester in the other 50% of the biosphere. You have not shown any of these conditions to be true. Indeed, plausibly, the degradation of the ability to sequester scales with the biomass. That is, plausibly we have degraded the ability of the terrestial biosphere to sequester CO2 by the ratio of cumulative LUC emissions (160 GtC) to total terrestial biosphere Carbon (2500 GtC), or by 6.4%.
3) Whatever the degradation of the ability to sequester is, the fact is that the terrestial biosphere has sequestered 130 GtC, and that over the last few decades, total biosphere sequestration has exceded total emissions from LUC as shown by the O2 data (see my post @223). Ergo the increase in the ability of the terrestial biosphere to sequester CO2 due to the increase in temperature, humidity and CO2 concentration exceeds the degradation of the ability to sequester consequent on LUC.
I also have found very limited maths concerning this as well! It is an over looked but in my opinion highly important part of the problem! It's an oversite that in my opinion causes the IPCC analyses to be flawed! There is however some information out there. It just hasn't been rigorously applied to climate science models. At least not to my satisfaction.
But let's start with historical ecosystems prior to the anthropocene. (the proposed epoch that began when human activities had a significant global impact on the Earth's ecosystems)
https://www.zotero.org/jsebastiantello/items/itemKey/Z6B9F3QE
"the truly novel event of the Cenozoic was the evolution and expansion of grasslands, with their uniquely coevolved grasses and grazers. Neogene expansion of the climatic and geographic range of grasslands at the expense of woodlands is now revealed by recent studies of paleosols, fossils, and their stable isotopic compositions. Grasslands and their soils can be considered sinks for atmospheric CO2,CH4, and water vapor, and their Cenozoic evolution a contribution to long-term global climatic cooling. Grassland soils are richer in organic matter than are woodland and desert soils of comparable climates, and when eroded, their crumb clods form sediment unusually rich in organic matter. Grasslands also promote export of bicarbonate and nutrient cations to lakes and to the oceans where they stimulate productivity and C burial"
So according to Retallack, the primary driver that gave us the climate we humans evolved in was the grassland/grazer biome. Admittedly taking geological time to evolve. Grasslands/graziers didn't just pop into existence and immediately take over 1/2 the worlds forests. But the biome is the biome that once established did make a major contribution to our climate. So this is the biome that historically originally pulled down our carbon to pre-industrial levels. Simply removing that biome would tend to cause climate to rebalance at pre-Cenozoic levels. (much warmer and wetter than we are now)
Now look at agriculture. What is the primary agricultural ground? Yes some of it is cleared forests and alfisols. But they tend to loose their carbon and fertility quite rapidly. The prime agricultural land is regions like the midwest North American plains. Particularly the tall grass prairie. Why? because that's where the deep fertile mollic soils are primarily formed! But those ecosystems are largely extirpated and replaced by artificial agricultural ecosystems. Even in the dryer plains/savanna areas of the world, the grazers are largely extinct or extirpated, causing those grasslands to no longer effectively function as carbon sinks. Replaced once again with agriculture, either dryland crop production or livestock. Often many of those grasslands are burned due to there not being nearly enough animal impact to cycle the vegetation.
Because of this we get analysis from many sources already mentioned in this thread: "Since 1750, anthropogenic land use change have resulted into about 50 million km2 being used for cropland and pasture, corresponding to about 38% of the total ice-free land area (Foley et al., 2007, 2011)"
It's not just that 38% is in agriculture. But the prime arable land is almost completely under agriculture. It's not evenly distributed. Mountains and deserts have far less % of the land in agriculture. Agriculture rests primarily right in the middle of the best land, which also is the land responcible for mitigating carbon increases in the atmosphere! So that 38% is right in the same land that potentially would be mitigating our fossil fuel emissions. Quantifying it is hard though. Entire regions and whole trophic levels of the biomes are gone. We are not going to let loose millions and millions of bison in Iowa corn country and let them and the wolves roam freely to measure what carbon would have been sequestered if we hadn't extirpated them. Certainly can't bring back the extinct megafauna of the planet. So hard numbers on that are very difficult to get.
But what we can and have done is develope models of agriculture with farming methods that function as carbon sinks. They have been measured compared to conventional best management practises currently being used.
Here is an example: LINK
and
http://www.esajournals.org/doi/abs/10.1890/1051-0761(2001)011%5B0343:GMACIG%5D2.0.CO%3B2
These studies show that best management practises on both rangeland and planted pasture increases CO2 sequestration by 11 tons CO2/ha/yr simply by regenerating ecosystem function. You couldn't of course say all grassland does that, but it shows an INCREASE over conventional by that amount in those locations. Some areas like Iowa probably would be more as the conventional model there is corn fed instead of grass fed. Here is a white paper by the author of the first paper descibing the potential if that model were applied worldwide:
LINK
It's not as easy to restore ecosystem function without animal impact. But relatively good results have been achieved by David Brandt on traditional row crops. Documented by USDA NRCS on Brandts demonstration farm.
LINK
Unlikely to reach the historic 8-10% SOC with Brandts system as it doesn't include animals. But he has achieved results as high as 4-5% SOC sequestered in a decade even in a row crop model. (no til with multi species covers)
There are systems out there that integrate all three of the above that have achieved the historic 11%!
[RH] Shortened links that were breaking page format.
RedBaron @233.
Down this thread since #217, you have been presenting perhaps three separate arguments which may be why the responses haven't been quite hitting the mark for you.
Perhaps the least controversial (relatively) of your three proposals concerns sequestartion of CO2. There are people (coming from different directions) who advocate using grassland management techniques to improve sequestration of atmospheric CO2. It is usually at the same time also argued that such management of grassland would hughly incerease pastoral livestock production. Further I have seen such argument made in a general sense to cereal production as well.
These multiple approaches reaching similar conclusions would suggest there is merit in such arguments although the slow of progress made by such arguments suggests also that the benefits are not as straightforward as claimed (or as not so easily demonstrated as claimed). It also suggests that a discussion here will not easily provide a clear outcome.
However, it is the second argument that you present that is the main bone of contention within the thread. You are arguing that the rise in atmospheric CO2 results directly from changes in agricultural practice and such changes have caused CO2 emissions that remain unaccounted for by any of the studies of the likes of Houghton.
Such an argument is strong stuff. Yet in establishing such a hypothesis, I would say that I don't think you have begun even to scratch the surface.
But there is a third hypothesis that you are proposing. You suggest that it was the spread of grasslands during the Cenozoic that resulted in the fall in atmospheric CO2 levels over that period. Again, this is strong stuff.
Mixing up all this into one big debate will get us nowehre. Thus I would recommend that these three areas of discussion are addressed separately.
@MA Rodger,
I am not sure I am up to the monumental task you just outlined. But what I can say is that Greg Retallack and Richard Teague both spoke at the most recent Annual Review of Earth and Planetary Sciences conference. They appear to be in support of each other completely. Ie the paleo record supports the current observations and they both point to potential near future solutions of AGW.
[JH] Please document what Greg Retallack and Richard Teague said at the most recent Annual Review of Earth and Planetary Sciences conference. Where and when was this conference held? Who sponsors it? Were you in attendance?
RedBaron @235.
I assume this paper by Retallack will contain what you're advocating. And (I do hate linking to video - life is too short) this 24 minutes of somebody's life will explainwhat you mean by Teague (& this the Retallack equivalent).
Correction to #236. That Teague link is here.
[JH] Commenters like RedBaron are expected to document the source of their assertions about what others have supposedly stated. It they do not, or cannot, their comments are merely heresay hearsay.
OK I got the Name of the conference wrong, but here is a link.
http://bio4climate.org/conferences/conference-2014/program/
[PS] Fixed link
Here is the published text that support the conference lecture. That is what is in The Annual Review of Earth and Planetary Sciences. Sorry I got the conference name wrong by swapping it with his published paper.
http://www.annualreviews.org/doi/abs/10.1146/annurev-earth-050212-124001?journalCode=earth
[PS] FIxed link
RedBaron @239.
Fine. We are looking at the same sources. So where within this work of Rellatack or this work of Teague is there support for your assertion @225 that the IPCC AR5 Chapter 6 "have the numbers right for the land use change to agriculture, but are missing the land use changes within agriculture as methodologies change."?
MA Rodger,
You asked, "So where within this work of Rellatack or this work of Teague is there support for your assertion @225 that the IPCC AR5 Chapter 6 "have the numbers right for the land use change to agriculture, but are missing the land use changes within agriculture as methodologies change."?"
Retallack I used to establish a base line and context. So for example, when I speck about methodologies in agriculture that use biomimicry to restore ecosystem services function, it is important to define exactly what that means, and show evidence that indeed at one time ecosystems did function to sequester carbon and cause global cooling. So Retallack provides that evidence, context and helps one to exactly understand which ecosystem functions we are trying to restore, why. and how.
Teague is the direct answer to the question of changes in agricultural methodology, as several types of land use change within different management types of agriculture were directly measured on a real world working ranch scale. Now that was accomplished by using biomimicry, and the concepts being mimicked are evidenced by Retallack. So they are interconnected in that way although Retallack's research has nothing to do with agriculture directly. There are other methodologies that use biomimicry to accomplish carbon sequestration. I simply used Teague because his research is well documented and pretty robust. Many other carbon farming techniques are still in what we would call development and verification stage. I am deveoloping one myself in fact. But I couldn't use that here as it is unpublished original research. Teague's work is published reviewed and pretty strong evidence.
RedBaron @241.
So what you are saying is that these two Retallick & Teague do not accuse the IPCC or anybody else of failing to account properly for CO2 emissions from land use changes. Are there any other studies or published theories that lend support to accusations of such mal-accounting of emissions by the IPCC? Or is it all some analysis of your own invention? Perhaps you would like to share your detailed reasoning with us. Or perhaps it is not that well-founded and yet unready for the rough-&-tumble of public scrutiny.
@ MA Rodger,
Actually a closer aproximation of what I am saying is that the IPCC is vastly underestimating the problem, by ignoring much of the most basic underlying causes. This has also flawed their analysis of what needs to be done to fix the problem as well. Maybe if I approach it in more general terms you'll understand better. I admit I am not a very good "rough and tumble" public debate specialist. So you'll probably need to fill in some blanks yourself. But let's look at some disturbing trends. As a result of erosion over the past 40 years, 30 percent of the world's arable land has become unproductive. http://www.ids-environment.com/Common/Paper/Paper_83/Soil%20Erosion.pdf Now of course this is measured in terms of agricultural food production for humans. But if you understand that unproductive also means not feeding the soil food web that is responcible for the major part of the carbon cycle, you get an idea why the biosphere can't keep up with fossil fuel emissions. Or look at it from still another angle. The least efficient natural ecosystem for long term sequestration of carbon is forests, and forests currently occupy only 20-25% of the land surface of the planet, yet nearly all the carbon sequestered in world wide terrestrial ecosystems is in forests. Why? Because mismanagement of agricultural "artificial" ecosystems. Mismanagement that has turned the largest terrestrial carbon sink into an emissions source! Depending on how IPPC calculates it, it is either 8-10% of emissions, or calculated differently near net 0 effect. See references above. post 227 "Globally, the current flux from agricultural management is uncertain but probably not far from zero." See the IPPC got that part! But what they left out was that the same ecosystems that are currently "probably not far from zero" are the same ecosystems that pre-human intervention were the primary terrestrial sequesters of carbon. I am not sure how to explain the math flaw. If you have a negative and turn it into a positive, it is wrong to use the positive as the effect. So if you start with -A and later measure +B due to anthropomorphic changes. It is improper to use +B as the anthropomorphic effect. The real anthropomorphic effect is A+B. IPPC has vastly underestimated the effect of agriculture for this reason. Admittedly that is highly oversimplified, but it addresses the principle IPCC flaw. The effect of environment degradation is underestimated because the measurements are being done on the degraded ecosystems we see now, not the functioning ecosystems prior to humans degrading them. http://www.fewresources.org/uploads/1/0/5/2/10529860/3768968_orig.jpeg
Adding to the confusion, humans can actually improve on the natural ecosystems function beyond the natural pre-historical state (with intensive management). We haven't. We have done the opposite. But there is no reason we couldn't.
In response to Red Baron in general, Houghton et al (2009) itemizes total biomass/hectare for various ecosystems. Carbon constitutes about 50% of the biomass. Taking low values where two are given, we thus determine that the carbon content constitutes 95 Tonnes/Hectare (ie, Megagrams per Hectare) for tropical rain forest, and 28.5 Mg/Hectare for tropical savannah. The difference is 66.5 Tonnes per Hectare.
Figure 8 of Retallack et al (2013), shows the carbon content in Kilograms per meter squared for for various ecosystems in African and Australia by precipitation. In Australia, forests have a greater carbon content in soil than do grasslands (Mallee scrub). In Africa forests have less carbon in soil than do grasslands. Taking the largest difference (4 Kg/m^2) and converting units, that represents 40 Tonnes per Hectare. Therefore, using conservative estimates, and counting both soil carbon and biomass Tropical rainforests sequester 26.5 more tonnes/Hectare than do equivalent grasslands. Using more reasonable estimates, forests sequester as much as 126.5 tonnes/Hectare more carbon than do grasslands, ie, about twice the carbon per hectare.
Interestingly, Teague (in a book chapter for Geotherapy) shows a tabulation (table 17) of soil and total Carbon stored in various ecosystems from White (2000). He points out that globally, grasslands store more carbon in soil than do forests, although forests store more tonnes per hectare. That is true of soil carbon alone, but once biomass is included, forests store 90% more carbon as grasslands per unit area, globally averaged. White's results, as quoted by Teague, suggest the African situation is anonalous, and that the Australian situation where forests store more soild carbon than do grasslands is more typical. Indeed, on the White (2002) figures, forests store 50% more carbon in soil per unit area than do grasslands. (That may partially be because grasslands are typically found in more arid conditions than are forests.)
Of more direct interest to your vague theses, Teague also tabulates estimates of emessions from various sources, showing 136 GtC from land use conversions from 1750 onwards (compared to the 180 GtC estimated in AR5), with a further 320 GtC estimated emissions over the Holocene to 1750. The 136 GtC estimate for industrial era emissions compares to an estimated 270 GtC emitted from fossil fuels (compared to 365 GtC estimates in AR5). Part of the discrepancy between these estimates and those from AR5 may be due to the final date of the estimate.
Importantly, Teague is not suggesting that soil degradation is responsible for the hockey stick in atmospheric CO2 concentrations. He does suggest soil revitalization can eliminate excess CO2 from the atmosphere, but that is because he assumes the revitalization of soil degraded in the preindustrial era will contribute to the sequestration. The sharp increase in CO2 concentration, however, is due primarilly to the very sharp increase in fossil fuel use as shown in his post at 224.
Teague does, however, suggest that restoration of the grasslands could sequester sufficient CO2 to bring the atmosphere back to preindustrial levels. He writes:
I do not, however, trust his sums. First, 1ppmv of CO2 in the atmosphere is 2.12 GtC (AR5), not 2 as uses in his estimate. More importantly, just as only 44% of anthropogenic emissions have stayed in the atmosphere, only 44% of any carbon sequestration will result in a reduction on atmospheric CO2, the rest being compensated for by oceanic outgassing. Therefore, to reduce CO2 concentrations by 120 ppmv, we need to sequester 580 GtC. That is, he underestimates the task at hand by 60%. Put another way, we would need to sequester 27% more CO2 in the soil than he estimates to have come out of it since the start of agriculture to tackle global warming this way.
Second, he appears to fudge his figures. Ruddiman's estimates of preindustrial emissions include excess methane production from the spread of rice paddies, and emissions from deforestation. That is, they are not an estimate emissions of soil carbon. Indeed, even the industrial era emissions from LUC only include 78 Gigatonnes from soil itself. Assuming a similar proportion of preindustrial emissions are from soil, that means only 260 GtC have been emitted from soils due to human activities over the last 10 thousand years.
Given this, the idea that we can solve AGW simply by changing our pastoral practises is fanciful. (We may be able to help solve the problem by such changes, but it will only be a small contribution to the problem, most of which must be solved by reducing industrial emissions.)
RedBaron @243.
I fear you are straddling all three of your different arguments you have brought here with your comment. As I explained @234, this is a great impediment to getting anywhere in this discussion.
As I interpret it, your -A+B illustrates this situation of mixing these different arguments. The +B is the carbon sequestration from future improved agricultural practice that you contend is a way of reversing CO2 levels. The -A is (it seems) is not the carbon loss from present agricultural practice that you contend the IPCC is underestimating. Rather -A is some natural sink that has ceased due to human intervention, a third issue that you argue here.
Sticking with the IPCC underestimation before we address anything else (which makes things much less complicated), you again quote Houghton et al (2012) as referenced by IPCC AR5 which states "Globally, the current flux from agricultural management is uncertain but probably not far from zero." And for all the world, you are agreeing with this statement @243 - "See the IPPC got that part!"
So, as we both seem to agree with the IPCC, can we agree? The on-going management of agrcultural lands (as opposed to changing land use) is as the IPCC say roughly carbon neutral.
And if we can do that, do you then accept that the sources of carbon emissions set out by the IPCC are not in gross error?
Tom Curtis @244.
The error by Teague in suggesting that sequestering 2GtC from the atmosphere would reduce atmospheric CO2 by 1ppm(v) is identical to that made by Savory.
Continuing from #247 in the absence of a RedBaron reply.
I see no evidence that Houghton and others are in error over CO2 emissions from land use.
Concerning the issue of the role of soils in the reduction of atmospheric CO2 levels over the last 19 million years, this contention is based solely on the work of Retallack (eg Retallack 2013) which attempts to argue that there are three competing theories that could be responsible for this reduction, rock weathering, ocean up-take and soil creation and Retallack argues that soil creation is the most likely. Such argument is badly flawed as Retallack makes the same basic mistake as Teague & Savory described @244. From Retallack (2013):-
However, to draw down atmospheric CO2 to half the level, say by 700 PgC, there will also be a need to sequester the resulting emissions from the biosphere (350 PgC) and the oceans (2,450 PgC) as the atmospheric level is in balance with boisphere and ocean. This totals at 3,500 PgC. (These figures very roughly based on the work of David Archer.)
The colder oceans would have taken perhaps 1,400 PgC leaving 2,100 PgC but the oceans can be considered as a feedback mechanism due to global cooling. The appearance of deeper soils may have reduced the amount of rock weathering required to handle the 2,100 PgC, but if this was something like 600PgC, the largest contribution to CO2 draw-down remains rock weathering.
The final line of argument fron RedBaron was the use of agriculture to sequestrate CO2 from the atmosphere and reduce the atmospheric levels despite continuing emissions from fossil fuel use. Because of the basic error described above, this could only hold CO2 levels static. It could not reduce them with the present CO2 emission levels. That in itself would be a wonderful thing to achieve if it were possible but it would require a change in agricultural practices worldwide to get such a result, a task almost as difficult as weaning mankind off the fossil fuels which is the primary cause of our problem.
I find it rather odd that nobody ever brings up the fact that our Magnetosphere has been steadily weakening during all of this "climate change" nonsense.
It has been weakening by 5% per decade, this could very easily account for elevated temperatures and erradic weather patterns. Just food for thought.
[PS] Please substantiate your claim of 5% per decade and that this has only started happening over period of global warming, and how a weakening magnetosphere can warm the earth. Unsupported claims are sloganeering and violate comments policy.
Further - if you are linking to Svensmark cosmic ray hypothesis, then please see here for what the science has to say about this
Talvar is almost certainly referring to data from the Swarm satellites which recently showed that magentic field strength was changing ~10 times more rapidly than expected over a six month period. The expected rate, based on research suggesting that a magnetic pole reversal is underway, was approximately 5% per century... multiplied by ten yields his 5% per decade. However, as noted, that is based on six months worth of data from a new system. There is no evidence whatsoever that this has been going on for a long time as he implies.
Further, it just isn't relevant because this cannot "very easily account for elevated temperatures". To my knowledge no one has even suggested a mechanism to explain how variations in the Earth's magnetic field would cause massive planetary warning. If anyone ever tries they will have a fun time explaining why there seems to be no connection between the pattern of magnetic variation and the pattern of warming... e.g. during that six month period the magnetic field over the entire North America continent actually strengthed greatly (that change being offset by declines elsewhere around the globe), yet the western part of the continent was warmer than normal and the eastern portion colder.
@MA Rodger,
Sorry for the delay in replies. I realise I have probably poorly stated my argument. So I found a presentation explaining it online. I realise the presentation is not the same weight as a scientific study or even a synthesis. But I hope this will explain my position with more clarity. Please explain to me where you believe this guy is wrong. That will give you context and me a place to start digging.
https://www.youtube.com/watch?v=8Q1VnwcpW7E
PS. You said, "That in itself would be a wonderful thing to achieve if it were possible but it would require a change in agricultural practices worldwide to get such a result, a task almost as difficult as weaning mankind off the fossil fuels which is the primary cause of our problem." I would counter with the fact the green revolution happened almost overnight. A similar change to a carbon farming revolution could be equally rapid in my opinion.