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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Recommended supplemental reading:

The return of the iris effect? by Andrew Dressler, Real Climate, Apr 24, 2015

wili at 00:03 AM on 25 April 2015

University of Queensland offering free online course to demolish climate denial

('her' not 'here')

wili at 00:02 AM on 25 April 2015

University of Queensland offering free online course to demolish climate denial

Will it help me communicate with my students who claim that the promise God made to Noah proves that CC can't get that bad (without throttling here '-))?

MA Rodger at 22:14 PM on 24 April 2015

There's no empirical evidence

Tom Curtis @277.

For a second time we use slightly different forms of analysis (I was assuming %(CO2 emissions), you %(drawn-down CO2) using Law Dome data) but I haven't before considered using ice core data to extend analysis of atmospheric levels back before the Keeling curve.

While the Law Dome data does show some curious wobbles, it does allow a calculation of sorts for the Atmospheric Fraction back into the 1800s. There is no evidence from such a calculation that there was some grand absorbing sink of CO2 existing back then. (There's even an SKS post from 2010 that does a similar analysis with the same outcome.) This strongly suggests that the marked trashing of eco-systems over that period has not altered "ecosystem services" to any significant extent on a global scale.

Glenn Tamblyn at 19:28 PM on 24 April 2015

Changes in water vapor and clouds are amplifying global warming

rkrolph

Actually they aren't contradictory. There is a difference bewteen the net effect clouds have when the climate is in one state and the impact a change in their conribution has.

I am going on memory here but I think from the last IPCC report the contribution from clouds as 50 watts/m² of cooling and 30 watts/m² of warming for a net effect of 20 watts/M² of cooling.

Now hypothetically, if in a warmer world the cooling aspect increased to 55 watts/M² and the warming aspect to 37 watts/M², the net cooling is now 18 watts/M². A change of +2 watts/M². So they have acted as a warming feedback because they now contribute less cooling.

rkrolph at 18:47 PM on 24 April 2015

Changes in water vapor and clouds are amplifying global warming

Some statements in this article seem contradictory. It states "We know that clouds have a net cooling effect on the planet", but then says scientists describe clouds as "positive feedback". How can clouds have a net cooling effect yet be considered positive feedback? It seems like this study is saying clouds actually have a net heating effect.

Tristan at 14:43 PM on 24 April 2015

Changes in water vapor and clouds are amplifying global warming

Here's what I wonder:

If the TLT measurements turn out to be underestimating warming (which seems likely), how does that impact the conclusions of the study?

barry1487 at 11:41 AM on 24 April 2015

Changes in water vapor and clouds are amplifying global warming

Interesting development on a thorny issue.

"This new work confirms the opposite; it turns out Dr. Dessler was correct after all."

Confirms? Wouldn't "corroborates" be more appropriate? This paper is one more step towards understanding. How does John Abraham know it is definitive?

Thomas Huld at 08:08 AM on 24 April 2015

Changes in water vapor and clouds are amplifying global warming

The links to the works of Dr. Dressler don't work here (they are active in the Guardian article). Some way to fix it?

Moderator Response:

[JH] Link inserted.

Glenn Tamblyn at 07:20 AM on 24 April 2015

University of Queensland offering free online course to demolish climate denial

ryland

Yes, the course will be strongly forum based. Participation in the forums is part of the assessment. And yes we will be moderating firmly.

michael sweet at 05:04 AM on 24 April 2015

There's no empirical evidence

Red Baron,

You are not being silenced. If you want to continue the discussion you only have to cite peer reviewed papers that support your position. You must also address the data others have presented that argue against your position. In science you cannot continue to make unsupported claims and expect people to listen to you forever.

RedBaron at 04:32 AM on 24 April 2015

There's no empirical evidence

Apparently I am being silenced now. Fair enough. I suspected it would eventually happen. As much as I would hope that science was free of politics, it isn't. I'll leave you with some empirical evidence and it will be up to you to figure out why it shows the flaw in your numbers without commentary from me. Because quite frankly I am not interested in debating on a forum where discussing different interpretations of the same evidence is not allowed.

How ecological restoration alters ecosystem services: an analysis of carbon sequestration in China's Loess Plateau

Good luck

Andy Skuce at 03:10 AM on 24 April 2015

Permafrost feedback update 2015: is it good or bad news?

Thank you, HK. I was looking for permafrost in the "north" of that figure and couldn't see it. It makes sense now.

Apologies to everyone for any confusion caused by me not seeing what's in front of my nose.

I have now updated my previous comment.

HK at 02:09 AM on 24 April 2015

Permafrost feedback update 2015: is it good or bad news?

Andy:
Your figure from IPCC has the permafrost carbon in a separate box to the right of the vegetation/soils box and is estimated as ~1700 Gt. That brings the total soil + permafrost carbon up to 3200-4100 Gt, or very roughly 4-5 times the present reservoir in the atmosphere (~850 Gt), not very different from saileshrao’s calculation. It also implies that the permafrost contains between 41% and 53% of all soil carbon.

Tristan at 01:15 AM on 24 April 2015

University of Queensland offering free online course to demolish climate denial

I wouldn't be surprised if the discussion forums contained some robust (yet moderated) debate. That's usually the case with MOOC's that deal with any public policy area, regardless of what the content actually advances.

ryland at 23:20 PM on 23 April 2015

University of Queensland offering free online course to demolish climate denial

In many university courses free discussion is encouraged where opposing views can be aired and debated. As there are many who are not entirely convinced of all aspects of AGW will that be the case with this MOOC?

Tom Curtis at 19:32 PM on 23 April 2015

There's no empirical evidence

MA Rodger @276, I suggest you reread the first paragraph RedBaron's post @262, which I believe clearly indicates that he thinks anthropogenic emissions from LUC have followed a hockey stick. He can, of course clarrify this for himself.

I think he is furhter arguing that by reversing the degradation of the biosphere, it can absorb more than current FF + LUC emissions, thereby reversing global warming, but that that is for him a seperate but related thesis.

With regard to the biosphere in general, assuming that the biosphere is constantly fifty percent of the total sink, then the biosphere first becomes a net sink from 1942-1950. It returns to being a net sink again in 1960, and except for 1961, '67 and '68, remains so thereafter. I calculated this using CO2 concentration data from Law Dome. Using the same data and assumptions, the biosphere peaks as a source in the late 19th century, and follows a more or less linear trend downward since about the 1940s. Potentially it could be fitted to a quadratic after 1850, and presumably linear before 1850, making it an inverted hockey stick. If we take this seriously, that again contradicts either version of RedBaron's hypothesis. That is, LUC emissions have been an inverted hockey stick, not a hockey stick as required by the version you do not believe he holds; but also the biospheres capability to act as a sink has increased over time, contrary to that part of the theory we both think he holds.

Having said that, I do not think the assumption of a constant ratio of biosphere to oceanic sink is safe.

Moderator Response:

[DB] RedBaron's response to you was moderated out due to repetitive sloganeering (multiple simple assertions lacking any credible support).

uncletimrob at 17:41 PM on 23 April 2015

2015 SkS Weekly News Roundup #17A

The practice of either shutting down or hobbling an organisation that doesn't agree with your political agenda of appointing a stooge into a potentially influential position are the hallmarks of several state and federal administrations here in Oz.

Abbot has never reacanted his rant "The climate change argument is absolute crap, however the politics are tough for us because 80 per cent of people believe climate change is a real and present danger" , so I can only believe that he is still the scientific ignoramus that he was back then in 2010.

MA Rodger at 17:38 PM on 23 April 2015

There's no empirical evidence

Tom Curtis @275.

I think the term "hockey stick" used by RedBaron refers to the NH millenial temperature reconstructions and so means AGW. I don't think he refers to the atmospheric CO2 record.

My reading of what is being said @274 is that the levels of climate forcing from CO2 would be greatly reduced had not mankind done such damage to the biosphere around the world. Thus, "the ecological sink is far too small to actually counter Fossil Fuel emissions in its current degraded state."

The transition from the net LUC emissions & biosphere absorption being a source to becoming a sink depends on the ratio of chopping trees to burning FF. It is also dependent on the levels of absorption into the biosphere as CO2 levels rise. If we adopt a value of 25% for the proportion of our emissions currently absorbed by the biosphere, we can calculate a rough date for the biosphere becoming a net sink by using FF+cement emissions & LUC emissions - 1971.

I read RedBaron @274 arguing that the 25% value would be far higher had mankind not reduced the size of the biosphere by chopping it down or whatever. If the biosphere were, say, twice the size of its present diminished state, would it not absorb twice the CO2? With double the absorption, a the date of transition from source to sink occurs in 1930, even without adjustment to the LUC figures. Under such assumptions, if the biosphere were absorbing twice the amount of our emissions, the rise in atmospheric CO2 would be halved and atmospheric CO2 today would only be 337ppm.

Thus RedBaron concludes "the principle of the effect ecosystem services being capable of moderating atmospheric CO2 is proven by the very thing you mentioned." While this does amply demonstrate the influence of the biosphere on atmospheric CO2 levels, that is something I don't think is in dispute. And beyond that point, I don't see it supporting the various argument from RedBaron scattered down this thread.

Tom Curtis at 15:47 PM on 23 April 2015

There's no empirical evidence

RedBaron @274, if, as you suggest, LUC was responsible for the hockey stick in CO2 emissions, except for the last two decades when LUC plus land absorption became a net sink, there would have been a marked decrease in the rate of increase of CO2 concentration over those last two decades. You, however, take evidence that over the last two decades LUC plus land absorption was a net sink as proof that LUC plus land absorption was a net source that overwhelmed fossil fuel emissions in preceding decades, and then seemlessly converted to a sink with no alteration in the trend in CO2 concentration. Such a large change from source to sink should also be visible in the isotope data, and also in the relationship between CO2 concentrations and the integral of fossil fuel emissions:

Evidently your "rebutal" of the O2 evidence depends entirely on ignoring the other available evidence. This is on top of your startling rebutal of the isotope evidence of "I just won't look at it, and will not accept anybody who does look at it has sufficient knowledge to determine that the evidence rebuts my theory". I think at this stage we can appropriately call your theory the invisible gardener theory of global warming. We can also appropriately note that there is no point discussing evidence with anybody who conspicuously refuses to note any evidence contrary to his theory (which has been shown to not be supported by your sources, to contradict isotope evidence extending back to well before the preindustrial, and to contradict exact evidence from the last two decades).

RedBaron at 14:23 PM on 23 April 2015

There's no empirical evidence

@Tom,

You said, "it is known with certainty that the net effect of land interaction with CO2, including land uptake plus CO2 emissions from Land Use Change is a reduction in the amount of CO2 in the atmosphere, at least over recent decades."

I am glad you mentioned that actually. It in fact is the evidence of your error, but doubtful you are knowledgeable enough of other fields to understand this.

Temperate rainforests used to exist on almost every continent in the world, but today only 50 percent — 75 million acres — of these forests remain worldwide. Originally, 6 million square miles of tropical rainforest existed worldwide. But as a result of deforestation, only 2.4 million square miles remain. Between 2000 and 2012, 0.9 million square miles of forests around the world were cut down. That's roughly the size of all of the states in the U.S. east of the Mississippi River. Only 0.3 million square miles were replanted. There are only only four remaining intact temperate grasslands in the world and they are greatly reduced in size. For example the North American tallgrass prairie for all practical purposes is completely gone. About 5,000 years ago the great northern grasslands died out when humans exterminated the majority of the megafauna in the northern hemisphere, replaced now with boreal forest with shallow roots due to the thin soils. (luckily they can form peat at least) Most the grasslands of Austrailia that started desertifying 50,000 years ago due to the human eradication of Australia's megafauna were surveyed in the 1840's with many still containing deep A-horizons of 6%-20% SOM are now almost completely finished desertifying and contain usually around <1% SOM. The farmers of Australia now farm on sub-soil (B-horizon) as excepting a small band of tropical rainforest remaining, nearly all the top soil is now gone. China's Leoss plateau was completely destroyed (although now part of the largest ecosystem restorion project in the world) Green revolution agriculture is a carbon emissions source.

With all this and more ecosystem destruction world wide, the very few reminant functioning ecosystems left were still capable of making the entire terrestrial biosphere taken as a whole a net sink, at least over recent decades. Exactly like you said. But of course the ecological sink is far too small to actually counter Fossil Fuel emissions in its current degraded state. However the principle of the effect ecosystem services being capable of moderating atmospheric CO2 is proven by the very thing you mentioned. And inversly, the fact that human impact has largely destroyed that capability worldwide explains the hockey stick.

bozzza at 14:11 PM on 23 April 2015

2015 SkS Weekly News Roundup #17A

It is quite apparent the majority of Australia is appalled that the good name of UWA is now mud. The 'talking points' UWA have delivered to staff reveal this was a known quantity to have to deal with... given W.A. delivered the mining boom it will not be forgotten and will in my opinion be the continuing saga of what was always a global joke !

chriskoz at 13:45 PM on 23 April 2015

2015 SkS Weekly News Roundup #17A

Addendum to my @1. The news is developping fast:

Prime Minister Tony Abbott's office the origin for controversial Bjorn Lomborg centre decision

and confirms my opinion that our current PM should by default be blamed for all contrarian/science denying decisions.

PS: I appologise for mistyping Stephan Lewandowsky's surname @1. And would be happy if a mod could correct it.

chriskoz at 12:47 PM on 23 April 2015

2015 SkS Weekly News Roundup #17A

Signifficant story is developping on mitigation denial front:

Bjorn Lomborg, Abbott's Four Million Dollar 'Climate Contrarian'

also in smh: Bjorn Lomborg centre or the University of Western Australia

If I was affiliated with UWA, I would be outraged by Tony Abbott's efforts to introduce the climate change mitigation denialism into australian education system, and further force my uni to finance 2/3 of the cost.

John Cook, or Stephen, if you guys read it, can you explain what is the position of UWA on that story? Does UWA board really not mind bringing Lomborg's disinformation to their own classrooms at their own funding?

Tom Curtis at 08:46 AM on 23 April 2015

There's no empirical evidence

RedBaron continues to make his discussion uninteresting by his refusal to grapple with the evidence. This is noteworthy in his dismissal of the isotope evidence (which is sufficient to refute his thesis) on the grounds that he has not examined the issue and he will have to wait till "somebody expert" examines the issue. Given that clearly unscientific attitude, there is little point of any discussion with him. Despite that, I will add yet another distinct line of evidence refuting his claims.

Specifically, consider the reduction in atmospheric oxygen concentration over time in relation to the increase in CO2 concentration over time:

As we would expect, combustion of fossil fuels results in Carbon combining with Oxygen to produce Carbon Dioxide, thereby decreasing the O2 and increasing the CO2. Naively we might expect O2 to decline equally with the increase in CO2 when we burn fossil fuels. While that is true enough for Coal, however, natural gas (CH4) and petrol also produce water as combustion products, decreasing the oxygen concentration further. In general, for each molecule of CO2 produced by combustion, two molecules of H2O will be produced from methane, and slightly over one molecule of H2O will be produced by the combustion of oil products. Because these ratios are known, and the consumpton of various fossil fuels are also well known, it is possible to calculate the expect loss of O2 relative to the expected gain in CO2 with relative accuracy.

Further, the ocean uptake of CO2 is also relatively well known, both by direct measurements of increases in Dissolved Inorganic Carbon, and by changes in the C13/C12 isotope ratios. Ocean uptake, of course, involves no reduction in atmospheric oxygen.

Finally, the actual decrease in O2 and increase in CO2 is well known from observations.

Having constrained the well known values, we then place severe constraints on the poorly known values. Of these, Oxygen outgassing by the ocean involves no change in CO2 concentration, and is very small. So small it is often neglected. The last value, net land uptake combines the effects of both photosynthesis (producing one O2 for each CO2 drawn from the atmosphere) or respiration/combustion which reverses the process. The important thing is that because the other constraints are well known (or near negligible), it is known with certainty that the net effect of land interaction with CO2, including land uptake plus CO2 emissions from Land Use Change is a reduction in the amount of CO2 in the atmosphere, at least over recent decades.

It follows for RedBaron's thesis that any underestimate of LUC emissions such as he is arguing for must be matched by an increase in photosynthesis compensating for the underestimte almost exactly. Ergo, whatever the merits of RedBaron's thesis that CO2 emissions from LUC are greater than current estimates, it has no consequence at all for net emissions, because the O2 evidence shows that CO2 fertilization, increased rainfall, NH reforestation and the green revolution combined result in the fixing of more CO2 than is emitted by LUC, whatever the estimate of LUC emmissions happens to be.

Tom Curtis at 08:05 AM on 23 April 2015

New Video: The Trouble at Totten Glacier

michael sweet @3, there exists a geothermal hot spot under the West Antarctic Ice Sheet (WAIS) that generates heat flows as high as 0.08 W/m^2, and even hotter spots just off shore of the Antarctic Peninsula, where the heat flows may be as high as 0.095 W/m^2 (See fig 8 of Shapiro and Ritzwoller 2004). There has been subice volcanism associated with the hotspot under the WAIS as recently as 200 BC (Corr and Vaughan 2008). Because of that volcanism, the geothermal heat flow under the WAIS cannot be considered constant, and will peak at higher values in the case of volcanic erruptions. I am not aware of evidence of recent erruptions, however. Such erruptions would have been detected from associated earthquakes. Consequently, absent specific evidence to the contrary, there is no reason to believe that there has been a recent increase in geothermal heat flow at that location.

Even if there had been, of course, it would be almost irrelevant. Specifically, the topography is such that water melted by volcanism at that location will potentially lubricate the flow of the Pine Island Glacier, but that although:

"Pine Island Glacier lies in a deep subglacial trough, and this will isolate its subglacial hydrological system from neighbouring glaciers (Thwaites, Smith and Kohler). Therefore, even if continuous or episodic production of melt water from HMSV affects Pine Island Glacier, there is little likelihood that it could affect these neighbouring glaciers. It is thus possible that volcanic activity over HMSV contributed to some of the recent changes in velocity of Pine Island Glacier, but it cannot explain the widespread thinning that has been observed across these glacier basins in recent decades. We follow previous authors in favouring an oceanic driver as the likely cause for these changes."
(Corr and Vaughan)

In addition, there have been recently discovered (Schroeder et al, 2014) geothermal hotspots associated with Mount Takahe, and underlying the Thwaites glacier. The average inferred flux is 0.114 W/m^2, with hotspots exceeding 0.2 W/m^2. Given the association with Mount Takahe, whose last known eruption was in 5550 BC, it is unlikely though possible that that heat flow has increased recently. Certainly the rate of change of the heat flow has not been measured.

More generally, and of necessity, all ice sheets are "heated from below", although that heating may not rise above 0.02 W/m^2, and changes in the heating are likely to be a tenth or less of that. What is more, basic physics indicates that reduction of the thickness of the ice is likely to result in a lower heat flow at the base of the ice (although the rate of change is, if you will forgive the pun, glacial). The exception is where reduction in ice mass triggers volcanism, which is an interesting potential feedback ;)

Paisleg appears to have made the standard denier jump from "there has been newly discovered geothermal heat flow under the ice" to "the geothermal heat flow under the ice has suddenly increased"; and from "there exists a heating source in addition to that from global warming" to "the heating from global warming is irrelevant to what is going on". But are non sequiturs, and in addition extremely unlikely to be valid inferences. He will also be entirely unable to provide any evidence that either inference is justified.

Indeed, he goes even further and assumes that because some ice is heated by geothermal sources, it follows that that ice is not heated by global warming (even though there is clear evidence for both the Pine Island Glacier and the Thwaites Glacier that they are). The final clause of his post, therefore, is certainly absurd. I am unsure whether you are reacting to just that clause (which is simply false, and absurd) or the the whole sentence, the first clause of which is not false. Hence my discussion.

michael sweet at 05:18 AM on 23 April 2015

New Video: The Trouble at Totten Glacier

Paisleg,

While the Antarctic sea ice is high, according to the NSIDC, it is currently lower than it was in 2014 so it cannot be record high. It is close to the record.

Since this post is about land based ice, and land ice is reponding to AGW differently than sea based ice I do not see your point. The land ice raises the sea level while the sea ice does not affect sea level.

Your claim about heating from below is simply false. Please provide a citation to support your absurd claim. Why do you believe such transparently false information? Think to yourself: why do you read material from people who deliberately mislead you with false information?

paisleg at 04:22 AM on 23 April 2015

New Video: The Trouble at Totten Glacier

Antarctic ice extent is at record levels and continues to increase. It has been found that the West Antarctic Peninsula, about 2% of the land mass, is being heated from below and not by global warming.

Moderator Response:

[Rob P] - Antarctic sea ice extent has accelerated, but so too has the loss of land-based ice volume from the Antarctic continent. And the loss of land-based ice volume is six times larger. Globally, the loss in ice volume is about 50 times greater than the gain in Antarctic sea ice volume (over the last decade). This is what we'd expect in a warming world.

The interesting thing about Antarctic sea ice is that the increases are concentrated in the vicinity of the polar gyres - suggesting that the wind-driven ocean circulation has played a part. Now that the wind-driven ocean circulation appears to have changed course, it will interesting to see what happens to the Antarctic sea ice.

[TD] Please read the post "Is Antarctica Losing or Gaining Ice?"--first its Basic tabbed pane, then its Intermediate tabbed pane. Then read the counter to the myth "Arctic sea ice loss is countered by Antarctic sea ice gain"--both Basic and Intermediate tabbed panes. The sea ice extent increase is in spite of the Antarctic ocean and air having been directly measured to be warming.

[TD] Your claim of global warming not contributing to West Antarctic Peninsula land ice loss is incorrect. See the post "Why Do Glaciers Lose Ice?" I suspect I know the source of your distorted claim that heating from below is what's causing land ice loss, but please do cite your source so commenters here can provide a correct interpretation of that specific claim. (Hint: For increased land ice loss to be due to heating from the land below, the heating of the land below must be increasing. The mere discovery of heating where nobody had looked before does not qualify as "increasing.")

Andy Skuce at 03:18 AM on 23 April 2015

Permafrost feedback update 2015: is it good or bad news?

sailshrao: thanks.

Those comments and figures came straight out of the Schuur paper, so that's my primary reference.

However, this is from the AR5 Chapter 6 on the carbon cycle.

The numbers in black are the pre-industrial carbon reservoirs measured in billion tonnes. The soil carbon is given as 1500-2400 and the atmospheric carbon as 589 billion tonnes. That gives a soil-atmosphere ratio of 2.5-4. That's lower than the ratio you calculated from the round numbers I cited (especially considering that the IPCC atmosphere numbers are pre-industrial). I would have to dig deeper to see where the discrepancy comes from.

It looks to me that the IPCC estimate for the amount of carbon in soil could be wrong or out of date (or might not include permafrost soil, I don't know). Schuur et al's estimate for permafrost soils alone is 1330-1580 billion tonnes of carbon, which is bigger that the low IPCC estimate for all soil carbon and more than half of the IPCC upper estimate. If you look at both the Schuur and IPCC upper estimates, this implies that two-thirds of all soil carbon is in the Arctic, which can't be right.

Let me start over again, with a big nod to HK's comment immediately below for pointing out what should have been obvious to me.

The permafrost carbon reservoir ("underground" on the right-hand side) is 1700 billion tonnes, which is higher than Schuur et al.'s estimate of 1330-1580 billion tonnes, but when you include "the potential for ~400 Pg carbon in other deep terrestrial permafrost sediments" the numbers agree, more or less. So, according to the IPCC, 41-53% of all soil carbon is contained in permafrost. Most, but not all, permafrost is in the Arctic and boreal regions, so caution should be used in comparing IPCC numbers to the numbers from the Schuur paper, which confines itself to the Arctic and sub-Arctic.

According to the IPCC diagram, the atmosphere in 2011 contained 829 billion tonnes of carbon, so that the ratio of soil to atmospheric carbon is approximately 4-5 to 1. The ratio of permafrost carbon to atmospheric carbon, according to IPCC numbers, is about 2 to 1.

moreover at 00:30 AM on 23 April 2015

University of Queensland offering free online course to demolish climate denial

Here's the thing about MOOCs: You may not have the time or discipline to do the full course. But enrolling gives you access to superb course materials, or allow you to deepen your understanding of a specific issue.

In essence, it gives you a key to a new library.

saileshrao at 00:26 AM on 23 April 2015

Permafrost feedback update 2015: is it good or bad news?

Thanks again for a great article, Andy. I have a question:

You state:

"The Arctic contains huge stores of plant matter in its frozen soils. Over one-third of all the carbon stored in all of the soils of the Earth are found in this region..." and
"the amount of carbon in the permafrost is double the amount currently in the air."

Together, these would imply that carbon sequestered on land is 4-6 times the amount currently in the air. Do you have a reference for that estimate?

MA Rodger at 23:07 PM on 22 April 2015

There's no empirical evidence

Tom Curtis @271.

Thank you for spotting something was awry. I did drop a decimal point somewhere. But I still come out with larger ancient per capita emissions.

I think you can compare the two periods in a lot of different ways. I note that if the average emissions is used and the population calculated using the average of start & end population, you get a remarkably similar figure for the two periods.

I was specifically comparing the start of the first period 5,500BC with today. We seem happy with the 1000:1 ratio of population. Today's emissions are well defined c10GtC/y. Taking the 0.032GtC/y for the start period, and the data suggests these emissions were achieved from the off, the per capita ratio is 3.2:1.

I stand corrected that the ~320GtC applies to a proposal of actual emissions not including absented feedbacks.

Tom Curtis at 19:40 PM on 22 April 2015

There's no empirical evidence

MA Rodger @270, Ruddiman's hypothesis is that approx 320 GtC was released by humans over the approximately 10 thousand years prior to 1750. That works out at emission rates of 0.032 GtC per annum, or 0.015 ppmv per annum if it all accumulated in the atmosphere. Of course, most of it went into the oceans. Far more than the amount expected from current airbourne fractions because there is time for equilibriation with the deep ocean, and also take up of excess CO2 by chemical buffering in the ocean, and chemical weathering. Consequently the increase in atmospheric concentratin is less than 13% of the emissions (with further emissions of natural origin also contributing). In any event, the average annual emissions amount to 1 thousandth of current values. Given that the global population (approx 5 million) was about 1 thousandth (rising to about 1 seventh by 1750). Ergo their emissions per capita are on average less than today, not thirty times greater.

MA Rodger at 18:03 PM on 22 April 2015

There's no empirical evidence

RedBAron @267 says "Please go back to post #258..."

Myself, I haven't left #258. The first part of #258 is telling us that the initial assertion made by RedBaron @217 is now defunct. If it is said of Tristan & I "Both of you are correct, but only if that ~300 GtC emissions pior to 1850 that Ruddiman discusses is not included," then the wild assertion that "The hocky stick isn't fossil fuel emissions, it's agricultural degradation of the soils, particularly carbon." - that original assertion is dead.

We are then left with the ~300GtC of Bill Ruddiman. Yet this is a lot of carbon to be released by a small population. Yes the release is 30x slower (which is why they are so large yet only achieve a 25ppm CO2 rise), but the late stone-age human population can only have been a few millions, probably 1,000x smaller than today. So these vigorous ancestors, without access to any of today's 4x4s or Boeings manages 30x our present CO2 emissions per capita.

Don't get me wrong. I am not wholly dismissive of such a prospect. A single match can release a whole lot of CO2 from the countryside round here during dry spells, mainly during the school holidays. So without a fire brigade to dowse down the heathland, with big dry wilderness forests that could perhaps be converted into greater productivity with the timely application of fire-stick/tinder-box, a pre-historic society could potentially release great quantities of CO2 from the eco-system.

Further, Ruddiman's ~320GtC includes feedbacks (presumably) as the warming resulting from higher CO2 prevents CO2 absorption in an otherwise cooling climate. Halving the size of these proposed early anthropogenic emissions may well assist in getting the sums to add up.

But what is difficult to countenence is that late stone-age man's activities resulted in massive CO2 emissions from deep in the soil, this being the apparent contention of RedBaron @258. The predation of mega-fauna to their extinction - how does that release CO2? Converting significant parts of the steppe into the High Chaparral is well beyond the available technology or manpower. Plough-cultivation - ditto. The only mechanism that occurs to me is the trashing of vast swathes of land resulting in soil errosion, not the most sustainable of activities for communities reliant on that land. Yet such levels of trashed soils would leave obvious marks beyond atmospheric CO2. So is there such supporting evidence?

And it must not be forgotten that all this blather is based on the interesting but still speculative work of Bill Ruddiman.

@234 I argued that RedBaron was conflating three separate controversial assertions. Ruddiman makes that four. The fifth appeared @267. Now it it is being argued that the rise in CO2 is not directly from the soils but from FF yet the atmospheric CO2 increase also required the degradation of soils. If this was the"orignial premise" it was woefully described until now, and indeed the mechanism remains unexplained and without an evidential basis.

RedBaron at 18:02 PM on 22 April 2015

There's no empirical evidence

CBDunkerson,

If Greg Retallack's research and interpretation of the paleobotany and paleosols evidence is correct, and the unidirectional, stepwise, long-term climatic cooling, drying, and climatic instability was driven by the coevolution of grasses and grazers, then the loss of the megafauna and desertification that followed over large areas would have tended to force the stability of CO2 levels near where they were when that loss occurred. His hypothesis is therefore very consistent with Ruddiman and in fact helps explain the evidence Ruddiman falls somewhat short. (His so called "fatal flaw"). ie. Reducing the primary driver of climatic cooling wouldn't necessarily drive warming (depending on the degree), but it would tend to halt carbon sequestration and stop cooling. Then as other new anthropogenic drivers of warming are added to the biosphere (CO2, CH4), the ability to buffer that is also reduced. And yes the measured CO2 and CH4 levels seen in Ruddiman et al. roughly follow those trends. For this reason, Retallack's work supports and more fully explains Ruddiman. Neither works successfully explain the measured evidence alone, but combined they are quite close. Also since the loss of part of the grassland/grazer biome and early preindustrial agriculture would tend to result in carbon loss from the soil in a shallow top down manner (younger carbon), while industrial agriculture with it's turning over of deeper soil exposing older carbon more similar to fossil fuels in isotopes, it would seem to me that the isotope signal would likely very easily get lost in the "noise" of industrial fossil fuel use. I wouldn't say they are "vastly different" at all. I would suggest that this needs to be addressed by someone with that expertise though. My research is soils and agricultural systems, not atmospheric isotopes. It would help though if you explained exactly where you think these estimates are "vastly different".

Tristan at 12:29 PM on 22 April 2015

Global warming hiatus explained and it's not good news

What confuses me (and perhaps demonstrates something about eyeballing), is that from 1993, UAH and RSS seem pretty much in step, in the Santer graphic, but there's considerable disparity in the calculated trend.

Tom Curtis at 12:08 PM on 22 April 2015

Global warming hiatus explained and it's not good news

Joel_Huberman @52, two other minor but relevant points. First, the temperature series shown in Fig 1 C are only for 82.5 North to 70 South and therefore exclude part of the most rapidly warming region of Earth. Second, the observational records shown are tropospheric rather than surface records. The troposphere responds far more strongly to volcanic and ENSO influences than do surface records. Any dampening of the trend due to the small volcanoes in the satellite record will be greater than that at the surface. Ergo, it is likely that had surface records been used, and particularly truly global surface records such as GISS, or BEST, there would still have been a positive trend including the effects of the small volcanic erruptions.

jja at 10:32 AM on 22 April 2015

Permafrost feedback update 2015: is it good or bad news?

Andy,

Predicated on the idea that early arctic ice loss is not modeled under the scenario, that the albedo effects are underrepresented when they are included (due to algae bloom) and microbial heating effects are also not included then these emission profiles will be severely underrepresented.

If summer arctic ice loss occurs within this decade as opposed to late 2040 as is currently being modeled, then this will allow microbial heat-driven decomposition to occur much more rapidly than modeled in Hollensen.

With a 3-meter depth decomposition profile establishing as early as 2060.

Joel_Huberman at 07:12 AM on 22 April 2015

Global warming hiatus explained and it's not good news

Thanks, KR. Your comments have helped me to distinguish between what Santer et al. were trying to say and what Homewood wanted to say by carelessly (or intentionally) mis-interpreting Figure 1. Your comments prompted me to more carefully examine the paper by Santer et al. Although much of their paper involves statistical tests that are beyond me, my re-examination of their paper, combined with your comments, lead me to the following revised interpretation of Figure 1:

In Figure 1A (raw data), there's only a poor fit between CMIP-5 model predictions and the TLT data (RSS and UAH). In Figure 1b (ENSO removed), there's an excellent fit between data and model predictions up to 2002. That's because the CMIP-5 models were already adjusted to account for the El Chichón and Pinatubo eruptions but not for subsequent 21st-century minor eruptions. In Figure 1B, the model-predicted and satellite-observed cooling effects of the two big eruptions are evident in the big dips in 1983 and 1992. Notice that, when the effects of El Chichón and Pinatubo are also removed (Figure 1C), those big dips are remove, and the adjusted TLT data continue to agree with the adjusted model data until about 2002, but now both sets of adjusted data have consistently higher values (than in Figure 1B) from 1982 until 2000. In other words, removing volcanic influences causes the observed temperature data, as well as the model predictions, to increase during the time period of volcanic influence. One of the points that Santer et al. are trying to make is that failure to take cumulative 21st-century minor volcanic activity into account is what gives rise to the divergence between model-predicted (the models didn't account for these volcanoes) and observed (affected by these volcanoes) TLT data after 2000.

I think it's unfortunate that Santer et al. couldn't include a Figure 1D in which the effects of minor 21st century eruptions were removed from the TLT observations and then compared with the model predictions. I suspect such a figure would have shown significantly better agreement between models and data than in Figure 1C. In addition, such a figure would have shown a rising trend in the TLT data. I suspect that Santer et al. didn't want to create such a figure because our understanding and measurements of the effects of these minor eruptions are still too primitive to allow accurate graphing. Their doubts are reflected in the last sentence of their summary: "To reduce these uncertainties, better observations of eruption-specific properties of volcanic aerosols are needed, as well as improved representation of these eruption-specific properties in climate model simulations."

Thanks to your help, I no longer feel mystified by Figure 1, and I certainly no longer feel susceptible to Homewood's siren interpretation.

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