By WUWT Regular “Just The Facts”:
Note: This article builds upon a previous article, When Did Global Warming Begin?, which offers highly recommended background for this article.
There appears to be some confusion as to when humans might have begun to influence “Earth’s Temperature”. For example, “Global warming is the unusually rapid increase in Earth’s average surface temperature over the past century primarily due to the greenhouse gases released as people burn fossil fuels.” NASA Earth Observatory “Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are very likely due to human activities, and most of the leading scientific organizations worldwide have issued public statements endorsing this position.”
NASA Climate Consensus page “‘Global warming started over 100 years ago‘: New temperature comparisons using ocean-going robots suggest climate change began much earlier than previously thought”. The Daily Mail “The temperature, they pointed out, had fallen for much longer periods twice in the past century or so, in 1880-1910 and again in 1945-75 (see chart), even though the general trend was up. Variability is part of the climate system and a 15-year hiatus, they suggested, was not worth getting excited about.” Economist “Our Earth is warming. Earth’s average temperature has risen by 1.4°F over the past century, and is projected to rise another 2 to 11.5°F over the next hundred years.” EPA
However, there is not compelling evidence that anthropogenic CO2 was sufficient to influence Earth’s temperatures prior to 1950, i.e. “Climate model simulations that consider only natural solar variability and volcanic aerosols since 1750—omitting observed increases in greenhouse gases—are able to fit the observations of global temperatures only up until about 1950.” NASA Earth Observatory “The observed global warming of the past century occurred primarily in two distinct 20 year periods, from 1925 to 1944 and from 1978 to the present. While the latter warming is often attributed to a human-induced increase of greenhouse gases, causes of the earlier warming are less clear since this period precedes the time of strongest increases in human-induced greenhouse gas (radiative) forcing.” NASA Geophysical Fluid Dynamics Laboratory / Delworth et al., 2000 “Internal climate variability is primarily responsible for the early 20th century warming from 1904 to 1944 and the subsequent cooling from 1944 to 1976.” Scripps / Ring et al., 2012: “There exist reasonable explanations, which are consistent with natural forcing contributing significantly to the warming from 1850 to 1950”. EPA
So how to clear up this confusion? Let’s take a look at the data…
If you look at Global CO2 Emissions from Fossil-Fuels;
Global CO2 from Fossil-Fuel Emissions By Source;
and Cumulative Anthropogenic CO2 Emissions from Fossil-Fuels,
you can see that Anthropogenic CO2 Emissions from Fossil-Fuels did not become potentially consequential factor until approximately 1950, and then grew rapidly thereafter. Per the Economist, “The world added roughly 100 billion tonnes of carbon to the atmosphere between 2000 and 2010. That is about a quarter of all the CO₂ put there by humanity since 1750. And yet, as James Hansen, the head of NASA’s Goddard Institute for Space Studies, observes, ‘the five-year mean global temperature has been flat for a decade.’” The large increase in Anthropogenic CO2 Emissions from Fossil-Fuels since 1950 is quite clear in this Global Per Capita Carbon Emissions graph:
There have also been claims made that Land Use Changes measured as Annual Net Flux of Carbon to the Atmosphere were a significant source of Anthropogenic CO2 i.e.:
However, when you look at the Net Flux of Carbon to the Atmosphere from Land-Use Changes from 1850 to 1990;
it is apparent that the majority of the increase occurred after 1950, and the change between 1900 and 1950 was de minimis. Furthermore, the Houghton data these graphs are based upon is highly suspect, i.e. from IPCC AR4: “Although the two recent satellite-based estimates point to a smaller source than that of Houghton (2003a), it is premature to say that Houghton’s numbers are overestimated.” Houghton’s method of reconstructing Land-Use Based Net Flux of Carbon appears arbitrary and susceptible to bias; i.e. “Rates of land-use change, including clearing for agriculture and harvest of wood, were reconstructed from statistical and historic documents for 9 world regions and used, along with the per ha [hectare] changes in vegetation and soil that result from land management, to calculate the annual flux of carbon between land and atmosphere.” Furthermore Houghton’s findings have varied significantly over time, i.e. in Houghton & Hackler, 2001 they found that, “The estimated global total net flux of carbon from changes in land use increased from 397 Tg of carbon in 1850 to 2187 Tg or 2.2 Pg of carbon in 1989 and then decreased slightly to 2103 Tg or 2.1 Pg of carbon in 1990“. However, by Houghton, R.A. 2008 he found, “The estimated global total net flux of carbon from changes in land use increased from 500.6 Tg C in 1850 to a maximum of 1712.5 Tg C in 1991“.
Given Houghton’s overestimations, arbitrary reconstruction method and highly variable results, his Net Flux of Carbon to the Atmosphere from Land-Use Change data is not credible. However, even if it was, Net Flux of Carbon to the Atmosphere from Land-Use Change was inconsequential prior to 1950;
and it appears that Land and Ocean Sinks would have absorbed any increace, along with much of the minimal pre-1950 Anthropogenic CO2 Emissions from Fossil-Fuels. This is supported by the findings of Canadell et al., 2007 that, “Of the average 9.1 PgC y −1 of total anthropogenic emissions (F Foss + F LUC) from 2000 to 2006, the AF was 0.45; almost half of the anthropogenic emissions remained in the atmosphere, and the rest were absorbed by land and ocean sinks.” Furthermore, they found “increasing evidence (P = 0.89) for a long-term (50-year) increase in the airborne fraction (AF) of CO2 emissions, implying a decline in the efficiency of CO2 sinks on land and oceans in absorbing anthropogenic emissions.” Thus absorption rates of Land and Ocean Sinks were likely significantly higher prior to 1950.
As such, since there is not compelling evidence that Anthropogenic CO2 was sufficient to have ab influence Earth’s temperatures prior to 1950, Anthropogenic CO2 cannot be the cause of the warming that occurred before 1950. However, this doesn’t mean that CO2 based Anthropogenic Global Warming began in 1950, because if you look at the Met Office – Hadley Center HadCRUT4 Global Surface Temperature record for the last 163 years you can see that temperatures didn’t warm during the 1950s, nor the 60s:
In fact it was not until approximately 1975 that temperatures began to rise. However, this doesn’t mean that CO2 based Anthropogenic Global Warming began in 1975, because as Phil Jones noted during a 2010 BBC interview, “As for the two periods 1910-40 and 1975-1998 the warming rates are not statistically significantly different.” As such, the warming from 1910 – 1940, before Anthropogenic CO2 became potentially consequential, is “not statistically significantly different” from the warming during the period from 1975 – 1998 when the IPCC AR5 claims to be ” extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century”. Given that “causes of the earlier warming are less clear“, our understanding of Earth’s climate system is rudimentary at best, and our historical record is laughably brief, it is confounding how the IPCC can be so “extremely” sure “that human influence has been the dominant cause of the observed warming since the mid-20th century”, which is “not statistically significantly different” from the natural warming that occurred between 1910 – 1940.
Regardless, claims that “Global warming is the unusually rapid increase in Earth’s average surface temperature over the past century” are erroneous and indicative of either ignorance or duplicity on the part of NASA’s Earth Observatory, NASA’s Climate Consensus page, The Daily Mail, the EPA and many others. So what do you think? When Did Anthropogenic Global Warming Begin?
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Bill Parsons says: March 30, 2014 at 11:24 am
Just the Facts: Where above do you actually prove that CO2 at ANY level can cause temperature to go up? I’m not talking about correlation, but causation. If you can’t show that it causes a temperature increase, it’s hard to insinuate when it’s effects started.
No where above did “I actually prove that CO2 at ANY level can cause temperature to go up”, thus I am going to poach from Roy Spencer on this one, i.e.:
“7) Is Increasing CO2 Even Capable of Causing Warming? There are some very intelligent people out there who claim that adding more carbon dioxide to the atmosphere can’t cause warming anyway. They claim things like, “the atmospheric CO2 absorption bands are already saturated”, or something else very technical. [And for those more technically-minded persons, yes, I agree that the effective radiating temperature of the Earth in the infrared is determined by how much sunlight is absorbed by the Earth. But that doesn’t mean the lower atmosphere cannot warm from adding more greenhouse gases, because at the same time they also cool the upper atmosphere]. While it is true that most of the CO2-caused warming in the atmosphere was there before humans ever started burning coal and driving SUVs, this is all taken into account by computerized climate models that predict global warming. Adding more “should” cause warming, with the magnitude of that warming being the real question. But I’m still open to the possibility that a major error has been made on this fundamental point. Stranger things have happened in science before.”
http://www.drroyspencer.com/my-global-warming-skepticism-for-dummies/
Thank you for your reply.
WRT Spencer’s.
I’m not sure if he’s making a defense of the models (or some of the models) or just being ironic about them. My impression is that the modelers so far have failed to explain:
Where natural sources of CO2 leave off and human sources begin
What amount of CO2 in the atmosphere engenders ANY warming?
Why warming is bad
What amount (if any) represents a so-called “tipping point” of runaway warming?
If, as he says, “Adding more (CO2) ‘should’ cause warming, with the magnitude of that warming being the real question…” then the minuscule amount of CO2 / methane created by paleo societies in their forest-burning agriculture 5,000 years ago had some part in creating the anthropocene. Voila: the Ruddiman hype (othesis) is vindicated.
MarkB says: March 30, 2014 at 12:12 pm
Dennis L. Hartmann – Click the pic to view at source[/caption]
Dennis L. Hartmann – Click the pic to view at source[/caption]
Maybe I’m the only one having trouble here, but I don’t understand why you’ve presented an argument based on emissions and land use data estimates when the significant parameter (atmospheric CO2 concentration) has been more directly and precisely measured via ice core data. I presume you’re making the link to “anthropogenic”, but it seems that leaves the problem of explaining CO2 rise in the more reliable data set.
Because they are two separate and distinct questions involved, i.e. Firstly, did Anthropogenic CO2 help to supplement the natural increase is CO2 that has been occurring since the end of the interglacial;
[caption id="" align="alignnone" width="600"]
and the end of the Little Ice Age:
[caption id="" align="alignnone" width="600"]
especially between 1900 and 1950? Secondly, if yes to the first question, then was the influence of this incremental increase in CO2 concentrations on Earth’s temperature?
My other point of confusion is that you’re declaring “significance” of the effect without a clear criteria for what is and isn’t significant.
I think you may be confused because your didn’t read the article. At no point did I refer to the significance of the anthropogenic influence on the increase in CO2 prior to 1950, nor the significance of of the increase in CO2 on Earth’s temperatures, thus there was no need to define “clear criteria for what is and isn’t significant”.
Per my crap data source (and consistent with ice cores) the atmospheric CO2 100 years ago was about 300 ppm. In 1950 it was 310 ppm.
What portion of this increase in CO2 was natural versus anthropogenic?
If one grants that forcing is proportional to the logarithm of concentration then current CO2 forcing (about 400 ppm) above baseline (280 ppm) is a little over 5 times greater than 1914 and about 3.5 times greater than 1950.
You are erroneously assuming that all of the increase in CO2 between 1900 and 1950 was Anthropogenic, and furthermore, the 1950 concentration is irrelevant, as the warming stated in 1910 and continued only until 1940. The question is whether Anthropogenic CO2 was potentially consequential on the Earth’s warming between 1910 and 1940.
If 3.5 is your threshold for significance, so be it, but it seems kind of arbitrary. I prefer, as I tried to indicate above, a point where the CO2 forcing is plausibly of similar magnitude to confounding effects in the temperature record. You asked the question, I posed an answer and gave my rational.
It is all arbitrary and I have zero confidence in our ability to accurately measure / estimate Earth’s temperature, CO2 concentrations and Anthropogenic contributions to CO2 prior to 1950. As such, I restate my conclusion that, “there is not compelling evidence that Anthropogenic CO2 was sufficient to have an influence Earth’s temperatures prior to 1950”.
“Because they are two separate and distinct questions involved, i.e. Firstly, did Anthropogenic CO2 help to supplement the natural increase is CO2 that has been occurring since the end of the interglacial;”
Assume you mean since the end of the last glacial phase, not interglacial, in one of which we currently are. CO2 fell from the previous interglacial, the Eemian, during the next glacial phase, the Wisconsin (most of North America), Tioga (Sierra Nevada), Merida (northern Andes), Llanquihue (Southern Andes), Devensian (Britain), Würm (Alps) or Weichselian (Scandinavia) glaciation.
justthefactswuwt says:
March 30, 2014 at 3:08 pm
. . .
It is all arbitrary and I have zero confidence in our ability to accurately measure / estimate Earth’s temperature, CO2 concentrations and Anthropogenic contributions to CO2 prior to 1950. As such, I restate my conclusion that, “there is not compelling evidence that Anthropogenic CO2 was sufficient to have an influence Earth’s temperatures prior to 1950″.
It might have saved us both a bit of time had you said so from the outset.
milodonharlani says: March 30, 2014 at 3:30 pm
Assume you mean since the end of the last glacial phase, not interglacial, in one of which we currently are.
Correct, that should be the end of the last glacial period or the beginning of the current interglacial, and not a combination thereof.
MarkB says: March 30, 2014 at 4:31 pm
It might have saved us both a bit of time had you said so from the outset.
Again, if you took the time to read the article and associated comments, then you’d know these things…
I posted this on Joanne Nova’s site on the weekend unthreaded.
I took the HadCRUT4 global mean data and did a moving linear regression over 12 months and then smoothed it with a simple 15 year moving average to get a useful plot of the rate of warming. I then fitted a simple model, a sine curve + a constant rate for warming from the LIA and an exponential for a contribution that is directly proportional to the rate of fossil fuel use that has been increasing roughly exponentially. This is the result. http://s5.postimg.org/q1poyaoo7/image002.png
This is the cumulative plot. http://s5.postimg.org/vr5xiluuf/image003.png
The red line is the estimate of the amount of warming that could be attributed to fossil fuel use (or any contribution that is growing exponentially). Note, it is on par with what many have found to be the amount by which the temperatures have been adjusted.
It pretty much backs up your argument that anthropogenic contribution could only have commenced after 1950. It also gives some weight to the argument that humans have warmed the Earth, but if I had done the same with the 1981 data of Hansen (or current data adjusted back to be more like that plot) there would be a zero contribution from humans.
JTFs: The IPCC attribution statement is limited to the period since 1950 precisely because studies fail to attribute a significant amount of warming before then to anthropogenic forcing. The explanation for pre-1950 temperature change (a subject AR4 WG1 avoided discussing) is natural variability (volcanos and solar) and unforced (internal) variability. Depending on precisely when one starts, about 0.2 degC of warming took place before 1950 (with an unknown fraction of this warming possibly due to weak human forcing) and 0.6 degC of warming afterwards. Your single-minded focus on CO2 emission is misleading, the atmospheric concentration of CO2, other GHGs and aerosols all contribute to the net radiative forcing the planet has experienced. Comparing total forcing and warming is the only sensible approach, but the contribution from aerosols is highly uncertain. It’s interesting that graphs of CO2 vs time are easy to find, but graphs of total forcing with time are rare.
When did AGW begin?
We cannot tell if it began at all because the radiative forcing of atmospheric CO2 since the pre-industrial era is 1.66 W/m^2. The uncertainty in aerosol forcing is -2.5 W/m^2. Therefore it is possible the aerosols cancelled the CO2 forcing and the warming since 1950 is naturally caused. The 1978-1998 warming may be caused by the PDO warm phase in the same period.
PDO can also explain the 1925-1944 warming and the 1944-1976 cooling. See this PDO index chart. http://www.globalwarminghoax.com/globalwarming_images/newspost_images/ecinfigtwo.jpg
justthefacts said:
“Again, if you took the time to read the article and associated comments, then you’d know these things…”
I just read the article again, and my tiny brain couldn’t find the bit where you covered that. Could you quote it for me?
drumphil says: March 31, 2014 at 6:35 am
I just read the article again, and my tiny brain couldn’t find the bit where you covered that. Could you quote it for me?
Sure, In this comment;
http://wattsupwiththat.com/2014/03/29/when-did-anthropogenic-global-warming-begin/#comment-1601090
I addressed the issues surrounding our ability to measure temperature and the suspect adjustments that have been made to temperature record in order to attempt to account for them:
“If the highly suspect Sea Surface Temperature “Bucket Model” adjustments are removed, then the warming during the first half of the 20th century would be significantly larger than than the warming during the second half of the century…”
In the article I explain the issues surrounding the Houghton Land-Use Based Net Flux of Carbon data :
Houghton data these graphs are based upon is highly suspect, i.e. from IPCC AR4: “Although the two recent satellite-based estimates point to a smaller source than that of Houghton (2003a), it is premature to say that Houghton’s numbers are overestimated.” Houghton’s method of reconstructing Land-Use Based Net Flux of Carbon appears arbitrary and susceptible to bias; i.e. “Rates of land-use change, including clearing for agriculture and harvest of wood, were reconstructed from statistical and historic documents for 9 world regions and used, along with the per ha [hectare] changes in vegetation and soil that result from land management, to calculate the annual flux of carbon between land and atmosphere.” Furthermore Houghton’s findings have varied significantly over time, i.e. in Houghton & Hackler, 2001 they found that, “The estimated global total net flux of carbon from changes in land use increased from 397 Tg of carbon in 1850 to 2187 Tg or 2.2 Pg of carbon in 1989 and then decreased slightly to 2103 Tg or 2.1 Pg of carbon in 1990“. However, by Houghton, R.A. 2008 he found, “The estimated global total net flux of carbon from changes in land use increased from 500.6 Tg C in 1850 to a maximum of 1712.5 Tg C in 1991”
In this comment;
http://wattsupwiththat.com/2014/03/29/when-did-anthropogenic-global-warming-begin/
I address the fact that;
“CO2 levels were rising naturally before 1900;” and “CO2 levels only increased from 295.7 ppm in 1900 to 311.3 ppm when the warming concluded in 1940. NASA GISS, Anthropogenic CO2 emissions were minimal prior to 1950;”
indicating that the attribution of increased CO2 concentrations to anthropogenic sources during the first half of the 20th century is highly questionable.
In this comment;
http://wattsupwiththat.com/2014/03/29/when-did-anthropogenic-global-warming-begin/#comment-1601359
I pointed out that model based anthropogenic attribution methods are highly suspect, i.e.;
“Where the simplistic model couldn’t explain the observations, it was assumed that anthropogenic influences must exist:”
“In conclusion, our model results indicate that the range of NH-temperature reconstructions and natural forcing histories (cosmogenic isotope record as a proxy for solar forcing, and volcanic forcing) constrain the natural contribution to 20th century warming to be 0.2°C. Anthropogenic forcing must account for the difference between a small natural temperature signal and the observed warming in the late 20th century.”
http://www.pnas.org/content/104/10/3713.full.pdf
In this comment;
http://wattsupwiththat.com/2014/03/29/when-did-anthropogenic-global-warming-begin/#comment-1601182
I addressed the long term “Human Impact on Climate” and Ruddiman’s graphs, which;
“appear to have been drawn and offer no indication that any actual data was used in their development”.
To gbaikie:
You wrote: “…so it’s Napoleon assaulting Russia in early winter all over again…”
That’s not correct. Napoleon began his campaign in June, 1812. One week
after the bloody battle of Borodino, on the 7th of September, 1812, Napoleon
entered Moscow with his Grande Armee already severely depleted.
(Among other factors, the French army suffered severely from an outbreak
of typhus.)
His real mistake was lingering in the vicinity of Moscow, waiting for the Czar
to surrender, for over a month before beginning to retreat. So–he didn’t
attack “in early winter”, he attacked in summer, achieved his goal of capture
of the enemy’s capital–but did not appreciate that the Czar and the Russian
army would continue to resist after losing Moscow. He had no backup plan
to meet that contingency, and fumbled his response.
Dr. Strangelove says:
March 31, 2014 at 12:10 am
You’re right, & IMO, the net effect of human activity since c. AD 1950 has been to cool rather than warm the planet, although not much in either direction. The cooling effects more than cancel out the warming “forcings”.
vicgallus – Replace the straight line with the time-integral of sunspot numbers (with appropriate proxy factor), and, the sine curve with a saw-tooth profile with amplitude +/- 0.18 K, period 64 years, last max in 2005 (representing net of all ocean oscillations). The result is correlation coefficient 0.95 with measured anomalies since before 1900 and credible trend back to the LIA. And it is all natural. See it graphed at http://agwunveiled.blogspot.com/
OUT. STAND. ING. I’ve been wondering exactly this — when exactly in the temperature data can one first detect the alleged signal of human emissions? As far as I can tell, the official answer for FAR, SAR, and 3AR was “after WW II”. The new answer appears to be “you shouldn’t ask that” or “it depends on this year’s narrative”.
Dan – I just had a quick look at what you have written and it is interesting. I will read it thoroughly soon.
With regards to what I did, it was mostly to point out that the fitting a model to the rate of change in temperature would be more enlightening when arguing how much contribution from human development there could be (what would be the contribution that increased exponentially). There was no attempt to explain what the causes were so the model needed to be simple and number of variably parameters kept to a bare minimum. That exponential contribution could still be natural (as it looks like you have shown) or even the way the data was collated.
Its more the maximum that could be claimed is due to human fossil fuel use rather than is a measure of how much.
Justthefactswuwt:
How does any of those quotes equate to: “I have zero confidence in our ability to accurately measure / estimate Earth’s temperature, CO2 concentrations and Anthropogenic contributions to CO2 prior to 1950.”
You don’t directly state that anywhere in the quotes your provide. Referring to certain records as suspect isn’t the same as directly stating that you have 0% confidence in temp and CO2 figures prior to 1950.
I’m with MarkB on this one. Why not just state it, rather than expecting people to infer it from other things you’ve said, especially when those other things don’t explicitly infer your absolute position on the issue. I would have to make many assumptions to come to the statement in question, purely based on what you said previously.
We are an ice planet, and there have been many inter-glacials that don’t effect all the globe for starters. The problem here is that humans and their precursors, didn’t live long like us today, and that if they had a warm period that only lasted 100 years that could account for 4 generations. In the last 2,000 years, famines did affect those that could not move away to find greener pastures (includes wild animals) disease like the black death and small pox, killed millions and millions. The same as wars. Add a cold period and malnutrition results in early death as well as syphilis, TB, that killed huge amounts of Londoners and young people and children.
SMOGs in London in the Victorian era and in the 1950s killed thousands, and ill health of course for innumerable people. Even Prince Albert Queen Victoria’s husband died of Typhoid.
There are billions of people living in subsistence farming communities, and displaced because of human caused wars and subsequent famines. Get the UN to help these unfortunate people.
Bangladesh was once considered in danger of flooding, yet they depend on annual floods so that was a big porky (lie). Cities create their own micro-climates and UHI, and attract huge populations because of work availability. Subsequently they are subject to their own pollution.
Don’t live on a river bank or coast because of floods and tsunamis, or a volcano, (look at Mt.Vesuvius’ eruptions and wonder what they can do to save millions if he explodes again. They can’t insure their homes by the way) and build cyclone and earthquake proof homes and buildings. Levies around flood prone regions, and make sure your dams are not vulnerable.
Anyway said my bit, but one last point. When the ABC interviewed a business man in the snowy mountains who runs seasonal ski resorts regarding the lPCC dire warnings for Australia. “He replied ‘ we have lived with the weather for years, and we have good seasons and poor ones.. we have learned to adapt to this and expect it…”
As far as droughts in Australia are concerned, ‘what’s new’. 50 miles in from the coast precipitation decreases anyway.
Excuse the rant. But if we have another cold period or ice age, the seas will drop eventually, not over night, and precipitation patterns will change.
PDO can explain the temperature trends last century and the “pause” since 1998.
See chart http://www.nwfsc.noaa.gov/research/divisions/fe/estuarine/oeip/figures/Figure_PDO-01.JPG
Warm phase 1925-1944
Cool phase 1944-1976
Warm phase 1978-1998
Cool phase 1998-2014
There’s a short warm phase in 2005 perhaps this is why the trend is flat rather than cooling.
drumphil says: March 31, 2014 at 6:29 pm
Meehl et al., 2004 – Click the pic to view[/caption]
How does any of those quotes equate to: “I have zero confidence in our ability to accurately measure / estimate Earth’s temperature,
Because the measurements are so bad, and the adjustments are so large, that the data is now arbitrary. Did you read this article?
http://wattsupwiththat.com/2013/05/25/historical-sea-surface-temperature-adjustmentscorrections-aka-the-bucket-model/
This one is also informative:
http://wattsupwiththat.com/2013/05/12/met-office-hadley-centre-and-climatic-research-unit-hadcrut4-and-crutem4-temperature-data-sets-adjustedcorrectedupdated-can-you-guess-the-impact/
CO2 concentrations and Anthropogenic contributions to CO2 prior to 1950.
Because the Houghton Land Use change Carbon Flux data appears arbitrary, and even the IPCC had to acknowledge that his numbers might be overestimated. Ruddiman looks like he drew his graphs and provided no references as to what data they were based upon. Amman used a modeling approach that boils down, we can’t figure it out, so it must be anthropogenic. Lastly, if you look at the actual CO2 data NASA GISS you’ll note that it is a hodgepodge of different sources evolving over time, i.e.:
1850-1957 is based on Law Dome Ice Core Data Adjusted for Global Mean: “D.M. Etheridge, L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M. Barnola and V.I. Morgan, 1996, J. Geophys. Res., 101, 4115-4128, “Natural and anthroupogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn”.”
1958-1974 is SIO Mauna Loa and South Pole Adjusted for Global Mean: “Means of Scripps Institution of Oceanography Continuous Data at Mauna Loa and South Pole provided by KenMaarie (personal communication)”
1975-1982 is CDML InSitu Manuna Loa & South Pole: “Means of NOAA/CMDL in-situ data at Mauna Loa and South Pole. (P. Tans and K.W. Thoning, ftp://ftp.cmdl.noaa.gov/ccg/co2/in-situ)”
1983-2003 is CMDL Flask Mean of Many Sites: “Global means constructed using about 70 CMDL CCGG Sampling Network station data. (P.P. Tans and T.J. Conway, ftp://ftp.cmdl.noaa.gov/ccg/co2/flask)”
2004-2007 is NOAA/ESRL/trends change added to 2003 data: “Global mean growth rates. (T. Conway, ftp://ftp.cmdl.noaa.gov/ccg/co2/trends)”
If the 1850-1957 data provided the desired accuracy, why do you think there have so many improvements/adjustments since?
Furthermore, if you look at the Law Dome reference, i.e. Etheridge et al. (1996)
http://cdiac.ornl.gov/trends/co2/lawdome.html
you find that;
“Preindustrial CO2 mixing ratios were in the range 275-284 ppm, with the lower levels during 1550-1800 A.D., probably as a result of colder global climate (Etheridge et al. 1996).”
meaning that CO2 mixing ratios appear to follow temperature changes and not the other way around. Furthermore;
“The Law Dome ice core CO2 records show major growth in atmospheric CO2 levels over the industrial period, except during 1935-1945 A.D. when levels stabilized or decreased slightly.”;
which happens to be the period of the most rapid warming of the first half of the 20th century:
[caption id="" align="alignnone" width="581"]
I’m with MarkB on this one. Why not just state it, rather than expecting people to infer it from other things you’ve said, especially when those other things don’t explicitly infer your absolute position on the issue. I would have to make many assumptions to come to the statement in question, purely based on what you said previously.
Because that wasn’t the point of the article, the point of the article is that;
“claims that “Global warming is the unusually rapid increase in Earth’s average surface temperature over the past century” are erroneous and indicative of either ignorance or duplicity on the part of NASA’s Earth Observatory, NASA’s Climate Consensus page, The Daily Mail, the EPA and many others.”
and no one has even come close to refuting that point. However, given your and MarkB’s interest in evaluating the accuracy of CO2 measurements and the anthropogenic contribution to them, I have started to build out the WUWT CO2 Reference Page;
http://wattsupwiththat.com/reference-pages/atmosphere-page/co2-page/
and will be sure to address your interests in a future in-depth article…
Interesting. But serious global warming started around 12,000 years ago, when the planet slowly saw a gradual warming from the last glacial period. Thank goodness. With a few hotter and colder phases in between. It doesn’t seem that some tossers have realised this. But their fault is to blame human activities. What the UNIPCC are describing is what could happen if the weather globally gets colder.
My issue was more with you saying to MarkB:
“Again, if you took the time to read the article and associated comments, then you’d know these things…”
So, I went and read your article and the comments, and thought “no, you wouldn’t know those specific things from what was said.”
There would be no need for further explanation if you had explained sufficiently to be sure that you weren’t just saying there were weakness in certain records, but were rather saying that the records were totally useless.
It is not reasonable to expect someone else to have inferred that from your statements without further guidance as to exactly what you think those things mean.
I know what you mean now, thanks to the discussion with MarkB, but I wouldn’t know what I do now without it, just going on what was already presented.
AGW & CC is a political agenda which even the best Science will not deter as good Scientists are very few while there are bad-uns galore.