Humans' 10,000-Year Warming Habit

BBC ^ | 12-10-2003 | Richard Black

[3Lean]

Regarding Figure 1-3, it never ceases to amaze me that trained scientists will publish data like the chart you included. Are they really suggesting that they have the ability to measure temperature via tree rings, ice cores, etc. to an accuracy any where close to 1 degree Celsius?
In a past life I had the mind-numbing task of calibrating thermometers (ISO 9000), the only diversion provided was the shock I experienced when I realized how many "scientific" thermometers were not capable of +/-1 degree accuracy.
If Mr. Ruddiman was at all honest he would concede that his 1 degree estimate has a fair amount of inaccuracy associated with it (maybe 5 degrees or more) so in reality his conclusions are meaningless.

[ancient_geezer]

Regarding Figure 1-3, it never ceases to amaze me that trained scientists will publish data like the chart you included. Are they really suggesting that they have the ability to measure temperature via tree rings, ice cores, etc. to an accuracy any where close to 1 degree Celsius?

Absolute temperature is a problem differences are more readily determined, through the study of the proxies used, specifically C¹⁴, Be¹⁰ and O¹⁸ created by the effect of solar activity on cosmic ray intensity.

The concentration of these isotopes and relation to temperature is demonstrated very well in the current era as well as going back in the paleo record. The temperature deviations are derived from correlating a multitude of such measures as well as growth rates of vegetation, sedimentary deposits and many other factors that are temperature related and not on the strenght of any single one of them.

[lepton]

Professor Weiss said it was something of an irony that natural changes in climate made modern society possible, whereas society was now changing the climate in ways which threatened its existence stabilizing climate change.

[lepton]

Let me cover animals first. In a state of nature there are X number of cattle on the planet. They pass methane, which is a greenhouse gas. Now, with humans and modern farming methods, the number of cattle on the planet is probably "X times 10,000"

Let me cover animals first. In a state of nature there are X number of cattle, and Y number of Bison on the planet. They pass methane, which is a greenhouse gas. Now, with humans and modern farming methods, the number of cattle on the planet is probably "X times 10,000", while numbers of Bison have plummetted to an insignificant fraction - though the flatulence of ill-fed cattle is higher than those that are well fed, and the cattle in India are among the most flatulent of all.

[lepton]

If you do slash and burn like in the Amazon [- to support alcohol as a fuel -] you immediately release the carbon into the atmosphere, and the land may be so poor when you're done farming it that it won't grow much of anything for a long, long time.

So it's the environmentalists fault?

[SevenDaysInMay]

Coincidence has its headlines.

What of other interglacial periods?

What happened 5,000 years ago?

What were the pre-Holocene populations of termites? ( a leading producer of methane)

Could the sublimating methane ice on the ocean floor be a lagging indicator of the ice melt off?

These guys don't know and can't know. so, they just jump to a conclusion like watermellon headline writers.

[lepton]

New growth forests -- if managed right (like those planted by lumber/paper companies) -- give off far more O2 than old growth.

And support more quantiful and diverse life.

[3Lean]

I didn't ask how the temperatures (or differences) were measured. I asked what the accuracy of these measurements were. How does the error compare the the result of 1 degree C?

Your comment about temperature differences intrigues me. You are saying that one cannot determine if the mean global temperature 10,000 years ago was 10 C (for example) but one can determine that the mean global temp was lower by 1 C than it is today? Since we know (fairly accurately) what the mean global temp is today and we know the difference, don't we know the absolute temp then?
Or are you saying that we can't make the comparison between today and 10,000 years ago, but need to proceed in smaller steps (say 1000 years)then the error is compounded at each step.

[ancient_geezer]

We cannot even determing "Global" temperature today with certainty of better than 1/2 degree in absolute measure. Thus we can do no better in determining "absolute" temperature in historical reconstructions.

There are two separate sources of error, accuracy and precision of the measurement. The accuracy relates to errors in offset from true temperature, precision errors deal with the scale factor associated with relative measurements.

It is relatively easy to determine where temperatures must lay between some relative range of values measurable by a proxy quantities such as Be10 or C14 concentrations. It is a more difficult to endow such measurements with an absolute precision.

One can know for example the coldest of temperatures could not exceed a certain value and from that establish a linear relation between temperature and the proxies used. Such a measure yields a values of certain percentage precision of the measurement.

Establishing the absolute value as a fraction of a degree absolute is a separate issue altogether especially in regard to assigning it to a global measurement when one lacks the means of making "global" measures at specific times to weigh and define whatever the average may be. Any local temperatures measured reflect the changes global values assume in relative terms, but the absolute value will remain indeterminate.

[ancient_geezer]

The following is a comparative chart of temperature reconstruction for the last 2,000 years. Helps provide some perspective as reguards the precision of the measurements in relation to the insturmental record for 1850-2000 Northern Hemisphere Land Temperature variation. Note the shaded areas representing the error with respect to instrumental data.

No record can be said to be accurate in an absolute sense. Though they all indicate relative trends in the displayed period.

 

figure 1. Comparison of proxy-based NH temperature reconstructions [Jones et al., 1998; Mann et al., 1999; Crowley and Lowery, 2000] with model simulations of NH mean temperature changes over the past millennium based on estimated radiative forcing histories [Crowley, 2000; Gerber et al., 2002--results shown for both a 1.5°C/2*CO2 and 2.5°C/2*CO2 sensitivity; Bauer et al., 2003). Also shown are two independent reconstructions of warm-season extratropical continental NH temperatures [Briffa et al., 2001; Esper et al., 2002] and an extension back through the past two thousand years based on eight long reconstructions [Mann and Jones, 2003]. All reconstructions have been scaled to the annual, full Northern Hemisphere mean, over an overlapping period (1856-1980), using the NH instrumental record [Jones et al., 1999] for comparison, and have been smoothed on time scales of >40 years to highlight the long-term variations. The smoothed instrumental record (1856-2000) is also shown. The gray/red shading indicates estimated two-standard error uncertainties in the Mann et al. [1999] and Mann and Jones [2003] reconstructions. Also shown are reconstructions of ground surface temperatures (GST) based on appropriately areally-averaged [Briffa and Osborn, 2002; Mann et al., 2003] continental borehole data [Huang et al., 2000], and hemispheric surface air temperature trends, determined by optimal regression [Mann et al., 2003] from the GST estimates. All series are shown with respect to the 1961-90 base period.

 

However, looking at a much longer period using glacial ice core data (e.g. Be10, C14, & O18 proxies) gives a clearer view of Norther Hemisphere climate trends overall.

Figure 1-2 Climate of the last 2400 years

 

Figure 1-3 Climate of the last 12,000 years

[3Lean]

Very nice data, and I think it supports my original question. If we can't even measure current global temps to better than +/- 0.5 degree, and even relatively recent (<2000 years) projections have even greater errors (approaching +/- 1.0 degree, how can anyone claim to have detected a 1.0 degree warming trend over 10,000 years? The signal is lost in the noise (experimental error).

I'm pretty sure I know how my first job as a chemist would have ended had I gone to my boss and claimed to be able to measure low concentrations of a substance without mentioning that the levels I was claiming were far lower than the experimental error of my method.

How do these guys continue to get funding for such sloppy work? (That is a rhetorical question, the answer is politics, of course).

[ancient_geezer]

You haven't done much in the area of signal processing have you?

The key to measuring trend of a changing signal is time to filter out shorter term fluctuations. Trend (direct of change) has little to do with absolute magnitudes or quantities. Given a sufficient time series relative values can easily be measured through the sort of variation & random measurement errors you refer to.

Don't make the mistake of assuming a lack of precision on an instantaneous measurement means we cannot determine the overall nature of a signal in relative terms. Trends are all about relative changes not absolute magnitudes and being a relative measure can be separated from short term fluctuations and random errors in measuring absolute magnitudes.

[3Lean]

You havn't done much to answer my original quesion, have you?

I happen to have a bit of a signal processing background, I worked as a chemist developing analytical tools for detecting ppb levels of contaminants. That is also where my knowledge that signal processing does have a limit comes from.

My original question - once again - is what is the level of confidence in these measurements and why were they not stated in the article? No measurement has 100% certainty and very few scientists would publish data without considering and reporting the level of confidence they have calculated.

If you can't answer that quantitatively then discussions of relative error and trends are really quite meaningless.

[LRS]

Let's ride with the family down the street. Thru the courtesy of Fred's two feet.

[ancient_geezer]

My original question - once again - is what is the level of confidence in these measurements

Which measurements? The Mann study shown above displays 2 Standard Deviation limits, approx a 95% confidence level for +-0.5^oC. The others in comparison to the Mann "Hockey Stick" are within those limits.

and why were they not stated in the article?

Ask the author of the article, a "BBC science correspondent". I have rarely seen news/opinion article writers say anything about error or confidence limits about anything they write.

No measurement has 100% certainty and very few scientists would publish data without considering and reporting the level of confidence they have calculated.

True, but then you are looking at a popular news/opinion piece about a presentation made by a University of Virginia professor and interview with him, not a paper issued by the good professor.

The article is not mine, nor I do I support its conclusions.

If you can't answer that quantitatively then discussions of relative error and trends are really quite meaningless.

Obviously, I do not speak for the conclusions of the article. Only of the ability to establish general relative movements in temperature across multi-millenial time frames.

The conclusion of the article presumes CO2 concentration to be a prime driver of atmospheric temperature to come to the conclusion it does. A debatable presumption to begin with.

I do not make any such claim for CO2 or any minority gas. Water vapor and cloud cover in response to solar activity is a the dominant determinator of the overall temperature at the Earth's surface. Anything else is of marginal or short term importance.

As far as trends, and confidence limits and science involved, I suggest you go to the papers and studies published written for the scientific community for information not the second & third hand accounts of news/opinion piece writers for popular consumption.

[ancient_geezer]

My original question - once again - is what is the level of confidence in these measurements and why were they not stated in the article?

I suggest you check with the author of the study rather than the BBC's take on things:

The Anthropogenic Greenhouse Era Began Thousands of Years Ago
William F. Ruddiman Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904, U.S.A. E-mail: wfr5c@virginia.edu

abstract & paper available here-> http://journals.kluweronline.com/article.asp?PIPS=5145667

If you're that interested in determining what Ruddiman actually did, buy his paper and let us know what he is saying that is so outrageous and whether or not he discusses the error limits of his methodology.

From what I can determine, he's telling us that CO2 and Methane have increased beyond levels accountable for by natural sources alone a reasonable result. Then he draws an inference based on the presumption that CO2 is the prime determiner of global temperature change. Which is based on a highly debateable presumption that CO2 is the prime driver of climate change.

---

 

As far as conclusions go. If one is to assume CO2 and Methane are the primary determinates of global temperature, then one is justified in assuming an anthropogenic source for global warming it has been going on since the institution of agriculture began.

If one does not accept the premise that CO2 & Methane are primary movers of climate, but rather see changing solar activity, water vapor concentration and cloud density as the primary determiners of global temperature then the conclusions ascribed to Ruddiman regarding global warming are essentially hogwash.

 

The following global temperature reconstruction is composed of the sum of the relative contributions of Solar & CO₂ concentration as components of temperature.

The Solar Component(S) is the the solution of a linear regression of Solar Activity as measured by Lean '98 for (1956-1977) scaled and appended to the composite ACRIM Satellite data series (1978-2000) of total solar irradiance Frohlich and Lean '98 vs global instrumental land & ocean temperatures, Jones et.al '01.

T_s = 0.2685*S-366.95;
Stderror 0.17^oC,
Correlation (R) 0.722

The CO₂ component is the linear regression solution of the natural log of CO₂ concentration from Law Dome ice core data serie(1865-1978) scaled and appended to Mauna Loa Atmospheric CO2 record (1979-2000) vs the residual of the global intrumental temperature series minus the Solar Component above.

T_c=0.6318*ln(CO₂)-3.6324;
Stderror 0.17^oC,
Correlation (R) 0.25

 

 

Global Temperature Anomaly, ^oC
Instrumental Global Temperature(T), Jones et al. '01 (black solid line)
Reconstructed temperature (T_s + T_c) from linear regression components(red solid line)

 

 

CO₂ + Solar Temperature Anomaly Reconstruction, ^oC
CO₂ contribution to temperature (blue area)
Solar contribution to temperature anomaly (red area)

 

From the above it can be seen that change in solar actrivity is correlated with over 70% of the change in global temperatures. CO2 contributions (natural + anthropogenic) comprise less than 15% of the total variation.

[SunkenCiv]

Note: this topic is from 2003. Thanks blam.

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[SunkenCiv]

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[truth_seeker]

Early visitors to SoCal/Lost Angeles Basin in the 1700s and before remarked about the ever-present layer of smoke over the area, from the local Indians’ camp fires.

The area held one of the largest populations of natives in the new world, due to the mild climate, good ground for crops, water for irrigation, coastal areas for fishing, etc.

The globe here has been warm all along.