Holocene, historic and recent global temperatures from temperature proxies.
Guest post by: Frank Lansner, civil engineer, biotechnology
NOTE: Link to PDF of this article is HERE
In the climate debate, the temperatures of the past are used to determine if the present temperatures are unique and alarming. Any viewpoint can be supported by choosing specific science papers as reference
This paper is one of many attempts to give a realistic overview of the actual messages we get from the temperature proxies.
(“Temperature proxy”: Past temperatures reconstructed from samples using a row of techniques.
The “Spaghetti graphs” in the following gives an impression of the huge variability among the datasets. The essence of each graphic is the major trends. To enable display of multiple data series it was often necessary to interpolate temperature values to the specific years used in graphics.
To avoid most calibration problems, I have set specific years to zero for the different graphs I chose a year where practically all graphs has data, and no further calibration needed. In few cases I have calibrated from 1980-1990-2000 using UAH trend of approx. +0,1K/decade.)
Recent temperature proxies – 120 years
Fig 1: 10 multi proxies shown for the 20´th century. In addition 14 temperature proxy datasets. The black curve shows average of the 14 datasets as 1 multi proxy. This multi proxy + the 10 of the most used bigger multi-proxy series is the basis for the WHITE graph: “Average of 11 multi proxies”.
The temperature proxies does not show strong net warming since around 1940. In fact, proxy data does not show any warming since 1940. This is no news, it has been recognised for example here:
http://www.ldeo.columbia.edu/res/fac/trl/downloads/Publications/divergence2007.pdf
The authors call the missing global warming in proxies for “The Divergence problem”. And they try to give reasons for this problem using characteristics of trees. But since other proxies than using tree ring proxies also indicates no global warming after around 1940, the problem seems not related with tree rings measurements.
“The divergence problem”:
Fig 2: The “divergence problem”.
The “All China” multi proxy: A reliable work where 8 regions of China where studied and then yield the final China multi proxy temperature line. The “All USA”, NOAA raw, is the official measured USA temperatures minus the official correction, that is, the raw USA temperature dataset. I find it stunning how close All-China and All-USA matches each other, see fig 2! (- a dataset of measured temperature compared to a dataset of proxies). And unlike GISS 2009, the Northern Hemisphere temperature set of 1976 supports the raw trends of US and China. Several of the multi proxy series have been smoothed with a “50 year weighted Gaussian filter” etc. and therefore any bigger dive around 1970 could not be seen in the multi proxy graph.
We see a divergence after 1950 between:
- GISS 2009 vs. Average of the multi proxies, that is, the temperature evidence in the ground and trees.
- GISS 2009 vs. USA, CHINA and NH temperatures
- GISS 2009 vs. Solar activity.
So, at least when comparing with mostly raw datasets, the GISS 2009 dataset could seem to be the source of “the divergence problem” – “the outlier”. Problems for the GISS data set might be incorrect adjustments, problems with UHI and poor measuring sites, see www.surfacestations.org!!
The “divergence problem” also seems to vanish when using satellite data (UAH/RSS) in stead of GISS data:
Fig 3: A: Briffa´s 2001 illustration of tree ring proxies combined with the GISS dataset as “Observations” (as the adjusted GISS temperatures are called). B: Same, however this time “Observations” are raw satellite data UAH from 1980 – 2000 with a slope of 0,1K/decade.
There is no divergence problem when using satellite temperature data as “Observations”. We now have total compliance between proxy data and modern temperature measurements stating: No net warming since around 1940-50.
Historic temperature proxies – 1200 years
For this analysis 33 data sets was used. The first that strikes you when working with historic temperature proxies is the apparent chaos of data. However, after keying in 6-8 data sets the well known features “Middle age warm period” and “The little Ice Age” becomes clear. Keying in the rest of datasets doesn’t change much.
First, take a good look at the period 1900 to 2000..
Notice how these 33 datasets confirms the trends from fig 1, the recent temperature proxies. We can conclude that we have a good ability to reproduce the result quite accurate with quite different datasets, and thus, neither of the graphs ( fig 1 and fig 4) are likely to reflect “random” results. All data evidence used in fig 1. + fig 4. actually suggests that today’s temperatures resemble the temperatures of 1940-50. Yes, a divergence problem for the temperature data from GISS and Hadcrut.
Fig 4: Historic temperature proxy data. Practically all methods and regions of the globe are represented.
6 of the data sets originate from tree ring data.
We see the Medieval Warm Period apparently ongoing already in year 800 and goes on for 5-600 years. First around year 1400 the Little Ice Age really takes over. It was around year 1400 the Vikings left the freezing Greenland.
From year 800 to year 1300 temperatures appears around 0,3 K higher than today. And from around year 1400 to 1900 temperatures appears to be are around 0,4 K lower than today. A difference from MWP to LIA of 0,7 K in average globally. (Max difference approx 1,1 K),
We will return to these historic data later, but lets first take a look even further back in time.
Holocene temperature proxies – 12000 years
For this analysis 29 long datasets where used. All graphs are calibrated to zero for year 1000.
First focus on years 800 to 2000…
Once again we see a reproduced trend between 2 different data sets. And again, the accuracy is nice. The MWP here appears almost 0,8 K degrees celcius warmer than the LIA, very close to what we saw it on fig 4, the historic data 0,7K. This once again confirms the impressing usefulness of data despite the chaotic and random appearance. There is however a tiny difference between the 2 graphs, around 0,1K. But it should be noted, that for the Holocene temperatures, no tree ring data was used. According to Loehle 2007, tree ring data tends to suppress the MWP somewhat. This we will return to.
Fig 5: Holocene temperature data.
The data point for year 2000 are based on too few datasets to be really trustworthy. Therefore I have inserted the red star where I use the value of todays temperature taken from fig 4, historic temperatures. By doing so, temperature for year 2000 got 0,2 K warmer than from Holocene data.
Fig 5 also shows that the whole debate about MWP is irrelevant. Imagine there was no MWP. Practically ALL of the Holocene period the eath appears to be between 0,5 and 1,5 K warmer than today. The little ice age does resemble a mini ice age or at least it appears to be the coldest period in over 10.000 years.
Finally, the overall picture from the graph is an almost perfect mathematical curve that tops around 5-6000 years ago. These Data tells the story quite clear: We are on a down trend in temperatures globally, we should not fear warmth by now. How much lower can the temperatures on earth go before we reach a tipping point to much colder temperatures at earth?
Medieval warm period
Arguments against the MWP often focus on the “fact” that the warmer temperatures from that period are a phenomenon exclusively to have appeared on the northern hemisphere.
Fortunately, the results from fig 4 and fig 5 shows an excellent match for the period year 800 to year 2000. It thus makes very good sense to combine the datasets and then obtain a better data foundation to analyse the MWP.
Datasets from fig 4 and fig 5 combined, a northern/southern hemisphere display of the Medieval Warm Period:
Fig 6: Historic temperatures, North and south hemispheres separated. Let’s first see what the graph actually says, very roughly:
NH MWP, 42 datasets:
Ongoing in year 800, temperatures mostly 0,3-0,4 K higher than today.
The temperature creeps below today’s level and ends around year 1300.
SH MWP, 13 datasets:
Ongoing in year 800, temperatures mostly 0,2-0,3 K higher than today.
The temperature creeps below today’s level and ends around year 1350.
Northern hemisphere is still much better represented than the southern hemisphere, so what can we conclude on this ground? Can we conclude anything?
On this ground I find it safe to accept the NH MWP approximately as described above.
To accept that globally there where no MWP, we will have to accept the following:
The 2 hemispheres have the ability to maintain a quite different temperature development for at least 500 years and did so from year 800 to year 1300.
What can we demand to accept this idea? We can demand solid evidence.
Anyone claiming the above must present solid evidence for a MEDIEVAL COLD PERIOD on the southern hemisphere.
IF data showed that the southern hemisphere had a MCP where temperatures for 500 years was 0,3-0,4 degrees colder than today, would this “kill” the MWP? Certainly not. Because, then we would have had 500 years with global temperatures just like today globally… – In that case, certainly no reason to be alarmed about the temperatures today.
No, if today’s temperatures should be alarmingly warm, the S. hemisphere temperature should show a very strong MCP at least 0,4 degrees colder than today in the 500 year period.
Is there ANY indication of a 500-year strong MCP in the southern hemisphere indicated in the data above? No, certainly not. There are not that many SH data, but still, there is not the slightest indication of a strong MCP on the S. Hemisphere.
Until the strong 500 year long MCP on SH has been proven, there is nothing that shakes the acceptance of a global MWP with temperatures resembling or higher than today’s temperatures.
I believe a massive use of tree ring graphs exclusively might show a strong southern MCP. In this case, the idea that there is no MWP globally is dependent on only on one specific method of making temperature proxies, tree rings. Tree rings are 1 of at least 20 different methods to measure temperatures of the past. As such, they should never dominate the measurements.
The South pole and MWP:
While examining temperature proxies, I found some odd results:
Fig 7: -A stunning mismatch between 2 Antarctic data series.
Not only are they both from Antarctica, but they are both from near the south pole. The well known “MWP-signature” has found its way not only to the Southern hemisphere, but to the south pole. But in the near by Vostok location, for many centuries, there has been absolutely no sign of the MWP? Obviously this is absurd, so at least one of the two results is not accurate.
The black graph (from “Remote Plateau”) has a resolution of 1 – 3 years per sample, excellent. The blue graph (vostok) has approx 23 years between data points. Both series should be considered fine quality then.
How likely is it, that the “MWP/LIA-signature” has come up in “Remote plateau” (black graph) data by a coincidence? When it has also been spotted many other places on the SH? See fig 6: The Vostok data has a dotted red line. How well does vostok data then fit the rest of the Southern hemisphere data?
The use of vostok data also moves the SH temperature profile away from the NH average.
Tree rings
If the MWP only disappears using one a specific measuring method, the idea as well as the method is invalid.
Proxy temperature data from tree rings are easy to get, but the quality?
Craig Loehle: “There are reasons to believe that tree ring data may not capture long-term climate changes”.
Indeed. A good warm year will obviously help a tree growing, but decades of increasing temperatures could affect the whole area so for example more trees might be able to survive, the root nets would only be able to grow to some extend for other trees etc.
Example: Imagine that a warming after decades is accompanied by 10% more trees surviving in an area and eventually demands their “place in the sun”. By measuring tree rings for an individual tree you are not measuring the overall tree growth of the area. And measuring 10.000 trees does not change anything as all trees would have the same problem. Measuring tree pollen or isotopes etc in sediment cores avoids these problems and it makes me wonder how come so much energy has been used for tree ring analyses.
Selective adjustments?
Many kinds of adjustments are used in connection with climate results. But one adjustment I haven’t heard of is the down-adjustment of recent temperatures from temperature proxy data due to CO2-induced extra growth. If the CO2 level is indeed extraordinary high, then it is a fact that plants grow markedly more. And they grow at higher altitude etc.
Here is an impressing overview of plant response to extra CO2 in the atmosphere:
http://www.co2science.org/data/plant_growth/dry/dry_subject_p.php
I have chosen the letter P for the link since several tree ring analysis are made for pine trees. Check the responses for pine trees when adding extra CO2.
Therefore any temperature proxy based on plant growth should be adjusted down in times of high CO2. Otherwise you will measure CO2 and not heat. But this obvious kind of adjustment seems not to happen? Or? Can it really be, that the crew of alarmists so happy for adjusting for all kinds of tiny issues, simply don’t adjust when there is a really good reason to do so?
Fig 8: Historic temperature proxy data with focus on tree ring-method. In the analyses I have used, it turned out that 7 of 55 datasets where from tree rings. On this figure, these 7 datasets actually does seem to differ in trend from all the rest. The 7 tree ring datasets suggests no MWP, in fact, they suggest that the MWP was 0,3-0,4 K COLDER than today’s temperatures. Quite the opposite result than the majority of datasets concerning MWP.
On might say that these 7 datasets are too little a basis for any conclusion, and therefore I have included a bigger tree ring multi proxi, “Esper et al 2002” and the trend from the 7 tree ring datasets are confirmed:
Unlike all other methods, tree rings shows no warm MWP.
Example, the European Alps:
Fig 9: Here from fig 4, we have 2 different temperatures in the same area, the European Alps.
Quite like Antarctica, we have 2 datasets, one showing the well known “MWP/LIA-signature” and one not showing this. Both cannot be correct, so we know that at least one of the datasets is faulty.
In addition, these measurements where taken in the middle of Europe where we have an overwhelming amount of non-tree temperature proxy datasets confirming a very warm MWP.
Therefore, if the tree ring method was useful, we definitely should see a warm MWP from tree ring data in Europe. But we don’t. And unless all the other temperature proxy methods just shows a very warm MWP in Europe by coincidence, the tree ring method does appear to be the faulty method.
The tree graph appears flat compared to the other methods (- a “yummy” to use if you want to produce a hockey stick), but we are not here to produce a hockey stick, we seek the temperatures of the past.
Now it becomes relevant to examine jus non-tree temperature proxies (As Loehle concluded) for better accuracy:
Fig 10: The Historic temperature proxy trend based on 27 non tree ring proxies show a slightly warmer MWP than when including tree rings, fig 4. The average temperature for year 800-1400 is approx 0,4 K warmer than today, and the years 1400-1900 is around 0,4 K colder than today. So the non tree historic temperatures now gives a MWP/LIA difference of 0,8 K like the (non tree) Holocene temperatures, fig 5.
We even see “peaks” in the MWP up to 0,6K warmer than today, and now 1950 actually appears slightly warmer than today.
Fig 11: Briffa’s 2001 all tree ring proxy data, compared with non tree ring data.
First of all, I have every respect for the huge work done using tree rings. There are indeed many sources to errors (like the idea about different SH/NH temperature development etc.) – but despite all, this graph speaks a very clear language.
Here we see the 27 datasets of non-tree rings, together with the well known tree ring graphs.
It becomes clear, that the non tree rings world wide – THICK BLUE CURVE – matches extremely well in the 20’th century and all the way back to year 1450. Then exactly as the MWP starts, the tree rings and the non
tree rings simply “looses contact”.
What ever the reason for the differences between tree ring or non tree ring temperature proxies,
it becomes evident, that choosing tree rings or not is the same as choosing a MWP or not.
.
One partly explanation for this huge mismatch could be CO2. If indeed the CO2 concentration today is a lot higher in the atmosphere than it was in the MWP, then trees simply grows faster than in the MWP, apparently even though temperatures are not higher.
S
Conclusion:
– Its way too early to consider the MWP gone. There is a lot of scientific work to be done before any such conclusion has any weight. MWP disappears when using tree ring data.
– In this writing we see that 48 non tree ring temperature proxies combined shows a MWP around 0,4 K warmer than today, lasting at least 500 years.
– Besides the MWP discussion: 80-90% of the Holocene period (last 10-12.000 years) has been warmer than today. The last 6000 years, the general temperature trend has been steady cooling. The temperature levels in the Little Ice Age were the lowest in the Holocene period.
I find it relevant to study the consequences of further cooling.
– Except for strongly adjusted temperature data, there is compliance between recent temperatures measured from satellites, evidence from tree-proxies, evidence from non-tree-proxies and more showing that: It does not appear warmer today than around 1940-50.
This is in compliance with solar activity in the 20’th century.
This does not suggest a warming effect of CO2 in the atmosphere.
ome of the non-tree-ring measurement methods includes Be, O and C isotopes etc, that in some cases are more independent of changing tree growth or the like. These methods would be preferable if we wanted to clear CO2-induced errors on temperature measurements.
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Tom P (16:25:22) :
Im not shure i understand your critic with UAH.
I used the MAR 2009 display from WUWT:
http://wattsupwiththat.files.wordpress.com/2009/04/uah_global_temperature_anomaly_mar2009.png
I used UAH from the specific year 1980 to the specific year 2000.
Actually 2000 is slightly colder than 1980, so i drew a trend line getting starting from the year 1980 and forward. It gives the well known 0,1K/decade for UAH. This is what i used, to be 100% fair and avoid any critic on this.
I have seen the “adjustments” to UAH, and they are TINY. No way in a hundred years could anyone see the difference if I had used LT5.2 or LT5.1.
Therefore im not sure i understand what the issue really is, could you explain??
Frank,
The UAH linear trend, which I agree is all you need to draw on your plots, is 0.13 degC a decade, with a current value of 0.3 degC. Hence looking at fig. 11, today is warmer than a good portion of the MWP you have reconstructed, except for the two peaks. I’ve modified the figure to show how this looks:
http://img237.imageshack.us/img237/5131/fig11mod.png
Tom P.:
Those ‘two peaks’ cover a lot of years! Way more years than we’ve experienced recently, before temps started down again.
For some reason ‘except for the two peaks’ brings to mind the comment, “Other than that, Mrs. Lincoln, how did you like the play?”
Smokey,
Other reconstructions, which also like Frank’s work exclude tree-ring proxies, do not show such long-duration high-temperature peaks in the MWP. This is a set of such reconstructions from Climate Audit:
http://img6.imageshack.us/img6/1276/proxyq.png
E.M.Smith (14:16:04) :
Thank you for your posting — and for the work that preceded the posting. When GISS released its code over a year ago, did that code include algorithms for both the land and ocean temperatures?
Tom P.,
But that was your reconstruction! There are other reconstructions, too: click
The one here eliminates the falsified Michael Mann invention, and so is closer to the truth — which Mann doesn’t seem to be familiar with.
Here’s a fun one (and from a different “Mann”)…nice Mideval WP on this chart.
http://longrangeweather.com/images/GTEMPS.gif
Correction on my screen name above LOL. Type too fast
savethesharks (20:19:20) :
Here’s a fun one (and from a different “Mann”)…nice Mideval WP on this chart.
http://longrangeweather.com/images/GTEMPS.gif
Have you seen the current state of climate on that graph? It’s quite cool!
Unfortunately, I won’t be here for 2040 AD.
When I was a boy, Easter temps were typically 80-90 F. This was the 1970’s, BTW. Last few years have been significantly colder, with a snow squall today to liven things up.
Yup, thats global warming.
“If you meant glaciers retreating, i.e losing ice mass, then glaciers react to climate changes with a lag of decades to millenia.”
This is part of the recovery from the Little Ice Age. But advance can happen quite rapidly. Also there’s this paper:
Western Canadian glaciers advance in concert with climate change circa 4.2 ka
(Menounos 2008)
Now think about that for a moment. Those receding glaciers are exposing wood that dates to about 4k years ago. That means that 4k years ago, the area where those glaciers are now was forested. That means the area had been ice free for a long time, long enough for trees to become established. The glaciers advanced and are only now returning to where they were then.
That also means that the glaciers would been significantly smaller earlier in the Holocene than they are now. More indication that we have actually been cooling rather than warming. While the mention of in situ stumps means those items have probably not moved from where they grew, a lot of the other material grew even further up the glacial stream and has been brought down to its present location.
This matches other papers dating similar wood samples exposed by retreating glaciers in the Alps to about 5k years ago. So it can be said with fair confidence that the climate 4-5 thousand years ago was much warmer than it is now and had been warmer for long enough for trees to become established in what are now glacial valleys. And there wasn’t a single SUV, oil well or coal mine around to influence that climate.
Smokey (19:58:51) here are a couple more. This one is Craig Loehle’s onto which I added Mann et al in purple, to scale, to show the difference between tree rings and other (Loehle) proxies.
http://i39.tinypic.com/2q3arlw.jpg
This one is from the Page Science Center Site, on the Lake Powell website, government sponsored, this chart ‘disappeared’ from the site circa 2005. I can’t imagine why 😉
http://i39.tinypic.com/35hkz1d.jpg
Here is another one that certain parties would rather forget, IPCC 1990 Fig 7c:
http://i39.tinypic.com/bgemm9.jpg
Smokey,
“But that was your reconstruction!”
No it wasn’t. It came from McIntyre, S. How do we “know” that 1998 was the warmest year of the millennium?. Ohio State University Seminar, May 16, 2008
I’m not sure what is the basis of calculation of these “reconstructions”:
http://i224.photobucket.com/albums/dd137/gorebot/nwarm05.gif
http://longrangeweather.com/images/GTEMPS.gif
http://i39.tinypic.com/bgemm9.jpg
but I don’t think they’ve been calculated by combining time series of proxy data, as Frank has taken the trouble to do for this article.
Steve,
“This one is Craig Loehle’s onto which I added Mann et al in purple, to scale, to show the difference between tree rings and other (Loehle) proxies.”
This one certainly is a temperature reconstruction using proxies. Loehle used the same premise as Frank in his 2007 paper “A 2000-Year Global Temperature Reconstruction Based on Non-Tree Ring Proxies “:
http://www.ncasi.org/publications/Detail.aspx?id=3025
Frank should be aware of this work, which concludes:
“the MWP peak remains 0.07 Deg C above the end of the 20thCentury values [0.34 degC], though the difference is not significant.”
Tom P:
All respect that you go into the matter and try to find the truth!
But then you have found that UAH today should be 0,4 K warmer than in the year 1980..!
Come on! You use your temp-increase/decase also in the decade 2000 – 2010 where UAH was NOT increasing !!
http://www.climate-movie.com/wordpress/wp-content/uploads/2008/10/uah_global.gif
On this graph you can see, that an averaged curve in:
1980 is 0,1 K lower than year 2000 !
1980 is 0,2 K lower than year 2008, and if you go longer than the average cuve temperatures temperatures goes down again.
Even though the average graph says that year 2000 is only 0,1 K warmer than 1980 i used 0,2 K so that NO ONE with any weight could argue with this.
If you take a close look here again:http://www.climate-movie.com/wordpress/wp-content/uploads/2008/10/uah_global.gif
at the actual 1980 level, you will see, that the average curve is considerably under the actual values for 1980. This is because that values in 1979 is under 1980 level and that these lower values has been accounted for.
At NO time does the average curve go more than around 0,26 K over 1980 average level. that happened with the average around 2005-6, but as i said 2008 is back to 0,20000 K over 1980.
So you 0,4 K is far out, honestly.
(If you look at the specific values – not averageded) of UAH, today is around 0,1 K warmer than 1980.
I could have used 0,1K in difference between 1980 and 2000 (because thats what the graph says) but I used 0,2 K to be 100% fair.
Tom, another thing:
http://www.climate-movie.com/wordpress/wp-content/uploads/2008/10/uah_global.gif
If you want to compare the medieval warm period with for example the peak in approx 2006 where temp in UAH was 0,27 K over 1980 level, then you have to ask your self an important question:
“Was there no peaks in the MWP?”
You see, when adding alle these differen temperature proxies with different methods and definetly some timing problems, the resulting MWP curve is a very flattened MEAN temperature curve.
Obviously there has been Lots of EL NINO periods etc in the MWP (thats documented) Obviously a lot of periods in the MWP where temperature rose perhaps 0,3-0,5 K or more over the mean level of MWP that i reported.
So if you wanted to compare a PEAK of El nino years today with an average temperature of the MWP, obviously you would see a less warm MWP. But that not a scientific approach.
A real compare with mean trends of MWP should be at least year 2000 +/- 10 years, and its hard to make that 0,4 K over 1980 level.
The furthest i can get in your direction is the following:
If you take 1980 – 1990 average and compare with 2000-2010 average you get an increase of afpprox + 0,25 K over the 2 decades.
But then you have started with focus on the peak cold year 1985 and ended with the peak warm year 2005…
– And theres nothing that indicates that temperature from 2005 and 10 years ahead should continue increasing that rate or any rate, so honestly, 0,4 K is not a balanced view on the UAH increase 1980 – 2000.
0,2K or MAX 0,25 K is.
K.R Frank
Tom, i forgot an important point (!)
The 500 year long MWP i have talked about many times in the writing on many graphs was base ONLY on temperature proxies!!
The temperature proxies where the evidence that showed a strong 500 year long MWP.
I just showed that using UAH in stead of GISS changes Briffas hockey stick extremely much.
But this little UAH talk has nothing to do with what we can see from the temperature proxies: A 500 year long MWP.
Frank,
An up-to-data linear fit to the UAH data is here:
http://img12.imageshack.us/img12/6856/uah0309.png
which shows a 0.4 degC increase over the series.
0.3 degC for the current temperature does not seem unreasonable from the data and a slightly higher value of 0.34 degC was used by Craig Loehle in his analysis.
Your first article was reporting on the winter of 2002. Why did you pick an article that stops at 2002?
because for a LONG TERM LOOK at the first date of flowers showing up in the year, it doesn t matter what year i chose. i just picked one of the first articles that showed up!
Smokey (19:58:51) here are a couple more. This one is Craig Loehle’s onto which I added Mann et al in purple, to scale, to show the difference between tree rings and other (Loehle) proxies.
http://i39.tinypic.com/2q3arlw.jpg
the problem with the Loehle graph is, that it ends in 1935 (NINETEEN THIRTY FIVE). that is not exactly “today”.
if we take a detailed look at the spagettis presented by frank, we will most likely get a similar result.
Come on! You use your temp-increase/decase also in the decade 2000 – 2010 where UAH was NOT increasing !!
this is false. the slope is 0.13 °C per decade since 1980.
http://www.woodfortrees.org/plot/uah/from:1980/plot/uah/from:1980/trend
you cannot calculate the trend and then subtract the “flat” period at the end again.
and a one year comparison between 1980 and 2000 (or 2008) is simply stupid.
now add in error bars, (and any proxy reconstruction will surely have bars broader than modern measurement by a factor of 10), and the claim that a MWP was warmer than TODAY falls apart immediately.
But this little UAH talk has nothing to do with what we can see from the temperature proxies: A 500 year lon MWP.
as i said above, please think about the consequences of such an event!
we are talking about several hundred years with an ice free summer arctic. the alps being glacier free. spring plants showing up in december and a massive movement of plants and animals. (many of them don t need modern man to move them)
there simply is no evidence of such an event.
– And… Tom.
As i wrote in the article, Briffas and the other tree proxies are HEAVILY averaged, typically 50 years filters.
This is essential to our little UAH discussion, because the dive around 1970-80 using 50 filters is likely to be too too small in the Briffa tree ring graph.
Therefor we start the UAH on a probably too high point.
So on the bottom line is:
The temperature proxies tells that temperatures today a likely not to be higher than 1940-50 level, at leat not much higher.
The temperature proxies (Except for tree rings) tell that we have had a lon MWP that makes recent temperatures within normal range. Thats the point.
In holocene perspective we are generally in the coldest period in 10000 years. Since we have been in a temperature decline for 6000 years, it does become relevant to study the concequences if the trend does not change.
Using UAH in stead of GISS does appear to diminish the “divergence problem” beteween measured temperatures and temperature evidence from the ground, proxies. But “accuracy” on this matter is hard to get.
Tom, check out fig 2, the graphs without 50 year smotthing… you will see that the dive might be much much bigger, so whatever UAH graph you put in that abyss of 0,4 – 0,6 K dive, the UAH cannot produce temperatures today higher than 1940.
sod , about the MWP you say.
”
sod (02:45:06) :
there simply is no evidence of such an event.”
Look. I have shown you TONNES of evidence!!
Do you know how these temperature proxies – nontree rings are made?
Made are made from fauna/ flora related indicators in the ground. Like Pollen levels from the lake sediment cores, corals or other indicators of life in the ocean. These life-related indicators DOES show the increases implying warmer middle ages.
and on top og this, we have other indicators like isotopes telling the same story.
sod, another thing is as I wrote, the high CO2 levels is beyond any doubt influenting plant growth. This does complicate all indicators relates to plant growth. So if it is true that CO2 level today are higher than in the MWP, the use of many plant related indicators are likely to underestimate MWP. Therefore the MWP in my writing could be underestimated.
I wasn’t too clear in my earlier posts. Let me be more specific.
I will be referring to figure 5 in Frank’s article which you can see here:
http://wattsupwiththat.files.wordpress.com/2009/04/lanser_holocene_figure5.png
By looking closely at this chart you can see that temperatures increased rapidly after the last ice age and then leveled off to a moderate increase before starting a downward trend about 6000 years ago. Yiou may want to draw a trend “arc” over the entire plot to understand my thinking.
Based on this chart if you extrapolate from the more gradual decline right through the MWP and LIA and assume increasing negative slope to match the early increases in temperature at around the same temperature range, we should have a base anomaly rigth now of around -1K or lower. We should also have a downward trend that could be as much as -.05K/decade (also assumes a steeper slope similar to the increase in slope early in the chart). In addition, if you draw a line from the temperatures at the LIA across to the other side you will see we were in a period of extreme warming. If an interglacial is a symmetric process then it’s not out of the question that the LIA actually passed a cooling tipping point and we should be rapidly cooling at the persent time on the way to the next ice age.
From what I’ve been able to determine the current batch of GCMs assume a flat trend and a based anomaly of around -.2K (based on where the star is placed on figure 5. This means the GCMs are already starting too high and don’t account to the natural negative pressures on temperature. The primary reason for this is Mann’s hockey stick which utilized the tree proxies that Frank has shown to be questionable.
If these natural climate factors were incorporated into GCMs then, clearly, the increases normally shown would be less. This would most likely bring the GCMs into closer agreement with measured temperatures. The scenarios provided by the IPCC would suddenly look more realistic when super-imposed on a natural negative trend. This would also mean that many of the alarmist projections are significantly overstated since much of the heating from added CO2 is simply holding our current temperature steady. We should not see positive feedbacks because there is so little actual warming.
This could also explain the NH/SH anomaly. Since the NH has both soot (warming aerosols) [see NASA article] and CO2 while the SH has much less soot. We should see a stronger warming signal in the NH. However, CO2 would still be warming the SH over and above the natural cooling. That would eliminate one the prolbems that skeptics have with the current situation. Essentially, the scientists have much of the physics right, they are just applying it to an incorrect baseline. By adding this declining trend and soot the GCMs may be much closer to reality.
Finally, this would mean that we are in a very delicate climate. If we stop adding CO2 and soot to the atmosphere we could set off catastrophic cooling. However, if we add too much we really could set off more significant warming.
sod,
You seem to understand that the woodfortrees interactive site is a cherrypicker’s delight. Right?
From that site I can make a chart showing any trend. For instance: click
Don’t misunderstand, I like woodfortrees’ site. But when someone uses it to make a point, I look at their claim with a jaundiced eye.
And regarding your statement: “there simply is no evidence of such an event,” I’ll quote a better man than I: “Absence of evidence is not evidence of absence.”