Guest post By Girma Orssengo, MASc, PhD
Comparison of the claims by the Intergovernmental Panel on Climate Change (IPCC) of 1) “Most of the observed increase in global average temperatures since the mid-20th century is very likely” man made, and 2) “For the next two decades a warming rate of 0.2 deg C per decade is projected” are shown in this article not to be supported by the observed data, thus disproving IPCC’s theory of man made global warming.
FIRST IPCC CLAIM
In its Fourth Assessment Report of 2007, IPCC’s claim regarding global warming was the following [1]:
Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.
Let us verify this claim using the observed data from the Climate Research Unit (CRU) of the University of East Anglia [2]. In this claim, “mid-20th century” means year 1950. As a result, according to the IPCC, global warming since 1950 is mostly man made.
To verify the claim that global warming since 1950 is mostly man made, we may compare the global warming rate in degree centigrade (deg C) per decade in one period before 1950 to that of a second period after 1950 to determine the effect of the increased human emission of CO2. To be able to do this, we need to identify these two periods, which may be established from the Global Mean Temperature Anomaly (GMTA) data of the CRU shown in Figure 1.
In Figure 1, the GMTA could be visualized as the sum of a Linear GMTA that has an overall warming rate of 0.6 deg C per century and an Oscillating GMTA that oscillates relative to this overall linear warming trend line. This Oscillating GMTA indicates the relative warming and cooling phases of the globe.
As our objective is to verify the claim that global warming since 1950 is man made, we need to identify two global warming phases before and after 1950. To clearly see the global warming and cooling phases, we plot just the Oscillating GMTA, which is the GMTA relative to the overall linear warming trend line shown in Figure 1. This can be done by using an online software at www.woodfortrees.org by rotating the overall linear warming trend line to become horizontal by using a detrend value of 0.775 so that the Oscillating GMTA has neither overall warming nor cooling trend. The noise from the Oscillating GMTA is then removed by taking five-years averages (compress = 60 months) of the GMTA. The result thus obtained is shown in Figure 2.
”]
Figure 2 shows the following periods for relative global cooling and warming phases:
- 30-years of global cooling from 1880 to 1910
- 30-years of global warming from 1910 to 1940
- 30-years of global cooling from 1940 to 1970
- 30-years of global warming from 1970 to 2000
If this pattern that was valid for 120 years is assumed to be valid for the next 20 years, it is reasonable to predict:
- 30-years of global cooling from 2000 to 2030
Figure 2 provides the two global warming phases before and after 1950 that we seek to compare. The period before 1950 is the 30-years global warming period from 1910 to 1940, and the period after 1950 is the 30-years global warming period from 1970 to 2000.
Figure 2 also provides the important result that the years 1880, 1910, 1940, 1970, 2000, 2030 etc are GMTA trend turning points, so meaningful GMTA trends can be calculated only between these successive GMTA turning point years, which justifies the calculation of a GMTA trend starting from year 2000 provided latter in this article.
Once the two global warming periods before and after mid-20th century are identified, their rate of global warming can be determined from the GMTA trends for the two periods shown in Figure 3.
”]
According to the data of the CRU shown in Figure 3, for the 30-years period from 1910 to 1940, the GMTA increased by an average of 0.45 deg C (3 decade x 0.15 deg C per decade). After 60 years of human emission of CO2, for the same 30-years period, from 1970 to 2000, the GMTA increased by an average of nearly the same 0.48 deg C (3 decade x 0.16 deg C per decade). That is, the effect of 60 years of human emission of CO2 on change in global mean temperature was nearly nil, which disproves IPCC’s theory of man made global warming.
SECOND IPCC CLAIM
In its Fourth Assessment Report of 2007, IPCC’s projection of global warming was the following [5]:
For the next two decades, a warming of about 0.2 deg C per decade is projected for a range of SRES emission scenarios. Even if the concentrations of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1 deg C per decade would be expected.
Let us verify this projection using the observed data from the CRU [2]. This may be done by comparing the global warming rate between the last two decades as shown in Figure 4. In this figure, the global warming rate decelerated from 0.25 deg C per decade for the period from 1990 to 2000 to only 0.03 deg C per decade for the period since 2000, which is a reduction by a factor of 8.3, which further disproves IPCC’s theory of man made global warming. If the current global warming trend continues, the GMTA will increase by 0.27 deg C (0.03 x 9) by 2100, not the scary 2.4 to 6.4 deg C of the IPCC.
Note that the projection for the current global warming rate by the IPCC was 0.2 deg C per decade, while the observed value is only 0.03 deg C per decade. As a result, IPCC’s Exaggeration Factor is 6.7.
”]
SUMMARY
As shown in Figures 3 and 4, claims by the IPCC of 1) “Most of the observed increase in global average temperatures since the mid-20th century is very likely” man made, and 2) “For the next two decades a warming rate of 0.2 deg C per decade is projected” are not supported by the observed data, thus disproving IPCC’s theory of man made global warming.
According to the CRU data shown in Figure 3, the 30-years global warming from 1970 to 2000, after human emission of CO2 for 60 years, was nearly identical to the 30-years global warming from 1910 to 1940. In the intervening 30-years, there was a slight global cooling from 1940 to 1970. Furthermore, since year 2000, as shown in Figure 4, the global warming rate decelerated by a factor of 8.3 compared to the decade before. This is the story of global mean temperature trends for the last 100 years!
Does not the observed data in Figures 1 and 2 show a cyclic global mean temperature pattern with an overall linear warming rate of 0.6 deg C per century?
Dear citizens of the world, where is the catastrophic man made global warming they are scaring us with?
Or is the scare a humongous version of the “Piltdown man”?
REFERENCES
[1] IPCC: “Most of the observed increase in global average temperatures since the mid-20th century is very likely” man made
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/spmsspm-understanding-and.html
[2] Global Mean Temperature Anomaly from Climate Research Unit of the University of East Anglia (GRAPH)
[2] Global Mean Temperature Anomaly from Climate Research Unit of the University of East Anglia (RAW DATA)
[3] Oscillating Global Mean Temperature Anomaly
[4] Comparison of global warming rates before and after mid-20th century (GRAPH)
[4] Comparison of global warming rates before and after mid-20th century (RAW DATA)
[5] IPCC: “For the next two decades, a warming of about 0.2 deg C per decade is projected”
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/spmsspm-projections-of.html
[6] Deceleration of global warming rate in the last two decades
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Mike Hohmann
August 6, 2010 at 1:55 am
It would be excellent if we could provide links for your list of CO2 proportions from various sources.
Hi Girma,
I first came across of the list as quoted in Robert M Carter: ‘Climate: the Counter Consensus — a Palaeoclimatologist Speaks’, Stacey International, London 2010, page 269, endnote #84. Professor Carter there quotes the ‘Canada Free Press’ of 13 June 2008 as his source, to be found at
http://canadafreepress.com/index.php/article/3482
I would say that Bob Carter’s book is essential reading! I quoted these figures on my blogsite — no response pro or con from anyone to date (Google now provides an excellent statistics counter for blogger sites, free, added to any blogger blog with a single mouse click; fantastic details provided). My immediately previous blog leads to Burt Rutan’s website where apart from his most recent fantastic presentation, there are, amongst many other leads, also four videos by Bob Carter, I think as given to the Australian parliament (?).
Hope this may all be of interest. Mike, your CleanEnergyPundit
Mike Hohmann
Thank you for providing the link.
Girma,
For the two periods in question, each decade is greater than the one before. And the last decade’s average temperature exceeded that of 1910 – 1940.
But you cannot determine a reliable climate trend from 10 years of data.
Bear with me and I’ll show you why:
————————————————————————————–
I plot the first two decades in the period 1910 – 1940, which we learn has warmed at 0.15C over a thirty year period. If ten years is sufficient to determine a climate trend, any ten year trend within that period should be on or close to 0.15C.
1910 – 1920 and 1920 – 1930
The trend for 1910 – 1920 is 0.2/dec
The trend for 1920 – 1930 is 0.07/dec
The first decade diverges from the trend by 33%
The second sample diverges from the-term trend by more than 50%.
Ten year’s data is insufficient to reflect the 30-year trend.
————————————————————————————–
If you followed that, what do you think?
Barry
I agree with your previous post.
How about if we compare the global warming rate since 2000 with all the other 10-years global warming rates for the two warming periods of 1910-1940 and 1970-2000 as shown in the following graph:
http://www.woodfortrees.org/plot/hadcrut3vgl/from:1910/to:1940/compress:12/plot/hadcrut3vgl/from:1910/to:1920/trend/plot/hadcrut3vgl/from:1920/to:1930/trend/plot/hadcrut3vgl/from:1930/to:1940/trend/plot/hadcrut3vgl/from:1970/to:2000/compress:12/plot/hadcrut3vgl/from:1970/to:1980/trend/plot/hadcrut3vgl/from:1980/to:1990/trend/plot/hadcrut3vgl/from:1990/to:2000/trend
Here are the periods and their corresponding global warming rate in deg C per decade.
For the first 30-years warming period of 1910-1940
1910-1920=>0.21
1920-1930=>0.07
1930-1940=>0.22
For the second 30-years warming period of 1970-2000
1970-1980=>0.09
1980-1990=>0.07
1990-2000=>0.25
When you compare the global warming rate since 2000 of 0.03 deg C per decade with the above results, we see the current warming rate is about half of the minimum rate of 0.07 deg C per decade above, showing that the current global warming rate has decelerated.
Don’t you agree?
Just testing how to post URL links
REPLY: just put in the URL and don’t worry about it, wordpress will auto-link any valid URL
Global Warming Rates Per Decade
Anthony
The HTML help just below the comment box for URL links should be
\title\
instead of
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REPLY: No, it shouldn’t
Anthony
The instruction given at the bottom of the comment does not work.
This one works
“title”
sorry
< a href=”url” tilte=”title” > does not work
I wish I could preview before commenting
Sorry Anthony
If you are talking about weather trends, yes. If you are talking about climate trends, no.
We’re agreed that 10-year trends are too short to reflect climate trends. This is seen with the data you have provided on decadal trends and the climate periods nominated in the original post. (30 years is a statistically valid length of time to measure climate)
Now, if ten-year trends are too short to reflect climate, let’s use time periods that are long enough. 20 years is a valid minimum period.
I will plot the temperature from 1980 – 2000. This is a 20 year period, the minimum we can safely use.
Then I will plot the period 1980 – 2010 to compare.
If global warming has ‘decelerated’ in the last 10 years, we would expect to see the second trend line at a lower rate than the first, right?
Here is the result.
Let’s try the same thing with the period 1970 – 2000, and then add ten more years up to 2010 and compare the trends.
Here is the result.
The logic of doing it this way is as follows.
1) We are using time periods that are statistically significant with respect to climate
2) Both trend analyses use the same data, and the second adds the last ten years (we’re comparing apples to apples)
Let’s use the most up to date data in 20 year blocks. I will plot the trend lines 1970 – 1990, and 1990 – 2010 to compare.
Here is the result.
Global warming, with respect to climate, has not decelerated in any of these analyses. In each case, it has accelerated slightly.
Other notes:
In the top post, the 0.03C/dec temperature trend is calculated for the period January 2000 to December 2009 inclusive. However, we have data up to June 2010. What happens if we include that in the analysis?
The trend 2000 to present is 0.053/dec, an increase of 84% in just six months. Clearly, weather variance is the dominating factor in this time period.
What is the variance if we use 20 years 1990 – 2010, and then add the last six months?
Here is the result.
The trends diverge from each other by 1.1%.
A side issue…
The top post looks at only one data set – HADCrut. What are the trends, 2000 to present, for the other global temperature data sets?
Here are the results.
RSS = 0.11C/dec
GISS = 0.16C/dec
UAH = 0.14C/dec
HadCRUt = 0.053C/dec
Are the other data sets telling us that global climate warming has continued? No. The time period is too short.
If we run the trends for 20 years on each data set, one thing we notice immediately is that there is much less divergence between them.
The trends now are:
UAH = 0.18C/dec
GISS = 0.19C/dec
RSS = 0.19C/dec
HadCRUt = 0.17C/dec>
Weather variation plays a very small part in the differences between these trends. The primary reason there is a slight difference between them is the different methodologies applied to each.
While there are various issues with the analysis in the top post, three that stand out after our discussion are:
1) The author does not consider attribution in any way, but rather makes implicit assumptions about it
2) The analysis of temp trends for the last ten years is statistically invalid with respect to climate
3) The author chose to use the data set that has by far the lowest trend for that ten-year period
Barry
You wrote:
I disagree.
As the day time temperature cannot tell you the average for the 24 hours, half years GMTA averages cannot tell you the average for the whole year. As a result, you must include the average for the whole your in your calculation of trends. We have to wait until December to calculate the new value for the warming trend since 2000.
You wrote:
I disagree.
As shown in Figure 2, there is a GMTA turning point at year 2000. As a result, it is not meaningful to calculate trends for the last 20 years, which includes the GMTA turning point. You need to start your calculation for current trends from year 2000.
You wrote:
Barry, we only have two long range datasets: gistemp & hadcrut3vgl
Unfortunately, gistemp manipulates its data as shown here:
http://jonova.s3.amazonaws.com/graphs/giss/hansen-giss-1940-1980.gif
As a result, the gistemp data is not cyclic and there is no GMTA turning points for 2000 or for any year since then as shown below:
http://www.woodfortrees.org/plot/gistemp/from:1880/to:2010/compress:60/detrend:0.746/offset:0.394/plot/gistemp/from:1880/to:2010/trend/detrend:0.746/offset:0.394
As a result, unfortunately, the deceleration of GMTA & Cyclic GMTA does not apply for the gistemp data. I wish I could get the untempered gistemp data.
For the CRU data, GMTA has decelerated as CLEARLY shown in Figure 4 of my article.
Barry
You wrote:
I disagree.
As the day time temperature cannot tell you the average for the 24 hours, half years GMTA averages cannot tell you the average for the whole year. As a result, you must include the average for the whole year in your calculation of trends. We have to wait until December to calculate the new value for the warming trend since 2000.
You wrote:
I disagree.
As shown in Figure 2, there is a GMTA turning point at year 2000. As a result, it is not meaningful to calculate trends for the last 20 years, which includes the GMTA turning point. You need to start your calculation for current trends from year 2000. GMTA trends should be calculated only between GMTA turning points.
You wrote:
Deceleration of global warming rate for all dataset in the last 20 years can be clearly seen in the following graph:
http://www.woodfortrees.org/plot/uah/from:2003/plot/rss/from:2003/plot/gistemp/from:2003/plot/uah/from:2003/trend/plot/rss/from:2003/trend/plot/gistemp/from:2003/trend/plot/hadcrut3vgl/from:2003/plot/hadcrut3vgl/from:2003/trend/plot/none
For UAH, from 0.26 to 0.07 deg C per decade
For RSS, from 0.32 to 0.02 deg C per decade
For GIS, from 0.17 to 0.01 deg C per decade
For HADCRU, from 0.25 to 0.03 deg C per decade
Barry, I want also to remind you the reply from the General from the AGW camp:
http://news.bbc.co.uk/2/hi/science/nature/8511670.stm
Barry, we only have two long range datasets: gistemp & hadcru
Unfortunately, gistemp manipulates its data as shown here:
http://jonova.s3.amazonaws.com/graphs/giss/hansen-giss-1940-1980.gif
As a result, the gistemp data is not cyclic and there is no GMTA turning points for 2000 or for any year since then as shown below:
http://www.woodfortrees.org/plot/gistemp/from:1880/to:2010/compress:60/detrend:0.746/offset:0.394/plot/gistemp/from:1880/to:2010/trend/detrend:0.746/offset:0.394
As a result, unfortunately, cyclic GMTA does not apply for the gistemp data. I wish I could get the untempered gistemp data.
Deceleration of global warming rate for all dataset in the last 20 years can be clearly seen in the following graph:
http://www.woodfortrees.org/plot/uah/from:2000/to:2010/plot/rss/from:2000/to:2010/plot/gistemp/from:2000/to:2010/plot/hadcrut3vgl/from:2000/to:2010/plot/uah/from:2000/to:2010/trend/plot/rss/from:2000/to:2010/trend/plot/gistemp/from:2000/to:2010/trend/plot/hadcrut3vgl/from:2000/to:2010/trend/plot/uah/from:1990/to:2000/plot/rss/from:1990/to:2000/plot/gistemp/from:1990/to:2000/plot/hadcrut3vgl/from:1990/to:2000/plot/uah/from:1990/to:2000/trend/plot/rss/from:1990/to:2000/trend/plot/gistemp/from:1990/to:2000/trend/plot/hadcrut3vgl/from:1990/to:2000/trend
For UAH, from 0.26 to 0.07 deg C per decade
For RSS, from 0.32 to 0.02 deg C per decade
For GIS, from 0.17 to 0.01 deg C per decade
For HADCRU, from 0.25 to 0.03 deg C per decade
Barry
Actually, there is a much simpler way of using results from all datasets instead of just one. This is done using the WoodForTrees Temperature Index, which is the mean of HADCRUT3VGL, GISTEMP, UAH and RSS.
As a result, the declaration of the global warming rate since year 2000 compared to the decade before can be seen in the following graph:
http://www.woodfortrees.org/plot/wti/from:1990/to:2000/plot/wti/from:2000/to:2010/plot/wti/from:1990/to:2000/trend/plot/wti/from:2000/to:2010/trend
This result shows a declaration of global warming rate from 0.25 to 0.06 deg C per decade, which is a deceleration by a factor of 4.2!
Gah. Please mods delete the last post. I’ve fixed the formatting in this one (I hope).
You miss the point. I was showing that a mere six months additional can alter a ten year trend by a significant amount. I’m not trying to figure out the new trend, just to show how much it deviates if you use time periods that are too short.
But, to satisfy you, I will demonstrate by adding one whole year, and I will use a time period within the period 1970 – 2000.
I’ve plotted 1988 – 1998, and 1988, – 1999 here.
The first trend is 0.1C/dec
The second trend is 0.23C/dec
The deviation is greater than 100%
The point is, these analyses are not of any climate trend, but instead reflect the variability in the data. I chose this series because 1998 was an extraordinarily hot year.
Now let’s see what happens if I use a 20 year period that ends with the anomalously high 1998.
Plot
As expected, there is a noticeable deviation because the end of the series includes an extreme anomaly, but the deviation is reduced to 30%. If we add more data, say by starting from 1970, we get a more robust result.
By the way, there is no reason to restrict my analyses to within the nominated 30-year periods. The point of running a long term trend through the last GMTA is to explore whether the decade 2000 – 2010 has introduced a cooling to the global climate. It hasn’t. Even though the period itself is one of little warming. If we’re talking about interannual variability, then the last decade has slowed from the previous. but this, as we agree, is not telling us anything about climate. 10 years of data tells us more about the variability than the trend.
I’m not sure what point you are attempting to make here, but Jones is saying what I am, except he is referring to a 15-year period. 1995 – 2010 is not statistically significant with respect to climate. I bolded the key part of the question that many people seem to misunderstand.
Actually, we have 5, but only two are used at woodfortrees. We also have two satellite temperature records available at that site. All of these have data for the last decade, and they all show a higher trend than HadCRUt, which should be at least mentioned in any analysis.
It should also have been mentioned the analysis of the top post that 10 years of data is not meaningful with respect to climate. Instead, 10 the ten year trend is pitched as a climate indicator. We don’t have nearly enough data to work out what the climate trend is for the current GMTA.
All global temperature records are adjusted, including HadCRUt, to account for inhomogeneities in the data sets and to try and balance the weighting of locations around the world. For the periods 1900 – 2009, 1960 – 2009, and 1978 – 2009, GISTEMP has the lowest trends against HadCRUt and analyses done by skeptics using raw data. (The link is to a skeptical site)
The satellite records, of course, have no urban heat bias to influence them, the measuring devices are not located near any city.
True, but as these are in 10-year blocks, we’re not assessing climatic trends. We’re looking at trends that are heavily influenced by the year-to-year variability, as you agreed in a previous post.
As you’ve agreed that ten year trends do not reflect climate trends, we should let go of the idea that the last 10 years is telling us anything about the supposed GMTA period (2000 – 2040), right?
Barry
Agreed.
But, you also need to agree that it is meaningless for the AGW camp to shout “the nth global temperature since record begun”. If you agree that a 10-year trend is not that meaningful, you need to agree that an individual annual GMTA value does not tell us much.
Phil Jones (5-Jul-2005), (Five years ago!)
http://www.eastangliaemails.com/emails.php?eid=544&filename=1120593115.txt
The global warming rate from 1998 to 2005 was 0.06 deg C per decade
The global warming rate from 1998 to 2010 is 0.00 deg C per decade
http://www.woodfortrees.org/plot/hadcrut3vgl/from:1998/to:2005/plot/hadcrut3vgl/from:1998/to:2005/trend/plot/hadcrut3vgl/from:1998/to:2010/plot/hadcrut3vgl/from:1998/to:2010/trend
After 5 more years of Phil’s statement above, the global mean temperature trend still does not show any global warming. How many more years do you require to declare the global warming rate is flat?
Absolutely. A single year tells us nothing about a climate trend.
If we abide by the 20-year benchmark, we have to wait another 7.5 years if we start the trend analysis in 1998. But we must be cautious here.
When starting or ending a series with an extreme anomaly (1998 was the hottest year so far), that variation will have a bigger impact on the trend than if it appeared in the middle. As I demonstrated above, there is a 30% deviance in a 20-year trend with 1998 and then 1999 as the end year. While 20 years is sufficient, a longer time period will give us a clearer trend.
You see a lot more variation in 20-year trends in the satellite records (el Nino years are hotter, and la Nina years cooler in the satellite records compared to the surface records). Consequently, they need longer time periods to achieve statistical significance. Sea ice trends, on the other hand, show less variance, and don’t need as long periods of data for deriving statistically significant trends.
Barry
So you agree that the science of man made global warming is not settled yet?
But don’t you agree that it is more in favor of the no “man-made global warming” camp than the AGW camp? (as our position of no global warming was true for the last 12.5 {20 minus your 7.5} years)
Hi everyone,
please help me, because I think this discussion is missing to recognise ‘the wood’ by only looking at the ‘trees’ (of temperature trends alone). Are the following figures anywhere near correct (if not, who knows of any more authorative ones):
<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>
Or, please, tell me where I am wrong in crediting the above figures (haven’t found any better ones) or in arriving at the musings about what constitutes the real problem facing ‘my grandchildrens’ grandchildren’. Yes, the research about what influences climate needs to go on by those equipped to deal with that (I definitely am not one of those, but I can read and count to 200+ and muster the 3 Rs and a bit more), but not at the expense of just exposing the IPCC Lysenkoism and thereby missing what the problem is (starting with my Clean Energy Primer, perhaps).
here is what’s missing between the <<>> marks above:
Consider published estimates of annual global carbon dioxide emissions in Gt C/year (Gigatonnes of carbon per year):
Gt C/year: estimated range, average, % :
Respiration (humans, animals, phytoplankton) 43.5-52, avge 47.75, = 22.96%
Ocean outgassing (tropics) 90-100, avge 95, = 45.68%
Soil bacteria, decomposition 50-60, avge 55, = 26.45%
Volcanoes, soil degassing 0.5-2, avge 1.25, = 0.60%
Forest cutting, forest fires 0.6-2.6, avge 1.6, = 0.77%
Anthropogenic emissions (2005) 7.2-7.5, avge 7.35, = 3.53%
TOTAL 192-224, avge 207.95, = 100.00%
I find it hard to believe that about 7 Gt C/year out of total global emissions amounting to some 200 Gt C/year should alone and exclusively be responsible for affecting ‘global climate’, no less.
I think, like all climate scientists, skeptical and otherwise, that if CO2 accumulates in the Earth’s atmosphere, the planet will warm. I think this is ‘settled’ science. How much the planet will warm is less certain.
No – I think the planet is still warming. Picking a 12.5-year trend starting from an extreme anomaly is completely and utterly statistically invalid. When one uses time periods that are statistically valid (long enough), there has been no deceleration of global warming with respect to climate.
As an exercise, try averaging every five years from the present back in time. I think you’ll find that every five year average is warmer than the last for the last 40 years. Each decade has been warmer than the last for the last 40 years.