IPCC AR5 Claims in review – Last decades unusual?

Claim:  Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850.

I will be using GISTemp, which is available from 1880.

Decadal temperatures (GISTemp land stations)

2014-03-31 22_41_44-Microsoft Excel - GISSRunAndRankGlobal2014Land.xls

As a starting observation, 78.6% of ALL decades are ranked number one.  This ranking is taken since the beginning of the series, so a ranking of one means that the previous first rank was exceeded.  Here is the chart:

2014-03-31 23_00_57-Microsoft Excel - GISSRunAndRankGlobal2014Land.xls

Now to the question at hand… Is it unusual for the last 3 decades to successively warmer, and warmer than any other decade since 1850?  We can answer the question since 1880 with this dataset.  We can’t test the claim before 1900 since we need 3 successively warmer decades AND warmer than anything previous.


2014-03-31 23_35_14-Microsoft Excel - GISSRunAndRankGlobal2014Land.xls

Answer:  No, since 54% of ALL decades will make the claim true.  Notice also that the claim is not unusual before CO2 emissions became “important” by IPCC standards, at around 1945.  The decades before and since all have similar probabilities for making the claim true.

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Posted by on March 31, 2014 in Climate


December 15th World Sea Ice

December 15th World Sea Ice

No trend once cyclical signals are removed.

Inspired by: Steve Goddard.

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Posted by on December 19, 2013 in Climate



UAH Global: Trend and cyclical analysis as of July 2012: Zero trend.


UAH Global temperature trend and acceleration after removing best fit cyclical variables.  Trend: 0.00002°C/year.  Acceleration: 0.0000094°C/yr^2.  “For entertainment purposes”, this is extended to 2100:  Note that the timing of the end of cooling has moved a little compared to many other datasets.  This one reaches a minimum in 2034, most others reach minimum around 2028 / 2030

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Posted by on August 4, 2012 in Climate


Colorado Drought

How can there be a drought:

When CO has received 4 to 10″ of rain in the last 60 days?


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Posted by on August 2, 2012 in Climate


Colorado Annual Temps

The trend is half what NCDC claims (even using their wildly adjusted data).

Once you take out the cyclical component, the trend is 0.079°C per decade…

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Posted by on June 30, 2012 in Climate


In response to:

The trend is down, at -.189 million km^2/yr.


Trend is still down…


Posted by on April 28, 2012 in Climate


Northern Hemisphere UHI CRUTem3

This article describes another way to look at the northern hemisphere CRUTem3 data studied by Dr. Roy Spencer in the WUWT article here:

Dr. Spencer identifies a spurious Urban Heat Island (UHI) influence of about 0.13°C per 39 years based on using 3 population density classes out of a possible 5.  He shows that this results in a UHI caused overstatement of the temperature trend by about 15% as he describes in the paragraph below:

The CRUTem3 temperature linear trend is about 15% warmer than the lowest population class temperature trend. But if we extrapolate the results in the first plot above to near-zero population density (0.1 persons per sq. km), we get a 30% overestimate of temperature trends from CRUTem3.

In Spencer’s chart below, he shows about 0.13°C over 39 years or about 0.0033°C per year exaggeration in the CRUTemp3 record caused by UHI:

The chart above shows spurious UHI content of about 0.0033°C per year (chart by Dr. Roy Spencer)

I used a method to remove cyclical signals from the entire dataset.  It is a technique I developed to minimize the least squares error by using a dual signal cyclical and exponential model of the temperatures (or anything else).  You could argue I have too many degrees of freedom to play with when I curve fit it, and you would be right, but the chart below represents a model with the least error that I could generate.  Other combinations work reasonably well too, but have more error than this one.

The section of the NH temperature dataset that Dr. Spencer chose to analyze from 1973 to 2011 is on one of the repeating sawtooth steeper areas of the temperature curve.  1973 was near the bottom of one of the last cooling cycles, right around the time of “the next ice age” scary news stories of the day.  This section of the curve also coincides with the steepest part of the sine components that fit well in my analysis.  So I would argue that this is much steeper than the long term trend and that Dr. Roy’s analysis therefore underestimates UHI.

As I show in the chart below, the section of the curve that Spencer analyzes is increasing at about 0.0163°C per year, of which 0.0033°C is UHI.  On my chart, that is about 20%; he uses 15% as a linear fit.  But the long term trend after removing cyclical items is only 0.0066°C per year.  So the UHI component is 50% of the long term trend (click to enlarge).

Dr. Spencer goes on to say that if more population classes were used, the amount of UHI increases dramatically, but since there are fewer items in each class, the data is statistically less reliable.

The conclusion I am pointing out here is that even without using more classes, I get a UHI contribution 2.5x higher since my divisor (slope) is lower comparing long term versus short term.  Using the paragraph above, if Spencer was able to get from 15% UHI influence to 30% UHI (2x) by extrapolating toward zero population (at 0.1 people per km^2), AND if I can get from 20% to 50% UHI (2.5x) by comparing the short term versus long term, is it possible that UHI in fact accounts for ALL or MORE than 100% of the observed increase in NH CRUTem3 data?

Summary / calculations:

0.0033°C/yr UHI Spencer basis * 2.5 LT.vs.ST * (2x extrapolation to zero population)=0.0165°C/yr.

The long term slope is only 0.0066°C per year, the short term slope is only 0.0163°C/yr.

Has Dr. Spencer found UHI accounting for more than 100% of the total measured increase?  It looks possible.

Now start adding classes which adds another very steep multiplier.  How important is UHI at much more than 100% of total influence?  Probably worth looking into!

Comments welcome.

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Posted by on March 31, 2012 in Climate


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