Digital Diatribes

A presentation of data on climate and other stuff

Overall HadCrut trends as of March month-end 2012

Posted by The Diatribe Guy on May 14, 2012

Time for an update on the HadCrut data set.

I plan on submitting separate posts over the next few days taking a look at the different time horizons on the charts.

Today’s submission is just the overall total trend, and the current longest period length of time backwards from current that demonstrates a flat or cooling trend in the data.

The Data
As can be expected, the overall chart from inception does not change much over the course of a year, but it is presented for completeness. However, I’ll speak to a few of the numbers as they’ve transpired since my last series of posts last year.

From December 2010 through December 2011 we had 13 consecutive months where the anomaly was lower than the previous year. As such, the trend lines have predictably declined in magnitude over that period of time. The January anomaly of 21.7 was slightly above the 2011 January value of 19.4, otherwise we’d be at a stretch of 16 consecutive cooler months on a year over year basis.

From inception (January 1850) through March 2012 the slope values are as follows:
Per month (degrees Celsius): +0.0003757
Per year: +0.0045085
Per Decade: +0.0450854
Per Century: +0.4508542

As demonstrated in the past, the temperature has not increased in anything resembling a straight line, but instead has seemed to follow a cyclical pattern that I have fitted relatively closely to a dual sine wave. However, the wave fits along the increasing line, so there does seem to be an upward trend in temperature that follows the straight line fairly well over that period. But it is less than a half-degree per Century rate.

The current anomaly of 30.50 is the lowest March anomaly since 1999.

Chart below:

Global Temps - HadCrut

Overall Trend in Global Temps – HadCrut

The other chart I’ve updated and am presenting here is the latest period of flat or cooling temperature anomalies. This is just using the latest month as an endpoint and seeing how far back we can draw a line where we can demonstrate straight from the data that temperature has not increased during that period. By implication, we must understand that drawing the line back to any prior point will show that there is a positive slope to average temperature. So, this is not attempting to demonstrate that temperatures have not increased at all over time, just that there has not been warming for some period of time. The period we can go back to under this measure is January 1997. In other words, we can draw a line back more than fifteen years such that the best fit trend line shows no warming in the global temperature anomalies.

Looking at the chart, At the time of my update last year there had been an increasing trend in the anomalies, elevating the trend line a bit. Since then, it’s been continually lower, and you can see the impact of the lower temps on the graph. Chart below:

Current Flat Trend Period - HadCrut

Current Flat Trend Period – HadCrut

I’ll be updating the 5, 10, 15, 20, 25, and 30 year trend lines over the next couple weeks. I am also planning on doing a 60-year line, since that seems to be about the period of time that a full cycle takes place.


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