Digital Diatribes

A presentation of data on climate and other stuff

RSS – What Have the Tropics Been Up To? (Or Down to…)

Posted by The Diatribe Guy on October 31, 2008

I decided that it may be nice to run the same analysis that I’ve been doing for the global temperature (which you can find here) on some of the specific geographic zones highlighted in the RSS data.

I’m starting with the tropics for no other reason than the next column over in the data set is that of the tropics (between 20 degrees latitude South and North).

DATA
The information is found here.

The September anomaly is 13.50 (in terms of 0.01 degree Celsius – the data in the link is in terms of degrees Celsius.). The global anomaly was 21.10.

HISTORICAL COMPARISON OF THE SINGLE DATA POINT
*It is 0.0990 degrees cooler than September 2007
*It is 0.1260 degrees warmer than August 2008

RANK
*It is the 11th warmest September anomaly (20th coolest) of all Septembers in the data set
*It is the 138th warmest (220th coolest) anomaly in the total of 357 observations
*It is the highest anomaly since September 2007

AVERAGES
*The latest 12-month average is now -13.30, which continues a steady decline.
*The 12-month average is the lowest since the period ending September 2000.

STREAK
*This is the 12th consecutive year over year decrease in the anomaly reading
*There have been a number of cooling stretches at least this long in the data set

SLOPES AND CHANGES IN SLOPE
*Overall trend line since inception is presented below. This represents warming of 1.534 degrees per Century. The history of this data only goes back to January 1979. This is slightly lower in slope than the global measure.

*Current running negative slope extends back to June 1996, or 147 months (graph below)
*This cooling trend goes back 9 more months than the global trend line

*Current 60-month slope is -0.8035, which is a pretty steeply negative trend line.
*This is down from the peak trend line shown below:

*You can see how the slopes have trended down from this peak value in this chart:

*Current running 120-month slope is 0.1512
*This is the highest slope value since April 2006
*It is apparent that the temperature in the tropics is affected by the same El Nino/La Nina effects that are apparent in the global temperature data sets, and the impact of the 1998/99 El Nino really impacts how the 120-month trend line has shifted.

*We can see how the 120-month slopes have cycled during the course of this data set:

*180-month slope is 0.0430, continuing to decrease as time goes on.
*This is the lowest trend value since the period ending July 1994

*The slopes have declined from the most recent peak value as follows:

*240-month slope is currently at 0.1738 (actually a bit higher than the global trend)
*This is at its lowest value since January 2007
*We can see how the 240-month slopes have tracked over time:

*300-month trend is at 0.1747 (almost identical to the global trend line)
*This is the lowest it’s been since the period ending April 2008
*Shown below is the slope most recent trend in the slopes, followed by how these slopes have tracked over the data set

I’d like to say that anything above has the “wow” factor, but the most I can say is that it looks like, overall, the tropics have not warmed as much as global temps, and the cooling trend line goes back almost a year further. But, in general, it looks like the peaks and valleys that drive global temperature show similar impacts on the tropics, and all in all the trends aren’t all that much different.

I’ll be tacking other regions as time allows.

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