Digital Diatribes

A presentation of data on climate and other stuff

Posts Tagged ‘Tropics’

Update on What’s Going on in the Tropics – RSS

Posted by The Diatribe Guy on September 8, 2009

Continuing my series (Antarctica, Arctic) of looks at the more regional breakdown of the RSS Temperature Anomaly Data, I am now moving on to the Tropics.

This is actually a fairly interesting region to observe. This, along with the Antarctic(ish) region was a contributor to the higher July anomaly.

Data Point
The July anomaly was 57.90 units (where 1 unit = 0.01 degrees Celsius). This was a pretty warm anomaly, ranking 14th out of 367 total observations in the data set, and ranking tops as the warmest July on RSS record (31 years of records). The increase over last July was 54.10 units, and the increase over June 2009 was 36.1 units. It would have been a great time for your equatorial vacation if you like running around in a Speed-o (note to readers: I do not wear a Speed-o).

It should be noted that the overall average anomaly in the data set is actually 6.27, and not zero. So, if one considers the overall average to be the point of departure from which an anomaly should be measured, the values are slightly overstated. Not as much as in the Arctic, but overstated nonetheless. This may seem conniving, but I don’t read much into it. Restating all historical anomalies every month to consider the latest average makes it difficult for the casual reviewer to come to grips with trends, and since all values would be changing, some may question whether or not the change is anything more than a readjustment to baseline. No, it probably is best to make only the occasional adjustment if and when the average drifts too far from zero. In this case, I probably would leave the Tropics as is. One could probably argue that the Arctic baseline should be changed and the anomalies adjusted, but it all really only matters if you let the perception of a high number cloud the issue. Unfortunately, too many people – including those who probably know better – will tend to look at the magic number of 100.00, for example, and freak out about the high number.

Streaks
One of the interesting things I noted in the anomaly record was the tendency of this region to have some persistency in relative temperature. Starting with April 2004, we saw a stretch of 9 consecutive months where the anomaly was cooler than previous year. That was followed by a stretch of 9 consecutive months with anomalies warmer than previous year. After that, we had a stretch of 12 consecutive months where the anomaly was cooler than previous year. In the next year, 10 of the 12 months were warmer than previous year. Then, we saw 12 consecutive months of anomalies that were cooler than previous year. We are now in the midst of a stretch of warmer-than-previous-year anomalies, with July being the 10th consecutive such month.

Averages
Thanks to the last couple higher anomalies, the 12-month average is 15.3, which is the highest average since the year ending January 2008. The 12-month average reached a low of -13.1 10 months ago and has steadily increased since then to current level.

Trends:

Overall:

rsstropicsoverall200907

RSS TROPICS Overall Trend Line

Read the rest of this entry »

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Posted in Climate Change, Earth, Global Warming, RSS, Temperature Analysis, Tropics | Tagged: , , , , , | 1 Comment »

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.

Posted in Climate Change, Earth, Global Warming, RSS, Science, Temperature Analysis, Tropics | Tagged: , , , | Leave a Comment »