Digital Diatribes

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Archive for the ‘Tropics’ Category

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.

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.

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.




RSS TROPICS Overall Trend Line

Read the rest of this entry »


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

June 2009 Update on Global (and Regional) Temperature – RSS

Posted by The Diatribe Guy on June 5, 2009

The RSS Data has been released. I thought I’d take this opportunity to not only look at the global value, but also the northernmost satellite data (Arctic), the equatorial regions (Tropics), and the southern-most readings (near Antarctic – the satellite coverage doesn’t reach all the way to the pole).

Since I’m hitting all the regions, I won’t get present all the backup charts, but I will provide a numerical update on the trends. For each, I’ll simply show the overall trend using all RSS data, and the furthest line back where we can draw a flat or negative trend line.

Data Point
The anomaly for the month of May was 0.090 (will be heretofore presented in 0.01 degrees Celsius, or 9.0). This is 11.2 lower than the previous month, April 2009 and 16.8 higher than May 2008.

Ranking: 16th largest anomaly out of 31 May readings (48th percentile) and 177th of 365 total anomalies (51st percentile).

12-month average = 18.2. This increased over last month due to last year’s very low anomaly dropping from the average. Thus, it is the highest average since March 2008.

May was the sixth consecutive month for which the monthly anomaly exceeded the previous year’s anomaly, despite the drop from previous month.

Global Overall Trend Line since 1979:


RSS Global Overall Trend

The overall trend dropped from 0.12904 to 0.12802. This represents the units, in 0.01 degrees Celsius, of trending per month. It corresponds to an overall temperature trend of 1.54 degrees per Century.

Flat/Cooling Trend Line:


RSS Global Flat/Cooling Trend

The length has now increased another month on the back end, and also on the front end. The flat line now extends back to February 1997, making its length 12 years and 4 months.

There is no other period in the RSS data set where cooling occurred over a 12-year, 4-month period. The data set, however, only extends back to 1979.

As an aside, I like to take a look at some posts on boards where my information is posted. Last month, someone posted the link where I pointed out that we have now gone past 12 years without a warming trend. A responder glibly replied something along the lines of “How embarrassing for that author. RSS and UAH post the decadal trends in their data.” He pointed out the positive decadal trends.

What is embarrassing is the complete lack of comprehension in the difference in what is being presented. It would have taken that person all of 10 seconds to see my longer-term trends where I state the per-century trend in temperature according to the slope. The fact that I presented a recent, isolated period of no trending doesn’t in any way conflict with a longer-term decadal trend. I never cease to be amazed at the lack of understanding people have – or at least seem to have – on such basic statistical presentations.

What’s Happening with the various trend lines?
60-month: -0.307510 (-3.69 degrees per Century). Looks to decline to the steepest negative value since the mid-80’s soon.

120-month: +0.058601 (0.70 degrees warming per Century). Now back to the level seen in June 2008, and expected to go negative by year end.

180-month: 0.077408 (0.93/C). Lowest slope since the period ending September 1995. This could go as low as 0.05 by the end of the year.

240-month: 0.151595 (1.82/C). This is a steeper slope, but is now at its lowest point since July 2001.

300-month: 0.163786 (1.97/C). This is the lowest since August 2003. The 25-year slope is the steepest of the measures.

360-month: 0.126892 (1.52/C). Lowest of the 6 observed data points.

What does it all mean? Well, we have cooled recently. But those things can happen. The 12+ falt period is getting long enough to become statistically relevant, but looking at the RSS data set just doesn’t give us a large enough data set to compare likelihood. Longer term periods definitely show that we have warmed over a lengthier period of time – that’s not really in dispute. However, any claims of acceleration in warming are simply false, as can be shown by the fact that ALL trend line measures are declining. If warming were accelerating, we would see slopes increasing.



RSS Near-Antarctic Overall Trend

Only one chart is provided, since the overall data set is also the longest cooling period. The chart, however, pretty much shows a flat line. And even though we have this lengthy cooling trend, it jumps back and forth depending on your starting point whether the trend is warming or cooling – which pretty much means it’s a flat line.

Starting at the beginning with January 1979, it’s a negative trend. Here are all the reversals that take place (starting points to current): April 1981 (+); October 1982 (-); November 1982 (+), May 1989 (-), February 1990 (+), April 1990 (-), June 1990 (+), July 1990 (-), August 1990 (+), October 1990 (-), January 1991 (+), June 1996 (-), August 1996 (+), January 2000 (-). All starting points since then show a negative slope.

The May anomaly was 30.9, which was 86.8 higher than last month, but 7.5 lower than last year.

Rank: 10th of 31 Mays (67th percentile) and 87th of 365 total, 76th percentile.

No major streaks. 9 of the last 12 anomalies have been less than prior year.

The 60-month trend is quite steeply negative (-0.297491). All the other trend measures are either slightly negative or slightly positive (from -0.0113 to + 0.0343). The 300 month value of 0.0269, however, represents a peak value in the data set for any 25-year period of time. In its history, the low was -0.042.



RSS Arctic Overall Trend

The May anomaly was 44.6. This is lower than last month by 14.3 and lower than last year by 87.1 (hundredths of a degree Celsius, remember).

The May anomaly ranked 14th of 31 Mays (54th percentile) and 126th of 365 total (65th percentile).

The 12-month average anomaly is 47.3. It’s still high, but coming down. This is the lowest 12-month average since the period ending January 2005.

The Arctic has most certainly trended up fairly high over time (overall slope is 0.27081, or 3.25 degrees warming per Century), but the recent trend has been downward:


RSS Arctic Flat/Cooling Trend

Currently, we can fit a flat/negative trend line back to May 2001.

Other Trends:
The current 60-month trend line is very negative (-0.42606, -5.11/C). Obviously, this fluctuates a lot, but it is currently the lowest since January 2000.

120-month: The 10-year trend is still very positive (+0.25886, 3.11/C), but is at its lowest level since the period ending December 2004 and is trending down.

180-month: the 15 year trend is even higher (0.30129, 3.62/C) but has also trended down, and is at its lowest value since August 1998.

240-month: The 20-year slope is the steepest positive slope (0.43829, 5.26/C). Despite its high slope, it’s actually trending down and is at its lowest value since the period ending October 2005.

300-month: The 25 year slope (0.386403, 4.64/C) is a slight tick up from last month, which had otherwise been its lowest slope value since the period ending January 2007.

360-month: The 30-year vlaue of 0.262441 is a data set low (6 observations).



RSS Tropics Overall Trend

May anomaly = 8.4. This is down 9.6 from last month and up 42.9 from last year.

It ransk 13th of 31 Mays (58th percentile) and 163rd of 365 total (55th percentile).

The 12-month average of 7.9 is the highest since February 2008.

It is the eight consecutive month with current anomalis greater than previous year.


RSS Tropics Flat/Cooling Trend

The tropics show a flat/cooling trend back to March 1996.

Other trends:

60-month: The short-term trend line is very negative (-0.719114, -8.63/C). The steepest negative trend line occurred the period ending September 2008 (-0.814854) and had been the steepest negative trend line since the period ending June 2002.

120-month: +0.076548 (+0.92/C) is the lowest value since the period ending December 2007.

180-month: +0.029744 (+0.36/C) is the lowest value since the period ending September 1994.

240-month: +0.127287 (1.53/C) is the lowest value in the data set, the first data point being December 1998.

300-month: +0.158974 (1.91/C) is the lowest slope value since the period ending January 2005.

360-month: +0.117065 (1.40/C) is the lowest of the 6 observed data points.

Posted in Antarctica, Arctic, Climate Change, Earth, Global Warming, RSS, Science, Temperature Analysis, Tropics | Tagged: , , , , | 10 Comments »

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).

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.

*It is 0.0990 degrees cooler than September 2007
*It is 0.1260 degrees warmer than August 2008

*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

*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.

*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

*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 »