Digital Diatribes

A presentation of data on climate and other stuff

April 2009 Update on Global Temperature – UAH

Posted by The Diatribe Guy on April 17, 2009

OK, I’ve spilled my guts on where I’ve been and what I’ve been doing. So, let’s get back to some temperature analysis…

Overall Trend

No major changes are afoot in the overall trends. The UAH overall data is presented here.

I had presented a chart taking a closer look at the UAH data, basically showing that the chart consists of a flat line from 1979 to 1998, and then another flat (or slightly cooling) line from 1998 to current. Just observing the raw anomalies, one can easily see this characteristic in the data. We had some cooler anomalies in 2008 that show up under the zero line of the chart, that are similar to some other lows in 1997 and 2000, but we have not seen low levels similar to those that occurred in the mid-1980s or early 1990s. Basically, I have posited that the key to this is the 1998 spike. I think it makes sense that we saw some elevation that we never completely recovered from, not as part of a gradual warming trend, but as more of an isolated event. However, this is related to the cycles I have also discussed regarding the PDO and AMO. The 1998 deviation, in respect to the point of the cycle where it is located, was not something that is outside of predictablility. It seems high on a chart where the basis is a linear measure, but if you incorporate the sine waves of the cycles, it rides that wave nicely. So, I think we saw a combination of cycle peaks and a fairly significant upward deviation. Then, after that, due to the natural greenhouse effect and continued elevated temperatures related to cycle peaks, we have not seen it subside greatly.

The AMO has peaked, and the PDO is entering its cold phase. The future is interesting.

UAH cooling Trend

The second part of that chart is flat to cooling, starting nearly 12 years ago. I may be able to declare a full 12-year non-warming trend next month.

Starting in May 1997, we have not cooled, based on the best fit trend line. This is simple observation. You will find other individuals on the internet with claims of fancy statistical backgrounds who will actually dispute this simple fact. But they are arguing a different thing. All I’m doing is showing the actual trend line. The fact is, that the trend line demonstrates that there has been no warming. If that lasts one more month, it will have gone on 12 years. Of course, we’ll be told that such a short time frame is insufficient. As we will be told when it’s 13, 14, and 15 years….

Now, you may wonder what there can be to dispute about a trend line? It’s a good question. You see, these people make the mistake of finding situations where a flat trend line of this length can exist within an overall warming trend, and then use this fact to imply that the trend line itself does not tell us what it tells us. This is like saying that parts of the earth are not actually flat because we all know that the earth is round. So, let’s be clear: (1) there is an actual, fitted, statistically viable trend line that is fitted that tells us that no warming has occurred in nearly 12 years; (2) the conclusion that can be drawn from this is exactly “there has been no warming in the last (nearly) 12 years.” (3) Using the last 12 years alone to argue that overall warming has stopped is a flawed application of the observation. (4) Using ARMA analysis or any other kind of analysis to suggest that the 12 year non-warming trend doesn’t actually exist is not just flawed, but simply incorrect on its face. (5) Using the fact that a 12-year non-warming trend can occur during a warming trend is not confirmation that it properly reflects the current situation.

Now, both sides can present other analysis to show why they believe the current trend is consistent with the longer-term view. But you can’t just dismiss the current trend as if it doesn’t exist. And the longer it goes on, the less appropriate it is to fail to give it attention.

60-month UAH trend

Speaking of short-term trends....

Now, I will wholeheartedly agree with some of the criticisms of looking at short periods and drawing broad conclusions. The 60-month trend has been negative since I’ve started looking at it on this blog. It is presented more from an interest standpoint. It fluctuates quite a bit over time, and we certainly can’t extrapolate it as an indication of anything except, perhaps, the very near term. Nonetheless, it does tell us what has happened to global temps in the last 5 years, and it is just another piece of the overall puzzle when questioning whether or not the global warming fears are warranted. It obviously has taken a breather lately if it exists at all.

Trend Cycles

We can get a feel for the fluctuation of the 60-month trends here.

We can see how the 60-month trends have cycled over the last 30 years. Given this chart, it’s not much of a surprise that we’d be seeing an increasing trend. We’ll see if anything shifts gears over the next few years.

180-month UAH slopes trend

While the 180-month trend is positive, we still continue toi see a very steady decline in the slope value. So, even if one argues that warming exists, any claims of acceleration are clearly false. While I only present the 180-month slope changes here, we see a similar story in all the longer periods.

It’s been a clear and steady decline in slope values for the 180-month trend over the last couple years. It will be interesting to see if the latest blip over the trend line is a reversal of this, or just a little “retracement.”

Here are some of the relevant stats:

Current (March) anomaly: 20.80 (stated in hundredths of a degree Celsius)

Ranking: 11th of 30 March anomalies; 89th of 364 overall anomalies in the data set

Deviations from previous: This is an increase of 11.90 increase over March 2008; it is a 13.90 reduction from the February 2009 anomaly

Averages: 12-month average of 11.50 is highest since the period ending May 2008. However, the 24-month average is the lowest since January 2002.

Consecutive Run:This is the fifth consecutive month where the anomaly is higher over the previous year.

60-month: The current slope of -.1802 (2.16 degrees cooling per century) is actually higher (less negative) than at any point since May 2008. So, while negative, we’ve seen a few straight months of moderation in the slope.

120-month: Current slope = 0.107107 (1.29 degrees warming/Century) is right around the level it’s been at for the last few months. This had trended down continuously until recently, when it flattened. We now wait to see if this is the start of a reversal, or if the reduced slopes will continue. I had predicted this based on the front-end temperatures. Within a few months, we should see the slopes continue to decline, barring some significant warm temperature anomalies.

180-month: Current slope = 0.096950 (1.16 degrees warming/century). This has now fallen to its lowest level since the period ending December 2001.

240-month: Current slope = 0.142172 (1.71 degrees Celsius/Century). This is at its lowest level since the period ending December 2006.

300-month: Current slope = 0.144783 (1.74 degrees Celsius/Century). This is at its lowest level since the period ending February 2006.

360-month: Current slope = 0.105704 (1.27 degrees Celsius/Century). There are only 5 observations of this slope measure, due to the limited data. This is in the ballpark of previous slope levels.

I’m going to try and get a couple more posts up this next week. Just a head’s up that after that the family and I are going on a two-week vacation. Of all places, we’re heading to Delaware… But I will not be posting during that time (April 25 through the first week of May).


One Response to “April 2009 Update on Global Temperature – UAH”

  1. […] April 2009 Update on Global Temperature – UAH […]

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