No Warming Trend for Over 12 Years – May 2009 Update on current temps – RSS
Posted by The Diatribe Guy on May 19, 2009
Yes, it’s true. We’re now at 12+ years and running with a flat trend line. We’ve discussed the viability of statistics like these before. Let me reiterate, because two things will happen with this: (1) pro-AGW theorists will immediately discredit the trend line as “too short” to be statistically viable, and some will actually bizarrely claim that the trend line isn’t factual and they can “prove it” through, for example, an ARMA analysis. (2) Those skeptical of AGW will proclaim warming to be dead.
Addressing the first point, the trend line is what it is. It is certainly within the bounds of good statistics to talk about how there can certainly be flat periods like this within an overall warming trend. Where the argument usually breaks down, though, is that those who point this out consider this an argument for continued warming. It is not. It is an argument for some probability of continued warming, and some probability of a flat line, and some probability of a reversal. These probabilities change over time for both the near term and the long term. The AGW proponents rightfully look at month-to-month changes as not dramatically changing the probability of the long term trends, but they often do so in ways that make you scratch your head. The trend line is a best-fit line. That’s all it is. The r-squared is low. Yep. That means that you could probably tilt the line up or down, without too much difference in the error term. It’s a valid point. What is implied is that the way you’d tip the line is up. But it could go either way. In this debate, I find a lot of valid points being made that are then applied dishonestly to come to a conclusion that is not in line with all the facts. Quite simply, the longer the trend goes where there is no warming, the higher the probability that we are wrong about runaway global warming. But it doesn’t completely eliminate the possibility.
As for the argument that warming has stopped, that’s in the eye of the beholder. Again, there can, in all probability be periods of a lull within a larger trend. Also, a best fit trend line only shows the trend over a particular period of time. In fact, while the 12-year trend is negative, the 10-year trend is positive. That’s because there was a little dip in anomalies between the 10-12 year mark in history that drives the front of the line down. The 10-year line is sure to decrease and go negative by the end of the year (unless anomalies shift upward considerably), but things like that can happen. So, we have a situation where we can say that the trend is negative over the last 12 years, but someone can accurately counter that the trend line is positive over the last 10 years.
There is always an argument about cherry-picking, and which trend is best. AGW proponents used to say that you needed at least 10-15 years of data. That used to be safe, but they never say that anymore. To be fair, though, I usually hear the 30-year period tossed out as the magic number. As best I can tell, there’s no good reason for that other than it has the feel of a long enough time period to matter, it currently gives an answer that supports their conclusion, and people have a tendency to think that only things that happen within the course of their own memory are relevant. However, my own analysis and research has led me to understand that the major Ocean cycles last anywhere from 60 to 100 years, and that these cycles surely help drive global temps. So it seems to me that anything short of 60 years is insufficient to discern the actual temperature trend, that 100 years is better, and more is even better. There will always be some issue with how out of whack the starting point of your trend is with the end point with regard to where we are in the various ocena cycles. Nobody seems to concern themselves with that, but I’ve shown the potential difference on that with the application of sine waves to the temperature anomalies. As far as I’m concerned, going back further is better.
Unfortunately, surface temps are the only measures we have that go back over 100 years. These data are rightly questioned for accuracy. Others have taken up that issue, so I have chosen simply to use the data as it is, simply with the caveat of “let the consumer beware.” The long term trend certainly appears to be up anywhere from 0.4 to 0.5 degrees Celsisus per Century over the full term. But when one accounts for the waves in the data, it has not accelerated as we have been told.
The satellite data have questions as well, but not nearly as many as the surface data. The issue here is that we only have 30 years to work with. So, that all said, I now get to showing you the updated RSS data.
Edit: It was noted that I failed to provide the link to the RSS data used in this post. My apologies. The link can be found to the right. Click on “RSS Data.” I often assume followers of this blog know that my sources are listed on the side of the page, but I often get linked to and those who are new to the site may not take the time to look at all the different links, or understand which links relate to a given post. I’ll try to remember to either put links in my posts, or direct people more clearly to the proper link. As an aside, I am often a bit confused about statements along the lines of “what makes Joe some kind of authority?” What confuses me is that my posts are not really anything more than data crunching that is presented for all to see. As an actuary, I do have some authority as it relates to helping people understand the statistical significance of what’s being presented, but I claim no particular authority on climatology. But the data isn’t an argument about climatology. It is a presentation of actual trends. My sources can be checked, and anyone else can duplicate exactly what I’m doing, check my accuracy, and correct as necessary. Questions of authority when presenting trend lines, in my opinion, simply show an unwillingness to absorb the information that’s being presented. Conclusions about the data can certainly differ, drawing upon other knowledge. But to just dismiss the trend because it’s “The Diatribe Guy” is pretty weak.
Current: The current anomaly for April is 0.2020 (in degrees Celsius).
Rank: The current anomaly ranks 11th out of 31 April anomalies (64th percentile); it ranks 102nd of 364 total anomalies (71st percentile).
Averages: The twelve month average = 16.8, which is the highest such average since the period ending April 2008. The most recent minimum average of 7.9 occurred last October.
Consecutive streak:This is the 6th consecutive anomaly higher than the previous year.
You may be looking at the increasing averages and consecutive streaks and asking, “Hey, Joe. How can the flat/cooling period actually have gone further back to March 1997 when we see higher anomalies over the last few months from prior year?” Good question. Thanks for asking. The recent anomalies are higher than prior year, and while that certainly will affect the trend line as far as it goes, the entire period is affected by the relative level of all periods within the data set. So, there is some positive anomaly that would drive the overall slope of the line higher, or move the period forward. Theoretically, that could be a lower anomaly that the previous year’s if the prior year values were very high. Lower from prior year or not, if the current value is still much higher than most anomalies, and in particular the front-end anomalies, then you will see an impact on the potential length of the line. What we see here is that a year ago we had some much lower anomalies than in recent years. The current values are a little above average compared to history (see ranks) and the trend line continues to lengthen. I took a quick look at the 10-year line, for example, to see what the next anomaly would need to be just to keep the slope the same next month. The anomaly would need to double. So, we could see a higher anomaly next month and still see a decrease in slope. It’s all in the math.
Trends: I won’t say too much about these. I’ve blabbed enough already. Presented here are the raw slopes for 60 month, 240 month, and 300 month periods. I presented the cycle of slope values for 120 month slopes, and presented a peak recent historical slope for the 180 month period. here they are: