No Warming Trend for Over 12 Years – May 2009 Update on current temps – RSS
Posted by Jeff Condon on May 20, 2009
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 pward 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.
For the graphs and the rest of the article, click the link.