April 2008 Update on Global Temperature, Part 3
Posted by The Diatribe Guy on April 11, 2008
If you read my post on March 2008 Update on Global Temperature Trends then you will recall that I focused on a 120-data point analysis of slope trends. I later provided an update here that expanded the analysis to a look at 60-month, 180-month, 240-month, 300-month, and 360-month trends.
Here I am going to provide the trends that I am seeing in the slopes of the 60-month analysis. This is still using the Global Land-Ocean GISS Temperature Index.
The First graph is the latest 60-month trend based on the raw anomaly data.
Notice the slope of -0.027. This represents a change in the anomaly per month, and is equivalent to a -.03 degrees Celsius dip per decade. Given the R-Squared and the fact that this is only a five year trend, it doesn’t make ssense to suggest long-term implications, but it does make sense to suggest some short-term expectations. But the latest 60-month slope changes over time, and temperatures aren’t really expected to follow a straight line. So, I also plotted the most recent 60-month peak/trough (it’s a peak) that is at least a few months back.
Here is the graph of the most recent peak trend line:
It is easy to see how the slope has changed since May 2007, when it was +0.2102 (a rate of warming of a quarter degree per decade).
I have plotted the 60-month slopes from January 2004 forward. I went back this far because, even thought most recent peak was May 2007, there has actually been a longer term trend. In early 2004, the slope was nearly 0.6, as can be seen on the chart below.
Notice the R-Squared value of 0.6579. This graph lends more credence to the idea that recent temperature trends do show a decline in the rate of warming, and are actually heading into an area of cooling. Should the trend continue, we can expect even lower slope values.
The question, of course, is how far along we can expect this to continue before the cycle might reverse. I will get into this question at a later time, as I have put toghether an analysis that should help answer this question, and may have preictive value in when we can anticipate such changes.
For now, it is simply an interesting point that, in summary: The most recent 60-month raw anomaly trend is toward slight cooling, that the current slope is well below the most recent peak slope (and very much below the antecedent peak), and that the trend in slope values has a relatively good fit that shows the definitiveness in a reduced warming trend, and if it continues, a cooling trend.
This analysis, as of yet, makes no claim to the future length of such a trend, but does indicate short-term lower anomalies. Check back for further analyses in the coming days.