March 2008 Update on Global Temperature Trends
Posted by The Diatribe Guy on March 10, 2008
The NASA global temps are out, located here. I am actually using this source because it seems to suggest higher anomalies than other sources. If the data here actually suggests something other than a warming trend, then it becomes more diffficult for the results to really be argued vehemently.
I have updated my trend analysis on the numbers to include these results, for any interested in scoring at home. The short-term cooling trend is continuing and the negative rate of change in the 120 data point average is also continuing. Here’s the skinny:
The February anomaly was 31 (where 1 = 0.01 degrees Celsius and the anomaly is the deviation for the 1950-1980 time period, which is about 14 degrees Celsius).
This is the same anomaly as January 2008, which at the time was the lowest such anomaly since July 2004. The anomaly’s positive number says it’s still above the base period average, and the base period is relatively close to overall average for the entire period from 1880-current.
The 2-month average anomaly of 31 is the lowest 2-month anomaly average since October-November 2000 (average was 29). The latest 12-month average anomaly of 62.7 is still relatively high by historical standards, but has been moving down over the last couple years. The last time it was at least this cool on a 12-month rolling average basis is the April 2004 – March 2005 period, where the average was 61.4.
This is the lowest February-specific anomaly since 1994. It was the 28th warmest February on record.
With this additional data point, we can map the most recent non-warming/cooling trend from Ocober 2001 – Current. Stated another way, applying a simple linear trend to the data, there has been no warming, and possible cooling, since October 2001. This encompasses 77 data points of anomalies. While this certainly could indicate a peak, or a downward trend, there have been similar periods in the past where we’ve seen this occur. The most recent 77 data-point period of cooling occurred from April 1990 – August 1996. We saw another spurt in the interim before we saw the more recent flattening. I do not point this out as an argument against cooling, but we also must be honest about the data we are looking at. In the event that there is, in fact, an overall warming trend underlying our climate, these cooling/flattening periods occur. Clearly, the longer it continues, the less likely it is that it is a blip, and the more likely it is that something has changed. It’s simply too soon to tell, and all we can do is look at the data. Right now, what we can say is that claims that warming is accelerating are flat-out false, and the most recent few years shows zero indication of warming. We cannot say that it indicates a definite reversal, nor that there may be a longer-term warming trend for which we are simply seeing an aberration.
As previously noted, I have tracked a 120 data point slope of the anomalies (rolling) to see what is occurring as far as a speeding-up/slowing-down of the rate of warming. There has been a consistent decline in the 120 data point slope over the last 70+ slope calculations. The trend in the change of the slope is now -.002774 anomaly change per month. The current 120 point slope is positive, but getting less positive, on average, by that amount over time (the last 6+ years).
Graph Explanation: y-axis represents the slope of rolling 120 data point anomalies. x-axis is the month of the slope calculation, where month 1 represents the 10-year period beginning in March 1992, and the final data point is the beginning of the latest 10-year period, beginning in March 1998. The fitted line is the trend line, showing a declining rate of warming (-.002774 anomaly change per month).
Last month, I presented my Required/Predicted Anomalies by month. These would be the anomalies required for that month to hit the trend line in order to continue the trend of decreased rate of warming. My required anomaly for February 2008 was 53.35. The actual anomaly of 31, then, comes in quite a bit lower, and the impact of this was to make the slope of the trend line slightly more negative. As of 2007 year-end, the trend analysis implied a 2008 predicted anomaly of 44.8. The updated analysis after January lowered that to 44.6. Remaining months were last predicted to be: March 47.4; April 46.0; May 37.5; June 31.6; July 24.7; August 38.8; September 65.7; October 55.8; November 59.8; December 43.7.
Because February came in so low, the required anomaly for March to maintain the current slope of the trendline has increased quite a bit. However, because the slope is now more negative, the succeeding anomalies on the trend line are slightly reduced after that. The “trend line anomalies” going forward are:
In laymen’s terms, an anomaly in March of 68.1 continues the decline in rate of global warming at the current level. An anomaly below that will actually indicate that the decline in the warming rate is steepening.
Using actual January/February anomalies and the trend line anomalies, the updated 2008 average anomaly would be 44.4. The last time we had a 12-month average anomaly at least that low was April 2000-March 2001 (43.5). The last Calendar year with an average that low was 2000 (41.8). This would be the 12th warmest year on record, which is sure to be the way the results are communicated. In reality, such a result would be perfectly consistent with the idea that we are in a cooling cycle, or at the very least, not in a warming cycle.