Wednesday, May 21, 2008

Ten Year HadCrut3 ENSO Effects

The issue that this post attempts to solve revolves around the claim by AGW proponents that the only reason that the temperature trend for the last 10 years is flat, is because the period begins with an El Nino and ends with a La Nina.

Using HadCrut 3 monthly data, I decided to try to isolate the ENSO events of the period under discussion in order to quantify the effect of each event on the slope of the complete chart. Since the complete chart yielded a trend line that was almost dead flat, I decided to use the value y of that trendline as the baseline against which to check the effects of the individual ENSO events.

Beginning with the first La Nina event of 98, I noticed that the La Nina yeilded 4 month of very high residual temperatures, even after the La Nina had ended according to NOAA tables. So I decided to include the four months on the chart, and to also include four months for all the other ENSO events as residual effects time periods. In general, this approach seemed to be very close to capturing the temperature result of each ENSO event.

Since there were only two month between the 98 El Nino and the 98 La Nina, using the four months residual left me with two month that were being used by both the first La Nina and the first El Nino. Since the temperatures for those months were very high, I decided to leave them with the El Nino period and remove them from the La Nina period.

April of 2008 is assumed to be a La Nina month, since the NOAA data is not yet available. But even if it turns out not to be a La Nina month, it would still be used as a residual month.

There were 7 ENSO periods during the decade of the chart. They were:
Jan 98 - April 98 El Nino
July98 - June 00 La Nina
Oct 00 - Feb 01 La Nina
May 02 - Mar 03 El Nino
Jul 04 - Feb 05 El Nino
Aug 06 - Jan 07 El Nino
Aug 07 - April 08 La Nina

Details of these periods may be seen in this NOAA chart:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml

Complete 10 year HadCrut 3 Temperature Anomoly chart with trend line.

First El Nino period with trendline:

First and second La Nina period with trendline:

Third (last) La Nina period with trendline:
Third and Fourth El Nino periods with trendline:
Second El Nino period with trendline:

The temperature anomoly effects of the ENSO components are:

El Nino 1 = -0.0744

La Nina 1 & 2 = +0.0992

El Nino 3 & 4 = +0.0372

La Nina 3 = -0.0494

Adding these together we get an ENSO effect of: +0.0126

In summation, all of the ENSO effects for the charted period would actually help the slope of the ten year trend be positive. Depending upon the months that are used, the number could be changed slightly. But in summation, ENSO had nothing to do with the flat temperature trend that we have experienced over the past ten years. The period is not cherry picked for an effect. The .2C per decade rising temperature trend that we should see according to the AGW proponents is not there, and it's abscence remains completely unexplained. The assertion by AGW proponents that the trend was made flat by choosing a period with an El Nino at the beginning and a La Nina at the end is simply untrue.

1 comment:

Dodgy Geezer said...

This is interesting work - it's a pity that no AGW supporter has come to investigate it. Have you though of taking the bull by the horns and mentioning it on CA and RC?