THE WORLD MEAN TEMPERATURE WARMS(/COOLS) IF THE IMPACT OF EL NINOS EXCEEDS(/DOES NOT EXCEED) THE IMPACT OF LA NINAS OVER A GIVEN EPOCH.
Distinct Epochs in the Earth's Atmospheric Circulation Patterns and the Earth Rotation
It shows the close correlation between the rotation rate of the Earth (measured by the Length-of-Day) and the zonal component of the Atmospheric Circulation Index (ACI). This graph shows that the zonal circulation patterns evident in the Earth's atmosphere can be broken up into four 30 year epochs starting in the years 1880-85 [LOD curve only], 1905-1910, 1940-1945 and 1970-1975.
The above graph shows that if you shift the LOD curve forward by ~ 6 years you get an excellent fit between LOD curve and the de-trended world mean temperature anomaly. Again the overall pattern can be broken up into four distinct 30 year epoch starting in the years 1880, 1910, 1940 and 1970.
C. The above graph comes from figure 2.23 of Klyashtorin, L.B., Climate Change and Long-Term Fluctuations of Commercial Catches - The Possibility of Forecasting, FAO Fisheries Technical Paper No. 410, Rome FAO, 2001.
The above graph shows that if you shift the ACI curve forward by ~ 4 years you get an excellent fit between LOD curve and the de-trended world mean temperature anomaly (dT). Again the overall pattern can be broken up into three distinct 30 year epoch starting in the years 1910, 1940 and 1970. The ACI index does not extend far enough back to set a starting date for the first epoch but the dT and LOD curves suggest a date sometime around 1875 to 1880.
The (Extended) Multivariate ENSO Index
The Multivariate ENSO Index is defined at the NOAA web site located at:
The Extended Multivariate ENSO Index is defined at the NOAA web site located at:
The important point to note is that Multivariate ENSO Index is the most precise way to follow variations in the ENSO phenomenon:
Negative values of the MEI represent the cold ENSO phase, a.k.a. La Niña, while positive MEI values represent the warm ENSO phase (El Niño).
The Cumulative Sum of the MEI
If the cumulative sum of the MEI over a given epoch steadily increase throughout the epoch then the impact of El Ninos exceed the impact of the La Ninas over this epoch.
If the cumulative sum of the MEI over a given epoch steadily decrease throughout the epoch then the impact of La Ninas exceed the impact of the El Ninos over this epoch.
The dotted red line in the above graph shows the cumulative sum of the extended Multivariate ENSO Index (MEI) between the years 1880 and 2000 A.D. The cumulative sum has been taken over each of the four 30 year epochs, starting in the years 1880, 1910, 1940, and 1970.
The solid blue line in the above graph shows the cumulative sum of the extended Multivariate ENSO Index (MEI) between the years 1886 and 2006 A.D. The cumulative sum has been taken over each of the four 30 year epochs, staring in the years 1886, 1916, 1946, and 1976.
It is clearly evident from this plot that whenever the cumulative MEI index is systematically decreasing over a 30 year epoch i.e. between 1886 and 1915, and between 1946 and 1975, the world's mean temperature decreases. It is also evident that whenever the cumulative MEI index is systematically increasing over a 30 year epoch i.e. between 1916 and 1945, and between 1976 and 2005, the world's mean temperature increases.
2. The cumulative MEI shows that since roughly 1880 there have been four main climate epochs, each 30 years long. There are have been two 30 year periods of cooling (i.e. from 1886 to 1915, and from 1946 to 1975) and two 30 year peiods of heating (i.e. from 1916 to 1945, and from 1976 to 2005).
3. Periods of warming occur whenever the impact of El Ninos exceeds the impact of La Ninas. Periods of cooling occur whenever the impact of La Ninas exceed the impact of El Ninos.
The cumulative sum of MEI index is confounded by ENSO measures thenselves being based on temperature. You would need to use an alternative index not including temperature to actually show something useful - like SOI.ReplyDelete
In fact, NOAA is going to rebaseline the ENSO index -- otherwise we'd soon be in permanent ENSO conditions. They write:
"Due to a significant warming trend in the Niño-3.4 region since 1950, El Niño and La Niña episodes that are defined by a single fixed 30-year base period (e.g. 1971-2000) are increasingly incorporating longer-term trends that do not reflect interannual ENSO variability. In order to remove this warming trend, CPC is adopting a new strategy to update the base period."
I.e., ENSO indexes themselves include the warming trend - so your analysis shows that the trend matches the trend quite well - imagine that.
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While it is not shown here, you can use the SOI [an atmospheric pressure based index] to demonstrate that ratio of the cumulative frequency and/or magnitude of El Nino events to La Nina events correlates with temperature. The correlation goes:ReplyDelete
When cumulative magnitude and/or frequency of El Nino exceeds that of La Nina - you get global warming.
When cumulative magnitude and/or frequency of El Nino is less than that of La Nina - you get global cooling.
It does not depend on using the MEI or any other temperature derived ENSO indices.