I have been comparing the response of global temperature to particular events that happen to the Earth’s climate. A quick look at any of the satellite records show that a good starting point is the ENSO cycle (El Nino/La Nina) in the Pacific Ocean. This led me to looking into how the station data sets (GHCN, CRU) respond to comparable events that cause a change in global temperature anomaly.
On average a significant ENSO event will cause the average temperature of the Earth to change by 0.27 °C. An El Nino in the positive direction and the La Nina in the negative direction. In fact the global temperature response is a good indicator in the overall strength of the ENSO event. The El Nino in 1998 stands out as an enormous event both as an El Nino and an increase in the global temperature, at least in the satellite temperature data.
Since satellite data only goes back to 1979, I was looking at the GHCN and CRU temperature records to look for ENSO events. I found major swings in temperature in 1957, 1964, 1973, 1974 that happened before satellite data was available. The average temperature response for these events was 0.28 °C. That is almost identical to the modern satellite response to ENSO.
Then I compared to the major ENSO event that took place in 1983-1984. That was a EL Nino in 1983 to a La Nina in 1984. Both the satellite and station temperature sets showed an almost identical global temperature response. The station sets a few percent higher for the El Nino and the satellite a few percent higher for the La Nina drop. The difference was insignificant as the difference was only a couple of percent.
This is when things got strange. The 1989 La Nina triggered a average temperature drop of -0.202 °C for the two satellite temperature sets. The station sets only showed a drop of -0.103 °C. The satellites showed a response that was 97% greater than the stations did. What had been an easy detector for ENSO in the station record suddenly did not show the same type of response in 1989.
Okay, one event doesn’t mean much, so I looked at the biggest El Nino ever recorded. The monster 1998 El Nino. The satellites clearly show a major response to that El Nino with a temperature increase of 0.46 °C. The stations decided that it was about the same as the El Nino in 1983 with a temperature change of 0.223°C. The satellites showed a stunning 106% more response to the largest El Nino ever recorded while the stations indicated nothing unusual.
Jump ahead to the major La Nina of 2008. The satellites once again responded as expected with a temperature drop of -0.210 °C. Based on historical responses, that is what is expected. The station response was that it didn’t happen. According to the CRU and GHCN temperature response, there was no La Nina that year as the temperature resopnse was only -0.096 °C. The satellite response was 119% greater than the stations.
Finally there is the 2010 La Nina El Nino. Certainly the stations would bounce back and pick up this La Nina. That would be incorrect. The global temperature response to that La Nina was a trivial and insignificant 0.063 °C. A total non event. The satellites disagreed with a global response of 0.238 °C. A strong El Nino, but nothing compared to the 1998 monster. The difference in response was an absurd 278%.
Even more odd is the fact that there is a trend in the percent difference between the satellite and the station responses to ENSO events. It isn’t just that the stations are showing less response, but in each event they are showing a consistently decreasing response to ENSO events. In the last 2010 El Nino event the stations response was 74% less than the satellite.
The satellites continue to show the typical response that the stations historically did, but the global station sets have stopped responding to ENSO events. They don’t cool, they don’t warm. They are starting to just stay the same.
The argument that the station temperature records simply don’t respond in the same manner is false. They used to. Up until 1984 the major ENSO events show up clearly in the global temperature record. Going back to 1900 I found the El Nino temperature signal in 1914, 1926, 1930, 1951, 1957, 1973 and 1977. Every one of those also happened to be part of an El Nino event and all showed more than twice the temperature response that the stations did in 2010.
I also found the major La Nina events in 1907, 1916, 1929, 1954, 1964 and 1974 that took place prior to the satellite era. All of them showed strong drops in global temperature in response to the cooler Pacific Ocean temperatures. All of them showed much stronger response that the same station temperature sets do today.
Global warming doesn’t explain it either because such warm ocean events do warm the atmosphere. The satellites clearly show the difference.
This leaves us with a mystery: Why have the station temperature sets stopped responding to ENSO events?
Update: Here is the monthly response to the 1998 El Nino event.