By Matti Vooro
Recently I happened to look through some scientific papers and articles on global warming and the various forcing factors that affect our climate.
One that caught my eye was a paper by N.A. Krivova and S.K. Solanki  called: Solar variability and global warming: a statistical comparison since 1850.
http://www.solen.info/solar/cyclcomp.html, web page prepared by Jan Alvestad
In the conclusions of the paper they state:
We have shown that even in extreme cases that solar variability caused all the global climate change prior to 1970, it cannot have been responsible for more than 30% (50% for the intercalibration Willson, 1997) of the strong global temperature rise since 1970.”
WUWT also reported the authors saying (emphasis added):
However, it is also clear that since about 1980, while the total solar radiation, its ultraviolet component, and the cosmic ray intensity all exhibit the 11-year solar periodicity, there has otherwise been no significant increase in their values. In contrast, the Earth has warmed up considerably within this time period. This means that the Sun is not the cause of the present global warming.”
While I agree that the sun was most likely behind all the warming since 1850 and earlier, I cannot agree that the sun was not behind the warming since 1970. The link may not be immediate or short term but a lagged connection nevertheless. The average decadal sunspot number during the 1980s, 1990s and 2000s were 84.2, 67.2 and 49.6 respectively. The average mean global temperature anomalies during the same decades (HADCRUT3GL) were +0.079°C, +0.235°C, and +0.411°C respectively.
I went back and crunched the numbers for UAH satellite global temperature data and got mean temperature anomalies of -0.135°C, -0.0295°C and 0.0178°C. So on a decadal basis the sun and the global temperatures seem not to be correlated when measured by satellite or ground stations during the last 3 decades. Was Solanki correct then after all?
No. And there may be a logical explanation. Let’s take a decade at a time. The two graphs at the end of this article illustrate the average decadal sunspot numbers and average global temperature anomalies (hadcrut3gl) for the period 1900- 2010. But first the last 3 decades:
2000-2009 average decadal sunspot number was 49.6, down from 67.2 the decade before. The average decadal mean global temperature anomaly was 0.411°C up from 0.235°C the decade before.
* The actual solar activity was naturally down since solar Cycle No. 23 was declining to its minimum.
* The decade’s temperatures were influenced by the lagged solar Cycle No. 22 and 23 which together had 4 active solar years averaging 113.
* PDO and AMO were mostly positive correlating with a warm mode in the Pacific and Atlantic. PDO stated to go negative in late 2007.
* North Pacific Ocean SST anomalies were rising and then declining after 2005 causing global atmosphere temperatures to stay high [but flat with no rise].
* There were 4 El Nino’s.
1990-1999 average decadal sunspot number was 67.2 down from 84.2 the decade before. The average decadal mean temperature anomaly was 0.235°C up from 0.079°C the decade before.
* The actual solar activity was higher than the following decade but lower than the previous with parts Cycle No. 22 and 23.
* The decade’s temperature was influenced by the lagged Cycle No. 21 and 22 which also had 5 active solar years 131.4.
* PDO was positive the entire decade, AMO was positive about half the decade.
* Significant El Nino in 1997/1998, 1994/1995, 1991/1992.
* North Pacific Ocean SST anomalies were mostly rising except after the 1997/1998 El Nino.
* There were 3 El Nino’s.
1980 1989 average decadal sunspot number was 84.2, up from 61.2, the decade before.
The average decadal mean temperature anomaly was + 0.079C, up from -0.103 C
* The actual solar activity was up with influence from solar cycles 21 and 22
* The decade’s temperatures were influenced by lagged solar cycle 20 and 21 which had 3 active solar years averaging 134
* PDO was positive or warm mode, AMO was negative
* Significant EL Nino 1986/1987 North Pacific Ocean SST anomalies were fluctuating
* There were 2 El Nino’s.
Effect of El Ninos
Bob Tisdale in his blog and his article called Can El NINO events explain all of the global warming since 1976 parts 1 and 2 explains how a series of El Niños events could account for the major changes in global temperatures since 1976 through certain key El Ninos . The more significant El Nino in effect were 1997/1998, 1991/1992 and 1994/1995 and 1987/1988. See the graph below from Bob’s blog.
From my own analysis, during positive or warm phase of PDO and AMO, there are significantly greater number (2.5 times) of strong El Ninos than strong LA Ninas and more El Nino months compared to La Nina months .There were less La Nina’s in total as well .
Strong ElNinos seem to follow about 9-11 years after the previous strong solar maximum. 2009/2010 El Nino followed about nine years after the solar maximum period (4 months) of Cycle No. 23. The El Nino of 1997/1998 followed the very active solar maximum period (5 months) of Cycle No. 22. The same happened with the biggest El Nino ever recorded in 1878 which followed the solar max of 1869-1872.
PDO index tracks a spatial pattern of SST anomalies that, when it is cold in the western and central part of the North Pacific and warm in the eastern part of the North Pacific, the index has positive values. A more positive PDO index is typically a result of both more positive and warmer SST anomalies in the NE Pacific in combination with more negative or cooler SST anomalies in the NW and Central Pacific.
The AMO has been basically warm or positive mode during the period 1995-2012. So we have both the PDO and AMO as positive correlating with more warmer water along the coast of North East Pacific ocean and the North Atlantic ocean.
There appears to have been a correlation between solar activity and global temperatures going back for thousands of years as given by many peer reviewed papers, some of which have been posted on this blog very recently. In my graphs, the correlation appears to be there for the decades 1900 to 1940′s as the decadal average sunspot number and
the decadal average mean global temperature anomalies seem to rise together. In the 1950′s solar activity and global temperature anomalies went in opposite directions when we had major solar activity (91.7 average decadal solar sunspot number) but the decadal global temperature anomalies were flat or slightly down as the PDO was negative correlating with more cooler water in Pacific North East than in the Northwest and Central Pacific. Also global SST were cooler in the 1950s. Scientists have been looking at
various lag factors and other concepts to get a better handle on the sun/ocean/atmosphere link.
In my judgment the reason why sometime global temperatures and solar activity do not correlate is that the ocean cycles are out of sync with solar effects during certain decades. This was apparent during the cool period of 1950’s to 1970’s where colder ocean cycles in the Pacific and Atlantic as correlated by negative PDO and negative AMO reduced the “lagged” warming effect of some strong solar cycles especially the strong solar maximum around 1956 -1960. Ocean cycles seem to overide or nullify decadal solar effects in certain decades.
Yet during the period 1980-2010, the solar activity was slowly declining but both the Pacific and Atlantic oceans were both positive correlating with a warm mode (AMO and PDO both positiv)], resulting in the global surface temperatures going up while the sunactivity was declining. It is no coincidence that during this last decade when the lagged
effects of the decline of last solar cycle# 23 and the decline of the ocean cycles as reflected by AMO and PDO indices, both of which are now in sync, that global temperatures should also decline. This makes sense to me and it disproves claims that solar effects were not responsible for the 1980 to 2010 global warming.
What follows is the mean global temperature anomaly for each decade. Note overall it correlates with sunpsot activity:
The following chart is from from Climate 4 You sun section web page and illustrates the trend of the sunspot number since 1700. Notice the dips that correspond to cooler periods for the global temperatures including the 1960s, 1970s:
Annual sunspot activity since 1700 according to the Solar Influences Data Analysis Center (SIDC). The blue line shows annual values, red line shows the running 11-year average. Last update: 5 February 2012.