Solar Trends: Comparison of TSI and GISS Temperature Anomaly Trends

This post continues my analysis of solar trends, this time comparing reconstructed total solar irradiance (TSI) and temperature anomaly (GISS) trends for the 1880 – 2009 period. I use 11 year moving averages to smooth both series so that we can see the longer term trends.   Links to a download-able copy  of my R script is  provided for those readers who wish to prepare their own charts.

Introduction

In 2 of my previous Solar Trends posts, I have charted sunspots and total solar irradiance (TSI). In this post I want to look at the relationship between solar activity and temperature anomaly. To me it is obvious that solar activity plays a role in the earth’s climate, I just want to get a graphical depiction of the  relationship.

There has been a great deal of investigation on this topic over many years. I’ll just highlight what’s been discussed on 2 of my favorite climate sites: John Cook’s   SkepticalScience and Bill Chameides’  The GreenGok.

John Cook at Skeptical Science has an interesting post on Solar activity and Climate that includes a trend chart showing both total solar irradiance and temperature anomaly. I’ll reproduce John’s chart in this post.

Bill Chameides at The GreenGok has an interesting post on The Waxing Sun and Warming Climate that does a nice job summarizing the solar activity – climate relationship. Bill’s post discusses climate forcings which is a topic I am working my way up to.

So for now, I’ll reproduce John Cook’s TSI – temperature anomaly chart.

TSI and Temperature Anomaly Chart

Here’s my R script based chart of TSI and GISS temperature anomaly trends (11 year moving average) for the 1880 – 2009 period. (Click to enlarge)

This chart shows the 11 year moving average trends for both the TSI (red) and GISS temperature anomaly (blue) series from 1880 to 2009.  Several points are apparent:

• TSI 11 yr moving average (MA) has a narrow range of 1365.3 to 1366.1 W/m^2
• TSI MA has increased from the 1880s until 1959-1960
• TSI MA  have been decreasing  since 1960
• GISS anomaly MA has increased from -0.32 in the 1880s to 0.5 in 2009
• GISS anomaly MA followed a similar rising trend as TSI MA  from 1880 to 1940
• GISS anomaly MA  was relatively flat in the 1940 to 1975 period even though TSI continued to increase until 1960 then decrease
• GISS anomaly MA resumed its increasing trend after 1975 even though the TSI MA was decreasing

Here’s the link to my R script on  Google documents. You can download the script and run it yourself. The script retrieves the GISS anomaly and TSI data directly from the source agencies on-line files and generates the chart.

What Have Others Said About TSI and Temperature Trends?

Many, many scientists have studied the link between solar activity and climate, including such greats as Croll and Milankovitch who studied the causes and timing of ice ages.  I will be posting on the Milankovitch cycles in future posts.

A July, 2004 paper by Usoskin, Schussler, Solanski and Mursula, available as PDF  here, reports on an interesting correlation analysis of 1150 years of solar activity and climate.  Several quotes from their paper:

• “The long-term trends in solar data and in northern hemisphere temperatures have a correlation coefficient of 0.7-0.8 at a 94% – 98% confidence level.”

• “The last 30 years were not considered,however. In this time the climae and solar data diverge strongly from each other.”

• “Note that the most recent warming, since 1975, has not been considered in the above correlations. During these past 30 years the solar total irradiance, solar UV irradiance and cosmic ray flux has not shown any significant secular trend, so that at least this most recent warming episode must have other sources.”

The Max Planck Institute for Solar System Research has a chart of TSI and temperature anomaly trends similar to my chart at this link.

Conclusion

The 1880 – 1940 temperature rise can be attributed, in part,  to TSI increases. The post 1975 temperature increases,however,  can not be attributed to TSI because temperatures were rising while TSI was decreasing. TSI only explains part of the temperature change puzzle. To understand post 1975 temperature change, we need to look at solar activity and other factors.

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