George Will’s claim about recent global temperature trends is similar to others:
- There Is a problem with global warming… it stopped in 1998 - Bob Carter in Telegraph, 4/16/06
- Has global warming stopped? by David Whitehouse in New Statesman, 12/19/07.
What’s the situation? Have George Will, Bob Carter and David Whitehouse interpreted the temperature trends correctly? This post looks at the long term global land and sea temperature anomaly trends to evaluate the accuracy of Mr. Will’s statement.
Global Land and Sea Temperature Trends
I’ve used NASA’s Goddard Institute of Space Studies‘s (GISS) global land and sea temperature anomaly data series to evaluate his claim, available at this link. Figure 1 shows my long term global land and sea temperature trend chart, showing monthly and annual anomalies, long term trend (lowess fit [(f = 0.15]) as well as the 2001-2008 trend. I prepared this chart using R.
The blue line shows the long term trends. There has been a substantial rise in global temperature since 1880. The temperature anomalies have significantly increased since 1880 with cyclical peaks and valleys and pause periods. Mr. Will didn’t mention that.
The red line shows the recent (2001-2008 ) period stressed by George Will. He focused on the past 8 – 10 years and ignored the fact that there have been comparable 8 – 10 years periods in the fluctuating upward trend in the 128 year GISS temperature data record. Mr Will made a shortsighted interpretation of a long term trend.
Impact of Volcanoes and El Nino – La Nina Events on Global Temperatures
What causes the up and down cycles in the global temperature record? Volcanoes and El Nino – La Nina events are two of the climate factors that contribute to the fluctuations in temperature trends. Let’s look at how they affect global temperature trend fluctuations.
Major volcanic eruptions affect global temperatures because they release large quantities of particulate material which circulate around the globe for several years, reducing the amount of solar radiation that reaches the earth (NASA discussion page). The Stratospheric Aerosol Optical (SATO) Index can be used to measure the optical effects of volcanic eruptions.
Figure 2 helps to explain the cyclical variations in the GISS temperatures. If we look closely, we see that periods of positive NINO34 Index (red fill areas) correspond to periods of rising GISS temperatures while periods of negative NINO34 Index correspond to decreasing GISS temperatures. This NINO34 – GISS anomaly relationship is altered in periods when the SATO index is elevated from volcanic events.
Look at the 1983-84 period. While NINO34 Index was positive the SATO Index was elevated from the El Chichon eruption, resulting in a decrease in global temperature. A similar situation occurred in 1992-93 when the NINO34 Index was positive and the SATO Index was elevated from the Pinatubo – Hudson eruptions, resulting in a decrease in global temperatures.
The 1998 positive NINO34 Index, followed by the 1999-2002 negative NINO34 Index resulted in increased temperatures in 1998 followed by decreased temperatures in 1999-2000. The 2001-2008 time frame had several negative NINO34 months, reducing the GISS temperature anomalies.
While the GISS temperature anomalies have gone through peaks and valleys, the long term trend is clear, rising , rising , rising. Mr. Will misses that because he selected a very short time frame, one of the pause periods in the long term trend.
What Do Others Say?
Here are links to several climate blog posts that discuss global temperature trends.
What do you Think?