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June 21 was not only the summer solstice for the Northern Hemisphere, it was also #MetsUnite day; a day for broadcast meteorologists to #ShowYourStripes.¹ Ed Hawkins, a climatologist at the University of Reading, created these banner-like graphics (Figure 1) that are colored to show how Earth has supposedly warmed since 1850.¹ Each vertical stripe represents one year of average temperature.¹
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| Figure 1. "Show Your Stripes" banner depicting global temperature trends. |
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| Figure 2. Warming stripes for Virginia from 1895 - 2018. |
So, how accurate are these #ShowYourStripes banners? Are they spot-on accurate, or are they a total waste of website bandwidth? Let's find out.
Before I discuss the temperature data, let's take a look at the number of Global Historical Climatology Network (GHCN) stations over time. As you can see in Figure 3 below, the number of stations reached a peak sometime between 1960 and 1980 with nearly 5,500 stations globally.³ In 1880, when temperature records began, there were only about 500 GHCN stations across the globe, and that number didn't cross 1,000 until the mid-1890s.³ The number of stations steadily grew from approximately 1,000 to nearly 3,000 from the 1890s leading up to the end of World War II.³ After World War II, only then did the number of stations skyrocket.³ Following a "boom" in station count, the number has been dropping consistently since the 1980s.³
Over that entire time period, the only country that has had an excellent temperature record is the United States, although there are a handful of other countries that have decent long-term records too. This is because the U.S. had and still has the most station coverage relative to it's landmass as compared to any other country. Thus, one can only conclude that temperature records from almost any other country are essentially worthless, let alone a global temperature record.
Over 6,000 stations have records shorter than 20 years, which isn't even long enough to officially calculate a "climate normal," which is 30 years.³ More than half of the GHCN stations have records no longer than 50 to 60 years, which is barely long enough to show cyclical changes in the climate on multidecadal time scales.³ (See Figure 4).
Before I discuss the temperature data, let's take a look at the number of Global Historical Climatology Network (GHCN) stations over time. As you can see in Figure 3 below, the number of stations reached a peak sometime between 1960 and 1980 with nearly 5,500 stations globally.³ In 1880, when temperature records began, there were only about 500 GHCN stations across the globe, and that number didn't cross 1,000 until the mid-1890s.³ The number of stations steadily grew from approximately 1,000 to nearly 3,000 from the 1890s leading up to the end of World War II.³ After World War II, only then did the number of stations skyrocket.³ Following a "boom" in station count, the number has been dropping consistently since the 1980s.³
Over that entire time period, the only country that has had an excellent temperature record is the United States, although there are a handful of other countries that have decent long-term records too. This is because the U.S. had and still has the most station coverage relative to it's landmass as compared to any other country. Thus, one can only conclude that temperature records from almost any other country are essentially worthless, let alone a global temperature record.
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| Figure 3. Number of global GHCN stations. |
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| Figure 4. Station record length. |
I find it very suspicious that we "have" an accurate global temperature record if there is a lack of long-term data and station coverage on a global scale. Because of these conditions, I want to lastly direct your attention to the United States, which without comparison, has the best temperature record in the world.
According to Ed's website, U.S. temperatures (Figure 5) are the warmest that they have ever been just in the last decade.
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| Figure 5. U.S. warming stripes. |
Actual raw data says otherwise. Since 1895, U.S. temperatures have seen no significant trend (Figure 6), yet the stripes at the end are showing that the U.S. is seeing it's warmest ever past few years (Figure 5).⁴
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| Figure 6. Average mean temperature vs. year for the U.S. |
I have no doubt in my mind that global temperatures have indeed risen since and much prior to 1880, there is plenty evidence of it. However, exactly how much warming we have seen globally since official records began in 1880 might not be 1°C (1.8°F), it could very well be a bit less, and without sufficient long-term data, nobody really knows. For example, there are only 522 GHCN stations (Figures 7 and 8) that have been active since 1900, and most of those are in the United States.³
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| Figure 7. NASA map of GHCN stations active in both January 1900 and May 2019 (NH). |
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| Figure 8. NASA map of GHCN stations active in both January 1900 and May 2019 (SH). |
The question isn't whether or not each individual station's data is accurate (more than likely is), it's a question of the global temperature record. Without sufficient long-term data from any other country except for the U.S., I remain skeptical of the accuracy of such graphs.
REFERENCES
[1] Shepherd, Marshall. "Why TV Meteorologists Will 'Show Their Stripes' For Climate on June 21st." Forbes. June 19, 2019. Accessed June 23, 2019. https://www.forbes.com/sites/marshallshepherd/2019/06/19/why-tv-meteorologists-will-show-their-stripes-for-climate-on-june-21st/.
[2] Hawkins, Ed. "#ShowYourStripes." #ShowYourStripes, University of Reading. Accessed June 23, 2019. https://showyourstripes.info/.
[3] Schmidt, Gavin A. "GISS Surface Temperature Analysis." NASA GISS. June 12, 2019. Accessed June 23, 2019. https://data.giss.nasa.gov/gistemp/stdata/.
[4] Heller, Tony. "UNHIDING THE DECLINE For Windows." The Deplorable Climate Science Blog. August 14, 2017. Accessed June 23, 2019. https://realclimatescience.com/unhiding-the-decline-for-windows/.
