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Human fingerprints on climate change
Presented to the Loudoun County Board of Supervisors – June 23, 2016
Tony Noerpel
Recently I was asked whether humanity’s fossil fuel use was the cause of the current global
warming. This is a good question and I’m not surprised that there is some confusion and indeed
acknowledging that the Earth surface is warming leads inevitably to this question.
The answer is yes we are the cause of 100% of the global warming taking place since 1970. For
example, solar radiation has been trending lower as shown in Figure 1.
“If the sun was causing global warming, we would see days warming faster than nights. We
see the opposite - nights warming faster than days - a characteristic of greenhouse warming.
Similarly, if the sun was causing global warming, we would see the upper atmosphere
warming as well as the lower atmosphere. Instead, we see the upper atmosphere cooling as
the lower atmosphere warms. Again, a distinct signature of greenhouse warming. The unique
signatures we'd expect from solar warming are strikingly absent.” [1]
I’ve compiled a list of 17 fingerprints pointing to a human cause with references. Items 4 through 12
are from reference [1].
I will finish with an interesting story. The physicist Richard Muller was a strident global warming
denier. He claimed the instrument temperature record was sloppy and inaccurate. Muller and his
team collected more data than was ever before analyzed and independently developed their own
algorithms and methodologies.
In March 2011 Muller reversed his position and concluded that the Earth surface was warming and
by a rate exceeding that published in the IPCC report [2-3]. I commented on his result in the Blue
Ridge Leader stating that Muller’s team had confirmed human-caused climate change. A reader
replied that all Muller confirmed was that the Earth surface was warming; not that it was caused by
humans. But nothing in nature works that fast (see points 14 and 15) and by confirming the fact of
the rate of global warming, Muller confirmed that it had to have a human cause. In 2012 Muller
clarified that indeed humans were 100% responsible for the recent climate change [4-5]. This is
settled science.
After my presentation to the Board of Supervisors, I was asked why attribution mattered. Denial is
about ideology and not about science and because of this economic ideology, deniers do not want to
cut carbon emissions. They have recently been willing to concede that the earth surface is indeed
warming but so long as they remain convinced it is not caused by human activities, there is no
reason to stop burning fossil fuels. In fact, there is a strong reason to continue. The more fossil
fuels we consume the more wealth we generate and therefore we are better able to afford
adaptation policies later. Only by realizing that we are the cause of global warming and that global
warming will soon be destroying wealth much faster than it can ever be generated can we realize we
have no choice but to stop burning fossil fuels as expeditiously as possible.
1. Svante Arrhenius accurately predicted that human emissions of carbon dioxide would warm
the planet in 1896 [6] and his estimate was accurate given he was using a slide rule. Others
have made similar forecasts since including Wally Broecker in 1975 in a paper published in
the journal Science [7]. His forecast proved accurate also. So the recent warming was
accurately predicted by the theory.
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2. The most authoritative and exhaustive summary published by the scientific community the
IPCC reports, confirm that the human cause is the consensus. Every major scientific
organization in the world including: AAAS, AGU, NAS, NASA, NOAA and ACS endorses the
consensus determination.
3. Humans are currently emitting around 39.3 billion tonnes of CO2 into the atmosphere every
year [8].
4. When we measure the type of carbon accumulating in the atmosphere, we observe more of
the isotope signature of carbon that comes from fossil fuels [9].
5. This is corroborated by measurements of oxygen in the atmosphere. Oxygen levels are
falling in line with the amount of carbon dioxide rising, just as you'd expect from fossil fuel
burning which takes oxygen out of the air to create carbon dioxide [9]
6. Further independent evidence that humans are raising CO2 levels comes from
measurements of carbon found in coral records going back several centuries. These find a
recent sharp rise in the type of carbon that comes from fossil fuels [10].
7. So we know humans are raising CO2 levels. What's the effect? Satellites measure less heat
escaping out to space, at the particular wavelengths that CO2 absorbs heat, thus finding
"direct experimental evidence for a significant increase in the Earth's greenhouse effect" [11].
8. If less heat is escaping to space, where is it going? Back to the Earth's surface. Surface
measurements confirm this, observing more downward infrared radiation. A closer look at the
downward radiation finds more heat returning at CO2 wavelengths, leading to the conclusion
that "this experimental data should effectively end the argument by skeptics that no
experimental evidence exists for the connection between greenhouse gas increases in the
atmosphere and global warming." [12]
9. If an increased greenhouse effect is causing global warming, we should see certain patterns
in the warming. For example, the planet should warm faster at night than during the day. This
is indeed being observed [13].
10. Another distinctive pattern of greenhouse warming is cooling in the upper atmosphere,
otherwise known as the stratosphere. This is exactly what's happening [14].
11. With the lower atmosphere (the troposphere) warming and the upper atmosphere (the
stratosphere) cooling, another consequence is the boundary between the troposphere and
stratosphere, otherwise known as the tropopause, should rise as a consequence of
greenhouse warming. This has been observed [15].
12. An even higher layer of the atmosphere, the ionosphere, is expected to cool and contract in
response to greenhouse warming. This has been observed by satellites [16].
13. The study considered temperature changes for the period of 1951–2010. During that time,
global surface temperatures warmed about 0.65°C. During that same period, their statistical
approach which combines observations and climate models outputs found that humans have
caused 0.67 ± 0.12°C warming, while natural factors have had essentially no effect on global
temperatures (-0.01 ± 0.02°C).
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Figure 2. The percentage contribution to global warming over the past 50-65 years in two
categories: human causes (left) and natural causes (right), from various peer-reviewed
studies. The studies are Tett et al. 2000 [17], dark blue, Meehl et al. 2004 (M04, red), Stone
et al. 2007 (S07, green), Lean and Rind 2008 (LR08, purple), Huber and Knutti 2011 [18],
Gillett et al. 2012 (G12, orange), Wigley and Santer 2012 (WG12, dark green), Jones et al.
2013 [19], IPCC AR5 [20-21], light green), and Ribes et al. 2016 [22] The numbers are best
estimates from each study. Illustration: Dana Nuccitelli
https://www.theguardian.com/environment/climate-consensus-97-percent/2016/apr/19/study-humans-have-caused-all-the-global-warming-since-1950
14. Fossil fuels are organic carbon which has been sequestered by plate tectonics into the
lithosphere within sedimentary rocks. It is being released into the atmosphere at a rate
(10,700 Mtonnes/year) about 100 times faster than Nature (volcanism) normally returns this
carbon to the surface [23,24,25].
15. The release of fossil carbon is happening ten times faster than the most extreme events
between surface reservoirs and the atmosphere [26].
16. Up until June 2010 there occurred a string of 304 consecutive months with mean surface
temperature exceeding the 20th century average. When the effect of GHGs is removed,
bootstrap simulation of the model reveals that there is less than a one in one hundred
thousand chance of observing this result. Since June 2010 this string has been extended
and the odds against human-caused climate change are even lower [27].
17. Human-caused climate change confirmed independently by the Berkeley Earth Surface
Temperature (BEST) Project.
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Figure 1: Annual global temperature change (thin light red) with 11 year moving average of temperature
(thick dark red). Temperature from NASA GISS. Annual Total Solar Irradiance (thin light blue) with 11 year
moving average of TSI (thick dark blue). TSI from 1880 to 1978 from Krivova et al 2007 (data). TSI from
1979 to 2009 from PMOD (see the PMOD index page for data updates). From [2]
References
[1] Source: SS(2010) http://www.skepticalscience.com/10-Indicators-of-a-Human-Fingerprint-onClimate-Change.html
[2] https://en.wikipedia.org/wiki/Richard_A._Muller
[3] Lauren Morello, "Study of Temperature Data Confirms Warming Trend, Scientist Tells House
Panel", The New York Times, March 31, 2011.
[4] Muller, Richard A. (July 30, 2012). "The conversion of a climate change skeptic". New York
Times.
[5] A video of Muller’s mea culpa: https://www.youtube.com/watch?v=Sme8WQ4Wb5w
[6] Svante Arrhenius, 1896b, On the Influence of Carbonic Acid in the Air upon the Temperature of
the Ground, London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science (fifth
series), April 1896. vol 41, pages 237–275
[7] Broecker, W.S. "Climatic change; are we on the brink of a pronounced global warming?" Science,
v 189, n 4201, p 460-3, 8 Aug. 1975.
[8] https://www.co2.earth/global-co2-emissions )
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[9] Andrew C. Manning and Ralph F. Keeling, Global oceanic and land biotic carbon sinks from the
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M. Lough, Bradley N. Opdyke, Preindustrial to Modern Interdecadal Variability in Coral Reef pH,
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Accepted 15 January 2001
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Group I to the fifth assessment report of the intergovernmental panel on climate change. Cambridge
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