Arguments
At a glance - Empirical evidence that humans are causing global warming
Posted on 18 July 2023 by John Mason, BaerbelW
On February 14, 2023 we announced our Rebuttal Update Project. This included an ask for feedback about the added "At a glance" section in the updated basic rebuttal versions. This weekly blog post series highlights this new section of one of the updated basic rebuttal versions and serves as a "bump" for our ask. This week features "Empirical evidence that humans are causing global warming". More will follow in the upcoming weeks. Please follow the Further Reading link at the bottom to read the full rebuttal and to join the discussion in the comment thread there.
At a glance
Empirical evidence? None? That's a big bold statement to make, so let's take a look. 'Empirical' is defined as something that may be actually measured and presented as a finding. Let's treat the topic as a criminal prosecution. The accused is CO2 and the accusation is that its increased levels through our emissions are warming the planet. As with all court cases, it's important to present an accurate account of events. So firstly, we'll examine the background to this particular case.
It all started in the 1820s, when French physicist Joseph Fourier had worked out that, at its distance from the Sun, Earth should be very cold. He proposed that Earth's atmosphere must contain something that kept the planet warm, like some invisible blanket. His ideas were, it turned out, correct albeit incomplete.
Some decades passed before the nature of Fourier's blanket was discovered. This was done through a series of experiments involving various gases. Interestingly, two investigators worked on it independently, John Tyndall, in the UK and Eunice Foote in the USA. Impressively, their results were virtually identical.
Foote, writing in 1856, was the first scientist to state that carbon dioxide can trap energy. She predicted that if there had been more CO2 in the atmosphere at times past, an increased temperature would have prevailed. That was something the geologists already knew. Tyndall went on to write, in 1861, that on top of carbon dioxide, hydrocarbons - such as methane - would have even greater effects at very low concentrations. The greenhouse effect and its key players had been identified.
The landmark paper, "The Carbon Dioxide Theory of Climatic Change", was published just under a hundred years later. Essentially, it stated what we know now. Without the atmosphere and its greenhouse gases, Earth would be an uninhabitable iceball. As Fourier started to reason all that time ago, greenhouse gases act like a blanket. They keep Earth warm by inhibiting the escape of energy back into space. Humans are adding CO2 to the atmosphere, mainly by burning fossil fuels, thereby intensifying the effect.
That's the background. As we emit more greenhouse gases, the effect is like wrapping yourself in a thicker blanket. Even less heat is lost. So how can we tell that? How can we find hard evidence, like good CCTV footage of our suspect up to their mischief?
How about measuring it?
Satellites orbiting our planet carry sensitive instruments on board. Through them we can measure how much energy is arriving from the Sun. We can measure how much energy is leaving the Earth, out into space. So right there we have two things to compare.
What do the measurements tell us? Over the last few decades since satellites became available, there has been a gradual decrease in the energy heading from Earth's surface back into space. Yet in the same period, the amount of energy arriving from the Sun has hardly changed at all. Something is hanging onto that energy and that something is getting stronger. That something is carbon dioxide - doing exactly as Foote and Tyndall said it would 160 plus years ago.
Verdict: guilty on all counts.
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This brief greenhouse gas theory history omits the very important paper, "On the Influence of Carbonic Acid in the Air Upon the Ttemperature of the Ground,"the first true model of the effect, the hand-calculated model by Svante Arrhenius published in 1896. It modeled the atmosphere as a single layer and the effect of setting the concentration of CO2 to 2/3 of the value at his time, and at values up to 3 times higher, for 10 degree latitude steps both north and south, for 4 seasons and for the annual mean. His results for this simple model were within a factor of 10 of current calculations and measurements as the value has grown. His interest was in explaining newly discovered evidence of ancient ice ages.
You also omit Horace-Benedict de Saussures' important measurements (in "Continuation du Voyage Autour du Mont-Blanc," Chapter XIII, Voyages dans les Alpes VII, 1779, S . Fauche, Neuchatel, pp353-355, and pp365-367). The first demonstrates the existence of "chaleur obscure" (="dark heat" = infrared radiation) and its reflection and concentration, using metal mirrors, just like visible light. The second records measurements of the greenhouse effect temperature rise in a cubic foot wooden box, insulated on all but one side with blackened cork, and that side closed by two layers of glass. He placed thermometers between the glass layers and inside and outside the box, and traveled the assembly from sea level up to high altitude in the Alpes, measuring the temperatures inside and outside the box as he went. He ascribes the decrease of temperature with altitude to the increasing transparency of the air as you ascend. I made a translation from the French which is available upon request. Fourier refers to this work in the paper of 1827 cited above.
Re. #1, yes it does. At a glance is a very brief explanation aimed purely at the lay-person, who it is assumed has never heard of any of the figures involved in the history of climate science. We cover the latter topic in detail elsewhere at Skeptical Science.
However, your account of the experiments performed by Horace-Benedict de Saussures is very interesting and not widely known - evidently! It would fit well into The History of Climate Science:
https://skepticalscience.com/history-climate-science.html
We do update the history page as new information becomes available so if you could use the Contact link to email your translation to us, we can splice it in (with attribution) at some point - thanks in advance!