A Reality Check on Three Key Global Warming Claims

Earth is warmed almost completely by heat radiated from the sun. Anything with a temperature radiates heat, & the Earth in turn re-radiates this heat outward as infrared energy, cooling the Earth when that energy escapes into outer space. For Earth’s temperature to be stable over long periods of time, incoming & outgoing energy must be equal.

This warming & cooling process is not hypothetical, it is a measurable, physical system. Yet aspects of this system are the subject of public debate, insofar as they impact a larger question: is human activity warming the Earth? This is no surprise as interests on both sides of this question have much to gain by successfully persuading the public of an answer that recommends their business. But, as the debate concerns real, objective systems, the key questions should be settled by evidence, not politicians or lawyers. Accordingly, what follows is a review of facts that answer three questions fundamental to global warming claims.

1 Does Carbon Dioxide Heat the Earth?

Incoming sunlight & outgoing energy travel through Earth’s atmosphere, which is composed of a variety of gases. The most abundant allow solar & infrared radiation to pass through, but certain constituents called “greenhouse gases” absorb outgoing infrared energy radiated by the Earth. This warms greenhouse gases, which in turn radiate infrared energy outwards in all directions: out to space, towards neighbor gases, & back towards the surface of the Earth. This limits how much heat escapes into space & thereby limits cooling.

The behavior of greenhouse gases, as described, can be observed using spectroscopy, a scientific tool dating back to Isaac Newton. Spectroscopy is an analysis of the interaction between matter & electromagnetic radiation which reveals properties such as the chemical composition & temperature of a radiation source (Pavia, Lampman, Kriz, & Vyvyan, 2008). Spectroscopic study of downward infrared radiation from our atmosphere directly identifies its sources, the five most abundant of which are water vapor, carbon dioxide (CO₂), methane, nitrous oxide, & ozone. This direct measurement proves that atmospheric CO₂ warms the Earth with downward infrared radiation, alongside other greenhouse gases (Evans, & Puckrin, 2006).

Further evidence has been provided by the international satellites that have measured outgoing radiation escaping Earth’s atmosphere since 1970. This data corroborates measurements of downward infrared radiation & reveals a timeline of declining heat loss at wavelengths trapped by CO₂ (Chen, Harries, Brindley, & Ringer, 2007). None of this is speculative, these are all direct measurements.

2 Are rising CO₂ levels in the atmosphere the result of human activity?

Natural processes have been emitting greenhouse gases for billions of years, since well before humans started burning fossil fuels. Volcanoes, respiration, & wildfires continue to pump CO₂ into Earth’s atmosphere today. The rise of fossil fuel usage is correlated with rising levels of atmospheric CO₂, but correlation alone is not sufficient to establish causation & without a way to distinguish industrial CO₂ from natural CO₂, the source of increasing atmospheric CO₂ would be difficult to isolate, given the variety of CO₂ producers. Fortunately, simple chemistry & a well-known scientific tool can help with this distinction.

Carbon dating is a method for determining the age of organic material. Cosmic rays constantly bombard Earth & transform atmospheric nitrogen into carbon-14, an unstable, radioactive isotope of carbon, also known as “radiocarbon.” Atmospheric radiocarbon combines with atmospheric oxygen to form radioactive CO₂, which is incorporated into plants through photosynthesis, then animals eating plants, then animals eating those animals, etc, being ultimately distributed throughout organic life in similar proportions to those found in our atmosphere. When an organism dies it stops consuming carbon & falls out of equilibrium with carbon-14 levels in its environment as its own unstable carbon-14 isotopes “decay” into carbon-13 & carbon-12 isotopes over thousands of years. Carbon dating measures carbon decay to discover roughly when an organism died (Libby & Johnson, 1955).

Fossil fuels come from organisms that have been dead for millions of years & therefore have no remaining carbon-14. Most natural sources of CO₂ are living or recently dead & contain the same proportion of carbon-14 to carbon-12 as Earth’s atmosphere. With this in mind, levels of atmospheric carbon-14 & carbon-12 can be compared over time to determine whether or not there are increasing contributions from disproportionately carbon-12-heavy sources. A larger proportion of carbon-12 relative to carbon-14 indicates increasing atmospheric contributions from ancient carbon sources, like fossil fuels, & this is exactly what measurements show (Lehman et al. 2013).

Volcanic activity is the only natural source of CO₂ that emits only carbon-12, like fossil fuels. Its CO₂ output, averaging about 600 million metric tons per year, does not show a trend towards increased activity that could explain increasing atmospheric CO₂ levels (Gerlach, 2011; Burton, Sawyer, & Granieri, 2013). Fossil fuels produce around 33.1 billion metric tons of CO₂ per year, more than 50 times average volcanic contributions, with an upwards trend mirroring increased levels of atmospheric carbon-12 (International Energy Agency, 2019). The correlation of rising fossil fuel use with rising levels of the specific atmospheric carbon isotope produced by fossil fuel use, without another source that could be responsible for the rise, proves that fossil fuel usage is causing increased atmospheric CO₂ levels.

3 Is The Earth Warming?

Spectroscopy & carbon dating have provided answers to questions that may have seemed impossible to answer with certainty. Questions about temperature can be answered with a more familiar tool: the thermometer. The challenge presented in the analysis of Earth’s temperature comes with the scope of the project; Earth is a big place & weather varies geographically, seasonally, moment to moment, etc. Climate, as opposed to weather, is the average state of weather conditions for a particular region over a 30 year period. Global warming looks at these long-term trends, climate change versus short-term, local fluctuations in weather. These long-term trends provide a baseline upon which short-term, local weather fluctuates. Agencies across the world measure temperature from a variety of locations, &, averaging these together, a worldwide warming trend can be seen that roughly correlates with increased fossil fuel use.

The mechanisms affecting Earth’s temperature are plentiful & ultimately comprise a more complex picture than what is covered in this review. There are further questions that may not yield conclusive answers. But the impartial, reproducible evidence covered in this review is foundational to an understanding of the discussion on global warming, and it should be appreciated as the objective reality that it is.