CFACT to EPA: The demonization of CO2 must end!

By Collister Johnson

Additional comments to EPA on reversing its ill-conceived “endangerment finding”

Scientific understanding of atmospheric CO2 has advanced significantly since the EF was enacted in 2009. The logarithmic warming effect of CO2 indicates no danger of runaway warming from a doubling or tripling of current levels. The greening effect of CO2 demonstrates that substantial increases would yield a net benefit for human existence. Water vapor, accounting for 95% of atmospheric heat retention, ensures a stable temperature range as long as oceans exist. CO2’s critical role in oxygen production establishes it as essential for life, not a “pollutant” that could “endanger human health and welfare.”

The EF’s lack of logic, scientific rigor, and compatibility with geologic and atmospheric history renders it “arbitrary and capricious.” It exemplifies confirmation bias, with data cherry-picked to support a preordained conclusion. Rescinding the EF will restore reason to the CO2 debate, undermine harmful policies like “carbon capture” and “carbon taxes,” and eliminate the false narrative of the “social cost of carbon.” In truth, there is no social “cost” to carbon; CO2 is essential for life. Conversely, zero atmospheric CO2 would result in the catastrophic loss of all life on Earth.
The demonization of CO2 must end. At best, the theory of CO2 as a pollutant was an unscientific delusion; at worst, it was a cynical scheme by elites and politicians to extract profits and power. For these reasons, the Committee for a Constructive Tomorrow respectfully requests that the EPA rescind the Endangerment Finding.

September 20, 2025

U.S. Environmental Protection Agency Docket ID No. EPA-HQ-OAR-2025-0194 Submitted via email at a-and-rDocket@epa.gov

Founded in 1985 and headquartered in Washington, D.C., the Committee for a Constructive Tomorrow (CFACT) is a nonprofit public policy and educational organization dedicated to protecting both people and the planet.

There are compelling reasons to reverse the 2009 Endangerment Finding (EF). The clearest and most persuasive reason is that it is simply impossible for CO2—an odorless, colorless, tasteless trace gas essential for life on Earth—to be classified as a “pollutant” under the Clean Air Act.

The rationale for reversal is grounded in the laws of physics, the geologic and atmospheric history of the Earth, and plain common sense.

The saturation effect of CO2 and its plant fertilization capability represent new information and changed circumstances that were not considered by the EPA when promulgating the Endangerment Finding.

Courts have upheld the reversal of prior regulations when based on “new information and changed circumstances.”

Two significant developments in atmospheric science have emerged in the sixteen years since the EF was issued.

First, expert scientists with impeccable credentials have demonstrated that current atmospheric CO2 levels are “saturated” with respect to their ability to warm the planet. Eminent physicists William Happer, Richard Lindzen, and Steven Koonin published two studies, Fossil Fuels and Greenhouse Gases (April 2024) and Greenhouse Gases Cannot Cause Dangerous Warming, Extreme Weather, or Any Harm (June 2025), which utilized state-of-the-art physics, thermodynamics, and quantum mechanics to show that a doubling of current CO2 levels would result in a global atmospheric temperature increase of only 1 degree Celsius. They demonstrated that current CO2 levels of approximately 400 ppm are effectively incapable of trapping significant additional heat in the atmosphere.

Their studies establish that even a doubling or tripling of CO2, which at current rates would take centuries, would have a negligible impact on temperature.

Other physicists have corroborated these findings, confirming that the heat-trapping capability of current CO2 levels is saturated. See, e.g., Archbold, D., “The Logarithmic Effect of Carbon Dioxide,” Watts Up With That? (2010); Schildknecht, D., et al., “CO2 Back Radiation: Sensitivity Studies Under Laboratory and Field Conditions,”

Atmospheric and Climate Sciences, Vol. 14, pp. 492–429 (2024). An excellent summary of studies verifying the limited potency of CO2 and its declining, logarithmic impact on temperature is found in Simpson, M., “The Scientific Case Against Net Zero: Falsifying the Greenhouse Gas Hypothesis,” Journal of Sustainable Development, Vol. 17, No. 6 (2024).

Notably, the Intergovernmental Panel on Climate Change (IPCC) agrees that the heat-trapping capability of CO2 is nonlinear and logarithmic. Using the IPCC’s own formulas for CO2 heat retention, scientists have shown that additional heat generation by CO2 above 400 ppm is trivial. Thus, it is impossible for CO2 increases to trigger the large atmospheric temperature increases relied upon by the EPA to support the EF. See Archbold, D., “The Logarithmic Effect of Carbon Dioxide,” Watts Up With That? (March 2010).

Furthermore, it is undisputed that water vapor (H2O) is the dominant greenhouse gas, maintaining Earth’s temperature at levels suitable for human habitation. On average, there are twenty times more water vapor molecules in the atmosphere at sea level than CO2. See van Wijngaarden and Happer, “Infrared Forcing by Greenhouse Gases,”

June 2019. The EPA’s failure to consider the impact of water vapor and cloud cover on Earth’s climate when promulgating the EF represents a significant oversight for an agency tasked with conducting its own scientific evaluation of atmospheric warming.

In short, the laws of physics render it impossible for CO2 to be designated as a “pollutant” that may “reasonably endanger human health and welfare.” CO2 is incapable of substantially heating Earth’s atmosphere. Without appreciable atmospheric temperature increases, CO2 cannot cause the catastrophic outcomes—such as melting glaciers, rising sea levels, increasing droughts, dying reefs, more frequent hurricanes, or stronger tornadoes— claimed by proponents of man-made warming and relied upon by the EPA to justify the EF. Reversing the Endangerment Finding would end the misguided “net zero” experiment increasingly abandoned by Western governments.

Second, the EPA failed to address the significant benefits of increasing CO2 for Earth’s plant life, including essential food crops, when formulating the EF. It is indisputable that higher CO2 levels enhance plant growth. Commercial greenhouse operators often increase CO2 levels to 1,200 ppm to stimulate plant growth. NASA satellite data since 2009 show that one-quarter to one-half of Earth’s temperate zones have experienced enhanced vegetation over the past 30 years, with approximately 70% of this greening attributed to increased atmospheric CO2. Major food crops worldwide have seen impressive yield increases over recent decades—10–25% for C4 crops like corn and 30–40% for C3 crops such as rice, soybeans, and wheat. See Zhu, et al., “Greening of the Earth and Its Drivers,” Nature Climate Change, Vol. 6, pp. 792–795 (2016).

By promulgating the Endangerment Finding, the EPA either failed to recognize or discounted the beneficial effects of increasing CO2. This omission of CO2’s positive aspects, while focusing solely on purported negatives, is a serious flaw that undermines the EF’s legal validity. How can the EPA determine whether CO2 endangers public health and welfare without conducting a serious cost-benefit analysis of increasing atmospheric CO2? This failure renders the EF “arbitrary and capricious” under the legal standard articulated by the Supreme Court, as it entirely failed to consider an important aspect of the problem” and “the relevant data.” Motor Vehicle Manufacturers Association of the United States v. State Farm Mutual Automobile Insurance Company, 463 U.S. 29, 43 (1983). A thorough and fair cost-benefit analysis would conclude that Earth’s atmosphere could benefit from more CO2, not less.

The geologic and atmospheric history of the Earth persuasively demonstrates that the Endangerment Finding is erroneous.

The most accurate and scientifically rigorous way to assess CO2’simpact on climate is to examine Earth’s historical geologic and atmospheric record. Instead of relying on verified data, the EF depended primarily on computer model forecasts of future atmospheric temperatures. These General Circulation Models (GCMs) are not derived from historical data but are based on assumptions chosen by their authors, making them speculative opinions rather than science.

The primary flaw of GCMs is their reliance on a feedback loop asserting that heat generated by increasing CO2 will create more water vapor, leading to a cascading chain of increasing CO2and H2O, resulting in runaway warming. However, such CO2-driven runaway warming has never occurred in Earth’s 4-billion-year history. This extraordinary prediction requires extraordinary evidence, yet no such evidence exists in the historical record. It is hubristic to assume this phenomenon would emerge for the first time in the 21st century.

Moreover, over millions of years, there has been no long-term correlation between atmospheric CO2 and temperature. Since the Cambrian explosion 600 million years ago, when Earth’s life forms became oxygen-based, atmospheric CO2 has steadily declined from 5,000 ppm to 250 ppm in the pre-industrial era. During this period, Earth experienced both warm periods with minimal polar ice and intense glacial periods with significant ice coverage, yet there is no evidence that CO2 played a significant role in either extreme. See Temperature after C.R. Scotese, CO2 after R.A. Berner, 2001.

The Vostok ice cores from Antarctica show temperature and CO2 levels rising and falling together over the past 400,000 years. However, the critical insight is that CO2 levels rose after air temperature increased, not before. This indicates that rising CO2 cannot be the cause of increasing air temperature. Instead, warmer air temperatures cause oceans to release trapped CO2, similar to CO2 release from a warmed carbonated beverage.

The atmospheric record of the past 20,000 years is also instructive. During this period, Earth experienced a glacial episode with a vast ice sheet covering North America as far south as New York City. Atmospheric CO2 levels were low, in the 200–250 ppm range. As Earth warmed rapidly and ice sheets retreated over the next 15,000 years, CO2 levels remained low and played no role in the warming. Even during well-documented warm periods, such as the Medieval Warm Period 500–1,000 years ago, when grapes grew in England and Vikings colonized Greenland, CO2 levels remained around 250 ppm.

Throughout Earth’s 4-billion-year history, there has never been a CO2-driven “tipping point” or climate catastrophe. The last significant CO2 release occurred 67 million years ago when the Chicxulub meteor impacted the Yucatán peninsula, releasing vast amounts of CO2 from ash, soot, and wildfires. This event caused the extinction of 75–90% of animal life, including dinosaurs, yet no “tipping point” or irreversible recovery occurred. The geological record shows Earth recovered within a few thousand years. The gradual increase in present-day CO2 bears no resemblance to that catastrophic event.

In summary, historical records show CO2 levels are relatively high during cooling periods and relatively low during warming periods, contradicting the EF’s premise.

Logic and common sense support the rescission of the EF.

Even setting aside science and historical records, logic and common sense dictate that CO2 cannot be a “pollutant.”  All animal life requires oxygen, which is produced solely through photosynthesis by plants on land and phytoplankton in the ocean. Photosynthesis cannot occur without atmospheric CO2. No CO2means no plants, no oxygen, and no life on Earth.

Thus, some level of atmospheric CO2 is essential for human survival. The questions are: How much is needed? Can there be too much or too little?

It is well-documented that CO2 levels below 150 ppm cause plants to wither and die. Current levels of approximately 400 ppm are satisfactory but at the low end of the scale. Commercial greenhouses increase CO2 to 1,200–1,400 ppm to optimize plant growth, suggesting that higher CO2 levels would result in lush vegetation and prolific food crops.

Regarding “too much” CO2, experience in enclosed spaces like submarines and space capsules indicates that levels above 5,000 ppm are considered dangerous by the Navy and NASA. At current rates, reaching such levels would take over 1,000 years. Moreover, increasing CO2 levels stimulate plant growth, which absorbs more CO2, maintaining a natural balance known as the “carbon cycle.” This cycle has kept CO2 at tolerable levels for 600 million years.

From a logical standpoint, current atmospheric CO2 levels are benign and necessary to support human life.

Scientific understanding of atmospheric CO2 has advanced significantly since the EF was enacted in 2009. The logarithmic warming effect of CO2 indicates no danger of runaway warming from a doubling or tripling of current levels. The greening effect of CO2 demonstrates that substantial increases would yield a net benefit for human existence. Water vapor, accounting for 95% of atmospheric heat retention, ensures a stable temperature range as long as oceans exist. CO2’s critical role in oxygen production establishes it as essential for life, not a “pollutant” that could “endanger human health and welfare.”

The EF’s lack of logic, scientific rigor, and compatibility with geologic and atmospheric history renders it “arbitrary and capricious.” It exemplifies confirmation bias, with data cherry-picked to support a preordained conclusion. Rescinding the EF will restore reason to the CO2 debate, undermine harmful policies like “carbon capture” and “carbon taxes,” and eliminate the false narrative of the “social cost of carbon.” In truth, there is no social “cost” to carbon; CO2 is essential for life. Conversely, zero atmospheric CO2 would result in the catastrophic loss of all life on Earth.

The demonization of CO2must end. At best, the theory of CO2 as a pollutant was an unscientific delusion; at worst, it was a cynical scheme by elites and politicians to extract profits and power. For these reasons, the Committee for a Constructive Tomorrow respectfully requests that the EPA rescind the Endangerment Finding.

Collister Johnson, Jr. Senior Policy Advisor, Committee for a Constructive Tomorrow 

From cfact.org