Venus’ atmosphere is composed of about 96 percent carbon dioxide (CO₂) and is approximately 92 times denser than Earth’s.
Venus’ hot conditions, with an average surface temperature of 464°C (867°F), stem from intense atmospheric pressure due to the dense atmosphere, lack of water, and geology—not “too much CO₂” in the atmosphere.
Earth’s self-regulating systems, oceans, weathering, and plate tectonics prevent massive heating from a runaway greenhouse effect.
There is no chance that “Earth will become like Venus,” a common claim made by those who warn about a dangerous runaway greenhouse effect.
Short Summary:
Venus has an average surface temperature of 464°C (867°F), whereas Earth’s average surface temperature is 15°C (59°F).1
Venus’ extreme heat compared to Earth isn’t primarily the result of high levels of atmospheric carbon dioxide (CO2). Instead, it’s driven by immense atmospheric pressure, lack of water, and the absence of natural stabilizing geologic processes. Earth’s CO₂ levels, even when they were much higher in the past, never caused a runaway greenhouse effect because our planet’s unique systems naturally regulate temperature over time.
Venus’ atmosphere is composed of 96 percent carbon dioxide and is about 92 times denser than Earth’s.2 This immense pressure creates intense adiabatic heating, the same principle that warms compressed air in a bicycle pump.3 Simply put, the surface of Venus is hot in large part because its air is squeezed under the weight of an ultra-dense atmosphere.
Although Venus receives about 1.9 times more solar energy than Earth because it is closer to the Sun, its thick cloud cover reflects approximately 75 percent of that sunlight into space. Thus, Venus absorbs less solar energy overall than Earth does. Adiabatic pressure heating is the main driver of Venus’ temperature.
Carbon dioxide absorbs infrared energy in narrow wavelength bands, and these bands quickly become saturated as CO₂ levels rise.4 See Figure 1.
Figure 1: A graph of transparency of the atmosphere with three different concentrations of carbon dioxide.
On Earth, most CO₂ absorption bands are already effectively filled. Therefore, additional CO₂ has a progressively smaller influence on surface temperature. This diminishing impact follows a logarithmic pattern, meaning each doubling of CO₂ adds less warming than the previous one.5 See Figure 2.
Figure 2. The logarithmic heating effect of carbon dioxide in Earth’s atmosphere. At today’s CO2 concentration in the atmosphere of approximately 425 parts per million, additional CO2 concentrations have little ability to absorb heat and therefore is now a weak greenhouse gas. At higher concentrations in the future, the ability of future increases to warm the planet will be even smaller.
The notion of a runaway greenhouse effect on Earth overlooks the physics of this saturation and the fact that Earth’s atmosphere operates at low pressure compared to Venus.6
In the case of Venus, with no liquid water or active geology to remove CO₂ from the atmosphere or distribute heat, the Venusian climate system remains locked in a superheated equilibrium.7 Earth’s abundant water vapor not only amplifies warming but also moderates it through ocean heat sinks, condensation, clouds, and precipitation.8
Another difference between Venus and Earth is the latter’s carbonate–silicate weathering cycle, a natural thermostat that regulates CO₂ levels over geologic time.9 When CO₂ rises and the planet warms, chemical weathering of rocks accelerates, drawing carbon dioxide out of the atmosphere and locking it into carbonate rocks such as limestone; this process slows as the planet cools, maintaining long-term stability.
Unlike Venus, Earth has plate tectonics, which continuously recycle carbon dioxide (embedded in rocks) between the crust and the atmosphere, maintaining a balance that keeps the Earth temperate and habitable.10 Both geologic processes act over millennia, but prevent the runaway greenhouse effect from taking hold on Earth.
Thus, Venus’ intense heat is not a matter of “too much CO₂,” but rather the outcome of its unique combination of pressure, chemistry, and the absence of the stabilizing mechanisms found on Earth.
William Happer and Richard Lindzen, “Comment and Declaration on the SEC’s Proposed Rule: The Enhancement and Standardization of Climate-Related Disclosures for Investors,” File No. S7-10-22, 87 Fed. Reg. 21334, April 11, 2022, https://www.sec.gov/comments/s7-10-22/s71022-20132171-302668.pdf
Venus’ atmosphere is composed of about 96 percent carbon dioxide (CO₂) and is approximately 92 times denser than Earth’s.
Venus’ hot conditions, with an average surface temperature of 464°C (867°F), stem from intense atmospheric pressure due to the dense atmosphere, lack of water, and geology—not “too much CO₂” in the atmosphere.
Earth’s self-regulating systems, oceans, weathering, and plate tectonics prevent massive heating from a runaway greenhouse effect.
There is no chance that “Earth will become like Venus,” a common claim made by those who warn about a dangerous runaway greenhouse effect.
Short Summary:
Venus has an average surface temperature of 464°C (867°F), whereas Earth’s average surface temperature is 15°C (59°F).1
Venus’ extreme heat compared to Earth isn’t primarily the result of high levels of atmospheric carbon dioxide (CO2). Instead, it’s driven by immense atmospheric pressure, lack of water, and the absence of natural stabilizing geologic processes. Earth’s CO₂ levels, even when they were much higher in the past, never caused a runaway greenhouse effect because our planet’s unique systems naturally regulate temperature over time.
Venus’ atmosphere is composed of 96 percent carbon dioxide and is about 92 times denser than Earth’s.2 This immense pressure creates intense adiabatic heating, the same principle that warms compressed air in a bicycle pump.3 Simply put, the surface of Venus is hot in large part because its air is squeezed under the weight of an ultra-dense atmosphere.
Although Venus receives about 1.9 times more solar energy than Earth because it is closer to the Sun, its thick cloud cover reflects approximately 75 percent of that sunlight into space. Thus, Venus absorbs less solar energy overall than Earth does. Adiabatic pressure heating is the main driver of Venus’ temperature.
Carbon dioxide absorbs infrared energy in narrow wavelength bands, and these bands quickly become saturated as CO₂ levels rise.4 See Figure 1.
Figure 1: A graph of transparency of the atmosphere with three different concentrations of carbon dioxide.
On Earth, most CO₂ absorption bands are already effectively filled. Therefore, additional CO₂ has a progressively smaller influence on surface temperature. This diminishing impact follows a logarithmic pattern, meaning each doubling of CO₂ adds less warming than the previous one.5 See Figure 2.
Figure 2. The logarithmic heating effect of carbon dioxide in Earth’s atmosphere. At today’s CO2 concentration in the atmosphere of approximately 425 parts per million, additional CO2 concentrations have little ability to absorb heat and therefore is now a weak greenhouse gas. At higher concentrations in the future, the ability of future increases to warm the planet will be even smaller.
The notion of a runaway greenhouse effect on Earth overlooks the physics of this saturation and the fact that Earth’s atmosphere operates at low pressure compared to Venus.6
In the case of Venus, with no liquid water or active geology to remove CO₂ from the atmosphere or distribute heat, the Venusian climate system remains locked in a superheated equilibrium.7 Earth’s abundant water vapor not only amplifies warming but also moderates it through ocean heat sinks, condensation, clouds, and precipitation.8
Another difference between Venus and Earth is the latter’s carbonate–silicate weathering cycle, a natural thermostat that regulates CO₂ levels over geologic time.9 When CO₂ rises and the planet warms, chemical weathering of rocks accelerates, drawing carbon dioxide out of the atmosphere and locking it into carbonate rocks such as limestone; this process slows as the planet cools, maintaining long-term stability.
Unlike Venus, Earth has plate tectonics, which continuously recycle carbon dioxide (embedded in rocks) between the crust and the atmosphere, maintaining a balance that keeps the Earth temperate and habitable.10 Both geologic processes act over millennia, but prevent the runaway greenhouse effect from taking hold on Earth.
Thus, Venus’ intense heat is not a matter of “too much CO₂,” but rather the outcome of its unique combination of pressure, chemistry, and the absence of the stabilizing mechanisms found on Earth.
William Happer and Richard Lindzen, “Comment and Declaration on the SEC’s Proposed Rule: The Enhancement and Standardization of Climate-Related Disclosures for Investors,” File No. S7-10-22, 87 Fed. Reg. 21334, April 11, 2022, https://www.sec.gov/comments/s7-10-22/s71022-20132171-302668.pdf
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