Debunking Climate Myths: Why CO2 Drives Warming, Not Just Atmospheric Pressure

A recent tweet by Peter Clack promotes a standard climate denial narrative that misuses planetary science to dismiss CO2’s role in global warming. By misinterpreting the roles of atmospheric pressure and greenhouse gases on Venus and Mars, he attempts to undermine the well-established greenhouse effect on Earth.

Claim Post:
https://x.com/PeterDClack/status/1890498622472462400

Claim 1: The ‘Greenhouse Effect’ is fake.

Fact: False. The greenhouse effect is a proven process in which gases like CO2, CH4, and H2O trap heat, keeping Earth ~33°C warmer than otherwise. The greenhouse effect is fundamental to planetary climate systems. Greenhouse gases (GHGs) absorb and re-radiate infrared radiation, preventing excessive heat loss into space. Without this effect, Earth’s surface temperature would be around -18°C, making it inhospitable for life as we know it.

Decades of climate research, including NASA’s Atmospheric Infrared Sounder (AIRS) and satellite spectroscopy, have directly observed greenhouse gases trapping heat in Earth’s atmosphere. Furthermore, ice core data and paleoclimate studies confirm that CO2 concentrations have historically correlated with temperature changes. The role of greenhouse gases in climate regulation is not speculative but extensively documented through direct observations and climate models.

Claim 2: The greatest influence on planetary temperatures is known as the ideal gas law.

Fact: False. The ideal gas law explains pressure-temperature relationships but does not determine planetary temperatures. Greenhouse gases control heat retention. The ideal gas law (PV = nRT) describes how pressure, temperature, and volume interact in gases but does not account for radiative heat transfer, which is the primary driver of planetary climate. While atmospheric pressure affects temperature somewhat, it does not explain why some planets retain heat more effectively than others.

Scientific studies, such as those conducted by the Intergovernmental Panel on Climate Change (IPCC), show that greenhouse gases’ radiative forcing is responsible for long-term planetary heating. The impact of greenhouse gases has been observed on Earth and Venus, where heat-trapping CO2 plays a dominant role in increasing surface temperatures. Unlike pressure, which influences immediate gas behaviour, greenhouse gases dictate how much heat remains within an atmosphere over time.

Claim 3: Atmospheric pressure on Venus creates the stifling 465°C at the surface.

Fact: This is misleading. Venus is scorching due to its thick CO2 atmosphere, which causes a runaway greenhouse effect, not just high pressure. While Venus has a surface pressure of 92 times that of Earth, pressure alone does not account for its extreme heat. Venus’s atmosphere is 96% CO2, which traps heat efficiently and prevents it from escaping. This results in a runaway greenhouse effect, where incoming solar radiation is absorbed and re-radiated within the atmosphere, continuously heating the planet.

NASA’s Pioneer Venus and Magellan missions confirmed that Venus once had liquid water but lost it due to extreme greenhouse heating. Unlike Earth, where the carbon cycle and oceans help regulate CO2 levels, Venus’s dense CO2 atmosphere led to unchecked warming. The planet’s thick cloud layers also reflect sunlight, but the CO2 still retains immense amounts of heat, making pressure alone an insufficient explanation for its extreme temperatures.

Claim 4: A lack of pressure on Mars causes -65°C. It’s not caused by carbon dioxide.

Fact: False. Mars’ thin CO2 atmosphere provides little heat retention, but it still has a weak greenhouse effect. Cold temperatures result from low pressure, heat loss, and distance from the Sun. Mars has a 95% CO2 atmosphere, yet it remains cold because its atmosphere is thin (only 1% of Earth’s atmospheric pressure). This prevents significant heat retention. While CO2 contributes to a weak greenhouse effect, the primary reasons for Mars’ frigid climate are low atmospheric pressure, rapid heat loss, and greater distance from the Sun.

Mars also lacks substantial convective heat transfer and has minimal cloud cover to trap infrared radiation. Mars has too little atmospheric moisture to amplify CO2’s warming potential, unlike Earth, where water vapour significantly enhances the greenhouse effect. Data from the Mars Climate Sounder on the Mars Reconnaissance Orbiter indicates that seasonal CO2 ice sublimation on Mars causes minor temperature variations but does not negate the greenhouse effect’s role.

Human-Driven Greenhouse Effect: Why It Matters for Earth

The greenhouse effect is a natural and essential process that regulates Earth’s temperature. However, human activities—mainly burning fossil fuels—have dramatically increased CO2 levels from ~280 ppm (pre-industrial) to 419 ppm. This intensified greenhouse effect is raising global temperatures, melting polar ice, and increasing the frequency of extreme weather events.

Earth has a delicate carbon balance, unlike Venus or Mars, which has disrupted human activity. Industrial emissions, deforestation, and agriculture have injected excessive CO2 and methane into the atmosphere, leading to rapid warming. According to NOAA and NASA climate models, the rate of warming in the past century is unprecedented compared to natural climate variations over the past 800,000 years.

While Venus and Mars provide insights into planetary climates, misrepresenting their atmospheric conditions to deny CO2’s role in global warming is a misleading tactic used by climate change deniers. Scientific research consistently confirms that rising CO2 levels are the primary driver of modern climate change on Earth.

Peter Clack’s claims ignore basic atmospheric science and misinterpret planetary conditions to downplay the greenhouse effect. While atmospheric pressure influences temperature, greenhouse gases are the planet’s key regulators of heat retention. Using Venus and Mars as examples to deny CO2-driven warming on Earth is misleading and scientifically inaccurate.

Understanding and addressing human-caused greenhouse gas emissions is crucial to mitigating climate change and its global impacts. Extensive scientific research has demonstrated that the continued rise in greenhouse gases is directly linked to global temperature increases, polar ice loss, and sea-level rise. Without urgent intervention, Earth could face climate disruptions on a scale previously seen only in extreme geological events.

References:

https://www.europarl.europa.eu/topics/en/article/20230316STO77629/climate-change-the-greenhouse-gases-causing-global-warming#:~:text=What%20do%20greenhouses%20gases%20do,such%20as%20heatwaves%20and%20floods.

https://www.ipcc.ch/2021/08/09/ar6-wg1-20210809-pr/#:~:text=Faster%20warming,and%20how%20we%20can%20prepare.%E2%80%9D

https://www.esa.int/Science_Exploration/Space_Science/Venus_Express/Greenhouse_effects_also_on_other_planets

https://www.planetary.org/articles/what-would-it-be-like-to-stand-on-the-surface-of-venus

https://www.space.com/18527-venus-atmosphere.html

https://theconversation.com/climate-explained-why-mars-is-cold-despite-an-atmosphere-of-mostly-carbon-dioxide-126337#:~:text=The%20atmosphere%20of%20Mars%20is%20also%20rich%20in%20carbon%20dioxide,on%20Mars%20change%20a%20lot.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JE006150#:~:text=Using%20data%20from%20Mars%20Climate,(1)

https://www.epa.gov/climate-indicators/climate-change-indicators-atmospheric-concentrations-greenhouse-gases#:~:text=Carbon%20dioxide%20concentrations%20have%20increased,is%20due%20to%20human%20activities.

https://science.nasa.gov/climate-change/evidence

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