Here is a study examining the entire historical length of the relationship between CO2 and earth temperature.
"This study demonstrates that changes in atmospheric CO2 concentration did not cause temperature change in the ancient climate."
Chat is not a fan:
Is the following true: A prominent 15 million-year CO2 cycle coincides closely with identified mass extinctions of the past, suggesting a pressing need for research on the relationship between CO2, biodiversity extinction, and related carbon policies. This study demonstrates that changes in atmospheric CO2 concentration did not cause temperature change in the ancient climate.
ChatGPT said:
Short answer:
No — the claim is not accurate based on current scientific understanding.
Below is a breakdown of the issues:
There is
no well-established 15-Myr CO₂ cycle recognized in the paleoclimate literature.
- Some long-term cycles (e.g., ~26–32 Myr biodiversity or extinction periodicities) have been proposed, but they are controversial.
- CO₂ reconstructions over hundreds of millions of years show long-term trends and shorter fluctuations, but not a widely accepted 15-Myr periodic cycle.
So this part is
not supported by robust evidence.
This is
also not correct:
- Mass extinctions correlate more strongly with events like large igneous province eruptions, rapid climate change, ocean anoxia, bolide impacts, and major tectonic reorganizations.
- While CO₂ is often involved (e.g., volcanism releases CO₂), extinctions do not occur on a repeating 15-Myr schedule.
- Extinctions are episodic and irregular.
Thus, this correlation is
not established.
This is
contradicted by overwhelming scientific evidence.
Well-established paleoclimate relationships show:
- CO₂ and temperature co-vary strongly over tens of millions of years.
- High-CO₂ periods correspond to warmer climates (e.g., Cretaceous, early Eocene).
- Low-CO₂ periods correspond to cooler climates and ice ages.
- Climate sensitivity estimates based on ancient climates are consistent with the modern greenhouse effect.
Even when temperature appears to lead CO₂ at certain timescales (e.g., glacial cycles), CO₂ acts as a
feedback that amplifies temperature change, and on longer geological timescales it is a
primary driver.
So the claim that CO₂ did
not drive temperature change in ancient climates is
incorrect.
Conclusion
The combined statement is
not accurate:
- No recognized 15-Myr CO₂ cycle
- No matching periodicity with mass extinctions
- CO₂ did influence ancient climate
- The implication that CO₂ is unrelated to temperature contradicts paleoclimate physics
If you want, I can also:
Review the specific study that made this claim (if you provide the citation)
Explain how CO₂–temperature relationships are reconstructed in paleoclimate
Summarize what is known about extinction drivers and carbon cycles
You said:
Here is the study: The Relationship between Atmospheric Carbon Dioxide Concentration and Global Temperature for the Last 425 Million Years
ChatGPT said:
Good question. It’s useful that you shared the paper:
The Relationship between Atmospheric Carbon Dioxide Concentration and Global Temperature for the Last 425 Million Years (Davis 2017). I reviewed what that study claims — and also how the broader paleoclimate science community sees CO₂–temperature links. The short answer: the paper does make exactly those claims — but its conclusions are
highly contested, and
do not reflect the consensus. Here’s a breakdown
What the Davis (2017) paper claims
- The study assembles datasets of proxy-derived CO₂ concentrations and temperature proxies (δ¹⁸O-based) over the Phanerozoic (last ~425 My). MDPI+1
- It reports that over most of this long timeline, CO₂ concentration and temperature proxies are weakly or negatively correlated — often non-significantly. MDPI+2MDPI+2
- Based on that, the paper concludes that “atmospheric CO₂ … did not drive the ancient climate.” MDPI+1
- The authors also claim a ~15–20 Myr cycle in CO₂ (plus a longer ~60–70 Myr cycle), and suggest that peaks in CO₂ coincide with known mass-extinction events — which they argue merits “urgent research” into CO₂ → extinction links. MDPI+1
- They argue that at very high CO₂ (as in deep geological time), the “marginal radiative forcing” of additional CO₂ would be small (saturation), so large CO₂ swings may have little effect on global temperature. MDPI+1
Thus — the paper is indeed the source of the statements you asked about: a 15-Myr cycle, a claimed decoupling between CO₂ and temperature over deep time, and a skeptical interpretation of CO₂’s role in ancient warming.
Why many scientists and subsequent studies
While Davis (2017) presents its argument,
its interpretation is controversial and has been challenged. Some of the more important considerations:
- Proxy uncertainties & resolution: The δ¹⁸O proxy used for temperature has many confounding factors (ice volume, salinity, ocean chemistry, diagenesis). These can muddy the signal, especially over hundreds of millions of years. Davis acknowledges data resolution is low in many intervals. MDPI+1
- Other proxy methods suggest different results: For example, a landmark study using a different proxy approach (clumped isotopes in fossil shells) from the Palaeozoic — Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era (Came et al., 2007) — found that tropical sea-surface temperatures oscillated in concert with CO₂ and glacial-warm cycles, supporting CO₂’s role in climate over long time scales. Nature+1
- More recent modeling–data fusion studies find a substantial climate sensitivity over long timescales: For instance, A tighter constraint on Earth-system sensitivity from long-term temperature and carbon-cycle observations (Wong, Royer, et al., 2019) combines CO₂ and temperature data over 420 Myr with carbon-cycle modeling, deriving a median Earth-system sensitivity of ~3.4 °C for CO₂ doubling. arXiv
- Complex, multi-faceted climate system: Over geological times, many factors influence climate — solar luminosity, continental configurations, albedo (ice, vegetation), other greenhouse gases (methane, water vapor), ocean circulation, tectonics, chemical weathering. These can modulate, amplify or mask CO₂’s effect in ways that simple correlation analyses may miss. That complexity means a lack of correlation in a raw data comparison doesn’t automatically “prove absence of causation.”
- Time-scale and climate state dependence: Some studies — including CO2 and temperature decoupling at the million-year scale during the Cretaceous Greenhouse — suggest that during certain “greenhouse” climate states, CO₂ and temperature may decouple at Myr scales, even if on shorter scales (kyr–century) CO₂ remains critical. Nature
So: The paper exists — but it’s
The mainstream view remains that CO₂ has — and has had — a major influence on Earth’s temperature over geological and modern times. The dissent represented by Davis (2017) is
not a consensus. Indeed, many subsequent and independent studies support a strong long-term relationship between CO₂ and global temperature.
PubMed+3Nature+3Nature+3
What this means for interpreting the claim
- Yes — the statements you quoted correctly reflect what Davis (2017) claims.
- But no — you should not treat those claims as conclusive evidence that CO₂ is unimportant to climate, or that CO₂ changes never drove past temperature or extinction events.
- Rather — the paper is best seen as a provocative, but contested, contribution that highlights uncertainties in deep-time proxy data and calls for more research — not a refutation of the greenhouse-gas theory of climate change.
If you like, I can pull up
5–10 of the most influential recent studies (last ~5–10 years) that support a strong CO₂–temperature coupling over deep time — that way you can see the “state of the art.” Do you want me to build that “pro-CO₂ linkage” reading list now?
retractionwatch.com
The mods wind up deleting the threads. And you don’t understand how tariffs work anyway and I don’t want to explain it to you again. As for your concern, it’s not good news for your fav American Girl dolls. Do not feel bad that a doll news site saw the price increases from tariffs coming and you did not. 
Summary
