Uploaded August 2026 | Updated September 2026, 2 weeks ago
Were temperature changes responsible for atmospheric CO₂ fluctuations throughout Earth’s history? Yes, argues Gregory Wrightstone—but that does not mean temperature is the primary cause of the modern CO₂ increase.
In this presentation, Gregory Wrightstone, Executive Director of the CO₂ Coalition, presents multiple lines of evidence that the roughly 50% increase in atmospheric CO₂ since pre-industrial times has been driven primarily by human fossil-fuel emissions.
Wrightstone emphasises that this conclusion does not imply that rising CO₂ is dangerous. The CO₂ Coalition regards carbon dioxide as a highly beneficial gas that promotes photosynthesis, plant growth and global greening, while arguing that its warming effect has been greatly overstated.
The presentation, co-authored with Ferdinand Engelbeen, Renee Hannon and David Burton, examines:
• the geological origin of coal and other fossil fuels;
• temperature-driven CO₂ changes over geological timescales;
• why the modern era differs from previous climate periods;
• Antarctic ice cores as records of past atmospheric CO₂;
• uncertainties in plant-stomata reconstructions;
• problems with historical chemical CO₂ measurements;
• the carbon mass balance;
• changes in carbon-13 and carbon-14;
• declining atmospheric oxygen concentrations;
• increasing dissolved CO₂ and declining alkalinity in the oceans;
• the limited influence of modern warming on atmospheric CO₂.
Wrightstone argues that ice-core records are the most reliable evidence of past global atmospheric CO₂ levels. He concludes that modern concentrations of approximately 420 ppm are unprecedented over at least the last 800,000 years and cannot be explained by the relatively modest warming since the Little Ice Age.
He presents six lines of evidence that nature is currently a net carbon sink rather than a net source. His central argument is that cumulative human emissions are significantly larger than the measured atmospheric increase, meaning that oceans and the terrestrial biosphere are absorbing a large portion of those emissions.
The presentation is followed by a lively discussion. Demetris Koutsoyiannis disputes the interpretation of net sinks, carbon isotopes and mass balance. Peter Stallinga asks what the argument implies for the greenhouse effect, while Frans Schrijver questions the evidence derived from oxygen, ocean chemistry and the carbon-budget calculation.
Wrightstone maintains that fossil-fuel emissions are the main source of the modern CO₂ increase, while also arguing that climate sensitivity to a doubling of CO₂ is much lower than estimated by the IPCC.
Recorded during the Clintel Workshop on Recent Research Developments on Atmospheric Temperature, Carbon Dioxide and Their Relationship at the National Technical University of Athens on 19 September 2024.
This video was filmed, edited and produced by Aphroditi Katerinopoulou:
vimeo.com/user52800014
aphroditikat@yahoo.gr
Learn more about the CO₂ Coalition:
co2coalition.org
Learn more about Clintel and the World Climate Declaration:
clintel.org
Hoofdstukken
00:00 Introduction
00:38 Gregory Wrightstone joins from Florida
01:09 The central claim
01:45 Evidence to be examined
02:15 Did temperature drive CO₂ in the past?
03:19 The geological origin of fossil carbon
04:42 Why the modern period is different
05:40 Ice cores as the gold standard
06:39 CO₂ during previous interglacials
09:10 Problems with plant-stomata reconstructions
13:05 Historical chemical CO₂ measurements
15:19 Six lines of evidence
15:42 The carbon mass balance
16:52 Carbon-13 evidence
17:47 Carbon-14 and fossil fuels
19:35 Declining atmospheric oxygen
21:43 Are the oceans a net sink?
23:11 Temperature’s influence on modern CO₂
24:10 Conclusions
26:36 Questions and discussion
27:22 Demetris Koutsoyiannis disputes the evidence
29:42 Debate over the mass balance
31:12 Peter Stallinga asks about the greenhouse effect
33:34 Frans Schrijver questions the evidence
40:30 Measuring changes in ocean pH
Were temperature changes responsible for atmospheric CO₂ fluctuations throughout Earth’s history? Yes, argues Gregory Wrightstone—but that does not mean temperature is the primary cause of the modern CO₂ increase.
In this presentation, Gregory Wrightstone, Executive Director of the CO₂ Coalition, presents multiple lines of evidence that the roughly 50% increase in atmospheric CO₂ since pre-industrial times has been driven primarily by human fossil-fuel emissions.
Wrightstone emphasises that this conclusion does not imply that rising CO₂ is dangerous. The CO₂ Coalition regards carbon dioxide as a highly beneficial gas that promotes photosynthesis, plant growth and global greening, while arguing that its warming effect has been greatly overstated.
The presentation, co-authored with Ferdinand Engelbeen, Renee Hannon and David Burton, examines:
• the geological origin of coal and other fossil fuels;
• temperature-driven CO₂ changes over geological timescales;
• why the modern era differs from previous climate periods;
• Antarctic ice cores as records of past atmospheric CO₂;
• uncertainties in plant-stomata reconstructions;
• problems with historical chemical CO₂ measurements;
• the carbon mass balance;
• changes in carbon-13 and carbon-14;
• declining atmospheric oxygen concentrations;
• increasing dissolved CO₂ and declining alkalinity in the oceans;
• the limited influence of modern warming on atmospheric CO₂.
Wrightstone argues that ice-core records are the most reliable evidence of past global atmospheric CO₂ levels. He concludes that modern concentrations of approximately 420 ppm are unprecedented over at least the last 800,000 years and cannot be explained by the relatively modest warming since the Little Ice Age.
He presents six lines of evidence that nature is currently a net carbon sink rather than a net source. His central argument is that cumulative human emissions are significantly larger than the measured atmospheric increase, meaning that oceans and the terrestrial biosphere are absorbing a large portion of those emissions.
The presentation is followed by a lively discussion. Demetris Koutsoyiannis disputes the interpretation of net sinks, carbon isotopes and mass balance. Peter Stallinga asks what the argument implies for the greenhouse effect, while Frans Schrijver questions the evidence derived from oxygen, ocean chemistry and the carbon-budget calculation.
Wrightstone maintains that fossil-fuel emissions are the main source of the modern CO₂ increase, while also arguing that climate sensitivity to a doubling of CO₂ is much lower than estimated by the IPCC.
Recorded during the Clintel Workshop on Recent Research Developments on Atmospheric Temperature, Carbon Dioxide and Their Relationship at the National Technical University of Athens on 19 September 2024.
This video was filmed, edited and produced by Aphroditi Katerinopoulou:
vimeo.com/user52800014
aphroditikat@yahoo.gr
Learn more about the CO₂ Coalition:
co2coalition.org
Learn more about Clintel and the World Climate Declaration:
clintel.org
Hoofdstukken
00:00 Introduction
00:38 Gregory Wrightstone joins from Florida
01:09 The central claim
01:45 Evidence to be examined
02:15 Did temperature drive CO₂ in the past?
03:19 The geological origin of fossil carbon
04:42 Why the modern period is different
05:40 Ice cores as the gold standard
06:39 CO₂ during previous interglacials
09:10 Problems with plant-stomata reconstructions
13:05 Historical chemical CO₂ measurements
15:19 Six lines of evidence
15:42 The carbon mass balance
16:52 Carbon-13 evidence
17:47 Carbon-14 and fossil fuels
19:35 Declining atmospheric oxygen
21:43 Are the oceans a net sink?
23:11 Temperature’s influence on modern CO₂
24:10 Conclusions
26:36 Questions and discussion
27:22 Demetris Koutsoyiannis disputes the evidence
29:42 Debate over the mass balance
31:12 Peter Stallinga asks about the greenhouse effect
33:34 Frans Schrijver questions the evidence
40:30 Measuring changes in ocean pH
