Uploaded August 2026 | Updated September 2026, 2 weeks ago
In this presentation, hydrologist Demetris Koutsoyiannis critically examines the foundations of modern climate research and asks whether some of its central assumptions are supported by observational data.
Koutsoyiannis traces influential ideas associated with Svante Arrhenius, Guy Stewart Callendar and Charles David Keeling. He argues that the enormous role of the biosphere in the global carbon cycle has historically been underestimated, while disproportionate attention has been given to human CO₂ emissions.
Drawing on his published research, he discusses:
• the natural and human components of the carbon cycle;
• the atmospheric CO₂ “hockey stick”;
• carbon isotopes and the Suess effect;
• the concept of the airborne fraction;
• atmospheric residence time and carbon mass balance;
• the reduction in human emissions during the COVID-19 period;
• causality between atmospheric temperature and CO₂;
• the respective roles of water vapour, clouds and CO₂ in the greenhouse effect.
Koutsoyiannis presents a data-based and highly critical interpretation. He argues that temperature changes precede changes in atmospheric CO₂ across multiple timescales, that natural carbon flows deserve much greater attention and that observations do not support the importance commonly attributed to CO₂ in the greenhouse effect.
The presentation is followed by an extensive question-and-answer session in which participants challenge and discuss his modelling assumptions, the distinction between natural and anthropogenic effects, regional processes and the implications for climate policy.
This lecture was recorded during the Clintel Workshop on Recent Research Developments on Atmospheric Temperature, Carbon Dioxide and Their Relationship, held at the National Technical University of Athens on 19 September 2024.
Learn more about Clintel and the World Climate Declaration:
clintel.org
Hoofdstukken
00:00 Introduction
00:41 Opening remarks
01:26 The importance of the biosphere
02:58 Inspecting the foundations of climate research
04:22 Research into temperature and CO₂
06:51 Arrhenius and the origins of climate theory
08:25 Callendar’s contribution
09:17 Keeling and atmospheric CO₂ measurements
10:44 Carbon isotopes and the Keeling plot
12:23 The airborne fraction
13:49 The biosphere in the IPCC carbon balance
15:35 Carbon isotopes and the Suess effect
18:14 Modelling the atmospheric carbon cycle
22:37 Responding to criticisms of the model
26:25 Are natural processes always a net sink?
28:43 Temperature–CO₂ causality
30:07 The COVID-19 emissions experiment
33:36 Does CO₂ follow temperature?
35:59 The importance of CO₂ in the greenhouse effect
38:41 Conclusions
40:35 Questions and discussion
In this presentation, hydrologist Demetris Koutsoyiannis critically examines the foundations of modern climate research and asks whether some of its central assumptions are supported by observational data.
Koutsoyiannis traces influential ideas associated with Svante Arrhenius, Guy Stewart Callendar and Charles David Keeling. He argues that the enormous role of the biosphere in the global carbon cycle has historically been underestimated, while disproportionate attention has been given to human CO₂ emissions.
Drawing on his published research, he discusses:
• the natural and human components of the carbon cycle;
• the atmospheric CO₂ “hockey stick”;
• carbon isotopes and the Suess effect;
• the concept of the airborne fraction;
• atmospheric residence time and carbon mass balance;
• the reduction in human emissions during the COVID-19 period;
• causality between atmospheric temperature and CO₂;
• the respective roles of water vapour, clouds and CO₂ in the greenhouse effect.
Koutsoyiannis presents a data-based and highly critical interpretation. He argues that temperature changes precede changes in atmospheric CO₂ across multiple timescales, that natural carbon flows deserve much greater attention and that observations do not support the importance commonly attributed to CO₂ in the greenhouse effect.
The presentation is followed by an extensive question-and-answer session in which participants challenge and discuss his modelling assumptions, the distinction between natural and anthropogenic effects, regional processes and the implications for climate policy.
This lecture was recorded during the Clintel Workshop on Recent Research Developments on Atmospheric Temperature, Carbon Dioxide and Their Relationship, held at the National Technical University of Athens on 19 September 2024.
Learn more about Clintel and the World Climate Declaration:
clintel.org
Hoofdstukken
00:00 Introduction
00:41 Opening remarks
01:26 The importance of the biosphere
02:58 Inspecting the foundations of climate research
04:22 Research into temperature and CO₂
06:51 Arrhenius and the origins of climate theory
08:25 Callendar’s contribution
09:17 Keeling and atmospheric CO₂ measurements
10:44 Carbon isotopes and the Keeling plot
12:23 The airborne fraction
13:49 The biosphere in the IPCC carbon balance
15:35 Carbon isotopes and the Suess effect
18:14 Modelling the atmospheric carbon cycle
22:37 Responding to criticisms of the model
26:25 Are natural processes always a net sink?
28:43 Temperature–CO₂ causality
30:07 The COVID-19 emissions experiment
33:36 Does CO₂ follow temperature?
35:59 The importance of CO₂ in the greenhouse effect
38:41 Conclusions
40:35 Questions and discussion
