Uploaded August 2026 | Updated September 2026, 2 weeks ago
What is the difference between the residence time of an individual CO₂ molecule and the time required to remove an excess amount of CO₂ from the atmosphere?
In this presentation, Belgian chemical engineer Ferdinand Engelbeen addresses what he considers persistent misunderstandings about atmospheric CO₂, carbon mass balance and residence time. In contrast to several other speakers at the workshop, Engelbeen argues that human emissions are responsible for the long-term increase in atmospheric CO₂.
He distinguishes between three different concepts:
• a turnover or molecular residence time of approximately four years;
• a mass-based adjustment time of approximately 50 years;
• modelled atmospheric lifetimes of more than 100 years.
Engelbeen argues that the rapid exchange of individual CO₂ molecules between the atmosphere, oceans and biosphere does not imply an equally rapid removal of an atmospheric CO₂ surplus. According to his analysis, the natural carbon cycle is currently a net sink, absorbing roughly half of human emissions.
He also discusses:
• the relationship between cumulative human emissions and atmospheric CO₂;
• the influence of temperature on short-term CO₂ variability;
• why temperature cannot, in his view, explain the long-term trend;
• Antarctic ice-core records and their temporal resolution;
• carbon mass balance and the COVID-19 reduction in emissions;
• the distinction between temperature and its rate of change;
• one-way, two-way and multidirectional carbon flows;
• carbon-13, carbon-14 and atmospheric oxygen as tracers;
• CO₂ uptake by the oceans and observed changes in ocean chemistry.
Engelbeen concludes that temperature changes explain much of the short-term variability around the trend, but that cumulative human emissions explain the sustained rise in atmospheric CO₂.
The lecture is followed by a particularly lively scientific discussion. Demetris Koutsoyiannis, Hermann Harde, Frans Schrijver and other participants challenge Engelbeen’s treatment of mass balance, residence time, bidirectional carbon flows and the interpretation of observational data.
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 Clintel and the World Climate Declaration:
clintel.org
Hoofdstukken
00:00 Introduction
00:41 Ferdinand Engelbeen and his background
02:14 Why he began studying climate and CO₂
02:56 The CO₂ residence-time confusion
04:53 Human emissions versus temperature
06:23 What ice cores tell us
09:04 The temperature–CO₂ relationship
10:44 Temperature and oceanic CO₂
12:03 Emissions compared with the observed CO₂ rise
13:15 Are humans the cause of the long-term increase?
13:35 Temperature, emissions and the COVID period
15:26 Testing the carbon mass balance
18:12 Temperature versus its rate of change
20:27 Integrating temperature changes
21:19 Turnover time versus adjustment time
22:59 One-way and two-way processes
26:01 The multidirectional carbon cycle
27:10 An observed adjustment time of about 50 years
29:08 Checking the mass balance
30:29 Problems with CO₂ measurements over land
31:50 Carbon isotopes and other tracers
35:15 Conclusions
36:13 Questions and scientific discussion
37:42 Exchange with Demetris Koutsoyiannis
40:05 Questions about linear models and residence time
42:15 Response from Hermann Harde
43:11 Ocean uptake and acidification
44:43 Final discussion with Frans Schrijver
What is the difference between the residence time of an individual CO₂ molecule and the time required to remove an excess amount of CO₂ from the atmosphere?
In this presentation, Belgian chemical engineer Ferdinand Engelbeen addresses what he considers persistent misunderstandings about atmospheric CO₂, carbon mass balance and residence time. In contrast to several other speakers at the workshop, Engelbeen argues that human emissions are responsible for the long-term increase in atmospheric CO₂.
He distinguishes between three different concepts:
• a turnover or molecular residence time of approximately four years;
• a mass-based adjustment time of approximately 50 years;
• modelled atmospheric lifetimes of more than 100 years.
Engelbeen argues that the rapid exchange of individual CO₂ molecules between the atmosphere, oceans and biosphere does not imply an equally rapid removal of an atmospheric CO₂ surplus. According to his analysis, the natural carbon cycle is currently a net sink, absorbing roughly half of human emissions.
He also discusses:
• the relationship between cumulative human emissions and atmospheric CO₂;
• the influence of temperature on short-term CO₂ variability;
• why temperature cannot, in his view, explain the long-term trend;
• Antarctic ice-core records and their temporal resolution;
• carbon mass balance and the COVID-19 reduction in emissions;
• the distinction between temperature and its rate of change;
• one-way, two-way and multidirectional carbon flows;
• carbon-13, carbon-14 and atmospheric oxygen as tracers;
• CO₂ uptake by the oceans and observed changes in ocean chemistry.
Engelbeen concludes that temperature changes explain much of the short-term variability around the trend, but that cumulative human emissions explain the sustained rise in atmospheric CO₂.
The lecture is followed by a particularly lively scientific discussion. Demetris Koutsoyiannis, Hermann Harde, Frans Schrijver and other participants challenge Engelbeen’s treatment of mass balance, residence time, bidirectional carbon flows and the interpretation of observational data.
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 Clintel and the World Climate Declaration:
clintel.org
Hoofdstukken
00:00 Introduction
00:41 Ferdinand Engelbeen and his background
02:14 Why he began studying climate and CO₂
02:56 The CO₂ residence-time confusion
04:53 Human emissions versus temperature
06:23 What ice cores tell us
09:04 The temperature–CO₂ relationship
10:44 Temperature and oceanic CO₂
12:03 Emissions compared with the observed CO₂ rise
13:15 Are humans the cause of the long-term increase?
13:35 Temperature, emissions and the COVID period
15:26 Testing the carbon mass balance
18:12 Temperature versus its rate of change
20:27 Integrating temperature changes
21:19 Turnover time versus adjustment time
22:59 One-way and two-way processes
26:01 The multidirectional carbon cycle
27:10 An observed adjustment time of about 50 years
29:08 Checking the mass balance
30:29 Problems with CO₂ measurements over land
31:50 Carbon isotopes and other tracers
35:15 Conclusions
36:13 Questions and scientific discussion
37:42 Exchange with Demetris Koutsoyiannis
40:05 Questions about linear models and residence time
42:15 Response from Hermann Harde
43:11 Ocean uptake and acidification
44:43 Final discussion with Frans Schrijver
