The Global Carbon Cycle and Climate Change: Scaling Ecological Energetics from Organism to the Biosphere

By David E. Reichle

The Global Carbon Cycle and Climate Change: Scaling Ecological Energetics from Organism to the Biosphere, Second Edition examines the global carbon cycle and energy balance of the biosphere, following carbon and energy through increasingly complex levels of metabolism—from cells to ecosystems. Utilizing scientific explanations, analyses of ecosystem functions, extensive references, and cutting-edge examples of energy flow in ecosystems, this is an essential resource to aid in understanding the scientific basis of the role of ecological systems in climate change. Includes new chapters on dynamic properties of the global carbon cycle, climate models and projections, and managing carbon in the global biogeochemical cycle.

• Addresses the scientific principles governing carbon fluxes at successive hierarchical levels of organization, from cells to the biosphere
• Illustrates - through data and diagrams - the complex processes by which carbon moves in the global biogeochemical cycle
• Provides new information on tipping points for climate change and why there are climate deniers

• Language: English
• Publisher: Elsevier Science
• Release date: Feb 28, 2023
• ISBN: 9780443187742

David E. Reichle

David E. Reichle was the Associate Laboratory Director at the Oak Ridge National Laboratory for Environmental, Life, and Social Sciences, and the former director of its Environmental Sciences Division. He was also adjunct Professor of Ecology at the University of Tennessee. He has authored over 100 scientific articles on radionuclides in the environment and the metabolism of ecosystems, edited 4 books on productivity and carbon metabolism of ecosystems, and led development of several seminal government reports on greenhouse gas reduction technologies and carbon sequestration. He has served on many scientific advisory boards for the Department of Energy, the National Science Foundation, the Environmental Protection Agency, the National Academy of Sciences, and other academic institutions and business organizations. He is a Fellow of the American Association for the Advancement of Science and a recipient of a Scientific Achievement Award from the International Union of Forest Research Organizations, a Distinguished Service Award from the U.S. Department of Energy, and a Muskingum University Distinguished Alumni Service Award. He also served on the national board of Governors of The Nature Conservancy, and as Chairman of TNC’s Tennessee state chapter.

Book preview

The Global Carbon Cycle and Climate Change

Scaling Ecological Energetics from Organism to the Biosphere

Second Edition

David E. Reichle

Associate Director, retired Oak Ridge National Laboratory

Table of Contents

Cover image

Title page

Copyright

Author biography

Foreword of first edition

Foreword of second edition

Acknowledgments

Timeline of major international programs about the Earth's biosphere and climate

Chapter 1. An introduction to ecological energetics and the global carbon cycle

Timeline of the physical and chemical bases of energy

Chapter 2. The physical and chemical bases of energy

2.1. Energy, work, and power

2.2. The different forms of energy

2.3. The Laws of Thermodynamics

2.4. Gaia hypothesis

2.5. Carbon and energy

Timeline of major developments in the field of energy exchange between organisms and the environment

Chapter 3. Energy relationships between organisms and their environment

3.1. Energy balance

3.2. Functional interrelationships affecting leaf temperature

3.3. Solar

3.4. Thermal energy

3.5. Energy balance of a leaf

3.6. Radiative energy balance of a forest

3.7. Energy exchange of animals

Timeline of major developments in the field of biological energy transformations by plants

Chapter 4. Biological energy transformations by plants

4.1. Solar radiation

4.2. Photosynthesis

4.3. Strategies for coping with environmental constraints

4.4. Energy conversion efficiencies

Timeline of major developments in the field of energy processing by animals

Chapter 5. Energy processing by animals

5.1. Metabolism

5.2. Free energy

5.3. Respiration

5.4. Energy value of foods

5.5. Digestion and assimilation

5.6. Respiration rates

5.7. Energy costs of digestion

5.8. Food energy budget for an individual

5.9. Why pork is cheaper than beef and chicken costs least of all

Timeline of major developments in the field of species adaptations to their environment

Chapter 6. Species adaptations to their energy environment

6.1. The limits of survival

6.2. Adaptation to the energy environment

6.3. How do plants measure their radiative environment and gauge temperature?

6.4. Phenological relationships

6.5. Extreme environments

Timeline of major developments in the field of food chain and trophic level transfers

Chapter 7. Food chains and trophic level transfers

7.1. Food chains

7.2. Population dynamics and food chains

7.3. Food webs

7.4. Trophic levels

7.5. Trophic level efficiencies

7.6. Trophic structure of different ecosystems

Timeline of major developments in the field of energy flow in ecosystems

Chapter 8. Energy flow in ecosystems

8.1. Ecosystem energetics

8.2. Ecosystem production equations

8.3. Measurement of pools and fluxes

8.4. The carbon cycle in ecosystems

8.5. Comparison of carbon metabolism among ecosystems

8.6. Net ecosystem production and net ecosystem exchange

8.7. Emergent properties of ecosystems

Timeline of developments in the field of ecosystem productivity

Chapter 9. Ecosystem productivity

9.1. Terrestrial ecosystems

9.2. Freshwater ecosystems

9.3. Marine ecosystems

9.4. Secondary production

9.5. Global biome-scale production

9.6. Remote sensing of productivity

9.7. Factors affecting global productivity

9.8. Scaling from stand to the planetary boundary layer

Timeline of developments in the field of the global carbon cycle

Chapter 10. The global carbon cycle and the biosphere

10.1. The components of the global carbon cycle

10.2. Units of measure for the global scale

10.3. Calculating turnover times

10.4. History of carbon dioxide in the atmosphere

10.5. The atmosphere in the carbon cycle

10.6. The terrestrial carbon cycle

10.7. The ocean carbon cycle

10.8. Models of carbon in the biosphere

Timeline of anthropogenic alterations to the global carbon cycle

Chapter 11. Anthropogenic alterations to the global carbon cycle and climate change

11.1. Changing atmospheric concentrations of CO2

11.2. The greenhouse effect

11.3. Climate change

11.4. The elements of weather and climate

11.5. Greenhouse gases

11.6. Anthropogenic contributions to atmospheric CO2

11.7. Where in the world are the CO2 emissions being generated?

11.8. Model projections of the future carbon cycle

Timeline of properties of the global carbon cycle

Chapter 12. Dynamic properties of the global carbon cycle

12.1. The complexities of nonlinear systems

12.2. Atmosphere

12.3. Terrestrial processes

12.4. Ocean processes

12.5. Feedbacks in the carbon cycle

12.6. Tipping points in the carbon cycle and climate system

12.7. Isotopic techniques used to measure dynamics

Timeline of major developments in the development of climate models

Chapter 13. Climate and climate models

13.1. Modeling climate

13.2. Climate models, data, and projections

13.3. Value of climate models to decision makers

13.4. Climate model uncertainties and confidence in predictions

13.5. Carbon cycle model projections of future atmospheres

13.6. Indicators of climate change

13.7. Climate model projections of the effects of climate change

13.8. Climate change risk assessment – The effects of climate change

13.9. Climate change and extreme weather-Effects if climate change

Timeline of managing carbon in the global biogeochemical cycle

Chapter 14. Managing carbon in the global biogeochemical cycle

14.1. Decarbonization of the energy system

14.2. Management of greenhouse gas emissions through natural pathways

14.3. Mitigation and adaptation

14.4. Geoengineering

Timeline of major developments in the field of carbon, climate change, and public policy

Chapter 15. Carbon, climate change, and public policy

15.1. What are the potential consequences of inaction?

15.2. Do we know enough?

15.3. International accords

15.4. The economics of clean energy

15.5. What has been the impedance?

15.6. Better communicating science

15.7. Is it too late to act?

Bibliography

Subject Index

Author Index

Copyright

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Author biography

David E. Reichle was the Associate Laboratory Director of the Oak Ridge National Laboratory for Environmental, Life, and Social Sciences, and the former Director of its Environmental Sciences Division. He was also an Adjunct Professor of Ecology at the University of Tennessee. He has authored over 100 scientific articles on radionuclides in the environment and the metabolism of ecosystems, edited 4 books on productivity and carbon metabolism of ecosystems, and led development of several seminal government reports on greenhouse gas reduction technologies and carbon sequestration. He has served on many scientific advisory boards for the Department of Energy, the National Science Foundation, the Environmental Protection Agency, the National Academy of Sciences, and other academic institutions and business organizations. He is a fellow of the American Association for the Advancement of Science and recipient of the Scientific Achievement Award from the International Union of Forest Research Organizations, a Distinguished Service Award from the U.S. Department of Energy, and the Muskingum University Distinguished Alumni Service Award. He also served on the national board of governors of The Nature Conservancy and as Chairman of TNC's Tennessee state chapter.

Foreword of first edition

Bioenergetics has long been a subject of research in animal husbandry and ecological research, where it served as an organizing principle in early ecosystem research (Odum, 1959). The metabolism of ecosystems and ecological energetics are subject areas that I always found to be fascinating, and ones that were researched intensely at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee. I was recruited to ORNL as a new PhD from Northwestern University in 1964 to study the behavior of radionuclides in food chains uptake, bioaccumulation, and potential pathways leading to human exposure. My postdoctoral fellowship was sponsored by what was then the US Atomic Energy Commission (now the US Department of Energy). One of the little-known facts in the history of American science is that the AEC was the first significant sponsor of modern ecological research in the United States, this role only several decades later being assumed by the National Science Foundation (Egerton, 2017). The Manhattan Project's 1943 Clinton Laboratories, managed by the University of Chicago's Metallurgical Laboratory, was the predecessor of ORNL; Union Carbide Corporation assumed responsibilities in 1947. By the time that I had arrived, World War II was over and research had shifted to the peaceful uses of atomic energy. My job title was biophysicist in the Radiation Ecology Section of the Health Physics Division; the Section was later to become the internationally renowned Ecological Sciences Division at ORNL (Auerbach, 1993). Our research team's scope quickly grew from examining the fate and effects of radionuclides in food chains leading to humans to study the natural biogeochemical cycles that governed the movement of radionuclides in the environment, all of which were ultimately regulated by the metabolism of ecosystems.

Few in the scientific community, much less in the general public, knew what ecology was when the US Atomic Energy Commission began its ecological research programs in the early 1950s (Reichle and Auerbach, 2003). These programs, which antedated major support for ecosystem research by the National Science Foundation by several decades, were the foundation for modern ecosystem research in the United States (Coleman, 2010). Since ecologists at ORNL had been researching ecosystem carbon metabolism, we became the US R&D center for forest ecology and ecosystem modeling when US participation (1964–74) began in the International Biological Program (Smith, 1968; NAS, 2019). International collaboration continued for many years thereafter, and results of research on the deciduous forest biome culminated with publication of Dynamic Properties of Forest Ecosystems (Reichle, 1981). This research experience was an important reason why the AEC's successor, the Energy Research and Development Administration, and later the US Department of Energy (DOE), became a leading US agency studying the global carbon cycle.

In May 2022, the US National Oceanographic and Atmospheric Administration (NOAA) announced that the atmospheric CO2 level at the Mauna Loa Observatory had peaked at 421 ppm – a further increase of 1.8 ppm over the previous year. Prior to the Industrial Revolution, CO2 levels were consistently around 280 ppm for almost 6000 years of human civilization. Since then, humans have generated an estimated 1.5 trillion tons of CO2 pollution offsite, much of which will continue to warm the atmosphere for thousands of years. Atmospheric CO2 levels are now comparable to the Pliocene Climatic Optimum, between 4.1 and 4.5 million years ago, when they were close to, or above 400 ppm. During that time, sea levels were between 5 and 25 meters higher than they are today. NOAA Administrator, Richard Spinrad states that, The evidence is irrefutable: humans are altering our climate … we need to take urgent, serious steps to become a more Climate Ready Nation.

The mission of DOE and its national laboratories was to promote the safe development of all energy technologies. Both the scientific experience gained from studying the carbon metabolism of ecosystems (Reichle and Auerbach, 1972) and the development of climate models to follow global fallout from weapons testing and the concern about a nuclear winter from nuclear weapons deployment, the national laboratories became early leaders in climate change research. The scientific experience gained in early environmental studies of the nuclear industry came full circle in the 1980s to examine the environmental consequences of a fossil fuel–based energy economy.

Ecological energetics is the study of the metabolism of plants, animals, microbes, and ecosystems. Knowledge about the functioning of ecological systems is necessary for our understanding of the metabolism of the biosphere, essential in addressing human-induced climate change, and quite possibly critical to protecting our global environment. This book is the product of a course in ecological energetics that I offered in the early 1970s in the then Graduate Program in Ecology at the University of Tennessee. I had intended the syllabus to be the basis for a textbook in bioenergetics, but somehow never found the time to write the book. Now 45 years later in retirement, I have the time, the field of ecology has matured, and bioenergetics, while an interesting chapter in basic ecology texts of the 1950–70s, has now assumed new societal relevance. Ecological energetics is the foundation for both understanding the metabolism of the biosphere and also the basis for addressing the potential future environmental impacts of climate change.

This book is a journey in time, scale, and complexity. It will be a journey following the flux of solar energy from the sun and carbon from the atmosphere, through the living systems on the earth. It will be a journey in scale from milligrams to gigatons, from seconds to years, from square centimeters to hectares, and from the cell to the biosphere. This journey has rules which will govern our passage for the principles of thermodynamics, biochemistry, physiology, and ecology. Let us begin.

In 2007, the IPCC and U.S. Vice-President Al Gore were jointly awarded the Nobel Peace Prize for their efforts to build up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change. Now the world meteorological community and the international science community have welcomed the awarding of the 2021 Nobel Prize in Physics to pioneering climate scientists who laid the foundations for our understanding of the role of human activities and greenhouse gases in climate change. The award is especially timely as it came on the eve of decisive UN Climate Change negotiations, COP26. The Royal Swedish Academy of Sciences cited American-Japanese Prof. Syukuro Manabe (Princeton University, Princeton, NJ, USA) and the German Prof. Klaus Hasselmann (Max Planck Institute for Meteorology, Hamburg, Germany), for the physical modelling of Earth's climate, quantifying variability and reliably predicting global warming.

Suggested reading

Archer D. The Global Carbon Cycle. Princeton: Princeton Univ. Press; 2010 pp. 216. https://press.princeton.edu/books/ebook/9781400837076/the-global-carbon-cycle/.

Coleman D.C. Big Ecology: The Emergence of Ecosystem Science. Berkeley-Los Angeles-London: University of California Press; 2010:236. https://epdf.pub/big-ecology-the-emergence-of-ecosystem-science.html.

Egerton F.N. History of Ecological Sciences, Part 59: Niches, Biomes, Ecosystems, and Systems. 2017. https://www.researchgate.net/publication/320227603_History_of_Ecological_Sciences_Part_59_Niches_Biomes_Ecosystems_and_Systems/.

Odum E.P. Fundamentals of Ecology, second ed. Philadelphia and London: W. B. Sanders Co.; 1959:546.

Reichle D.E, Auerbach S.I. U.S. Radioecological Research Programs of the Atomic Energy Commission in the 1950s. Oak Ridge, TN: ORNL/TM-2003/280. Oak Ridge National Laboratory; 2003. http://www.osti.gov/bridge/.

Smith F.E. The international biological program and the science of ecology. Proc. Nat. Acad. Sci. USA. 1968;60(1):5–11. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC539127/.

Foreword of second edition

As a result of the very positive response to The Global Carbon Cycle and Climate Change and the many scientific advances following its publication, I have updated the First Edition's text with new citations to the scientific literature, including developments following the new 2021 IPCC report by the IPCC (Intergovernmental Panel on Climate Change) and outcomes subsequent to the UN 2020 Conference of Parties (COP26).

For those who expressed interest in learning more about the development of knowledge on the global carbon cycle and climate change, historical timelines have been added preceding the subject matter in each chapter.

There is expanded discussion on feedbacks in the global carbon cycle, and new information is included on carbon cycle tipping points, I have also added information on the status of carbon cycle and climate models and their value to decision-makers.

A more detailed explanation of the chemistry of the ocean carbon cycle is provided. A new chapter introduces the management of greenhouse gas emissions along natural pathways and new geoengineering proposals, including increasing awareness of the increasing importance of methane as a greenhouse gas in climate change.

I have endeavored to make this text a resource for the advanced student, researcher, policy-maker, and all parties wishing to expand their understanding of the global carbon cycle. I hope that you share my fascination with this topic of major importance to humanity's ongoing challenge to address climate change.

David E. Reichle

Fripp Island, South Carolina

June 2022

Acknowledgments

My career in ecology has been stimulated by a large number of individuals: my graduate school professor, Orlando Park of Northwestern University, one of the authors of The Great Apes, Alee, Emerson Park, Park, and Schmidt's Principles of Animal Ecology (1949), one of the first and perhaps best ecology texts from the Chicago School of ecology; Stanley Auerbach, founder of the Ecological Sciences Division (ESD) at the Oak Ridge National Laboratory (ORNL), and mentors and colleagues in ESD: Dac Crossley, Jerry Olson, George Van Dyne, and Frank Harris; early leaders in ecological energetics: Howard Odum, Gene Odum, GeorgeWoodwell, Bob Whittaker, Dick Wiegert, David Gates, and Jerry Franklin; European ecologists John Phillipson, Amian Macfadyen, John Satchel, Kasimierz Petrusewicz, Lech Ryszkowski, Paul Duvigneaud, and Helmut Lieth influenced me profoundly, both personally and through their seminal publications. The book has its origin in a course in ecological energetics that I offered in the Graduate Program in Ecology at the University of Tennessee, decades of research at ORNL, and has been nurtured through the encouragement and patience of my wife, Donna. Brenda Wyatt provided invaluable technical records assistance, Deborah Reichle for editorial assistance with computer files, and I am grateful to ORNL for providing access to IT library resources.

Timeline of major international programs about the Earth's biosphere and climate

Timeline of major international programs

Chapter 1: An introduction to ecological energetics and the global carbon cycle

Abstract

The study of ecological systems utilizes bioenergetics to understand the functioning of entire ecosystems. Energy is essential for life on Earth. An organism with a positive energy balance is a successful organism in nature. Organisms and ecosystems have, consequently, evolved as highly efficient thermodynamic systems. Bioenergetics deals with the energy requirements and the processing of energy by organisms. Since biologically utilized energy is the energy stored in carbon molecules, ecosystem metabolism necessarily deals with the carbon balance of the entire ecosystem. Ecosystem carbon balances for different types of ecosystems form the basis for global carbon balance calculations.

Keywords

Bioenergetics; Carbon balance; Carbon chemistry; Carbon cycle; Carbon cycle models; Climate change; Ecological energetics; Ecosystem metabolism; Greenhouse effect

Carbon (C) is found in all living things in the biosphere, in soils and rocks of the geosphere, in the ocean (hydrosphere), and in the atmosphere. The cycle of atoms between living and non-living things in the Earth’s crust (lithosphere) is referred to as a biogeochemical cycle. All elements which are the constituents of living organisms have biogeochemical cycles. Carbon is the primary building block of life, and is the primary component of DNA, proteins, sugars and fats. The quantities of elements involved globally are huge, being expressed as giga tons (Gt) or 10⁹grams of the element. Much of the C on Earth is located in the geosphere, where it is a major component of limestone (CaCO3), coal (C137H97O9NS), oil (C8H18) and gas (CH4), collectively exceeding 6.5 x10⁹ Gt of carbon (Esser,1993). Inorganic carbon in the oceans amounts to 3.8 x 10¹⁰Gt. The most abundant C compound in the atmosphere is carbon dioxide (CO2) at 7.2 x 10¹¹ Gt. Carbon in the biomass (CH1.44O0.66) of the biosphere is 6.13 x 10² Gt, and is a critical link in the biogeochemical cycle of carbon. The biosphere is a major factor governing the fluxes between the atmosphere and the land and ocean. Carbon cycles through the atmosphere, biosphere, geosphere, and hydrosphere via processes that include photosynthesis, fire, the burning of fossil fuels, weathering and volcanism. The most important source of CO2 resulting from human activities are the emissions of CO2. In order to understand how human activities have altered the carbon cycle, we must understand the many changes in the climate, ecosystems and the C biogeochemical cycle that are occurring today, and why these rapid rates of change are mostly unprecedented in Earth’s history. Carbon forms the structural framework of compounds which contain the chemical energy which supports biological processes on Earth.

Energy is essential for life on Earth. An organism with a positive energy balance is generally a successful organism in nature. Organisms and ecosystems have, consequently, evolved as highly efficient thermodynamic systems. Bioenergetics deals with the energy requirements and the processing of energy by organisms. The term is most often used in reference to animals, but also applies to plants. Plants have evolved the unique photosynthetic process, using sunlight to split water molecules and manufacture organic carbon molecules from atmospheric CO2, thus converting radiant energy into chemical energy to support their metabolic requirements. In animal systems, bioenergetics encompasses the procurement of the chemical energy in food, the digestion of food, subsequent metabolism, and the eventual energy expenditures required for living and reproducing. Bioenergetics involves, therefore, many aspects of the organism's physiology, thermal relationships, and behavior, and becomes very complex and complicated to quantify. Bioenergetics has become a very sophisticated tool in animal husbandry, for it deals with the efficiency by which animal protein can be produced economically. By the 1960s, bioenergetics as applied to free-living animals had bifurcated into two fields of study, one approach emphasizing behavioral biology where the animal's activity patterns were studied in relation to its energy balance with its environment, and another physiological approach dealing with the metabolism of the free-living organism. In actuality, both these approaches are necessary to understand the thermodynamics of organisms in nature (Reichle et al., 1975).

The Earth’s carbon cycle regulates the concentration of oxygen and carbon dioxide in the atmosphere and oceans, and is essential in producing and maintaining a habitable planet. The carbon cycle operates on several different levels. In the biogeochemical processes at Earth’s surface, the shallow carbon cycle, there are about 45000 gigatons (Gt = 10¹⁵ g) of carbon in the atmosphere, oceans, and terrestrial biosphere (Tables 10.4 and 10.7). Large as this quantity is, it only amounts to a fraction of one percent of Earth's total carbon. The remaining carbon is in the deep carbon cycle, the geochemical movement of carbon through the Earth's mantle and core. Over 90% of this carbon may reside in the core, most of the rest being in the crust and mantle. It forms part of the Earth’s carbon cycle and is intimately connected to the movement of carbon in the Earth's surface and atmosphere. The deep carbon cycle operates on a geological time scale of millions of years and is strongly influenced by subduction of sedimentary material into the mantle. The composition of this sedimentary subduction flux has changed considerably over the Earth’s history. On a planetary scale, the process of subduction mediates the transfer of surface material, including carbon, into Earth’s mantle. Major changes in the physical, chemical, and biological conditions at Earth’s surface may thus be expected to exert a profound influence on the planet’s interior (Giuliani et al., 2022), and temporal variations in the carbon content or isotopic composition of the mantle can be used to track changes in Earth’s surface carbon cycle.

By the 1970s, the growing field of ecology began to utilize bioenergetics to understand the functioning of entire ecosystems. Thus, the study of ecological, or ecosystem, energetics developed. Ecosystem energetics addresses the energy balance of the entire ecosystem and all its trophic levels. It consists of the ecosystem's metabolism—its primary productivity, trophic level exchanges, turnover and decomposition of detritus, growth, and reproduction. Since biologically utilized energy is the energy stored in carbon molecules, ecosystem metabolism necessarily deals with the carbon balance of the entire ecosystem (Lindeman, 1942; Odum, 1957; Smalley, 1960; Teal, 1962; Macfadyen, 1964; Phillipson, 1966; Woodwell and Botkin, 1970; Reichle et al., 1973). Besides plant photosynthesis and trophic level energetics, understanding the carbon metabolism of the entire ecosystem, above and below ground, includes death and decomposition to complete the ecosystem's carbon balance (net ecosystem production) with the environment. This academically intriguing subject suddenly took on tremendous societal relevance beginning in the 1980s, with the growing concern over the combustion of fossil fuels and the resulting CO2 emissions to the atmosphere, leading to the greenhouse effect and global warming.

In this text we focus upon the shallow carbon cycle, herein described as the global carbon cycle, which has been altered over the past few centuries by the anthropogenic releases of carbon that have altered atmosphere CO2 levels. What did we know about the global cycle of carbon? And, when did we know it (Rich, 2018)?

While recent decades have seen growing concern over the climatic consequences of anthropogenic CO2 emissions to the atmosphere, serious scientific concern began with a series of publications by Revelle and Suess (1957), Charles Keeling in the 1970s and Keeling et al. (1982) of rising atmospheric CO2 levels, George Woodwell's 1972 symposium on Carbon and the Biosphere, and Takahashi and Broecker's (1977) publication on the fate of fossil fuel CO2 in the ocean. The summary of the global carbon cycle by Bolin et al. (1979) for the Scientific Committee on Problems of the Environment, established by the International Council of Scientific Unions, was a landmark assessment of the sources, sinks and interactions of carbon among the global carbon pools. In the early 1980s, the U.S. Department of Energy (DOE) as the then lead federal agency for the study of CO2, established the Carbon Dioxide Research Division in the Office of Basic Energy Sciences (Reichle et al., 1985; Trabalka, 1985; Trabalka and Reichle, 1985, 1986). The Environmental Sciences Division at the Oak Ridge National Laboratory served as the manager for DOE's extra-mural research program, summarizing as early as 1985 estimates of values and uncertainties for 28 key parameters in the global carbon cycle (Solomon at al., 1985) and publishing as early as 1986 projections of atmospheric CO2 levels using globally averaged carbon cycle models (Trabalka et al., 1986).

Ecosystem carbon balances for different types of ecosystems, when used with the geographic distribution of ecosystem types, or biomes, formed the basis for early global carbon balance calculations (Craig, 1957; Revelle and Suess, 1957; Bolin, 1970). As the modeling of ecosystem bioenergetics advanced, it became possible to construct dynamic global carbon models of the biosphere, which were functionally based and could, consequently, permit questions to be asked about the biosphere's response to changing atmospheric CO2 levels or rising temperatures or changing land use cover or feedback loops such as oxidation of Arctic tundra, glacial melting, and ocean outgassing (Trabalka, 1985; Trabalka and Reichle, 1986). These questions remain very pertinent and central to the debate today on the consequences of climate change.

Recognizing the spatial and temporal scale in the global carbon cycle is essential to understanding its reciprocal interactions with climate. As eloquently summarized by Govind and Kumari (2014):

The terrestrial carbon cycle has a great role in influencing the climate with complex interactions that are spatially and temporally variable and scale-related. Hence, it is essential that we fully understand the scale-specific complexities of the terrestrial C-cycle toward (1) strategic design of monitoring and experimental initiatives and (2) also developing conceptualizations for modeling purposes. These complexities arise due to the nonlinear interactions of various components that govern the fluxes of mass and energy across the soil-plant-atmospheric continuum.

This text begins with an introduction to ecological energetics in Chapter 1. Chapter 2 defines energy terms, introduces the physical laws of energy, and discusses how the basic principles of thermodynamics govern biological as well as physical systems. Chapter 3 is a primer on energy relationships between organisms and the environment. Chapter 4 covers the biological energy transformations of photosynthesis and energy conversion efficiencies. In Chapter 5, the energy processing by animals, their metabolism, and energy budgets is examined. Chapter 6 examines how species adapt thermally to their environments. Chapter 7 addresses the energy exchange between plants and animals, ecological energetics, food chains, and the trophic level concept. Then in Chapter 8, the complexities of energy flow in ecosystems are covered. Subsequently, Chapter 9 examines the concept of ecosystem productivity; and then in Chapter 10, the global carbon cycle and the biosphere are reviewed. Chapter 11 examines how the anthropogenic emissions of CO2 and land use change have altered the natural global carbon cycle and have influenced climate change. Chapter 12 examines the dynamic properties of the global carbon cycle. Chapter 13 looks at carbon and climate models and their use in decision making. Chapter 14 reviews the options for carbon management and geoengineering. Ultimately, humankind will have policy decisions to make about fossil energy use to avoid the negative climatic consequences of having changed the biosphere's carbon cycle (Chapter 15).

Before continuing, I need to make several brief comments about references. Much of the ecological energetics and productivity data from the decades of the mid-1960s to the mid-1980s, particularly during the International Biological Program, are contained in the proceedings of international conferences, which are now nearly inaccessible to many. I have identified these publications and extracted pertinent information from these sources so that it can remain in the mainstream of scientific literature. Secondly, I have sought permission to reproduce select graphs and illustrations contained in benchmark publications under copyright by publishers of books and scientific journals, so that they are available to those without the privileges of access to these sources through institutional library IT agreements. And lastly, when possible, I have referenced key data whenever they were published in government-sponsored symposia and reports; and since they are in the public domain, I have provided their URLs for convenient, direct IT access by the reader.

Recommended reading

1. Bolin B, Degens E.T, Kempe S, Ketner P, eds. The Global Carbon Cycle. SCOPE. vol 13. New York: John Wiley and Sons; 1979:491. https://www.researchgate.net/publication/40170880_The_Global_Carbon_Cycle_SCOPE_Report_13/.

2. Keeling C.D, Bacastow R.B, Whorf T.P. Measurement of the concentration of carbon dioxide at the Mauna Loa Observatory, Hawaii. In: Clark W.C, ed. Carbon Dioxide Review. New York: Oxford Univ. Press; 1982:377–385 469 pp.

3. Odum H.T. Trophic structure and productivity of Silver Springs, Florida. Ecol. Monogr. 1957;25:55–112. doi: 10.2307/1948571.

4. Phillipson J. Ecological Energetics. New York: St. Martin's Press; 1966:57. https://www.worldcat.org/title/ecological-energetics/oclc/220312888/.

5. Reichle D.E, O'Neill R.V, Harris W.F. Principles of energy and material exchange in ecosystems. In: van Dobben W.H, Lowe-McConnell R.H, eds. Unifying Concepts in Ecology. The Hague: W. Junk Pub; 1975:27–43 302 pp. https://link.springer.com/chapter/10.1007/978-94-010-1954-5_3/.

Timeline of the physical and chemical bases of energy

Chapter 2: The physical and chemical bases of energy

Abstract

Energy is the capacity to do work. Energy can exist in various forms, but those of greatest importance to living organisms are mechanical, chemical, radiant, and heat energy. All forms of energy are interconvertible; when conversions do occur, they do so according to rigorous laws of exchange. These are the Laws of Thermodynamics. Enthalpy is the total potential energy of a system. Entropy is a measure of the disorder, or randomness, of a system.

Keywords

Carbon; Carbon forms; Chemical energy; Energy forms; Enthalpy; Entropy; Gaia hypothesis; Heat energy; Power; Solar radiant energy; Temperature; Thermodynamic laws; Work

There is no better way to begin the study of ecological energetics than by starting with an understanding of the pertinent definitions and terminology of physics and physical chemistry. Learn this terminology early, become comfortable with the units of measure, and know the basic concepts, and bioenergetics will come a lot easier.

2.1. Energy, work, and power

Energy is the capacity to do work. The unit of measure for energy is the erg, which is the work performed when a force of 1 dyne acts through a distance of 1 cm. The unit of force, the dyne, yields a mass of 1 g with the acceleration of 1 cm per second (cm s −¹). Since an erg of energy is such a small quantity, a larger unit, the joule, which is equal to 10⁷ ergs, becomes a more convenient unit of measure. A unit of heat used frequently in physical chemistry is the calorie (= 4.184 J). The calorie is the heat energy required to raise the temperature of 1 g of water from 14.5 to 15.5°C. The calorie is defined as being equal to 4.1840 absolute joules. The calorie is a relatively small unit of measure, and for most chemical and biological calculations the kilocalorie (10³ calories) is used. The kilocalorie (kcal) is the unit which is typically used in discussing dietary intake and is often written as Calorie. A Calorie equals 10³ calories or a kcal.

2.1.1. Calories and joules

A calorie is an energy needed to raise the temperature of 1 g of water through 1°C (also expressed as 4.1868 J, the unit of energy in the International System of Units). A joule is the energy expended when 1 kg is moved 1 m by a force of 1 Newton (N). The use of joules is now recommended by international convention and is the preferred standard unit to measure heat (FAO, 1971). Nutritionists and food scientists concerned with large amounts of energy generally use kiloJoules (kJ = 10³ J) or megaJoules (MJ = 10⁶ J). For many decades, food energy has been expressed in calories, and studies in the field of ecological energetics have traditionally used calories as the measure of energy. In order to retain consistency with research reported in the scientific literature, the values used for energy in this book are in calories. The conversion factors for joules and calories are 1 cal = 4.184 and 1 J = 0.239 cal.

2.2. The different forms of energy

Energy can exist in various forms, but those of greatest importance to living organisms are mechanical, chemical, radiant, and heat energy (Table 2.1). Mechanical energy has two forms: kinetic and potential. Kinetic energy, or free energy, can be described as the useful energy that a body possesses by the value of its motion, and is measured by the amount of work which is done in bringing that body to rest. Examples would be a moving ball or the Brownian movement of molecules. Potential energy is stored energy, which is only potentially useful until its conversion into kinetic or free energy where it becomes available to accomplish work. Energy may be stored in a system by virtue of position, such as for example, a stone above the Earth's surface, a steel spring under compression, or by virtue of chemical properties due to the arrangement of atoms and electrons within a molecule. Conversion of energy from the potential form to the kinetic form involves movement, i.e., motion.

2.2.1. Chemical energy

All organisms must work to live, and they require a source of potential energy which can be utilized in order to perform the life processes. Chemical energy is a form of energy stored in the bonds of chemical compounds, which can be released to do work when a chemical reaction takes place. This energy can be found in the form of the chemical energy of biomass used as food. Energy can also be in the form of the chemical energy of inorganic molecules utilized as an alternative energy source to radiant energy by chemotrophs. Assemblies of atoms in the matter can be rearranged into different groups; thus, by the movement of atoms and the creation of different atomic bonds, chemical energy is liberated. The combustion (oxidation) of coal in a furnace, or food by the respiratory processes in a cell, releases energy which can be used to accomplish work. Both of these processes illustrate the conversion of chemical to mechanical energy. Life processes on this Earth have evolved around carbon chemistry, and most chemical energy sources are derived from organic compounds. However, as we shall see shortly, there are some notable exceptions.

Table 2.1

2.2.2. Radiant energy

The sun, a vast incandescent sphere of gas, releases energy by the nuclear transmutation of hydrogen to helium, and it is upon this energy source that life on Earth depends. Radiant energy is the energy of electromagnetic radiation. Because electromagnetic (EM) radiation can be conceptualized as a stream of photons, radiant energy can be viewed as photon energy. Alternatively, EM radiation can be viewed as an electromagnetic wave, which carries energy in its oscillating electric and magnetic fields. These two views are completely equivalent and are reconciled to one another in quantum field theory. Radiant energy includes electromagnetic radiation, such as radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma radiation; other forms of radiation include particle radiation, beta radiation and neutron radiation, acoustic radiation, and, gravitational radiation. Solar radiation is energy in the form of electromagnetic waves involving a rhythmic exchange between potential and kinetic energy. Electromagnetic radiation can have frequencies, or wavelengths, of different energy content and interactions (e.g., absorptivities) with the matter.

2.2.3. Heat energy

This is a very special form of energy resulting from the random movements of molecules, which by virtue of their motion, possess kinetic energy. Heat is the transfer of kinetic energy from one medium to another by conduction, convection, or radiation. Heat is evolved when all other forms of energy are transformed and work is performed. All work, including the growth and reproduction of living organisms, represents the transformation of energy and ultimately results in the production of heat. For example, when an animal during respiration releases the potential energy of glucose, approximately two-thirds of it is converted into mechanical energy to be used for work (activity and growth) and one-third is given off as heat.

There are instances of work where heat is absorbed (endodermic processes): the cooling unit of a refrigerator or the fixation of atmospheric nitrogen by certain bacteria are examples; but, these processes are not self-supporting energetically. Nitrogen fixation is always accompanied by the exothermic breakdown of organic substrates. The heat energy released by an exothermic process is never used with complete efficiency by the endergonic process, and so whenever work is done the trend is always toward heat production. In natural processes, changes from one form of energy to another (except for heat) are normally incomplete, because the movement, already shown to be necessary for energy conversion, involves either friction or heat production.

Temperature is the manifestation of thermal energy – the energy of motion of atoms constituting matter. Temperature is a measure of the kinetic energy of a substance, while heat is a measure of the energy transferred between two objects of different temperatures Temperature is the relative measure which is used to characterize the amount of heat present in a system. Several common systems are used, only two of which concern us: the Celsius and the Kelvin scales. The Celsius (centigrade) scale (oC) establishes zero (0°) as the freezing point of water and 100° as the boiling point of water. The Kelvin scale is an absolute measure which establishes zero at the temperature (−273°C) at which all molecular motion ceases. Because freezing and boiling points limit life processes, we will conventionally utilize the Celsius scale. Heat may be characterized by the properties of two phases: sensible heat and latent heat. The significance of each of these phases will shortly become apparent. Suffice at present to distinguish between the two phases as follows: sensible heat is that which can be measured by an increase in temperature of a body, for example, the warming action of sunlight irradiating a metal plate. Latent heat is the heat absorption by a body without an equivalent increase in temperature, such as the heat of freezing or vaporization of water (heat of vaporization of water = 539 cal at 100°C). Energy flow is expressed as the product of two factors: (1) an intensity factor (or gradient), and (2) a capacity factor (amount).

Energy, work, and heat are all expressed in the same units: calories, joules, or ergs. It should be evident that the different energies may be compared, but that no relationship exists between the capacity factors alone. For example, electric energy may be converted into heat energy, but the rise in temperature cannot be calculated from the voltage unless the number of coulombs and the heat capacity of the system is known. It is also clear that the same quantity of work can be accomplished by a small quantity of water passing through a turbine from a great height as by a large quantity of water passing through from a short distance.

Thus, arises one of the fundamental principles of thermodynamics—the interconvertibility of energy forms as well as the trade-offs between the intensity and capacity factors. All forms of energy are interconvertible; when conversions do occur, they do so according to rigorous laws of exchange. These are the Laws of Thermodynamics.

2.3. The Laws of Thermodynamics

Thermodynamics is the branch of physics that deals with heat and temperature, and their relation to energy, work, radiation and the properties of matter, explaining how thermal energy is converted to or from other forms of energy. The 0th Law of Thermodynamics states that if two thermodynamic systems are each in thermal equilibrium with a third one, then they are in thermal equilibrium with each other. In 1931 Ralph Howard Fowler (1889–1944), Chair of Theoretical Physics at the Cavendish Laboratory of Cambridge University, working on thermodynamics and statistical mechanics was the first to formulate and label the Zeroth Law of Thermodynamics. This law, dealing with thermal equilibrium, is fundamental to the first three laws.

First Law of Thermodynamics. The total energy of an isolated system is constant; energy can be transformed from one form to another but can be neither created nor destroyed. The change in the total internal energy of a closed system equals the heat supplied to the system subtracted by the work done by the system. As early as 1756, Gabrielle Émilie Le Tonnelier de Breteuil, Marquise du Châtelet (1706–49), French natural philosopher and mathematician, commented in her 1756 translation of Isaac Newton's 1687 book Principia, containing the basic laws of physics, on the postulate of an additional conservation law for total energy, of which kinetic energy of motion is one element. In 1840 James Prescott Joule (1818–89), an English brewer, determined that the heat (H) produced in an electric wire in the time dt is H = I²RT (Joules Law of electrical heating). In 1842 Julius Robert Mayer (1814–78), a German physician and physicist hypothesized the equivalence between physical work and heat and formulated the Law of Conservation of Energy. Later, in 1843, Joule determined the mechanical equivalent of heat and formulated the first Law of Thermodynamics, the Law of Conservation of Energy.

Second Law of Thermodynamics. Energy is conserved in any process involving the exchange of heat and work between a system and its surroundings. In every natural thermodynamic process, the sum of entropies of all objects is either unchanged (reversible process) or increased (irreversible process). In 1850 Rudolf Julius Emanuel Clausius (1822–88), Professor of Physics in the Royal Artillery and Engineering School in Berlin formulates the second Law of Thermodynamics and introduces entropy as the equation of state.

Third Law of Thermodynamics states that the entropy of a closed system in thermodynamic equilibrium approaches a constant value as its temperature approaches absolute zero. In 1912 Walther Hermann Nernst (1864–1941), of Göttingen University, formulated the heat theorem: entropy of a system at absolute zero is a defined constant, which led to the third Law of Thermodynamics.

Fourth Law of Thermodynamics. The principle of conservation of time states that all of space, matter, and energy is contained by time. Time is infinite and indestructible. Without time there could be no gravity, no matter, no space and consequently no energy.

The First and Second Laws of Thermodynamics govern the global carbon cycle and the energetics of the biosphere.

Remember that the capacity factor for mechanical and chemical energy is mass (m). Thus, Einstein showed that if there is a change in mass, Δm,

Equation 2.1.

(2.1)

where:

c is the velocity of light

Equation

Therefore, 1 g of water is equivalent to Equation ergs of energy. It should be evident that the Law of Conservation of Energy and the Law of Conservation of Mass are essentially the same, and that no violation of thermodynamics occurs when energy is converted into mass or mass is converted into energy. However, a change in energy of a system will be brought about if the system does work, or if it absorbs or evolves heat. Thus, when a change of any kind occurs in a closed system (where the amount of matter is fixed but energy is able to enter or leave) an increase or decrease occurs in the internal energy (E) of the system itself; heat (q) is evolved or absorbed, and work (w) is done:

Equation 2.2. (2.2)

2.3.1. Work

The work performed by a system is the energy transferred by the system to its surroundings. The negative value of work indicates that a positive amount of work done by the system has led to energy being lost from the system.

The First Law of Thermodynamics also encompasses the more specific relationship of constant heat sums, which is of considerable importance to biologists interested in energy transformations. In 1842 Julius Robert Mayer (1814–78), a German physician and physicist hypothesized the equivalence between physical work and heat It states that the total amount of heat produced, or absorbed, from a chemical reaction, which takes place in stages is equal to the total amount of heat evolved, or consumed when the reaction occurs directly in one step. The evolution of living systems has utilized biochemical mechanisms by which chemical compounds can be reduced in steps, thus enabling more efficient energy capture and utilization to occur. A good biological example is the metabolic oxidation of glucose to carbon dioxide and water:

Direct reaction (combustion) Equation of energy.

Two-stage reaction (fermentation)

(a) Equation

(b)

Equation

(a) + (b)

Equation

Thus, no matter which pathway a particular reaction follows, the total amount of heat evolved, or absorbed, is always the same. There will be more discussion about the biological significance of this phenomenon later. Several other energy relationships are also pertinent to bioenergetics.

2.3.2. Enthalpy

Enthalpy is the total potential energy of a system. In many cases, the only work w done on a system results in a change in the calorific value of the available mass. In other words:

Equation 2.1.

(2.3)

Therefore, the heat absorbed (q) in a process, measured under conditions of constant volume, is equal to the internal energy increase. According to this equation, if no outside work is done, the energy absorbed by the system is equal to the potential internal increase. A biological example of this would be the reverse of the previous chemical reaction or photosynthesis:

Equation

Enthalpy is defined as the heat content of a system. Bond energy is the amount of energy required to break a chemical bond. The total bond energy is equivalent to the total potential energy of the system, a quantity known as enthalpy (H). The heat absorbed in a process at constant pressure is equal to the change in enthalpy, ΔH. Since a change in enthalpy can occur through both a change in pressure or volume, as well as internal energy, another term is introduced to describe the heat capacity of a substance:

Equation 2.4. (2.4)

The specific heat of a substance is defined as the quantity of heat required to raise the temperature of 1 g of substance by 1°C. This is an extremely important relationship for biological systems. It explains the importance of water as a thermal buffer, since when compared to other solvents water possesses relatively high heat of vaporization and freezing.

The Second Law of Thermodynamics deals with the exchanges of heat and work between systems and their environment. We are all familiar with the fact that many energetic processes occur spontaneously. For example, water runs downhill; gases expand from regions of high pressure to regions of low pressure; chemical reactions proceed to equilibrium, and heat flows from warm bodies to cooler bodies. The Second Law of Thermodynamics states that processes involving transformations will not occur spontaneously unless there is a degradation of energy from a nonrandom (ordered) form to a random (disordered) form. In natural systems, spontaneous energy transformations result in the degradation of the energy state of the system from a useful form to a dissipated and less useable form of heat. Obviously, as spontaneous processes occur in a system the system loses the ability to do work.

Living (biological) systems have evolved to exploit these natural energy transformations and to utilize energy as it passes from ordered to random states.

All systems tend to approach states of equilibrium—in thermodynamic properties; this means complete randomness or energy degradation of the system. As a measure of the extent to which this equilibrium has been reached, another thermodynamic term, entropy is introduced.

2.3.3. Entropy

Entropy is a measure of the disorder, or randomness, of a system. Organized, useable energy has low entropy, whereas disorganized entropy such as heat has high entropy. The more the molecules in a system are distributed in a disordered or random manner, the more probable is the arrangement and the greater the entropy. The First Law of Thermodynamics recognizes the interconvertibility of all forms of energy, but it does not predict how complete the conversions will be. This applies to all energy conversions, except the transformation to heat, which is a property of molecules moving around at random. By contrast, all other forms of energy result from an ordered, nonrandom arrangement of the elementary particles of matter. Heat is the only form of energy due to disorder or random movement, and it is the most likely energy form to occur.

2.3.4. The thermodynamic rules governing bioenergetics

The first law of thermodynamics is a version of the law of conservation of energy. Adapted for thermodynamic processes, it distinguishes two kinds of transfer of energy, heat and thermodynamic work, and relates them to a function of a body's state, called internal energy. The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but it can be neither created nor destroyed. For a thermodynamic process without transfer of matter, the first law can be expressed as:

Equation 2.5. (2.5)

Equation 2.6. (2.6)

where, ΔU denotes the change in the internal energy of a closed system; Q denotes the quantity of energy supplied to the system as heat, and W denotes the amount of thermodynamic work done by the system on its surroundings.

The first law of thermodynamics provides the basic definition of internal energy, associated with all thermodynamic systems, and states the rule of conservation of energy. The second law is concerned with the direction of natural processes. The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time, and is constant if and only if all processes are reversible. Isolated systems spontaneously evolve toward thermodynamic equilibrium, the state with maximum entropy.

The Theory of Relativity states that mass and energy are actually the same thing, with one a tightly compressed manifestation of the other.

Equation 2.7. (2.7)

where:

E = the energy of an object at rest in Joules (kilograms per square meter per second or kg m² s−²),

m = mass (kilograms, or 10³ g), and

c = the speed of light in a vacuum (3.00 × 108 m² s−¹).

Thus, mass and energy are interchangeable or, in other words, interconvertible.

Mass. Mass and weight are different. Weight, w, is the gravitational force felt by an object, while mass, m, is the amount of matter in that object. Mass can only change if the object is physically altered, while weight changes depending on the gravity, g, of the environment that the object is in. Mass is measured in kilograms (kg) while weight is measured in Newtons (N). Similar to energy, mass can neither be created or destroyed, but it can change form. For example, water in an ice cube can melt into a liquid and its volume change, but it still has the same mass in both states. Mass and volume are not the same. An object can be stretched or compacted to change its volume, but the amount of matter it contains will stay the same.

Energy. There are many forms of energy including thermal, chemical, nuclear, electrical, and more. Energy can be neither created nor destroyed, it can only take a different form. For example, coal has potential energy that turns into thermal energy when it is burned; food has chemical energy, which is turned into heat when it is metabolized. Energy can be transferred between systems giving power to one system while taking it away from another.

Energy Conversion. Energy can be derived from the burning of coal or from the catabolism of sugars. Burning these substances takes advantage of their valence electrons (unpaired electrons in the outermost shell of an atom) and the bonds that they make with other elements. When these bonds are broken and the energy released can be used to power electrical grids, or a cell's metabolic processes, respectively. Obtaining energy this way is not very efficient. There is much more energy stored inside the nucleus of an atom than in its valence electrons. Almost all of the mass in an atom is located in the nucleus, where protons and neutrons are bound together very tightly. Nuclear fission breaks apart these tight bonds and converts some of the nucleus mass into energy. The energy released from splitting an atom in nuclear power production is much higher than that of breaking electron bonds, but the high energy state and heat produced in nuclear fission are impossible for biological systems to process and utilize.

Mass and Energy. Mass and energy are equivalent and interchangeable, E = mc². The equation states that mass and energy are similar, and defines how much energy is contained inside a given amount of mass. The equation states that a small amount of mass can be full of a large amount of energy.

Gravity. Gravity has energy. F = ma, and E = mc², are both encompassed, surpassed, and related by this most fundamental law in all of physics: inertial resistance is proportional to gravitational force/energy. The force of gravity, g, on an object at the Earth's surface is directly proportional to the object's mass. Thus, an object that has a mass of, m, will experience a force, F:

Equation 2.8. (2.8)

where, W, is the force, F, generated by the gravitational attraction, g, of the Earth:

Equation 2.9. (2.9)

Force. The Newton, N, is the standard unit of force in the Système International d'unités (SI), or International System of Units. One Newton is the force needed to accelerate 1 kilogram of mass at the rate of 1 meter per second squared in the direction of the applied force. Newton's second law of motion states that the force, F, exerted by an object's mass is directly proportional to the acceleration of that object:

Equation 2.1.

(2.10)

Where the proportionality constant, m, represents the mass of the object undergoing an acceleration, a. As a result, the Newton may be defined in terms of kilograms (kg), meters (m), and seconds (s) by:

Equation 2.11. (2.11)

Work. Work can be defined as weight lifted through a height, measured in kg⋅m²⋅s −². Work transfers energy from one place to another, or one form to another. Work, W, is the product of force and displacement. A force is said to do work if, when acting, there is a movement of the point of application in the direction of the force. The SI unit of work is the joule (J), which is