4. Revolutions

2016 ◽  
pp. 57-73
Author(s):  
Tim Lenton
Keyword(s):  
Biogeochemical Cycling ◽  
Oxygenic Photosynthesis ◽  
Earth System ◽  
Earth History ◽  
Evolution Of Life ◽  
Planetary Environment

How did today’s Earth system become so radically different from those of our planetary neighbours, Mars and Venus? The presence of life is clearly a big part of the answer. Earth system scientists now recognize that the evolution of life has shaped the planet, changes in the planetary environment have shaped life, and together they can be viewed as one process. ‘Revolutions’ shows that when this ‘co-evolution’ over Earth history is considered, three revolutionary changes leap out: the inception of life and biogeochemical cycling; the origin of oxygenic photosynthesis and the Great Oxidation; and the origin of complex life out of the Neoproterozoic environmental turmoil. Without them we would not be here.

Are there pre-Quaternary geological analogues for a future greenhouse warming?

2011 ◽  
Vol 369 (1938) ◽  
pp. 933-956 ◽  
Author(s):  
Alan M. Haywood ◽  
Andy Ridgwell ◽  
Daniel J. Lunt ◽  
Daniel J. Hill ◽  
Matthew J. Pound ◽  
...  
Keyword(s):  
Climate Change ◽  
Greenhouse Gases ◽  
Future Climate ◽  
Future Climate Change ◽  
Anthropogenic Emissions ◽  
Earth System ◽  
System Sensitivity ◽  
Earth History ◽  
Scientific Papers

Given the inherent uncertainties in predicting how climate and environments will respond to anthropogenic emissions of greenhouse gases, it would be beneficial to society if science could identify geological analogues to the human race’s current grand climate experiment . This has been a focus of the geological and palaeoclimate communities over the last 30 years, with many scientific papers claiming that intervals in Earth history can be used as an analogue for future climate change. Using a coupled ocean–atmosphere modelling approach, we test this assertion for the most probable pre-Quaternary candidates of the last 100 million years: the Mid- and Late Cretaceous, the Palaeocene–Eocene Thermal Maximum (PETM), the Early Eocene, as well as warm intervals within the Miocene and Pliocene epochs. These intervals fail as true direct analogues since they either represent equilibrium climate states to a long-term CO 2 forcing—whereas anthropogenic emissions of greenhouse gases provide a progressive (transient) forcing on climate—or the sensitivity of the climate system itself to CO 2 was different. While no close geological analogue exists, past warm intervals in Earth history provide a unique opportunity to investigate processes that operated during warm (high CO 2 ) climate states. Palaeoclimate and environmental reconstruction/modelling are facilitating the assessment and calculation of the response of global temperatures to increasing CO 2 concentrations in the longer term (multiple centuries); this is now referred to as the Earth System Sensitivity, which is critical in identifying CO 2 thresholds in the atmosphere that must not be crossed to avoid dangerous levels of climate change in the long term. Palaeoclimatology also provides a unique and independent way to evaluate the qualities of climate and Earth system models used to predict future climate.

scholarly journals Cryptic oxygen cycling in anoxic marine zones

2017 ◽  
Vol 114 (31) ◽  
pp. 8319-8324 ◽  
Author(s):  
Emilio Garcia-Robledo ◽  
Cory C. Padilla ◽  
Montserrat Aldunate ◽  
Frank J. Stewart ◽  
Osvaldo Ulloa ◽  
...  
Keyword(s):  
Surface Layer ◽  
Carbon Fixation ◽  
Nitrogen Loss ◽  
Biogeochemical Cycling ◽  
Oxygenic Photosynthesis ◽  
Nitrite Oxidation ◽  
Tight Coupling ◽  
Expression Of Genes ◽  
Aerobic Processes ◽  
Oxygen Cycling

Oxygen availability drives changes in microbial diversity and biogeochemical cycling between the aerobic surface layer and the anaerobic core in nitrite-rich anoxic marine zones (AMZs), which constitute huge oxygen-depleted regions in the tropical oceans. The current paradigm is that primary production and nitrification within the oxic surface layer fuel anaerobic processes in the anoxic core of AMZs, where 30–50% of global marine nitrogen loss takes place. Here we demonstrate that oxygenic photosynthesis in the secondary chlorophyll maximum (SCM) releases significant amounts of O2to the otherwise anoxic environment. The SCM, commonly found within AMZs, was dominated by the picocyanobacteriaProchlorococcusspp. Free O2levels in this layer were, however, undetectable by conventional techniques, reflecting a tight coupling between O2production and consumption by aerobic processes under apparent anoxic conditions. Transcriptomic analysis of the microbial community in the seemingly anoxic SCM revealed the enhanced expression of genes for aerobic processes, such as nitrite oxidation. The rates of gross O2production and carbon fixation in the SCM were found to be similar to those reported for nitrite oxidation, as well as for anaerobic dissimilatory nitrate reduction and sulfate reduction, suggesting a significant effect of local oxygenic photosynthesis on Pacific AMZ biogeochemical cycling.

scholarly journals The Habitable Zone of Inhabited Planets

2014 ◽  
Vol 11 (6) ◽  
pp. 8443-8483 ◽  
Author(s):  
J. I. Zuluaga ◽  
J. F. Salazar ◽  
P. Cuartas-Restrepo ◽  
G. Poveda
Keyword(s):  
Numerical Models ◽  
Physical Phenomenon ◽  
Life Forms ◽  
Habitable Zone ◽  
Earth System ◽  
Abiotic Environment ◽  
Physical Conditions ◽  
The Earth ◽  
Life Itself ◽  
Planetary Environment

Abstract. In this paper we discuss and illustrate the hypothesis that life substantially alters the state of a planetary environment and therefore, modifies the limits of the HZ as estimated for an uninhabited planet. This hypothesis lead to the introduction of the Habitable Zone for Inhabited Planets (hereafter InHZ), defined here as the region where the complex interaction between life and its abiotic environment is able to produce plausible equilibrium states with the necessary physical conditions for the existence and persistence of life itself. We support our hypothesis of an InHZ with three theoretical arguments, multiple evidences coming from observations of the Earth system, several conceptual experiments and illustrative numerical simulations. Conceptually the diference between the InHZ and the Abiotic HZ (AHZ) depends on unique and robust properties of life as an emergent physical phenomenon and not necesarily on the particular life forms bearing in the planet. Our aim here is to provide conceptual basis for the development of InHZ models incorporating consistently life-environment interactions. Although previous authors have explored the effects of life on habitability there is a gap in research developing the reasons why life should be systematically included at determining the HZ limits. We do not provide here definitive limits to the InHZ but we show through simple numerical models (as a parable of an inhabited planet) how the limits of the AHZ could be modified by including plausible interactions between biota and its environment. These examples aim also at posing the question that if limits of the HZ could be modified by the presence of life in those simple dynamical systems how will those limits change if life is included in established models of the AHZ.

scholarly journals Stepwise Earth oxygenation is an inherent property of global biogeochemical cycling

Science ◽  
2019 ◽  
Vol 366 (6471) ◽  
pp. 1333-1337 ◽  
Author(s):  
Lewis J. Alcott ◽  
Benjamin J. W. Mills ◽  
Simon W. Poulton
Keyword(s):  
Theoretical Model ◽  
Biogeochemical Cycling ◽  
Biogeochemical Cycles ◽  
Oxygenic Photosynthesis ◽  
Planetary Surface ◽  
Earth Surface ◽  
External Forcing ◽  
Simple Consequence ◽  
Inherent Property

Oxygenation of Earth’s atmosphere and oceans occurred across three major steps during the Paleoproterozoic, Neoproterozoic, and Paleozoic eras, with each increase having profound consequences for the biosphere. Biological or tectonic revolutions have been proposed to explain each of these stepwise increases in oxygen, but the principal driver of each event remains unclear. Here we show, using a theoretical model, that the observed oxygenation steps are a simple consequence of internal feedbacks in the long-term biogeochemical cycles of carbon, oxygen, and phosphorus, and that there is no requirement for a specific stepwise external forcing to explain the course of Earth surface oxygenation. We conclude that Earth’s oxygenation events are entirely consistent with gradual oxygenation of the planetary surface after the evolution of oxygenic photosynthesis.

scholarly journals Marine geochemical data assimilation in an efficient Earth System Model of global biogeochemical cycling

2007 ◽  
Vol 4 (1) ◽  
pp. 87-104 ◽  
Author(s):  
A. Ridgwell ◽  
J. C. Hargreaves ◽  
N. R. Edwards ◽  
J. D. Annan ◽  
T. M. Lenton ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Biogeochemical Cycling ◽  
Earth System Model ◽  
Atmospheric Co2 ◽  
System Model ◽  
Geochemical Data ◽  
Model Parameters ◽  
Earth System ◽  
Export Production ◽  
Ocean Carbon

Abstract. We have extended the 3-D ocean based "Grid ENabled Integrated Earth system model" (GENIE-1) to help understand the role of ocean biogeochemistry and marine sediments in the long-term (~100 to 100 000 year) regulation of atmospheric CO2, and the importance of feedbacks between CO2 and climate. Here we describe the ocean carbon cycle, which in its first incarnation is based around a simple single nutrient (phosphate) control on biological productivity. The addition of calcium carbonate preservation in deep-sea sediments and its role in regulating atmospheric CO2 is presented elsewhere (Ridgwell and Hargreaves, 2007). We have calibrated the model parameters controlling ocean carbon cycling in GENIE-1 by assimilating 3-D observational datasets of phosphate and alkalinity using an ensemble Kalman filter method. The calibrated (mean) model predicts a global export production of particulate organic carbon (POC) of 8.9 PgC yr−1, and reproduces the main features of dissolved oxygen distributions in the ocean. For estimating biogenic calcium carbonate (CaCO3) production, we have devised a parameterization in which the CaCO3:POC export ratio is related directly to ambient saturation state. Calibrated global CaCO3 export production (1.2 PgC yr-1) is close to recent marine carbonate budget estimates. The GENIE-1 Earth system model is capable of simulating a wide variety of dissolved and isotopic species of relevance to the study of modern global biogeochemical cycles as well as past global environmental changes recorded in paleoceanographic proxies. Importantly, even with 12 active biogeochemical tracers in the ocean and including the calculation of feedbacks between atmospheric CO2 and climate, we achieve better than 1000 years per (2.4 GHz) CPU hour on a desktop PC. The GENIE-1 model thus provides a viable alternative to box and zonally-averaged models for studying global biogeochemical cycling over all but the very longest (>1 000 000 year) time-scales.

scholarly journals Revolutions in energy input and material cycling in Earth history and human history

2016 ◽  
Vol 7 (2) ◽  
pp. 353-370 ◽  
Author(s):  
Timothy M. Lenton ◽  
Peter-Paul Pichler ◽  
Helga Weisz
Keyword(s):  
Free Energy ◽  
Social Organization ◽  
Energy Input ◽  
Energy Use ◽  
Industrial Revolution ◽  
Oxygenic Photosynthesis ◽  
Human History ◽  
Unequal Distribution ◽  
Earth History ◽  
Material Cycling

Abstract. Major revolutions in energy capture have occurred in both Earth and human history, with each transition resulting in higher energy input, altered material cycles and major consequences for the internal organization of the respective systems. In Earth history, we identify the origin of anoxygenic photosynthesis, the origin of oxygenic photosynthesis, and land colonization by eukaryotic photosynthesizers as step changes in free energy input to the biosphere. In human history we focus on the Palaeolithic use of fire, the Neolithic revolution to farming, and the Industrial revolution as step changes in free energy input to human societies. In each case we try to quantify the resulting increase in energy input, and discuss the consequences for material cycling and for biological and social organization. For most of human history, energy use by humans was but a tiny fraction of the overall energy input to the biosphere, as would be expected for any heterotrophic species. However, the industrial revolution gave humans the capacity to push energy inputs towards planetary scales and by the end of the 20th century human energy use had reached a magnitude comparable to the biosphere. By distinguishing world regions and income brackets we show the unequal distribution in energy and material use among contemporary humans. Looking ahead, a prospective sustainability revolution will require scaling up new renewable and decarbonized energy technologies and the development of much more efficient material recycling systems – thus creating a more autotrophic social metabolism. Such a transition must also anticipate a level of social organization that can implement the changes in energy input and material cycling without losing the large achievements in standard of living and individual liberation associated with industrial societies.

scholarly journals Revolutions in energy input and material cycling in Earth history and human history

2016 ◽  
Author(s):  
T. M. Lenton ◽  
P. P. Pichler ◽  
H. Weisz
Keyword(s):  
Free Energy ◽  
Social Organization ◽  
Energy Input ◽  
Energy Use ◽  
Industrial Revolution ◽  
Oxygenic Photosynthesis ◽  
Human History ◽  
Unequal Distribution ◽  
Earth History ◽  
Material Cycling

Abstract. Major revolutions in energy capture have occurred in both Earth and human history, with each transition resulting in higher energy input, altered material cycles and major consequences for the internal organization of the respective systems. In Earth history, we identify the origin of anoxygenic photosynthesis, the origin of oxygenic photosynthesis, and land colonization by eukaryotic photosynthesisers as step changes in free energy input to the biosphere. In human history we focus on the Paleolithic use of fire, the Neolithic revolution to farming, and the Industrial revolution as step changes in free energy input to human societies. In each case we try to quantify the resulting increase in energy input, and discuss the consequences for material cycling and for biological and social organization. For most of human history, energy use by humans was but a tiny fraction of the overall energy input to the biosphere, as would be expected for any heterotrophic species. However, the industrial revolution gave humans the capacity to push energy inputs towards planetary scales and by the end of the 20th century human energy use had reached a magnitude comparable to the biosphere. By distinguishing world regions and income brackets we show the unequal distribution in energy and material use among contemporary humans. Looking ahead, a prospective sustainability revolution will require scaling up new solar energy technologies and the development of much more efficient material recycling systems – thus creating a more autotrophic social metabolism. Such a transition must also anticipate a level of social organization that can implement the changes in energy input and material cycling without losing the large achievements in standard of living and individual liberation associated with industrial societies.

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