Climate-vegetation-fire interactions and feedbacks: trivial detail or major barrier to projecting the future of the Earth system?

The Earth's chemical composition far from chemical equilibrium is unique in our Solar System, and this uniqueness has been attributed to the presence of widespread life on the planet. Here, I show how this notion can be quantified using non-equilibrium thermodynamics. Generating and maintaining disequilibrium in a thermodynamic variable requires the extraction of power from another thermodynamic gradient, and the second law of thermodynamics imposes fundamental limits on how much power can be extracted. With this approach and associated limits, I show that the ability of abiotic processes to generate geochemical free energy that can be used to transform the surface–atmosphere environment is strongly limited to less than 1 TW. Photosynthetic life generates more than 200 TW by performing photochemistry, thereby substantiating the notion that a geochemical composition far from equilibrium can be a sign for strong biotic activity. Present-day free energy consumption by human activity in the form of industrial activity and human appropriated net primary productivity is of the order of 50 TW and therefore constitutes a considerable term in the free energy budget of the planet. When aiming to predict the future of the planet, we first note that since global changes are closely related to this consumption of free energy, and the demands for free energy by human activity are anticipated to increase substantially in the future, the central question in the context of predicting future global change is then how human free energy demands can increase sustainably without negatively impacting the ability of the Earth system to generate free energy. This question could be evaluated with climate models, and the potential deficiencies in these models to adequately represent the thermodynamics of the Earth system are discussed. Then, I illustrate the implications of this thermodynamic perspective by discussing the forms of renewable energy and planetary engineering that would enhance the overall free energy generation and, thereby ‘empower’ the future of the planet.

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Emergent Constraints on Climate-Carbon Cycle Feedbacks

Current Climate Change Reports ◽

10.1007/s40641-019-00141-y ◽

2019 ◽

Vol 5 (4) ◽

pp. 275-281 ◽

Cited By ~ 4

Author(s):

Peter M. Cox

Keyword(s):

Climate Change ◽

Carbon Cycle ◽

Future Climate ◽

Future Climate Change ◽

Climate Projections ◽

Earth System ◽

Model Errors ◽

The Earth ◽

The Future ◽

Emergent Constraints

Abstract Purpose of Review Feedbacks between CO2-induced climate change and the carbon cycle are now routinely represented in the Earth System Models (ESMs) that are used to make projections of future climate change. The inconclusion of climate-carbon cycle feedbacks in climate projections is an important advance, but has added a significant new source of uncertainty. This review assesses the potential for emergent constraints to reduce the uncertainties associated with climate-carbon cycle feedbacks. Recent Findings The emergent constraint technique involves using the full ensemble of models to find an across-ensemble relationship between an observable feature of the Earth System (such as a trend, interannual variation or change in seasonality) and an uncertain aspect of the future. Examples focussing on reducing uncertainties in future atmospheric CO2 concentration, carbon loss from tropical land under warming and CO2 fertilization of mid- and high-latitude photosynthesis are exemplars of these different types of emergent constraints. Summary The power of emergent constraints is that they use the enduring range in model projections to reduce uncertainty in the future of the real Earth System, but there are also risks that indiscriminate data-mining, and systematic model errors could yield misleading constraints. A hypothesis-driven theory-led approach can overcome these risks and also reveal the true promise of emergent constraints—not just as ways to reduce uncertainty in future climate change but also to catalyse advances in our understanding of the Earth System.

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Why Simulate?

Numerical Adventures with Geochemical Cycles ◽

10.1093/oso/9780195045208.003.0003 ◽

1991 ◽

Author(s):

James C. G. Walker

Keyword(s):

Global Change ◽

Trace Element Composition ◽

Atmospheric Composition ◽

Earth System ◽

Earth System Science ◽

System Science ◽

The Past ◽

The Earth ◽

The Future ◽

Systems Simulation

Our world is a product of complex interactions among atmosphere, ocean, rocks, and life that Earth system science seeks to understand. Earth system science deals with such properties of the environment as composition and climate and populations and the ways in which they affect one another. It also concerns how these interactions caused environmental properties to change in the past and how they may change in the future. The Earth system can be studied quantitatively because its properties can be represented by numbers. At present, however, most of the numbers in Earth system science are observational rather than theoretical, and so our description of the Earth system's objective properties is much more complete than our quantitative understanding of how the system works. Quantitative theoretical understanding grows out of a simulation of the system or parts of the system and numerical experimentation with simulated systems. Simulation experiments can answer questions like What is the effect of this feature? or What would happen in that situation? Simulation also gives meaning to observations by showing how they may be related. As an illustration, consider that area of Earth system science known as global change. There is now an unambiguous observational record of global change in many important areas of the environment. For elements of climate and atmospheric composition this record is based on direct measurement over periods of a decade to a century. For other environmental variables, particularly those related to the composition of the ocean, the record of change consists of measurements of isotopic or trace-element composition of sediments deposited over millions of years. This evidence of global change is profoundly affecting our view of what the future holds in store for us and what options exist. It should also influence our understanding of how the interaction of biota and environment has changed the course of Earth history. But despite the importance of global change to our prospects for the future and our understanding of the past, the mechanisms of change are little understood. There are many speculative suggestions about the causes of change but few quantitative and convincing tests of these suggestions.

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7. Sustainability

Earth System Science: A Very Short Introduction ◽

10.1093/actrade/9780198718871.003.0007 ◽

2016 ◽

pp. 107-123

Author(s):

Tim Lenton

Keyword(s):

Earth System ◽

Earth System Science ◽

System Science ◽

Earth History ◽

The Earth ◽

The Future ◽

Human Transformation

Whilst human transformation of the planet was initially unwitting, now we are increasingly collectively aware of it. This changes the Earth system fundamentally, because it means that one species can consciously and collectively shape the future trajectory of our planet. We know our current way of living is unsustainable, but we are still trying to work out what a sustainable and prosperous future looks like. This is an opportunity for Earth system science, because it can tell us what makes a sustainable Earth system and what does not. ‘Sustainability’ outlines how Earth system science can help humanity in our quest for long-term sustainability, starting with the lessons we can learn from Earth history.

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6. Projection

Earth System Science: A Very Short Introduction ◽

10.1093/actrade/9780198718871.003.0006 ◽

2016 ◽

pp. 91-106

Author(s):

Tim Lenton

Keyword(s):

Climate Change ◽

Human Activities ◽

Global Changes ◽

Earth System ◽

System Models ◽

The Earth ◽

The Future ◽

Earth System Models ◽

Specific Challenge

Where is the Earth system heading in the Anthropocene? To even begin to answer this question requires a model of how the Earth system works, and the answer depends on our collective activities as a species, and how the Earth system responds to those. The model’s role is to forecast the consequences of different assumptions about future human activities. ‘Projection’ introduces ‘Earth system models’ and some of the crucial assumptions that go into using them to forecast the future. It outlines their projections, going from shorter to longer timescales, and from the specific challenge of projecting climate change to the broader challenge of exploring other global changes.

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When Silence Strikes: Derrida, Heidegger, Mallarmé

Oxford Literary Review ◽

10.3366/olr.2018.0254 ◽

2018 ◽

Vol 40 (2) ◽

pp. 238-262

Author(s):

Rodrigo Therezo

Keyword(s):

The Earth ◽

The Future ◽

The Way

This paper attempts to rethink difference and divisibility as conditions of (im)possibility for love and survival in the wake of Derrida's newly discovered—and just recently published—Geschlecht III. I argue that Derrida's deconstruction of what he calls ‘the grand logic of philosophy’ allows us to think love and survival without positing unicity as a sine qua non. This hypothesis is tested in and through a deconstructive reading of Heidegger's second essay on Trakl in On the Way to Language, where Heidegger's phonocentrism and surreptitious nationalism converge in an effort to ‘save the earth’ from a ‘degenerate’ Geschlecht that cannot survive the internal diremption between Geschlechter. I show that one way of problematizing Heidegger's claim is to point to the blank spaces in the ‘E i n’ of Trakl's ‘E i n Geschlecht’, an internal fissuring in the very word Heidegger mobilizes in order to secure the future of mankind.

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