arXiv subjects

Ugo Bardi

Publications and source records attributed to Ugo Bardi.

14 recordsLinked to original sources

arXiv2025

Seeing Forests Through Clouds: Comment on "Recent global temperature surge amplified by record-low planetary albedo" (arXiv:2405.19986)

Goessling et al. (1) link the record-breaking warming anomaly of 2023 to a global albedo decline due to reduced low-level cloud cover. What caused the reduction remains unclear. Goessling et al. considered several geophysical mechanisms, including ocean surface warming and declining aerosol emissions, but did not discuss the biosphere. We propose that disruption of global biospheric functioning could be a cause, as supported by three lines of evidence that have not yet been jointly considered.

physics.ao-ph↗

arXiv2024

Carbon Dioxide as a Pollutant. The Risks of Rising Atmospheric CO$_2$ Levels on Human Health and on the Stability of the Biosphere

Carbon dioxide is a chemically active molecule that plays a vital role in Earth's ecosphere. CO$_2$ affects the acidity of seawater and has multiple negative effects on marine organisms. It is also a fundamental component of the photosynthesis and respiration reactions. There is evidence that higher CO$_2$ concentration can make the photosynthetic reaction faster in some plants, but also negatively impact the respiration reaction in aerobic lifeforms. The effects of this chemical and biochemical perturbation on the biosphere and on human health may be more important than generally highlighted in the discussion on CO$_2$, usually focused on thermal effects only. These considerations stress the importance of rapidly reducing CO$_2$ emissions and, whenever possible, remove the excess from the atmosphere. They also show that geoengineering technologies based on Solar Radiation Management (SRM) alone cannot be sufficient to contrast the negative effects of CO$_2$ anthropogenic emissions.

q-bio.OT↗

arXiv2023

The role of ecosystem transpiration in creating alternate moisture regimes by influencing atmospheric moisture convergence

The terrestrial water cycle links the soil and atmosphere moisture reservoirs through four fluxes: precipitation, evaporation, runoff, and atmospheric moisture convergence (net import of water vapor to balance runoff). Each of these processes is essential for human and ecosystem well-being. Predicting how the water cycle responds to changes in vegetation cover remains a challenge. Recently, changes in plant transpiration across the Amazon basin were shown to be associated disproportionately with changes in rainfall, suggesting that even small declines in transpiration (e.g., from deforestation) would lead to much larger declines in rainfall. Here, constraining these results by the law of mass conservation, we show that in a sufficiently wet atmosphere, forest transpiration can control atmospheric moisture convergence such that increased transpiration enhances atmospheric moisture import and resulting water yield. Conversely, in a sufficiently dry atmosphere increased transpiration reduces atmospheric moisture convergence and water yield. This previously unrecognized dichotomy can explain the otherwise mixed observations of how water yield responds to re-greening, as we illustrate with examples from China's Loess Plateau. Our analysis indicates that any additional precipitation recycling by additional vegetation increases precipitation but decreases local water yield and steady-state runoff. Therefore, in the drier regions and early stages of ecological restoration, the role of vegetation can be confined to precipitation recycling, while once a wetter stage is achieved, additional vegetation enhances atmospheric moisture convergence and water yield. Evaluating the transition between regimes, and recognizing the potential of vegetation for enhancing moisture convergence, are crucial for characterizing the consequences of deforestation and for motivating and guiding ecological restoration.

physics.ao-ph↗

arXiv2022

How transpiration by forests and other vegetation determines alternate moisture regimes

The terrestrial water cycle links the soil and atmosphere moisture reservoirs through four fluxes: precipitation, evaporation, runoff and atmospheric moisture convergence. Each of these fluxes is essential for human and ecosystem well-being. However, predicting how the water cycle responds to changes in vegetation cover, remains a challenge (Lawrence and Vandecar, 2015; Ellison et al., 2017; te Wierik et al., 2021). Recently, rainfall was shown to decrease disproportionally with reduced forest transpiration following deforestation (Baudena et al., 2021). Here, combining these findings with the law of matter conservation, we show that in a sufficiently wet atmosphere forest transpiration can control atmospheric moisture convergence such that increased transpiration enhances atmospheric moisture import. Conversely, in a drier atmosphere increased transpiration reduces atmospheric moisture convergence and runoff. This previously unrecognized dichotomy can explain the seemingly random observations of runoff and soil moisture sometimes increasing and sometimes reducing in response to re-greening (e.g., Zheng et al., 2021). Evaluating the transition between the two regimes is crucial both for characterizing the risk posed by deforestation as well as for motivating and guiding global ecosystem restoration.

physics.ao-ph↗

arXiv2021

Revisiting the Mousetrap Experiment: Not Just About Nuclear Chain Reactions

We present quantitative measurements on a classic experiment proposed for the first time in 1947 to illustrate the phenomenon of a chain reaction in nuclear fission. The experiment involves a number of mousetraps loaded with solid balls. Once one trap is made to snap, it releases two balls that cause other traps to snap more traps and the result is a chain reaction. We report for the first time that the mousetrap experiment can be fitted by a simple dynamic model. We also discuss the significance of this experiment beyond nuclear chain reactions, as providing insight in a variety of fields involving complex, adaptive systems.

physics.pop-ph↗

arXiv2021

The Sixth Law of Stupidity: A Biophysical Interpretation of Carlo Cipolla's Stupidity Laws

Carlo Cipolla's stupidity quadrant and his five laws of stupidity were proposed for the first time in 1976. Exposed in a humorous mood by the author, these concepts nevertheless describe very serious features of the interactions among human beings. Here, we propose a new interpretation of Cipolla's ideas in a biophysical framework, using the well-known predator-prey or "Lotka-Volterra" model. We find that there is indeed a correspondence between Cipolla's approach, based on economics, and biophysical economics. On the basis of this examination, we propose a sixth law of stupidity, additional to the five proposed by Cipolla. The law states that humans are the stupidest species in the ecosystem.

q-bio.PE↗

arXiv2019

MEDEAS-World model calibration for the study of the energy transition

MEDEAS (Modelling the Energy Development under Environmental And Socioeconomic constraint) World is a new global-aggregated energy-economy-environmental model, which runs from 1995 to 2050. In this work, we tested the MEDEAS world model to reproduce the IPCC (International Panel on Climate Change) GHG (Green House Gases) emission pathways consistent with 2 °C Global Warming. We achieved parameter optimizations of the MEDEAS model related to different scenarios until 2050. We chose to provide a sensitivity analysis on the parameters that directly influence the emission curves focusing on the annual growth of the RES (Renewable Energy Sources), GDP (Gross Domestic Product) and annual population growth. From such an analysis, it has been possible to infer the large impact of GDP on the emission scenarios.

physics.soc-ph↗

arXiv2019

Pattern Analysis of World Conflicts over the past 600 years

We analyze the database prepared by Brecke (Brecke 2011) for violent conflict, covering some 600 years of human history. After normalizing the data for the global human population, we find that the number of casualties tends to follow a power law over the whole data series for the period considered, with no evidence of periodicity. We also observe that the number of conflicts, again normalized for the human population, show a decreasing trend as a function of time. Our result agree with previous analyses on this subject and tend to support the idea that war is a statistical phenomenon related to the network structure of the human society.

stat.AP↗

arXiv2018

Toward a General Theory of Societal Collapse. A Biophysical Examination of Tainter s Model of the Diminishing Returns of Complexity

The collapse of large social systems, often referred to as civilizations or empires, is a well known historical phenomenon, but its origins are the object of an unresolved debate. In this paper, we present a simple biophysical model which we link to the concept that societies collapse because of the diminishing returns of complexity proposed by Joseph Tainter. Our model is based on the description of a socioeconomic system as a trophic chain of energy stocks which dissipate the energy potential of the available resources. The model produces various trajectories of decline, in some cases rapid enough that they can be defined as collapses. At the same time, we observe that the exploitation of the resource stock (production) has a strongly nonlinear relationship with the complexity of the system, assumed to be proportional to the size of the stock termed bureaucracy. These results provide support for Tainter s hypothesis.

physics.soc-ph↗

arXiv2016

Dynamic patterns of overexploitation in fisheries

Understanding overfishing phenomenon and regulating fishing quotas is a major global challenge for the 21st Century both in terms of providing food for humankind and to preserve the oceans ecosystems. However, fishing is a complex economic activity, affected not just by overfishing but also by such factors as pollution, technology, financial factors and more. For this reason, it is often difficult to state with complete certainty that overfishing is the cause of the decline of a fishery. In this study, we developed a simple dynamic model based on the earlier, well-known Lotka-Volterra model or Prey-Predator model. To describe exploitation patterns, we assume that the fish stock and the fishing industry are coupled stock variables in the model and they dynamically affect each other, with the fishing yield proportional to both the fishing capital and the fish stock. The model is based on the concept that the fishing industry acts as the predator of the resource and that its growth and subsequent decline is directly related to the abundance of the fish stock. If the model can be fit historical data relative to specific fisheries, then it is a strong indication that the fishing industry is strongly affected by the magnitude of the fish stock and that, in particular, the decline of the yield and the decline of the stock are linked to each other. The model does not pretend to be a general description of the fishing industry in all its varied forms; however, the data reported here show that the model can indeed qualitatively describe several historical case of the collapse of fisheries. The model can also be used as a qualitative guide to understand the behavior of several other fisheries. These result indicate that one of the main factors causing the present crisis of the world's fisheries is the overexploitation of the fish stocks.

q-bio.PE↗

arXiv2016

The Sower's way. Quantifying the Narrowing Net-Energy Pathways to a Global Energy Transition

Planning the appropriate renewable energy installation rate should balance two partially contradictory objectives: substituting fossil fuels fast enough to stave-off the worst consequences of climate change while maintaining a sufficient net energy flow to support the world's economy. The upfront energy invested in constructing a renewable energy infrastructure subtracts from the net energy available for societal energy needs, a fact typically neglected in energy projections. Modeling feasible energy transition pathways to provide different net energy levels we find that they are critically dependent on the fossil fuel emissions cap and phase-out profile and on the characteristic energy return on energy invested of the renewable energy technologies. The easiest pathway requires installation of renewable energy plants to accelerate from 0.12TWp/year in 2013 to peak between 6.6 and 10.4 TWp/year, for an early or a late fossil-fuel phase-out respectively in order for emissions to stay within the recommended CO2 budget.

physics.soc-ph↗

arXiv2015

What future for the Anthropocene? A biophysical perspective

The Anthropocene is a proposed time subdivision of the earth's history correlated to the strong human perturbation of the ecosystem. Much debate is ongoing about what date should be considered as the start of the Anthropocene, but much less on how it can evolve in the future and what are its ultimate limits. It is argued here that the phenomena currently defining the Anthropocene will rapidly decline and disappear in times of the order of one century as a result of the irreversible dispersal of the thermodynamic potentials associated to fossil carbon. However, it is possible that, in the future, the human economic system may catalyze the dissipation of solar energy in forms other than photosynthesis, e.g. using solid state photovoltaic devices. In this case, a strong human influence on the ecosystem may persists for much longer times, but in forms very different than the present ones.

nlin.AO↗

arXiv2015

A Net Energy-based Analysis for a Climate-constrained Sustainable Energy Transition

The transition from a fossil-based energy economy to one based on renewable energy is driven by the double challenge of climate change and resource depletion. Building a renewable energy infrastructure requires an upfront energy investment that subtracts from the net energy available to society. This investment is determined by the need to transition to renewable energy fast enough to stave off the worst consequences of climate change and, at the same time, maintain a sufficient net energy flow to sustain the world's economy and population. We show that a feasible transition pathway requires that the rate of investment in renewable energy should accelerate approximately by an order of magnitude if we are to stay within the range of IPCC recommendations.

physics.soc-ph↗

arXiv2013

Declining trends of healthy life years expectancy (HLYE) in Europe

We examine the trends in Healthy Life Years Expectancy (HLYE) at birth during the past few decades in Europe. We observe that several European countries show a significant drop in HLYE at birth starting from 2003; interrupting what had been a previous continuous increase. We discuss the possible causes of this drop, including a possible correlation with climate change in terms of the heat wave experienced in Europe in 2003. It is not possible, at present, to propose a single explanation for this phenomenon, however the trend is worrisome and its causes should be investigated further.

stat.AP↗