Axel Kleidon

Max Planck Institute for Biogeochemistry Jena | BGC · Group of Biospheric Theory and Modelling

Energy scenarios and transition pathways require estimates of achievable technical wind energy potentials to evaluate the integration of large scale wind energy into the electrical grid. Technical potential refers to the projected electrical generation from regional scale wind turbine deployments, while accounting for the actual area available, tur...

Optimality concepts related to energy and entropy have long been proposed to govern Earth system processes, for instance in the form of propositions that certain processes maximize or minimize entropy production. These concepts, however, remain quite obscure, seem contradictory to each other, and have so far been mostly disregarded. This review aim...

Land surface temperatures (LSTs) are strongly shaped by radiation but are modulated by turbulent fluxes and hydrologic cycling as the presence of water vapor in the atmosphere (clouds) and at the surface (evaporation) affects temperatures across regions. Here, we used a thermodynamic systems framework forced with independent observations to show th...

Temperature extremes have been related to anomalies in large-scale circulation, but how these alter the surface energy balance is less clear. Here, we attributed high extremes in daytime and nighttime temperatures of the eastern Tibetan Plateau to anomalies in the surface energy balance. We find that daytime high-temperature extremes are mainly cau...

Zusammenfassung Die Windenergienutzung in Deutschland soll bis 2050 mit bis zu 200 Gigawatt ausgebaut werden, was in etwa einer Vervierfachung im Vergleich zu heute entspricht. Diese Windturbinen werden der Atmosphäre dabei Windenergie entziehen und damit die Atmosphäre beeinflussen. Dies wirkt sich auf die Effizienz der Windenergienutzung aus, wei...

The transition of our energy system to renewable energies is necessary in order not to heat up the climate any further and to achieve climate neutrality. The use of wind energy plays an important role in this transition in Germany. But how much wind energy can be used and what are the possible consequences for the atmosphere if more and more wind e...

A dominant term in the surface energy balance and central to global warming is downwelling longwave radiation (Rld). It is influenced by radiative properties of the atmospheric column, in particular by greenhouse gases, water vapour, clouds and differences in atmospheric heat storage. We use the semi-empirical equation derived by Brutsaert (1975) t...

Many aspects of anthropogenic global change, such as shifts in land cover, the loss of biodiversity, and the intensification of agricultural production, threaten the natural biosphere. The implications of these specific aspects of environmental change are not immediately obvious; therefore, it is hard to obtain a bigger picture of what these change...

The wind blows stronger and more reliably over the sea than over land. Thus, offshore wind energy is expected to make a major contribution to the energy transition in Germany, especially in the German Bight. But what happens when a growing number of wind farms extract more and more wind energy from the atmosphere?

Ein wesentlicher Beitrag zur Energiewende wird von Offshore‐Windenergie in der deutschen Bucht erwartet. Wegen der starken und steten Winde erscheint die Offshore‐Stromerzeugung als sehr effizient. Für 2050 geht die Bundesregierung von einer installierten Leistung von 70 GW aus, also einer Verzehnfachung im Vergleich zu heute. Was passiert aber, we...

The rapid increase in world's installed wind energy capacity may have masked the power loss caused by declining global surface wind speed (termed ‘global stilling’), particularly for China with huge wind energy investments. Here, we estimated the potential impact of global stilling on wind energy production in China, using data from 1226 meteorolog...

Energy scenarios and transition pathways need estimates of technical wind energy potentials. However, the standard policy-side approach uses observed wind speeds, thereby neglecting the effects of kinetic energy (KE) removal by the wind turbines that depletes the regional wind resource, lowers wind speeds, and reduces capacity factors. The standard...

Many aspects of anthropogenic global change, such as land cover change, biodiversity loss and the intensification of agricultural production, threaten the natural biosphere. These aspects seem somewhat disjunct and specific so that it is hard to obtain a bigger picture of what these changes imply and to distinguish beneficial from detrimental human...

Climate models predict an intensification of precipitation extremes as a result of a warmer and moister atmosphere at the rate of 7 % K−1. However, observations in tropical regions show contrastingly negative precipitation–temperature scaling at temperatures above 23–25 ∘C. We use observations from India and show that this negative scaling can be e...

Optimality concepts related to energy and entropy have long been proposed in Earth system science, yet they remain obscure, seem contradictory regarding their goal to either maximize or minimize, and have so far only played marginal roles. This review aims to clarify the role of thermodynamics and optimality in Earth system science by showing that...

The diurnal variations of surface and air temperature are closely related, but their different responses to evaporative conditions can inform us about land–atmosphere interactions. Here, we evaluate the responses of the diurnal ranges in surface (Δ T s ) and air (Δ T a ) temperature to evaporative fraction at 160 FLUXNET sites and in the ERA5 reana...

Recent research explored an alternative energy-centred perspective on hydrological processes, extending beyond the classical analysis of the catchment's water balance. Particularly, streamflow and the structure of river networks have been analysed in an energy-centred framework, which allows for the incorporation of two additional physical laws: (1...

Climate models predict an intensification of precipitation extremes as a result of a warmer and moister atmosphere at the rate of 7 %/K. However, observations in tropical regions show contrastingly negative precipitation-temperature scaling at temperatures above 23°–25 °C. We use observations from India and show that this negative scaling can be ex...

With the use of the appropriate technology, such as photovoltaics and seawater desalination, humans have the ability to increase sustainably their production of food and energy while minimising detrimental impacts on the Earth system. Focussing on energy conversion and dissipation allows us to compare human activity with Earth system processes at a...

Der diesjährige Physik-Nobelpreis für bahnbrechende Beiträge zum Verständnis komplexer Systeme geht zu einer Hälfte an die Klimaforscher Syukuro Manabe und Klaus Hasselmann, zur anderen Hälfte an den Theoretiker Giorgio Parisi.

The Mississippi River Basin is a vast near-planar surface, an area upon which sunlight falls and wind flows. Its gently banked geomorphology channels precipitation, sediment, biota, and human activity into a dynamic locus of regional Earth system interactions. This paper describes the major features of this region’s energy exchanges from a thermody...

Recent developments in hydrology have led to a new perspective on runoff processes, extending beyond the classical mass dynamics of water in a catchment. For instance, stream flow has been analysed in a thermodynamic framework, which allows the incorporation of two additional physical laws and enhances our understanding of catchments as open enviro...

Zusammenfassung Seit langer Zeit ist gut dokumentiert, dass die Photosynthese mit einem sehr geringen Wirkungsgrad von weniger als 3 % aus Sonnenlicht chemische Energie gewinnt. Aber warum ist der Prozess so ineffizient? Schließlich hatte die Photosynthese mehr als drei Milliarden Jahre in der Erdgeschichte Zeit, sich zu optimieren. Diese Frage wir...

How much wind energy does the atmosphere generate, and how much of it can at best be used as renewable energy? This review aims to give physically-based answers to both questions, providing first-order estimates and sensitivities that are consistent with those obtained from numerical simulation models. The first part describes how thermodynamics de...

We seek to model the coupled evolution of a planet and a civilization through the era when energy harvesting by the civilization drives the planet into new and adverse climate states. In this way we ask if triggering "anthropocenes" of the kind humanity is experiencing now might be a generic feature of planet-civilization evolution. In this study w...

Recent developments in hydrology have led to a new perspective on runoff processes, extending beyond the classical mass dynamics of water in a catchment. For instance, stream flow has been analyzed in a thermodynamic framework, which allows the incorporation of two additional physical laws and enhances our understanding of catchments as open enviro...

We employ the approach of Roderick and Farquhar (2011) to assess the sensitivity of runoff (R) given changes in precipitation (P), potential evapotranspiration (E p), and other properties that change the partitioning of P (n) by estimating coefficients that predict the weight of each variable in the relative change of R. We use this framework using...

With the current expansion of wind power as a renewable energy source, wind turbines increasingly extract kinetic energy from the atmosphere, thus impacting its energy resource. Here, we present a simple, physics-based model (the Kinetic Energy Budget of the Atmosphere; KEBA) to estimate wind energy resource potentials that explicitly account for t...

Diurnal temperature variations are strongly shaped by the absorption of solar radiation, but evaporation, or the latent heat flux, also plays an important role. Generally, evaporation cools. Its relation to diurnal temperature variations, however, is unclear. This study investigates the diurnal response of surface and air temperatures to evaporativ...

The diurnal cycle of solar radiation represents the strongest energetic forcing and dominates the exchange of heat and mass of the land surface with the atmosphere. This diurnal heat redistribution represents a core of land-atmosphere coupling that should be accurately represented in Land-Surface Models (LSM) which are critical parts of weather and...

How much wind energy does the atmosphere generate, and how much of it can at best be used as renewable energy? This review aims to give first-order estimates and sensitivities to answer these questions that are consistent with those obtained from numerical simulation models. The first part describes how thermodynamics determines how much wind energ...

Photosynthesis converts sunlight into the chemical free energy that feeds the Earth's biosphere, yet at levels much lower than what thermodynamics would allow for. I propose here that photosynthesis is nevertheless thermodynamically limited, but this limit acts indirectly on the material exchange. I substantiate this proposition for the photosynthe...

With the use of the appropriate technology, such as photovoltaics and seawater desalination, humans have the ability to sustainably increase their production of food and energy while minimising detrimental impacts on the Earth system.

The notion that the whole is more than the sum of its parts has a long tradition in science. This, of course, also applies to the Earth system. With its myriad of processes, spanning from purely physical to life and human activity, the Earth is a vastly complex system. It may thus seem that there is nothing simple and general to say because of this...

Nonrainy days have rather different hydrologic and radiative conditions than rainy days, but few investigations considered how these different conditions contribute to the observed global warming. Here, we show that global warming is considerably stronger on nonrainy days using observations from China. We find that trends in mean temperature on non...

Abstract. With the current expansion of wind power as a renewable energy source, wind turbines increasingly extract kinetic energy from the atmosphere, thus impacting its energy resource. Here we present a simple, physics-based model (KEBA) to estimate wind energy resource potentials that explicitly account for this removal effect. The model is bas...

Photosynthesis converts sunlight into the chemical free energy that feeds the Earth's biosphere, yet at levels much lower than what thermodynamics would allow for. I propose here that photosynthesis is nevertheless thermodynamically limited, but this limit acts indirectly on the material exchange of water and carbon dioxide. I substantiate this int...

Abstract. Diurnal temperature variations are strongly shaped by the absorption of solar radiation, but evaporation, or the latent heat flux, also plays an important role. Generally, evaporation cools. Its relation to diurnal temperature variations, however, is unclear. This study investigates the diurnal response of surface and air temperatures to...

Zusammenfassung Die Verbrennung von fossilen Energieträgern hat den atmosphärischen Treibhauseffekt verstärkt, was zur Erderwärmung führt. Doch woher wissen wir, dass der Treibhauseffekt einen so entscheidenden Einfluss auf das Klima hat? Alternativ könnte auch eine ansteigende Sonnenaktivität hinter der Erwärmung stecken. Doch ein erhöhter Treibha...

Many fluxes in Earth systems are not homogeneously distributed across space, but occur highly concentrated in structures, such as turbulent eddies, river networks, vascular networks of plants, or human-made infrastructures. Yet, the highly-organized nature of these fluxes is typically only described at a rudimentary level, if at all. We propose tha...

Surface topography is an important source of information about the functioning and form of a hydrological landscape. Because of its key role in explaining hydrological processes and structures, and also because of its wide availability at good resolution in the form of digital elevation models (DEMs), it is frequently used to inform hydrological an...

Abstract Estimates of radiative fluxes under cloud‐free conditions (“clear‐sky”) are required in many fields, from climatic analyses of solar transmission to estimates of solar energy potential for electricity generation. Ideally, these fluxes can be obtained directly from measurements of solar fluxes at the surface. However, common standard method...

Crop phenology changes are important indicators of climate change. Climate change impacts on crop phenology are generally investigated through statistical analysis of the relationship between growth period length and growth period mean temperature. However, growth periods may be either earlier or later in a given year; hence, changes in mean temper...

The reactive trace gases nitric oxide (NO) and nitrous acid (HONO) are crucial for chemical processes in the atmosphere, including the formation of ozone and OH radicals, oxidation of pollutants, and atmospheric self-cleaning. Recently, empirical studies have shown that biological soil crusts are able to emit large amounts of NO and HONO, and they...

Zusammenfassung Die Energiewende hat zum Ziel, den Energiebedarf Deutschlands komplett aus erneuerbaren Energiequellen zu decken. Ist das innerhalb des Landes möglich? Im Prinzip ja, zeigen Abschätzungen. Der Schlüssel ist die direkte Nutzung der Solarenergie, denn sie liefert mehr als genug erneuerbare Energie. Erneuerbare Energiequellen wie Wind,...

Plain Language Summary Tropical deforestation impacts the local energy and water exchange between land surface and atmosphere, typically resulting in regionally warmer and drier climates. General circulation models still disagree in reproducing these changes and little has been done to derive them from first principles. Here, we present an alternat...

Generally, surface and air temperatures seem closely related but we show that they respond differently to evaporative conditions. We evaluate the temperature increase in response to solar radiation for different evaporative fractions, using observations from the Southern Great Plains. The warming rate of air temperature decreases only by 1.7×10‐3K/...

Surface topography is an important source of information about the functioning and form of a hydrological landscape. Because of its key role in explaining hydrological processes and structures, and also because of its wide availability at good resolution in the form of digital elevation models (DEM), it is frequently used to inform hydrological ana...

The present study confirms that a thermodynamic perspective on soil water is well suited to distinguishing the typical interplay of gravity and capillarity controls on soil water dynamics in different landscapes. To this end, we express the driving matric and gravity potentials by their energetic counterparts and characterize soil water by its free...

The planning of the energy transition from fossil fuels to renewables requires estimates for how much electricity wind turbines can generate from the prevailing atmospheric conditions. Here, we estimate monthly ideal wind energy generation from datasets of wind speeds, air density and installed wind turbines in Germany and compare these to reported...

While modeling approaches of evapotranspiration (λE) perform reasonably well when evaluated at daily or monthly timescales, they can show systematic deviations at the sub-daily timescale, which results in potential biases in modeled λE to global climate change. Here we decompose the diurnal variation of heat fluxes and meteorological variables into...

WINDENERGIE | Die Energiewende in Deutschland hat gerade einen neuen Rekord erreicht. Fast 40 % des erzeugten Stroms kamen im Jahr 2018 aus erneuerbaren Quellen, allein 17 % aus Windkraft. Damit trägt die Windenergie etwa in dem Maße zum Strommix bei, wie unter den Windbedingungen in Deutschland zu erwarten ist. Das haben Forscher des Max-Planck-In...

The reactive trace gases nitric oxide (NO) and nitrous acid (HONO) are crucial for chemical processes in the atmosphere, including the formation of ozone and OH radicals, oxidation of pollutants and atmospheric self-cleaning. Recently, empirical studies showed that biological soil crusts are able to emit large amounts of NO and HONO and they may th...

Turbulent fluxes strongly shape the conditions at the land surface, yet they are typically formulated in terms of semiempirical parameterizations that make it difficult to derive theoretical estimates of how global change impacts land surface functioning. Here, we describe these turbulent fluxes as the result of a thermodynamic process that generat...

Non-vascular vegetation has been shown to capture considerable quantities of rainfall, which may affect the hydrological cycle and climate at continental scales. However, direct measurements of rainfall interception by non-vascular vegetation are confined to the local scale, which makes extrapolation to the global effects difficult. Here we use a p...

The increasing diversity and resolution of spatially distributed data on terrestrial systems greatly enhance the potential of hydrological modeling. Optimal and parsimonious use of these data sources requires, however, that we better understand (a) which system characteristics exert primary controls on hydrological dynamics and (b) to what level of...

The diurnal forcing of solar radiation is the largest signal within the Earth system and dominates the diurnal cycle of the turbulent heat fluxes and evapotranspiration (λE) over land. Incoming solar radiation (Rsd) also shapes temperature, vapor pressure deficit and wind speed known as important controls on λE. Current process-based λE schemes use...

The present study corroborates that the free energy state of soil water offers a new perspective on storage dynamics and similarity of hydrological systems that cannot be inferred from the usual comparison of soil moisture observations or groundwater levels. We show that the unsaturated zone of any hydrological system is characterized by a system-...

We present a framework for studying generic behaviors possible in the interaction between a resource-harvesting technological civilization (an exo-civilization) and the planetary environment in which it evolves. Using methods from dynamical systems theory, we introduce and analyze a suite of simple equations modeling a population which consumes res...

Turbulent fluxes strongly shape the conditions at the land surface, yet they are typically formulated in terms of semi-empirical parameterisations that make it difficult to derive theoretical estimates of how global change impacts land surface functioning. Here, we describe these turbulent fluxes as the result of a thermodynamic process that genera...

Although gridded air temperature datasets share much of the same observations, different rates of warming can be detected due to different approaches employed for considering elevation signatures in the interpolation processes. Here, we examine the influence of varying spatiotemporal distribution of sites on surface warming in the long-term trend a...

The increasing diversity and resolution of spatially distributed data on terrestrial systems greatly enhances the potential of hydrological modeling. Optimal and parsimonious use of these data sources implies, however, that we better understand (a) which system characteristics exert primary controls on hydrological dynamics and (b) to what level of...

Phosphorus (P) availability decreases with soil age and potentially limits the productivity of ecosystems growing on old and weathered soils. Despite growing on ancient soils, ecosystems of lowland Amazonia are highly productive and are among the most biodiverse on Earth. P eroded and weathered in the Andes is transported by the rivers and deposite...

Observations and climate model simulations consistently show a higher climate sensitivity of land surfaces compared to ocean surfaces. Here we show that this difference in temperature sensitivity can be explained by the different means by which the diurnal variation in solar radiation is buffered. While ocean surfaces buffer the diurnal variations...

We develop a classification scheme for the evolutionary state of planets based on the non-equilibrium thermodynamics of their coupled systems, including the presence of a biosphere and the possibility of what we call an agency-dominated biosphere (i.e. an energy-intensive technological species). The premise is that Earths entry into the Anthropocen...

Observations and climate model simulations consistently show a higher climate sensitivity of land surfaces compared to ocean surfaces, with the cause for this difference being still unclear. Here we show that this difference in temperature sensitivity can be explained by the different means by which the diurnal variation in solar radiation is buffe...

Interception of precipitation by forest canopies plays an important role in its partitioning to evaporation, transpiration and runoff. Field observations show arboreal lichens and bryophytes can substantially enhance forests’ precipitation storage and evaporation. However, representations of canopy interception in global land surface models current...

Amazonian ecosystems are of global importance for the climate system and biodiversity. Phosphorus (P) is suggested to be a limited nutrient in many Amazonian ecosystems because soils are ancient, highly weathered, and nutrient depleted. Recently, it has been suggested that large herbivores may play a major role in the Amazon nutrient cycle. Here, w...