How much warmer is the day compared to the night? Or, in other words, how large is the diurnal air temperature range (DTR)? This might seem like a simple question, but the DTR actually varies in surprisingly complex ways across regions and periods. What shapes these variations? What happens to DTR on cloudy days and under clear skies? How does it respond to how wet or dry the land is? And what happens to DTR as the planet warms? We answer these questions in our new study led by Sarosh, published in Geophysical Research Letters. Our goal was to understand the physics behind the DTR using an approach that links the short and long-term variations in DTR to things we can observe and measure, like clouds, sunlight, and surface dryness.
Continue reading “New Article: Explaining observed daily variations and decadal trends in the diurnal air temperature range”Category: Climatology
Neu auf youtube: Warum extreme Temperaturen so viel häufiger werden
35 Grad im Sommer – ist das noch normal? Nein, ist es nicht. Es ist der Klimawandel. Im neuen Youtube Video und diesem Blogbeitrag erkläre ich es mit etwas Physik – was Temperaturen im Wesentlichen prägt, wie Variabilität entsteht, und warum Extreme so viel häufiger werden.
Continue reading “Neu auf youtube: Warum extreme Temperaturen so viel häufiger werden”Touring India 2025: A short course in Roorkee, and visits with talks in Gandhinagar, Bombay, and Pune to discuss and interact on entropy and the powers of the Earth system
We were back in India, spending a week at the IIT Roorkee to teach a short course on the Second Law in the Earth System Science, giving talks and having discussions at IIT Gandhinagar, IIT Bombay, IISER Pune and IITM. Find out more on what we did and discussed, look at a few photos, and some related papers in this blogpost.
Neues Video: Wie man Muster der globalen Klimaerwärmung allein durch Strahlungstransport verstehen kann
Im neuen Video zum Kraftwerk Erde geht es um den atmosphärischen Treibhauseffekt – speziell, um die Rolle des atmosphärischen Fensters. Über die Faktoren, die die Größe und Durchlässigkeit dieses Fensters beeinflussen, kann man recht einfach, aber physikalisch, direkt Muster der globalen Klimaerwärmung erklären. Im Blogbeitrag gibt es die Referenzen dazu.
Notes from vacation: Thoughts on why climate change impacts in the Alps and Italy are already much more severe than what a 1.5 degree target suggests
We just finished our summer vacation, but that‘s no break from feeling the impacts of global warming. This year we crossed the Austrian Alps and the Appenin mountains in central Italy with our bikes – but where were the ice-covered peaks and why was Italy so hot? Some thoughts on the basic physics involved and why climate change may already be more severe than what some models anticipate.
Continue reading “Notes from vacation: Thoughts on why climate change impacts in the Alps and Italy are already much more severe than what a 1.5 degree target suggests”Warum der Klimawandel in Deutschland stärker als erwartet ausfällt. Und ganz klar sichtbar ist, wenn man nachsieht.
Es gibt sie ja immer noch, Klimawandelleugner und Akteure, die aus Eigeninteresse Falschinformationen und Zweifel zum Klimawandel verbreiten. Als Physiker kann ich da nur fassungslos mit dem Kopf schütteln, weil Beobachtungen und Physik den Klimawandel zweifelsfrei bestätigen. Es gibt aber auch Mitmenschen, die den Klimawandel nicht wahrnehmen, und das ist ja was ganz Menschliches. Wer erinnert sich schon an das Klima vor dreizig Jahren? Der Klimawandel hat Deutschland schon deutlich zugeschlagen, und man kann ihn physikalisch nachvollziehen – dazu dieser Blogpost mit Analysen, die ich kürzlich mit Messungen an Wetterstationen in Deutschland durchgeführt habe und weiterführende Links. Und sie zeigen, dass der Klimawandel schon krasser gekommen ist als erwartet.
Continue reading “Warum der Klimawandel in Deutschland stärker als erwartet ausfällt. Und ganz klar sichtbar ist, wenn man nachsieht. “Neuer Artikel und Youtube Video: Wie Energie und Thermodynamik den Wasserkreislauf formt. Und wie dies mehr Trockenheit und Starkregen im globalen Klimawandel erklären kann.
Es braucht nur etwas grundlegende Physik, um das Wesentliche des Wasserkreislaufs zu beschreiben. Damit können wir klimatologische Variationen und die Änderungen mit dem globalen Klimawandel sehr gut wiedergeben. Dies ist im gerade veröffentlichten Aufsatz beschrieben und in diesem Youtube Video erklärt.
Continue reading “Neuer Artikel und Youtube Video: Wie Energie und Thermodynamik den Wasserkreislauf formt. Und wie dies mehr Trockenheit und Starkregen im globalen Klimawandel erklären kann.”Neu auf Youtube: Wie der Ansatz vom „Kraftwerk Erde“ einfache, aber physikalisch-basierte Klimaforschung und das Nachrechnen von Temperaturmustern und Trends ermöglicht
In der zweiten Folge der Serie zum Kraftwerk Erde geht es um die Temperaturen der Erde. Thermodynamisch gesehen erzeugen räumliche und zeitliche Unterschiede in der Erwärmung durch Sonnenlicht und der Kühlung durch Abstrahlung ins Weltall Temperaturunterschiede, also Zustände von thermodynamischen Nichtgleichgewicht. Dieses wird vom „Kraftwerk Atmosphäre“ genutzt, um Arbeit zu leisten, Luft zu bewegen, Wärme zu verteilen, und Nichtgleichgewicht abzubauen. Mit Datensätzen vom Strahlungsantrieb und der maximalen Leistung dieses Kraftwerks lässt sich dann wunderbar nachvollziehen, warum Wüsten wärmer sind als Regenwälder, warum sich im globalen Klimawandel Land stärker erwärmt als der Ozean, und warum sich Deutschland in den letzten Dekaden so stark erwärmt hat.
Continue reading “Neu auf Youtube: Wie der Ansatz vom „Kraftwerk Erde“ einfache, aber physikalisch-basierte Klimaforschung und das Nachrechnen von Temperaturmustern und Trends ermöglicht”Neu auf Youtube: Kraftwerk Erde – Wie Energie den belebten Planeten prägt. Jetzt auf Urknall, Weltall und das Leben
Die Erde arbeitet wie ein Kraftwerk und folgt dabei den Hauptsätzen der Thermodynamik. Dabei wandelt sie Sonnenenergie in andere Energiearten um und prägt so die Dynamik des Erdsystem. Allein durch diesen grundlegenden physikalischen Ansatz kann man schon erstaunlich viel vom Erdsystem verstehen, von den Hauptfaktoren, die Temperatur und Wasserkreislauf bestimmen, die Vegetation begrenzen bis zu den Auswirkungen des Klimawandels und den Grenzen erneuerbaren Energien.
Das Video vom Vortrag vom 07. November 2023 vor den Freunden des Planetariums Göttingen ist jetzt auf youtube zu sehen. Auf dem Blog sind die Folien sowie Verweise zu Hintergrundliteratur.
New paper: Working at the limit – how entropy, work and limits shape Earth system functioning. Here is a simple, but long summary of the key points.
Entropy has intrigued me for a long time – it usually comes up at the very end of asking “why” questions. It is such a fundamental concept in physics, but then – why does nobody talk about it in Earth system science? My review paper just published in Earth System Dynamics explains why entropy is so essential to understand the dynamics of the Earth system: because it limits how much work can be done, and work is at the very core of what we call dynamics.
Continue reading “New paper: Working at the limit – how entropy, work and limits shape Earth system functioning. Here is a simple, but long summary of the key points.”#EGU23: It’s April again, and Vienna is calling. We share our recent insights from following the energy through the Earth system. @akleidon @s_ghausi @yinglin_tian
Just like in pre-Corona times, April is the month in which Europe’s largest geosciences union convenes for its General Assembly in Vienna, Austria. We are excited to be there, present our latest research, and look forward to seeing and talking to you there!

New Blogpost: How much energy will I consume to keep our home warm this winter? A simple estimate, utilizing climate data, gas meter readings, and past gas bills. And yes, the second law comes into play as well.
Winter is coming, snow is falling, and here in Jena we will need gas to heat our homes. Gas prices are at their all-time high, so how much heat do I need and how can I reduce it? I describe a simple, physical way to estimate how much energy I should need to heat our home, and how this can help to find out how effective measures are to reduce energy consumption.
Continue reading “New Blogpost: How much energy will I consume to keep our home warm this winter? A simple estimate, utilizing climate data, gas meter readings, and past gas bills. And yes, the second law comes into play as well.”#AGU22: We will be in Chicago next week to present our updates about thermodynamic and energetic controls on land-atmosphere exchange and Arctic sea ice loss events
It is that time of the year again and the AGU Fall Meeting is all set to take place in the hybrid format. This year two members of our lab Sarosh Alam Ghausi and Yinglin Tian will be presenting their research in person at the conference.
Continue reading “#AGU22: We will be in Chicago next week to present our updates about thermodynamic and energetic controls on land-atmosphere exchange and Arctic sea ice loss events”Can we infer rainfall sensitivity to global warming using observations of precipitation and temperature? Not quite, until you correct for the cooling effects of clouds.
Rainfall events are expected to become heavier as the hydrologic cycle intensifies with global warming. To determine this strengthening, many studies use observed precipitation events and test how these change with observed temperatures. These so-called scaling rates differ from what is expected from theory, showing a decline above temperatures of around 23° – 25°C. This breakdown in scaling makes it difficult to interpret the precipitation response to global warming and its cause further remains unclear. It also raises the question of whether a high-temperature threshold limits the increase in the intensity of precipitation events with temperature. We resolve this in our latest paper by showing that the break in scaling primarily occurs due to radiative effect of clouds on surface temperatures that leads to a covariation between the two variables.
Continue reading “Can we infer rainfall sensitivity to global warming using observations of precipitation and temperature? Not quite, until you correct for the cooling effects of clouds.”How much does evaporation affect temperature variations during the day? That’s what we looked at in a paper just published online in the Journal of Climate. @annuPanwar_sci @ametsoc @MPI_BGC
Over land, there is a marked variation in surface and air temperature during day and night, with the amplitude described by the diurnal temperature range. What are the main factors that determine its magnitude across regions and how much is it shaped by evaporation? This is what Annu Panwar looked at in her last part of her PhD using FluxNet observations and the ERA 5 reanalysis products, with the results just published online in the Journal of Climate. What this analysis shows is that energy balances go a long way to explain the main influences and that evaporation does not have quite such a strong effect as one may think.
Continue reading “How much does evaporation affect temperature variations during the day? That’s what we looked at in a paper just published online in the Journal of Climate. @annuPanwar_sci @ametsoc @MPI_BGC”We’ll be at #EGU22, showing how radiation and maximum power shape temperatures, their extremes, the atmospheric circulation and the wind energy resource. @akleidon @s_ghausi @yinglin_tian
Corona is still around, also in Vienna, but the EGU General Assembly will nevertheless happen again, in a hybrid form. We are thrilled to be there physically, giving our 6 minute short talks on our work, and look forward to seeing and talking to you there!
Continue reading “We’ll be at #EGU22, showing how radiation and maximum power shape temperatures, their extremes, the atmospheric circulation and the wind energy resource. @akleidon @s_ghausi @yinglin_tian”Interested in how the Earth system works? I have a #PostDoc opening available in my group, applying thermodynamics, max. power, and optimality to Earth system science. @MPI_BGC
The position is in my research group, which focuses on how the Earth functions as a whole system, the role of life within it, and what a sustainable human future might look like. We take a unique Earth system approach that focuses on thermodynamics, energy conversions, and limits/optimality such as maximum power.
We are seeking a motivated and interested person to help us further develop this approach, evaluate it using observational data, and/or compare it to climate model results. More details are provided in the formal job announcement, which you can find here. More background information in this post.
Continue reading “Interested in how the Earth system works? I have a #PostDoc opening available in my group, applying thermodynamics, max. power, and optimality to Earth system science. @MPI_BGC”Last week our group member @annuPanwar_sci successfully defended her PhD thesis on diurnal temperature variations and how they are affected by evaporation and vegetation. Very well done, and congratulations, Annu! @mpibgc
Evaporation cools, right? What may sound so obvious was the topic of Annu’s PhD thesis: to look into observations and find the effects of evaporation in how surface and near-surface air temperatures vary throughout the day. The results are not quite as obvious, and we learned a lot. Here is a brief summary of her thesis, with its contents spread over three papers. Very nice work!
Continue reading “Last week our group member @annuPanwar_sci successfully defended her PhD thesis on diurnal temperature variations and how they are affected by evaporation and vegetation. Very well done, and congratulations, Annu! @mpibgc”Can we solve the freshwater problem by taking moisture out of the atmosphere with dehumidifiers? When we look at how the hydrologic cycle does its work, we get a straight and clear answer: no, we don’t solve the problem!
In Germany, the construction of Tesla’s Gigafactory near Berlin draws its attention, including its substantial need for freshwater. Despite its many lakes, the area around Berlin is among the driest in Germany. The atmosphere contains water vapor, and it seems like a tempting source for freshwater, just sitting there to be harvested by some form of technology. This is what a company claims to do (and quite a few others elsewhere as well). But can this promise hold up?
Continue reading “Can we solve the freshwater problem by taking moisture out of the atmosphere with dehumidifiers? When we look at how the hydrologic cycle does its work, we get a straight and clear answer: no, we don’t solve the problem!”“Kraftwerk Erde: Wie der belebte Planet Energie umwandelt” – Vortrag bei #FasziAstroOnline, heute Abend, 13.01.2022, 19 Uhr, live auf youtube. Mehr Infos im Blog. @MPI_BGC @HdAstro
Die Erde arbeitet wie ein Kraftwerk, indem sie Sonnenenergie in andere Formen umwandelt, die die Winde der Atmosphäre, den Wasserkreislauf, und auch das Leben und die Menschheit auf der Erde erhalten. Diese Umwandlungen folgen den Gesetzen der Thermodynamik, die sowohl die Richtung als auch die Grenzen setzt. Aber Erdsystemprozesse beeinflussen sich auch gegenseitig, sodass man einen Blick auf das Gesamtsystem braucht. In diesem Vortrag zeige ich, dass man allein durch diesen grundlegenden physikalischen Ansatz schon erstaunlich viel vom Erdsystem verstehen kann – über die fundamentalen Rolle von Energie und Entropie, wie Leben den Planeten verändert, aber auch zu angewandten Themen wie dem Klimawandel und warum die Photovoltaik die Technologie ist, die bei weitem den größten Beitrag zur Energiewende liefern wird.
Continue reading ““Kraftwerk Erde: Wie der belebte Planet Energie umwandelt” – Vortrag bei #FasziAstroOnline, heute Abend, 13.01.2022, 19 Uhr, live auf youtube. Mehr Infos im Blog. @MPI_BGC @HdAstro”At #AGU21, we present updates on understanding diurnal temperature variations on land and on deriving precipitation sensitivities from observations using “clear-sky” temperatures and maximum power
Corona has not yet gone away, but the AGU Fall Meeting nevertheless takes place, in a hybrid format. Annu Panwar will be physically there, giving an invited talk on her PhD thesis on diurnal temperature variations (see, e.g., her paper in HESS) and a poster, while Sarosh Alam Ghausi will be giving his poster on precipitation scaling virtually.
Continue reading “At #AGU21, we present updates on understanding diurnal temperature variations on land and on deriving precipitation sensitivities from observations using “clear-sky” temperatures and maximum power”#vEMS21: Our updates on using #thermodynamics for land-atmosphere interactions, the precipitation response to #globalwarming, and the #windenergy potential in the German bight
With summer coming to a close, we are back to present new insights from ongoing research in extreme precipitation events, offshore wind energy and thermodynamics at the European Meteorological Society Annual Meeting 2021. The event, which will be held online next week (6 – 10 September 2021), focuses on weather and climate research and services for the achievement of the UN Sustainable Development Goals. Read on to find out more details about when and what each of us will be presenting.
Continue reading “#vEMS21: Our updates on using #thermodynamics for land-atmosphere interactions, the precipitation response to #globalwarming, and the #windenergy potential in the German bight”#vEGU21 Next week we’ll present our work on precipitation scaling, diurnal temperature range, offshore wind, and limits to vegetation productivity based on our thermodynamic Earth system view
Thermodynamics rules the world, as well as the science that we present at this year’s EGU General Assembly, which is, alas, virtual rather than in Vienna. It may not be obvious, and our contributions are spread across different sessions. But in the end, we follow the solar energy as it passes through the Earth system, seeking simple, physics-based explanations to simple phenomena: precipitation scaling with temperature found in observations, the diurnal temperature range across regions and vegetation types, also in observations, limits to offshore wind energy in the North sea and what these imply for renewable energy scenarios, and how the really low efficiency of photosynthesis fits to the notion of vegetation being optimal.
Continue reading “#vEGU21 Next week we’ll present our work on precipitation scaling, diurnal temperature range, offshore wind, and limits to vegetation productivity based on our thermodynamic Earth system view”Why does wind energy become less efficient when used at larger scales? Basic physics explains this effect, starting with a very limited ability of the atmosphere to generate wind energy from radiation, as described in my new review just published.
Wind energy plays an important role in the transition to a carbon-neutral, sustainable energy system and is rapidly expanding. So it is a good time to ask how much wind energy there actually is, whether we get close to the limits anytime soon, and why the efficiency of wind energy must decline when used at larger scales. These are basic science questions: How, and why, does the atmosphere actually generate motion, how much does it generate, and how much of it can at most be used? These questions I address in a review paper just published in which I show that it does not take much physics to answer these.
Continue reading “Why does wind energy become less efficient when used at larger scales? Basic physics explains this effect, starting with a very limited ability of the atmosphere to generate wind energy from radiation, as described in my new review just published.”AGU Fall Meeting 2020: A brief summary of our contributions and takeways
Corona has impeded everything in 2020 including researchers’ involvement in scientific conferences. However, innovation and the internet made it possible to contribute to large and much anticipated conferences like the AGU Fall Meeting ‘20. Thus, 2 of our PhD researchers, Annu Panwar and Jonathan Minz, presented their scientific results, keeping the spirit of science communication alive, despite tough times.
Continue reading “AGU Fall Meeting 2020: A brief summary of our contributions and takeways”Which factors make forests cooler: Evaporation or their high aerodynamic conductance? Our paper just published in HESS suggests that it is the latter.
Trees and plants moderate the Earth’s surface temperature. Generally, the cooling effect of vegetation is mainly attributed to the process of evapotranspiration. In our paper just published in HESS, we used observations to unravel the importance of evaporative cooling for short vegetation and forest in shaping diurnal variations in temperatures and found that, actually, it is not only evaporation that keeps the forests cool.
Continue reading “Which factors make forests cooler: Evaporation or their high aerodynamic conductance? Our paper just published in HESS suggests that it is the latter.”If you think surface and air temperature are basically the same thing, think again. Or read our new paper.
In meteorology, air temperature measurements are typically taken 2m above the surface. It is a routine measurement at weather stations, and this temperature is the basis for analyzing trends, such as global warming. The temperature of the surface is not so often measured, but it can be inferred by satellites from how much radiation is being emitted by the surface. Being only 2m apart, one may think that the temperatures basically reflect more or less the same, given their close proximity. We actually found out that this is not the case: surface temperature responds much more strongly to a lack of water than air temperature. This finding was just published in our article in the journal Geophysical Research Letters. Continue reading “If you think surface and air temperature are basically the same thing, think again. Or read our new paper.”











