Touring India 2026: Short courses/workshops/talks at Kanpur, Pune, and Bombay to discuss how many features of climate can be better understood with a little bit of more thermodynamicsโ€ฆ

Again we were in India in March. This year, we visited Sarosh at IIT Kanpur with a short course on โ€œThermodynamics for Climate, Water, and Urban Systems sustainabilityโ€, discussed thermodynamics, maximum power, glaciers and climate change in Pune at IITM and IISER, and visited IIT Bombay for a workshop and seminar. And talked a lot with colleagues and students. More in this blogpost.


Our trip to India seems to become a habit. It started in 2019, when Vinod Gaur contacted me because of his and his colleagues interests in thermodynamics. Since 2023, we have come back once a year, meeting old friends and new people, having short courses, talking and discussing a lot, and seeing places along the way. And it certainly has a longer-lasting impact: I met both, Sarosh and Tejasvi, on my first trip, and now we do research together.

Stop 1: Short course at IIT Kanpur

Our first stop was at the IIT Kanpur in Northern India. This year we held a short course on โ€œThermodynamics for Climate, Water, and Urban Systems sustainabilityโ€ at the Kotak School of Sustainability at the IIT Kanpur. Sarosh, now a professor there, organised the event. We started with general session on thermodynamics, and then covered climate, water and human/urban systems. As in the last year, we had a mix of participants, some were internal students from Kanpur, some were external. Also the lectures were mixed to provide some differing views on the same topics and to discuss how these link together. For instance, this year we had some very nice and stimulating interactions with a social scientist, Pritee Sharma from IIT Indore, on sustainability. This course was similar to those we gave in previous years at IIT Roorkee and in Kashmir. And, as always, afterwards we looked at which parts worked well and which did not – this year, we planned for too little time to interact with students.

We then spend one day in Kanpur to have a bit of time to interact informally with Sarosh and his group – having time to think and scribble things on blackboards. In the evening, Indra Sen, a geochemist from IIT Kanpur, kindly took us out for dinner. He was the Master thesis advisor of Saurabh and Vani, who are both doing their PhDโ€™s in my group.

The weekend: Mughal architecture in Lucknow

On Friday, we went to the nearby city of Lucknow. This city has some Mughal architecture worth looking at, Vinod recommended it. He needed to leave on Saturday, so Saurabh and I first took him to the airport and used the time to talk, generally about life, the universe, and thermodynamics, and more concretely about how to spread the importance of thermodynamics more effectively.

In the afternoon Saurabh and I went to look at the Bara Imambara, a memorial and mosque built about 250 years ago. On top of the main building, there was a maze for defense – a rather fascinating construction! We were glad to take a guide, who explained some of the marvels of the architecture that we looked at – and who took us out of the maze! In the evening, it was very nice to meet the parents of Saurabh and have dinner together.

Stop 2: IITM Pune

On Sunday we continued our trip to Pune. We visited the Indian Institute for Tropical Meteorology (https://www.tropmet.res.in), IITM, and stayed in their guesthouse. We had three days of lectures, an event organized by IITM as a further education for their students. One afternoon we spent discussing with the work groups of the institute, on climate change, monsoon predictions and land-atmosphere interactions. As usual, it was as an intense period of lecturing and stimulating interactions.

The Thursday – well, that was a fault in our planning. As it happened, the Thursday was a public holiday in the state of Maharashtra, the New Year started. A good occasion to do a bit of sightseeing. So Tejasvi, Saurabh, Vijayan (a geophysicist who joined from Bangalore and talked about GPS and atmospheric water) and myself first went to a fort about 30 minutes away in the mountains, a place that I visited already in 2019. While we explored the fort, we again discussed a lot, about science, general things, and trying to explain what we saw – like rather green trees despite the dryness of the landscape.

For lunch, we returned to Pune, having lunch at a South Indian restaurant, eating dosas. I donโ€™t think I ate those before, and they were delicious. After the lunch, we went to another fort in downtown Pune while Saurabh was taken to the airport because he needed to leave earlier to Germany. The fort was niceโ€ฆ although I found the Banyam trees more fascinating to look at, especially from the top of the wall of the fort. We then visited a well-known Hindu temple. There, it was incredibly crowded because of New Year celebrations, but we managed to get a special treatment and received our blessing for the New Year. All of this happened at quite some hot temperatures in the mid-30ies, so quite perfectly we finished our sightseeing trip with wonderful ice cream.

On Friday we met Argha Banerjee from IISER Pune, which is just across the street from IITM, and interacted with him and his group. Tejasvi also gave a seminar in his department in the afternoon.

The weekend: Buddhist caves near Lonavala and downtown Bombay

On Saturday we then went to Lonavala, a town on the way to Mumbai that is at the Western Ghats – the coastal mountain range that stretches along the western coast of India. Before we came to the town, we visited two nearby sites with ancient Buddhist caves, both about 2000 years old. The first was, may be, less spectacular in terms of the main hall, but had such a nice, peaceful setting that it was a pleasure to explore the place. The second place was a lot busier, also because a Hindu temple was built at the same site and that attracted a lot of visitors – because of the New Year.

On Sunday, I started my day with a long run – doing sports while it was still not too hot. From the hotel and up the hill it was quite easy to get out of town. While running, I could look at the magnificent landscape of the Western Ghats. Also, I did not run alone – a dog from one resort somehow joined me and accompanied me. On my way back, he took the right turn and went back home. How nice!

After breakfast we then left for Mumbai, on the freeway, and went straight to the guest house of the IIT. Tejasvi went off to see his wife and family, while Vijayan and I met a scientist from Subimal Ghoshโ€™s group, who kindly took us to visit downtown Bombay. We watched the sunset, looked at the Gateway to India monument, and went to a nice restaurant serving Indian seefood. And, the downtown was again really busy because of Eid and the New Year.

Stop 3: IIT Bombay

We stayed at the IIT to join a workshop on cloud bursts, which have become a real problem in the Himalayas. Also, the visit was accompanied with a seminar I gave on โ€œHow basic physics shapes the climate over landโ€, which included some more recent results from Sarosh and Tejasvi on how we can explain the diurnal temperature range and diurnal variations in relative humidity in rather simple terms, using a little bit of physics. It was very well received. I had a nice dinner together with the young faculty of the Center for Climate Studies (https://www.climate.iitb.ac.in), discussing science and active teaching methods. I also managed to talk to Basudev about scientific publications, met students, and had very stimulating discussions with Angshuman and Akshaya on climate change and moist static energy.

Final thoughts

As in the previous years, we return to Germany with many stimulating impressions, writing down notes and thoughts, and sketching plans about 2027. This year, there were more concrete interactions about collaborations and visits, e.g., via fellowships of the Humboldt foundation (https://www.humboldt-foundation.de) or a mobility grant from the Max-Planck Society, with topics becoming more concrete: Can we apply maximum power to infer valley breezes over glaciers? Or use our surface energy balance approach to understand why some glaciers melt faster than others? Or to understand why different climate models show different climate sensitivities? And then, there is still the Indian Monsoon as a thermodynamic system. Weโ€™ll see how things will evolve. It will be great to come back again next year.

New Article: Explaining observed daily variations and decadal trends in the diurnal air temperature range

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”

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.

Continue reading “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”

Neues Video: Wie man Muster der globalen Klimaerwรคrmung allein durch Strahlungstransport verstehen kann

Im neuen Video zum Kraftwerk Erde geht es um den atmosphรคrischen Treibhauseffekt – speziell, um die Rolle des atmosphรคrischen Fensters.ย  รœber die Faktoren, die die GrรถรŸe und Durchlรคssigkeit dieses Fensters beeinflussen, kann man recht einfach, aber physikalisch, direkt Muster der globalen Klimaerwรคrmung erklรคren. Im Blogbeitrag gibt es die Referenzen dazu.

Continue reading “Neues Video: Wie man Muster der globalen Klimaerwรคrmung allein durch Strahlungstransport verstehen kann”

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 thatโ€˜s no break from feeling the impacts of global warming.ย  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?ย  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”

Touring India 2024 – Stop 3: Workshop and inspiring discussions on sustainable cities, thermodynamics and fractals at IIT Kanpur

Our next stop is at the IIT Kanpur, 400 km east of Delhi at the banks of the Ganges river. Time passes quickly. We spend time preparing lectures, meeting Saurabh – our future new PhD student – and participated in a workshop on sustainable cities. There, we had enlightening discussions on fractals, power laws, and how these relate to thermodynamics and can be applied to cities.

Continue reading “Touring India 2024 – Stop 3: Workshop and inspiring discussions on sustainable cities, thermodynamics and fractals at IIT Kanpur”

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.”

New paper: Sustaining the biosphere in the Anthropocene – not as simple as it may sound

Sustainability is a popular topic these days, but what does it actually mean? What does it take to sustain life on Earth in the presence of increased human pressures, and what does it imply for a sustainable future? In a recent paper I combined thermodynamics with an Earth system approach to look at these questions. ย 

Continue reading “New paper: Sustaining the biosphere in the Anthropocene – not as simple as it may sound”

New Book Chapter:ย  Understanding the Earth as a Whole System: From the Gaia Hypothesis to Thermodynamic Optimality and Human Societies

โ€œThe whole is more than the sum of its partsโ€ – this has been said by smart people throughout human history, from Aristotle to Gibbs.  But how does it apply to the vastly complex Earth system?  In the book chapter just published I describe how this focus on the whole combined with a thermodynamic formulation of the Earth system including life helps us to understand that the whole is more, and simpler, than the sum of its parts.  This is because complex, natural systems appear to work at their thermodynamic limit.  The emergent functioning may then very well share characteristics similar to those postulated by the controversial Gaia hypothesis of James Lovelock, which states that life regulates the Earth for its own benefit.

Continue reading “New Book Chapter:ย  Understanding the Earth as a Whole System: From the Gaia Hypothesis to Thermodynamic Optimality and Human Societies”

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.”

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 23ยฐ – 25ยฐC. 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?ย  That’s what we looked at in a paper just published online in the Journal of Climate.ย  @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?ย  That’s what we looked at in a paper just published online in the Journal of Climate.ย  @annuPanwar_sci @ametsoc @MPI_BGC”

“Kraftwerk Erde: Wie der belebte Planet Energie umwandelt” – Vortrag bei #FasziAstroOnline, heute Abend, 13.01.2022, 19 Uhr, live auf youtube.ย  Mehr Infos im Blog. @MPI_BGC @HdAstro

Die Erde arbeitet wie ein Kraftwerk, indem sie Sonnenenergie in andere Formen umwandelt, die die Winde der Atmosphรคre, 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 – รผber die fundamentalen Rolle von Energie und Entropie, wie Leben den Planeten verรคndert, aber auch zu angewandten Themen wie dem Klimawandel und warum die Photovoltaik die Technologie ist, die bei weitem den grรถรŸten 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.ย  Mehr Infos im Blog. @MPI_BGC @HdAstro”

#goldschmidt2021 We contribute our work on dissipative dynamics and frequency distributions in river geochemistry and an update on the thermodynamics of planetary evolution.

Our work on thermodynamics and the Goldschmidt conference on geochemistry – well, that seems like an obvious match. But what we contribute is a little different, and the match is not quite so straightforward. What our perspective adds is (a) a focus on non-equilibrium thermodynamics and disequilibrium, and the processes that generate and dissipate this disequilibrium, and (b) a systemโ€˜s view which accounts for the environmental setting as well as the interactions and feedbacks within the Earth as an overarching thermodynamic system. Both of our contributions next week nicely illustrate these points and show how important it is to think โ€žthermodynamicsโ€œ beyond its more narrow application to geochemical reactions.

Continue reading “#goldschmidt2021 We contribute our work on dissipative dynamics and frequency distributions in river geochemistry and an update on the thermodynamics of planetary evolution.”

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.ย  It is a routine measurement at weather stations, and this temperature is the basis for analyzing trends, such as global warming.ย  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.ย  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.ย  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.”