Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

No Undo for Climate Change: Potential Pitfalls of Geoengineering

05.12.2013
Global warming alters the intensity of the water cycle, and the magnitude of these changes has now been explained by scientists of the Max-Planck-Institute for Biogeochemistry in Jena, Germany.

Using a simple physical approach, the study explains how the water cycle reacts to surface warming and that it responds differently to heating by sunlight or by a stronger atmospheric greenhouse effect. This has important consequences for potential interventions that aim to undo global warming by reflecting sunlight by geoengineering: While such interventions may cool down temperatures, simultaneous changes in the water cycle and the atmosphere cannot be compensated at the same time.


Water cycle
Annett Junginger; imaggeo.egu.eu

Precipitation should generally increase in a warmer world. When the surface warms due to a stronger atmospheric greenhouse effect, for instance due to more carbon dioxide in the atmosphere, the air near the surface is warmer and can hold more moisture. This should result in greater evaporation, greater rainfall, and thus a stronger cycling of water. With every degree of warming, air can hold about 7% more moisture. Climate model predictions generally show such an increase in rainfall with global warming, but they predict an increase of only about 2% per degree warming, which seems puzzling.

This puzzle has now been addressed in a study just published in the journal Earth System Dynamics of the European Geosciences Union, by scientists of the Max-Planck-Institute for Biogeochemistry in Jena, Germany. Dr. Axel Kleidon and his colleague Dr. Maik Renner looked at the processes that heat and cool the surface and how these change when the surface warms. Evaporation plays a key role here because it requires a lot of heat to evaporate water. Yet, the evaporated water from the surface also needs to be transported into the atmosphere. Kleidon and Renner applied a physical limit to this vertical transport and derived the same 2% increase in the water cycle predicted by climate models. They related this low increase, not to the general capacity of air to hold water vapor, but rather to the differential change in this capacity between the air near the surface and the air when it condenses in the atmosphere.

However, Kleidon and Renner also found that this 2% increase only applies to the case in which the surface warming was caused by a stronger atmospheric greenhouse effect. When the surface is heated more strongly by sunlight instead, they estimated that the water cycle would increase more strongly by about 3% per degree warming. This stronger increase is a consequence of the need to balance the greater energy input by sunlight with stronger cooling fluxes from the surface, which involves a stronger increase in evaporation.

“These different responses to surface heating are easy to explain”, says Kleidon, and uses a pot on the kitchen stove to illustrate. “The temperature in the pot is increased by putting on a lid, or by turning up the heat, but these two cases differ by how much energy flows through the pot”, he says. Similar effects take place when the surface warms: A stronger greenhouse effect puts on a thicker “lid” over the surface, whereas more heating by sunlight turns up the heat, enhancing the energy flow through the surface, and hence has a greater effect on the water cycle.

The consequences of these insights are profound. Studies of global warming generally lump sunlight and the atmospheric greenhouse effect into a single term, while Kleidon and Renner found that these two causes of surface heating have rather different impacts on the hydrologic cycle and on the vertical transport within the atmosphere. Their study provides important insights for understanding global climate change, specifically to the goals of geoengineering that attempts to compensate global warming by reducing the amount of sunlight reaching the surface by enhanced atmospheric reflection. When Kleidon and Renner applied their results to such a geoengineering scenario, they found that the compensation for a 2 degree warming weakens the water cycle by 2% and vertical transport by almost 8%. A similar response was also reported in a very recently published climate model intercomparison study on geoengineering. “It’s like putting a lid on the pot and turning down the heat at the same time”, explains Kleidon. “While in the kitchen you can reduce your energy bill by doing so, in the Earth system, this slows down the water cycle with wide-ranging potential consequences”, he concludes.

Weitere Informationen:
http://www.earth-syst-dynam.net/recent_papers.html
Publication
http://www.bgc-jena.mpg.de/index.php/BTM/Home
homepage A. Kleidon

Dr. Eberhard Fritz | Max-Planck-Institut
Further information:
http://www.earth-syst-dynam.net/recent_papers.html
http://www.bgc-jena.mpg.de/index.php/BTM/Home

More articles from Earth Sciences:

nachricht Ice cave in Transylvania yields window into region's past
28.04.2017 | National Science Foundation

nachricht Citizen science campaign to aid disaster response
28.04.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>