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 Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>