Weather extremes in the summer - such as the record heat wave in the United States that hit corn farmers and worsened wildfires in 2012 - have reached an exceptional number in the last ten years.
Man-made global warming can explain a gradual increase in periods of severe heat, but the observed change in the magnitude and duration of some events is not so easily explained. It has been linked to a recently discovered mechanism: the trapping of giant waves in the atmosphere. A new data analysis now shows that such wave-trapping events are indeed on the rise.
“The large number of recent high-impact extreme weather events has struck and puzzled us,” says Dim Coumou, lead author of the study conducted by a team of scientists from the Potsdam Institute for Climate Impact Research (PIK).
“Of course we are warming our atmosphere by emitting CO2 from fossil fuels, but the increase in devastating heat waves in regions like Europe or the US seems disproportionate.” One reason could be changes in circulation patterns in the atmosphere. By analysing large sets of global weather data, the researchers found an intriguing connection.
Rossby Waves: meandering airstreams
An important part of the global air motion in the mid-latitudes normally takes the form of waves wandering around the globe, called Rossby Waves. When they swing north, they suck warm air from the tropics to Europe, Russia, or the US; and when they swing south, they do the same thing with cold air from the Arctic.
However, the study shows that in periods with extreme weather, some of these waves become virtually stalled and greatly amplified. While a few warm days have little impact, effects on people and ecosystems can be severe when these periods are prolonged.
“Behind this, there is a subtle resonance mechanism that traps waves in the mid-latitudes and amplifies them strongly,” says Stefan Rahmstorf, co-author of the study to be published in the Proceedings of the US National Academy of Sciences (PNAS). Using advanced data analysis, the new study shows that when certain resonance conditions are fulfilled, the atmosphere tends to develop anomalously slowly propagating waves with large amplitudes, typically associated with extreme weather on the ground.
An important finding is that this phenomenon is occurring more often: After the year 2000, it has been almost twice as frequent as before. “Evidence for actual changes in planetary wave activity was so far not clear. But by knowing what patterns to look for, we have now found strong evidence for an increase in these resonance events.”
The Arctic factor: warming twice as fast as most other regions
Why would these events be on the rise? Both theory and the new data suggest a link to processes in the Arctic. Since the year 2000, the Arctic is warming about twice as fast as the rest of the globe. One reason for this is that because the white sea ice is rapidly shrinking, less sunlight gets reflected back into space, while the open ocean is dark and hence warms more.
“This melting of ice and snow is actually due to our lifestyle of churning out unprecedented amounts of greenhouse gases from fossil fuels,” says Hans Joachim Schellnhuber, co-author of the study and director of PIK. As the Arctic warms more rapidly, the temperature difference to other regions decreases. Yet temperature differences are a major driver of the atmospheric circulation patterns that in turn rule our weather.
“The planetary waves topic illustrates how delicately interlinked components in the Earth system are.” Schellnhuber concludes: "And it shows how disproportionately the system might react to our perturbations.”
Article: Coumou, D., Petoukhov, V., Rahmstorf, S., Petri, S., Schellnhuber, H.J. (2014): Quasi-resonant circulation regimes and hemispheric synchronization of extreme weather in boreal summer. Proceedings of the US National Academy of Sciences PNAS [DOI:10.1073/pnas.1412797111]
Weblink where the article will be published: www.pnas.org/cgi/doi/10.1073/pnas.1412797111
For further information please contact:
PIK press office
Phone: +49 331 288 25 07
Jonas Viering | PIK Potsdam
Researchers find higher than expected carbon emissions from inland waterways
25.05.2016 | Washington State University
Rutgers scientists help create world's largest coral gene database
24.05.2016 | Rutgers University
Permanent magnets are very important for technologies of the future like electromobility and renewable energy, and rare earth elements (REE) are necessary for their manufacture. The Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, Germany, has now succeeded in identifying promising approaches and materials for new permanent magnets through use of an in-house simulation process based on high-throughput screening (HTS). The team was able to improve magnetic properties this way and at the same time replaced REE with elements that are less expensive and readily available. The results were published in the online technical journal “Scientific Reports”.
The starting point for IWM researchers Wolfgang Körner, Georg Krugel, and Christian Elsässer was a neodymium-iron-nitrogen compound based on a type of...
In the Beyond EUV project, the Fraunhofer Institutes for Laser Technology ILT in Aachen and for Applied Optics and Precision Engineering IOF in Jena are developing key technologies for the manufacture of a new generation of microchips using EUV radiation at a wavelength of 6.7 nm. The resulting structures are barely thicker than single atoms, and they make it possible to produce extremely integrated circuits for such items as wearables or mind-controlled prosthetic limbs.
In 1965 Gordon Moore formulated the law that came to be named after him, which states that the complexity of integrated circuits doubles every one to two...
Characterization of high-quality material reveals important details relevant to next generation nanoelectronic devices
Quantum mechanics is the field of physics governing the behavior of things on atomic scales, where things work very differently from our everyday world.
When current comes in discrete packages: Viennese scientists unravel the quantum properties of the carbon material graphene
In 2010 the Nobel Prize in physics was awarded for the discovery of the exceptional material graphene, which consists of a single layer of carbon atoms...
The trend-forward world of display technology relies on innovative materials and novel approaches to steadily advance the visual experience, for example through higher pixel densities, better contrast, larger formats or user-friendler design. Fraunhofer ISC’s newly developed materials for optics and electronics now broaden the application potential of next generation displays. Learn about lower cost-effective wet-chemical printing procedures and the new materials at the Fraunhofer ISC booth # 1021 in North Hall D during the SID International Symposium on Information Display held from 22 to 27 May 2016 at San Francisco’s Moscone Center.
24.05.2016 | Event News
20.05.2016 | Event News
19.05.2016 | Event News
25.05.2016 | Trade Fair News
25.05.2016 | Life Sciences
25.05.2016 | Power and Electrical Engineering