Based on models and observations, climate scientists have devised a simplified formula to describe one of the consequences of climate change: regions already marked by droughts will continue to dry out in the future climate. Regions that already have a moist climate will experience additional rainfall. In short: dry gets drier; wet gets wetter (DDWW).
However, this formula is less universally valid than previously assumed. This was demonstrated by a team of ETH climate researchers led by Peter Greve, lead author of a study recently published in Nature Geoscience. Traditional analyses use metrics that can comprehensively describe climate characteristics above the ocean, but is problematic over land.
While this fact was mentioned in said studies, scientific and public discourse has overlooked this aspect so far. In their new study, the ETH researchers in the group headed by Sonia Seneviratne's, professor for land-climate dynamics, take into account the specific climatic properties of land surfaces, where the amount of available water is limited when compared with the ocean.
In their analysis, the climate scientists made use of measured data compiled solely on land, such as rainfall, actual evaporation and potential evaporation. The data derived from various sources was combined by Greve and his co-authors – this allowed them to extract trends in terms of a region's humidity and dryness. Furthermore, the researchers compared data from between 1948 and 1968 and 1984 to 2004.
Half of the surface areas show divergence
The evaluation shows no obvious trend towards a drier or wetter climate across three-quarters of the land are. There are solid trends for the remaining quarter. However, only half of this surface area follows the DDWW principle, i.e. one-eighth of the total landmass, while the trends seem to contradict this rule over the other half.
Some regions which should have become wetter according to the simple DDWW formula have actually become drier in the past – this includes parts of the Amazon, Central America, tropical Africa and Asia. On the other hand, there are dry areas that have become wetter: parts of Patagonia, central Australia and the Midwestern United States.
Nevertheless, the 'wet gets wetter' rule is largely confirmed for the Eastern United States, Northern Australia and northern Eurasia. 'Dry gets drier' also corresponds to indications in the Sahel region, the Arabian Peninsula and parts of Central Asia and Australia.
However, the DDWW principle does still applies to the oceans. "Our results emphasise how we should not overly rely on simplifying principles to asses past developments in dryness and humidity," Greve explains. This can be misleading, as it cannot do justice to the complexity of the underlying systems.
Greve P, Orlowsky B, Müller B, Sheffield J, Reichstein M, Seneviratne SI. Global assessment of trends in wetting and drying over land. Nature Geoscience, Advanced Online Publication 14th September 2014. DOI: 10.1038/ngeo2247
Peter Greve | ETH Zürich
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy