Klimaflüchtlinge? Afrika ist in den letzten 20 Jahren kräftig ergrünt

Am 20. Juni tritt Mojib Latif um 17:00 Uhr in der Berliner Urania auf:

Das Ende der Ozeane – Warum wir ohne die Meere nicht überleben werden
Die zunehmende Verschmutzung der Ozeane, sei es durch Öl, Plastik oder andere Stoffe, wie auch der Verlust der Artenvielfalt sind für die marinen Ökosysteme um einiges gefährlicher, wenn sich gleichzeitig die Umweltbedingungen ändern. So tritt beispielsweise die gefürchtete Korallenbleiche in den letzten Jahren immer häufiger auf. Das verwundert nicht, denn die Temperatur der tropischen Meere ist in den letzten Jahrzehnten infolge des Klimawandels um etwa ein halbes Grad gestiegen. Bei fortschreitender Erwärmung werden sich die Korallen nicht anpassen können. Die einzigartige Unterwasserwelt der Korallenriffe steht auf dem Spiel. Der Vortrag zeigt die Faszination, die von den Ozeanen ausgeht, aber auch wie bedroht sie sind.

Zur Vorbereitung seien die folgenden Artikel empfohlen:

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Ausgezeichneter Meinungsbeitrag von Josef H. Reichholf in der Welt vom 28. Mai 2017:

Schnell wird man als „Klimaleugner“ abgestempelt

Die globale Temperatur steigt trotz wachsenden CO2-Ausstoßes nicht an. Dies passt nicht in die Prognosen von Politik und Wissenschaft. Man muss darüber reden dürfen, ohne verunglimpft zu werden.

Die letzten eineinhalb Jahrzehnte lang stieg die globale Temperatur nicht mehr an. Diese Pause in der Erwärmung passte jedoch nicht zu den Prognosen. Ganz und gar nicht, wurde doch seit der Jahrtausendwende kontinuierlich mehr CO2 in die Luft gepustet. Also sollte es auch wärmer geworden sein. Jetzt weiß man, woran es lag. Für die Berechnungen hatte man die Messwerte verwendet, die passen. Mit den „richtigen“ stimmen die Ergebnisse mit den Klimamodellen überein. So einfach ist das: Die passenden Daten sind die richtigen! Die Wirklichkeit muss den Modellen entsprechen. Sonderbar? Weil nicht sein kann, was nicht sein darf? Auf die genehmen Daten kommt es an. Dann stimmt das Ergebnis. Bleibt da nicht ein flaues Gefühl? Darf das Ergebnis vorher festliegen? Müssen Messwerte so ausgewählt werden, dass sie passen?

Ganzen Beitrag auf welt.de lesen.

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Sciencenordic.com berichtete am 28. Mai 2017 Überraschendes: Afrika ist in den letzten 20 Jahren ergrünt, was so gar nicht zu den angeblichen Klimaflüchtlingen zu passen scheint:

Africa has become greener in the last 20 years

Despite climate change and a growing population, Africa has become greener over the past 20 years, shows new study.

In Africa, a fight is happening. On one side natural forces are making the continent greener, and on the other, people are removing trees and bushes from the continent. In densely populated regions, people are cutting down trees and forests, but elsewhere, where human populations are more thinly spread, bushes and scrub vegetation are thriving. Now, scientists have quantified for the first time how vegetation across the continent has changed in the past 20 years. Thirty six per cent of the continent has become greener, while 11 per cent is becoming less green. The results show that not all is lost for Africa’s nature, say the scientists behind the new research.

Weiterlesen auf Sciencenordic.com

Zu allem Überfluss ergrünt derzeit ja sogar die Antarktis, heißtt es. Siehe unseren Blogbeitrag “Die Sonne im April 2017 und antarktische Blütenträume“.

Bleiben wir in der Pflanzenwelt. Eine neue Blattzählung hat nun ergeben, dass es viel mehr Blätter auf der Erde gibt als zuvor angenommen. Die Auswirkungen auf den Klimawandel sind erfreulich: Kalte boreale Gebiete werden dadurch wärmer und heiße trockene Gebiete kälter. Das hört sich doch ganz nach einer Win-Win-Situation an. Pressemitteilung der American Association for the Advancement of Science vom 25. Mai 2017 (via Science Daily):

Increased leaf abundance is a double-edged sword

A new global assessment reveals that increases in leaf abundance are causing boreal areas to warm and arid regions to cool. The results suggest that recent changes in global vegetation have had impacts on local climates that should be considered in the design of local mitigation and adaptation plans.

A substantial portion of the planet is greening in response to increasing atmospheric carbon dioxide, nitrogen deposition, global warming and land use change. The increase in leafy green coverage, or leaf area index (LAI), will hold important implications for climate change feedback loops, yet quantifying these impacts on a global scale can be challenging. Here, Giovanni Forzieri and colleagues analyzed satellite data of global LAI coverage between 1982 and 2011. Their results varied depending on the local biome, where increased LAI in boreal regions caused a reduction in surface albedo (reflection of sunlight), and thus resulted in a warming effect; in contrast, increased LAI in arid regions caused an increase in transpiration, and thus drove a cooling effect.

What’s more, the authors found that these relationships between LAI and surface biophysics were amplified up to five times under extreme warm-dry and cold-wet years. They estimate that, across about 60% of the global vegetated area, greening has buffered warming by about 14%; for the remaining areas, which mostly include boreal zones, LAI trends have amplified the raise in air temperatures, leading to an additional warming of about 10%.

Giovanni Forzieri, Ramdane Alkama, Diego G. Miralles, Alessandro Cescatti. Satellites reveal contrasting responses of regional climate to the widespread greening of Earth. Science, 2017; eaal1727 DOI: 10.1126/science.aal1727

Siehe auch Beitrag auf Climate Change Dispatch.

Überhaupt hat man wohl die Pflanzenwelt viel zu wenig in den Klimamodellen beachtet. Erstaunlich, wenn man bedenkt, dass Bäume seit menschengedenken angenehmen Schatten im Hochsommer spenden. Vielleicht sollten die Damen und Herren Modellierer einfach mal ein bisschen mehr Zeit im Freien verbingen und sich von ihren Rechenkästen loseisen? Pressemitteilung der Columbia University vom 29. Mai 2017:

Hotspots Show that Vegetation Alters Climate by Up to 30%
Columbia Engineers find strong feedbacks between the atmosphere and vegetation that explain up to 30% of precipitation and surface radiation variance; study reveals large potential for improving seasonal weather predictions

A new Columbia Engineering study, led by Pierre Gentine, associate professor of earth and environmental engineering, analyzes global satellite observations and shows that vegetation alters climate and weather patterns by as much as 30 percent. Using a new approach, the researchers found that feedbacks between the atmosphere and vegetation (terrestrial biosphere) can be quite strong, explaining up to 30 percent of variability in precipitation and surface radiation. The paper, published May 29 in Nature Geoscience, is the first to look at biosphere-atmosphere interactions using purely observational data and could greatly improve weather and climate predictions critical to crop management, food security, water supplies, droughts, and heat waves.

“While we can currently make fairly reliable weather predictions, as, for example, five-day forecasts, we do not have good predictive power on sub-seasonal to seasonal time scale, which is essential for food security,” Gentine says. “By more accurately observing and modeling the feedbacks between photosynthesis and the atmosphere, as we did in our paper, we should be able to improve climate forecasts on longer timescales.”

Vegetation can affect climate and weather patterns due to the release of water vapor during photosynthesis. The release of vapor into the air alters the surface energy fluxes and leads to potential cloud formation. Clouds alter the amount of sunlight, or radiation, that can reach the Earth, affecting the Earth’s energy balance, and in some areas can lead to precipitation. “But, until our study, researchers have not been able to exactly quantify in observations how much photosynthesis, and the biosphere more generally, can affect weather and climate,” says Julia Green, Gentine’s PhD student and the paper’s lead author.

Recent advancements in satellite observations of solar-induced fluorescence, a proxy for photosynthesis, enabled the team to infer vegetation activity. They used remote sensing data for precipitation, radiation, and temperature to represent the atmosphere. They then applied a statistical technique to understand the cause and feedback loop between the biosphere and the atmosphere. Theirs is the first study investigating land-atmosphere interactions to determine both the strength of the predictive mechanism between variables and the time scale over which these links occur.

The researchers found that substantial vegetation-precipitation feedback loops often occur in semi-arid or monsoonal regions, in effect hotspots that are transitional between energy and water limitation. In addition, strong biosphere-radiation feedbacks are often present in several moderately wet regions, for instance in the Eastern U.S. and in the Mediterranean, where precipitation and radiation increase vegetation growth. Vegetation growth enhances heat transfer and increases the height of the Earth’s boundary layer, the lowest part of the atmosphere that is highly responsive to surface radiation. This increase in turn affects cloudiness and surface radiation.

“Current Earth system models underestimate these precipitation and radiation feedbacks mainly because they underestimate the biosphere response to radiation and water stress response,” Green says. “We found that biosphere-atmosphere feedbacks cluster in hotspots, in specific climatic regions that also coincide with areas that are major continental CO2 sources and sinks. Our research demonstrates that those feedbacks are also essential for the global carbon cycle—they help determine the net CO2 balance of the biosphere and have implications for improving critical management decisions in agriculture, security, climate change, and so much more.”

Gentine and his team are now exploring ways to model how biosphere-atmosphere interactions may change with a shifting climate, as well as learning more about the drivers of photosynthesis, in order to better understand atmospheric variability. Paul Dirmeyer, a professor in the department of atmospheric, oceanic and earth sciences at George Mason University who was not involved in the study, notes: “Green et al. put forward an intriguing and exciting new idea, expanding our measures of land-atmospheric feedbacks from mainly a phenomenon of the water and energy cycles to include the biosphere, both as a response to climate forcing and a forcing to climate response.”

Paper: Julia K. Green, Alexandra G. Konings, Seyed Hamed Alemohammad, Joseph Berry, Dara Entekhabi, Jana Kolassa, Jung-Eun Lee, Pierre Gentine. Regionally strong feedbacks between the atmosphere and terrestrial biosphere. Nature Geoscience, 2017; DOI: 10.1038/ngeo2957