Neue Studie: Steigender CO2 Gehalt wird Wassereffizienz von Weizen bis 2080 um mehr als ein Viertel erhöhen

Am 16. April 2016 brachte das Klimaretter-Blog einen verspäteten Aprilscherz:

Klimawandel: “97-Prozent-Studie” bestätigt
Was in der Wissenschafts-Gemeinde seit Jahren Konsens ist, aber in der Öffentlichkeit von Zeit zu Zeit angezweifelt wird, hat eine neue Metastudie untermauert: Der Klimawandel wird nach übereinstimmender Ansicht der Wissenschaft vor allem durch menschliche Tätigkeit verursacht.

Der Begriff “97-Prozent” ist mittlerweile zum wahren Scherzwort geworden. Ob die Klimaretter dies wissen? Daher war es schwer, bei der Lektüre des Blogartikels ein Schmunzeln zu unterdrücken. Die Originalstudie sagt nämlich etwas gänzlich anderes aus, als vom Klimaretter behauptet. 97% der Befragten halten einen wie auch immer gearteteten anthropogenen Einfluss auf das Klima für möglich. Das hört sich doch gleich ganz anders an als die falsche Klimaretter-Version “vor allem durch menschliche Tätigkeit“.

Das neue (2016) Aktivistenpaper hat den lustigen Titel:

Consensus on consensus: a synthesis of consensus estimates on human-caused global warming

Der ehemalige IPCC-Leitautor Richard Tol hatte bereits im Originalpaper schwerwiegende Fehler in er Studie gefunden und 2014 in einem Kommentar benannt. Es dauerte nicht lang, da entzauberte Tol auch die Neuauflage der 97-Prozent-Saga. In seinem Blog betitelte er seinen Artikel vom 20. April 2016 treffend:

Nonsensus on nonsensus

Eine Woche zuvor hatte Tol bereits diesen Beitrag im Blog gebracht:

Misrepresentation and the consensus

Im Prinzip ein unsinniges Thema (“Nonsensus”), mit dem wir nicht unsere Zeit verschwenden sollten. Vielen Dank an Richard Tol, der trotzdem gegen diesen Murks vorgeht. Weitere Hintergrundinformationen auch in Uli Webers Beitrag “Das siebenundneunzig Prozent-Problem: Welcher Konsens?“.

—————-

Unschöner Filz: Die Weltwoche berichtete am 13. April 2016 in der Rubrik “Personen-Kontrolle” über eine fragwürdige Verflechtung der Schweizer Klimaalarmisten-Szene mit der Versicherungswirtschaft:

Am Swiss Global Change Day, den die Schweizer Klimaforscher am Dienstag in Bern feierten, trat auch David Bresch als Referent auf: Der Chefexperte von Swiss Re sitzt für seinen Konzern in den Gremien zur Klimapolitik und lehrt jetzt auch als Professor an der ETH – an seinen Interessenkonflikten stört sich niemand. Der Klimagemeinde hatte David Bresch allerdings wenig Erfreuliches zu verkünden. Er wollte in einer Studie zeigen, wie sich das Kreditrisiko von Staaten aufgrund des Klimawandels erhöht, um sie zum Handeln zu bewegen. Er kam aber zum «ziemlich ernüchternden Befund», dass das Risiko von volkswirtschaftlichen Schäden aufgrund von Naturkatastrophen, das heute in wenigen Ländern erheblich ist, bis ins Jahr 2050 nur unwesentlich zunimmt. Hauptsache, Swiss Re schrieb in den letzten Jahren üppige Gewinne, weil die Naturkatastrophen, vor denen die Rückversicherung warnte und für die sie kräftig an ihren Prämien schraubte, nicht eintraten.

Passend zum Thema der folgende Beitrag von Larry Bell am 17. April 2016 auf EIKE:

Alarmistische Meeresspiegel-Daten lassen Kosten für Versicherung gegen Überschwemmungen steigen
Die Federal Emergency Management Agency FEMA in den USA, welche Landeigentümern in Hochrisikogebieten unrealistisch billige Versicherungen gegen Überschwemmungen anbietet, erlebt gerade eine hausgemachte Katastrophe – nämlich ein Bilanzdefizit, dass 24 Milliarden Dollar ,unter Wasser’ liegt. Die geplante Rettungsaktion sieht vor, die potentiellen Überschwemmungsgebiete aufgrund hypothetischer Projektionen des Meeresspiegel-Anstiegs neu zu kartieren. Damit sollen die Prämien steigen – und nicht das Bauen in für Überschwemmungen anfälligen Gebieten bestraft werden.

Weiterlesen auf EIKE

—————-

Kommen wir nun zur allseits geschätzten Rubrik ‘Neue Forschungsergebnisse, die Sie in keiner deutschsprachigen Zeitung lesen können’. Am 18. April 2016 berichtete das Earth Institute at Columbia University in einer Pressmitteilung, wie der steigende CO2-Gehalt der Atmosphäre das Pflanzenwachstum anfacht und negative Effekte durch erhöhte Temperaturen ausgleicht:

Could Global Warming’s Top Culprit Help Crops?
Study Looks at How Carbon Dioxide Might Cut Effects of Rising Heat

A new study tries to disentangle the complex question of whether rising amounts of carbon dioxide in the air might in some cases help crops. It suggests that while greater warmth will reduce yields of some, higher carbon dioxide could help mitigate the effects in some regions, unless other complications of global warming interfere.

Many scientists fear that global warming will hit staple food crops hard, with heat stress, extreme weather events and water shortages. On the other hand, higher levels of carbon dioxide–the main cause of ongoing warming–is known to boost many plants’ productivity, and reduce their use of water. So, if we keep pouring more CO2 into the air, will crops fail, or benefit? A new study tries to disentangle this complex question. It suggests that while greater warmth will reduce yields of some crops, higher CO2 could help mitigate the effects in some regions, unless other complications of global warming interfere.

The study, by 16 researchers from a half-dozen countries, uses newly available crop models and data from ongoing large-scale field experiments. It appears this week in the journal Nature Climate Change.

“Most of the discussion around climate impacts focuses only on changes in temperature and precipitation,” said lead author Delphine Deryng, an environmental scientist at Columbia University’s Center for Climate Systems Research, the NASA Goddard Institute for Space Studies and the University of Chicago’s Computation Institute. “To adapt adequately, we need to understand all the factors involved.” Deryng cautions that the study should not be interpreted to mean that increasing carbon dioxide is a friend to humanity–only that its direct effects must be included in any calculation of what the future holds.

Many studies say that as temperatures rise, crops across the world will suffer as average temperatures become unsuitable for traditionally grown crops, and droughts, heat waves or extreme bouts of precipitation become more common. Agricultural scientists say that losses could be mitigated to some extent by switching crops, developing varieties adapted to the new conditions, or moving some crop-growing regions poleward. But such adaptations pose daunting challenges.

Due to human activities, average global levels of atmospheric carbon dioxide have risen by more than a quarter since 1960; they now stand at around 400 parts per million, and are expected to keep increasing, along with temperature. At the same time, experiments since the 1980s have shown that higher levels of carbon dioxide in the air helps plants build biomass. The concept is relatively simple; plants take in carbon to build their tissues, and if there is more carbon around, they have an easier time. Leaves take in air through tiny openings called stomata, but in the process the stomata lose water; with more carbon available, they don’t have to open up as much, and conserve moisture.

However, much of the initial evidence for so-called CO2 fertilization has come from lab experiments on isolated plants. These do not account for environmental factors that might affect plants even more powerfully in a warming world, including possibly increased insect and fungus attacks. Thus, suggestions that the greenhouse gas itself might prove a boon to crops have aroused deep skepticism.

In 2014, Deryng and her colleagues published the first global calculation of how heat waves might affect crops, and found that maize, spring wheat and soybeans would all suffer. When they added the effects of carbon-dioxide fertilization, they found that maize yields would still go down–but that spring wheat and soybeans might actually go up. Some media misinterpreted the study to say that climate change might help agriculture overall. The picture is much more complicated, say the authors.

The new study looks at how rising temperatures and carbon dioxide along with changes in rainfall and cloud cover might combine to affect how efficiently maize, soybeans, wheat, and rice can use water and grow. It confirms that heat and water stress alone will damage yields; but when carbon dioxide is accounted for, all four crops will use water more efficiently by 2080.

Based on the current biomass of these crops, water-use efficiency would rise an average of 27 percent in wheat; 18 percent in soybeans; 13 percent in maize; and 10 percent in rice. All things considered, the study projects that average yields of current rain-fed wheat areas (mostly located in higher latitudes including the United States, Canada and Europe), might go up by almost 10 percent, while consumption of water would go down a corresponding amount. On the other hand, average yields of irrigated wheat, which account for much of India and China’s production, could decline by 4 percent. Maize, according to the new projections, would still be a loser most everywhere, even with higher water efficiency; yields would go down about 8.5 percent. The study is less conclusive on the overall effects on rice and soybean yields; half of the projections show an increase in yield and half a net decline.

Deryng says the study is sturdier than past research, because it uses new data from experiments done in actual farm fields, and a half-dozen global crop models, several of which only recently became available. Nevertheless, she says, the uncertainties remain large. Field experiments, which involve blowing CO2 over sizable farm fields for entire growing seasons, have been done only at a handful of sites in the United States, Germany, Australia, Japan and China–not in Africa, India or Latin America, where subsistence farming are mainstays of daily life. She noted that greater yield also might not translate to more nutrition. For example, greater carbon uptake might not be balanced by other nutrients such as nitrogen, and trace elements like zinc and iron that are needed to make crops nutritious.

Bruce Kimball, a retired researcher with the U.S. Department of Agriculture who has studied crop-CO2 interactions, said the paper does “a good job on a huge scale,” though, he said, “more data from more crops from more locations” is needed.” Kimball cautioned also that previous research has shown that the benefits of higher CO2 levels tend to bottom out after a certain point — but that the damage done by heat only gets worse as temperatures mount. “Thus, for greater warming and higher CO2 the results would likely be more pessimistic than shown in this paper,” he said.

Paper:

Delphine Deryng, Joshua Elliott, Christian Folberth, Christoph Müller, Thomas A. M. Pugh, Kenneth J. Boote, Declan Conway, Alex C. Ruane, Dieter Gerten, James W. Jones, Nikolay Khabarov, Stefan Olin, Sibyll Schaphoff, Erwin Schmid, Hong Yang, Cynthia Rosenzweig. Regional disparities in the beneficial effects of rising CO2 concentrations on crop water productivity. Nature Climate Change, 2016; DOI: 10.1038/nclimate2995

Siehe auch den folgenden Artikel in der Vancouver Sun vom 11. April 2016, in dem der steigende CO2-Gehalt zu verstärktem Wachstum der Wälder im westkanadischen British Columbia führt:

Forest growth accelerating in B.C. due to carbon dioxide ‘fertilizer effect’
Rising levels of carbon dioxide in the atmosphere are accelerating the growth of B.C.’s forests by one to three per cent a year, enough to cancel out the impact on the climate from the mountain pine beetle outbreak by 2020, according to a new study from the Pacific Institute for Climate Solutions. “This turnaround will happen much sooner than we had imagined,” said lead author and Environment Canada climate scientist Vivek Arora.

Weiterlesen in der Vancouver Sun