The world faces a small but substantially increased risk over the next two decades of a major slowdown in the growth of global crop yields because of climate change, new research finds.The authors, from Stanford University and the National Center for Atmospheric Research (NCAR), say the odds of a major production slowdown of wheat and corn even with a warming climate are not very high. But the risk is about 20 times more significant than it would be without global warming, and it may require planning by organizations that are affected by international food availability and price.”Climate change has substantially increased the prospect that crop production will fail to keep up with rising demand in the next 20 years,” said NCAR scientist Claudia Tebaldi, a co-author of the study.Stanford professor David Lobell said he wanted to study the potential impact of climate change on agriculture in the next two decades because of questions he has received from stakeholders and decision makers in governments and the private sector.”I’m often asked whether climate change will threaten food supply, as if it’s a simple yes or no answer,” Lobell said. “The truth is that over a 10- or 20-year period, it depends largely on how fast Earth warms, and we can’t predict the pace of warming very precisely. So the best we can do is try to determine the odds.”Lobell and Tebaldi used computer models of global climate, as well as data about weather and crops, to calculate the chances that climatic trends would have a negative effect of 10 percent on yields of corn and wheat in the next 20 years. This would have a major impact on food supply. Yields would continue to increase but the slowdown would effectively cut the projected rate of increase by about half at the same time that demand is projected to grow sharply.They found that the likelihood of natural climate shifts causing such a slowdown over the next 20 years is only 1 in 200. But when the authors accounted for human-induced global warming, they found that the odds jumped to 1 in 10 for corn and 1 in 20 for wheat.The study appears in this month’s issue of Environmental Research Letters. It was funded by the National Science Foundation (NSF), which is NCAR’s sponsor, and by the U.S. Department of Energy (DOE).More crops needed worldwideGlobal yields of crops such as corn and wheat have typically increased by about 1-2 percent per year in recent decades, and the U.N. Food and Agriculture Organization projects that global production of major crops will increase by 13 percent per decade through 2030 — likely the fastest rate of increase during the coming century. …Read more
For the first time, a field test has demonstrated that elevated levels of carbon dioxide inhibit plants’ assimilation of nitrate into proteins, indicating that the nutritional quality of food crops is at risk as climate change intensifies.Findings from this wheat field-test study, led by a UC Davis plant scientist, will be reported online April 6 in the journal Nature Climate Change.”Food quality is declining under the rising levels of atmospheric carbon dioxide that we are experiencing,” said lead author Arnold Bloom, a professor in the Department of Plant Sciences.”Several explanations for this decline have been put forward, but this is the first study to demonstrate that elevated carbon dioxide inhibits the conversion of nitrate into protein in a field-grown crop,” he said.The assimilation, or processing, of nitrogen plays a key role in the plant’s growth and productivity. In food crops, it is especially important because plants use nitrogen to produce the proteins that are vital for human nutrition. Wheat, in particular, provides nearly one-fourth of all protein in the global human diet.Many previous laboratory studies had demonstrated that elevated levels of atmospheric carbon dioxide inhibited nitrate assimilation in the leaves of grain and non-legume plants; however there had been no verification of this relationship in field-grown plants.Wheat field studyTo observe the response of wheat to different levels of atmospheric carbon dioxide, the researchers examined samples of wheat that had been grown in 1996 and 1997 in the Maricopa Agricultural Center near Phoenix, Ariz.At that time, carbon dioxide-enriched air was released in the fields, creating an elevated level of atmospheric carbon at the test plots, similar to what is now expected to be present in the next few decades. Control plantings of wheat were also grown in the ambient, untreated level of carbon dioxide.Leaf material harvested from the various wheat tests plots was immediately placed on ice, and then was oven dried and stored in vacuum-sealed containers to minimize changes over time in various nitrogen compounds.A fast-forward through more than a decade found Bloom and the current research team able to conduct chemical analyses that were not available at the time the experimental wheat plants were harvested.In the recent study, the researchers documented that three different measures of nitrate assimilation affirmed that the elevated level of atmospheric carbon dioxide had inhibited nitrate assimilation into protein in the field-grown wheat.”These field results are consistent with findings from previous laboratory studies, which showed that there are several physiological mechanisms responsible for carbon dioxide’s inhibition of nitrate assimilation in leaves,” Bloom said.3 percent protein decline expectedBloom noted that other studies also have shown that protein concentrations in the grain of wheat, rice and barley — as well as in potato tubers — decline, on average, by approximately 8 percent under elevated levels of atmospheric carbon dioxide.”When this decline is factored into the respective portion of dietary protein that humans derive from these various crops, it becomes clear that the overall amount of protein available for human consumption may drop by about 3 percent as atmospheric carbon dioxide reaches the levels anticipated to occur during the next few decades,” Bloom said.While heavy nitrogen fertilization could partially compensate for this decline in food quality, it would also have negative consequences including higher costs, more nitrate leaching into groundwater and increased emissions of the greenhouse gas nitrous oxide, he said.Story Source:The above story is based on materials provided by University of California – Davis. Note: Materials may be edited for content and length.Read more
July 15, 2013 — Under elevated carbon dioxide levels, wetland plants can absorb up to 32 percent more carbon than they do at current levels, according to a 19-year study published in Global Change Biology from the Smithsonian Environmental Research Center in Edgewater, Md. With atmospheric CO2 passing the 400 parts-per-million milestone this year, the findings offer hope that wetlands could help soften the blow of climate change.Plant physiologist Bert Drake created the Smithsonian’s Global Change Ecological Research Wetland in 1987 at Edgewater. Back then, most scientists thought plants would gradually stop responding to rising CO2. Whether or not terrestrial ecosystems could assimilate additional carbon—and act as powerful carbon sinks—was not known. This study tracked not only how much CO2 wetlands absorb, but also the impact of rising temperature and sea level, changing rainfall and plant type.To simulate a high-CO2 world, Drake’s team surrounded marsh plots with open-top Mylar chambers. For this study they left half of the chambers exposed to today’s atmosphere. In the other half they added CO2 and raised the level to 700 ppm, roughly doubling the CO2 concentration as it was in 1987. Other plots of land were left without chambers. They compared the levels of CO2 going in and CO2 going out to determine the carbon exchange between the wetland and the atmosphere.Two types of plants populate most of the world, and the experiment tested both. C3 plants—which include more than 95 percent of the plant species on earth, including trees—form molecules of three carbon atoms during photosynthesis, and they tend to photosynthesize more as atmospheric CO2 rises. …Read more
June 26, 2013 — Further evidence of climate change shifting atmospheric circulation in the southern Australian-New Zealand region has been identified in a new study.The study, in the Nature journal Scientific Reports, demonstrates that mid-latitude high pressure zones (30oS-45oS) are being pushed further into the Southern Ocean by rising global temperatures associated with greenhouse warming. This is despite more frequent occurrences of strong El Niños in recent decades, which should have drawn the high pressure zones in the opposite direction toward the equator.”What we are seeing,” says study lead author, Mr Guojian Wang “is a ‘tug of war’ between stronger El Niños driving the winds north and the greenhouse gas-warming effect driving the winds south.”Mr Wang, said the result confirms the robustness of the Southern Hemisphere circulation changes over the past three to four decades as the global temperature rose, “so much so that it overode the influence from strong El Niños during this period.”Study co-author, Dr Wenju Cai said the most conspicuous change is a rising sea level pressure in the mid-latitude bands and a decreasing sea level pressure over the Southern high latitudes (55o-70oS), a pattern referred to as the Southern Annular Mode. The changing pressures indicate a poleward or southward expansion of the tropical and subtropical atmospheric zones.In turn, this indicates that over the long-term, there is a relationship between a rising global mean temperature and an upward trend of the Southern Annular Mode.”The research reinforces our past work that climate change is altering Southern Hemisphere circulation and increases our confidence in this conclusion,” Dr Cai said.Dr Cai has previously reported on changes in atmospheric circulation that have been shifting and strengthening the Pacific Ocean winds poleward and in turn strengthening the ocean circulation, pushing the East Australian Current further south down the Australian coast.He said during El Niño, the warmer ocean releases heat to the atmosphere and global average temperatures increase. At the same time, warm ocean surface temperatures along the equator cause the tropical and subtropical atmospheric belts to move toward the equator, generating a ‘negative’ phase of the Southern Annular Mode.”On year-to-year time scales, higher global temperatures are associated with a negative phase of the Mode but over the past 35 years, when El Niño has been strong and conducive to a negative trend, we are seeing an opposite trend with the circulation systems moving southward impacting on regional climate,” he said.The project was funded through the Australian Climate Change Science Program.Read more
June 20, 2013 — On June 7, 2011, our Sun erupted, blasting tons of hot plasma into space. Some of that plasma splashed back down onto the Sun’s surface, sparking bright flashes of ultraviolet light. This dramatic event may provide new insights into how young stars grow by sucking up nearby gas.The eruption and subsequent splashdown were observed in spectacular detail by NASA’s Solar Dynamics Observatory. This spacecraft watches the Sun 24 hours a day, providing images with better-than-HD resolution. Its Atmospheric Imaging Assembly instrument was designed and developed by researchers at the Harvard-Smithsonian Center for Astrophysics (CfA).”We’re getting beautiful observations of the Sun. And we get such high spatial resolution and high cadence that we can see things that weren’t obvious before,” says CfA astronomer Paola Testa.Movies of the June 7th eruption show dark filaments of gas blasting outward from the Sun’s lower right. Although the solar plasma appears dark against the Sun’s bright surface, it actually glows at a temperature of about 18,000 degrees Fahrenheit. When the blobs of plasma hit the Sun’s surface again, they heat up by a factor of 100 to a temperature of almost 2 million degrees F. As a result, those spots brighten in the ultraviolet by a factor of 2 — 5 over just a few minutes.The tremendous energy release occurs because the in falling blobs are traveling at high speeds, up to 900,000 miles per hour (400 km/sec). Those speeds are similar to the speeds reached by material falling onto young stars as they grow via accretion. …Read more
June 19, 2013 — Differences between Martian meteorites and rocks examined by a NASA rover can be explained if Mars had an oxygen-rich atmosphere 4000 million years ago — well before the rise of atmospheric oxygen on Earth 2500m years ago.Scientists from Oxford University investigated the compositions of Martian meteorites found on Earth and data from NASA’s ‘Spirit’ rover that examined surface rocks in the Gusev crater on Mars. The fact that the surface rocks are five times richer in nickel than the meteorites was puzzling and had cast doubt on whether the meteorites are typical volcanic products of the red planet.’What we have shown is that both meteorites and surface volcanic rocks are consistent with similar origins in the deep interior of Mars but that the surface rocks come from a more oxygen-rich environment, probably caused by recycling of oxygen-rich materials into the interior,’ said Professor Bernard Wood, of Oxford University’s Department of Earth Sciences, who led the research reported in this week’s Nature.’This result is surprising because while the meteorites are geologically ‘young’, around 180 million to 1400 million years old, the Spirit rover was analysing a very old part of Mars, more than 3700 million years old.’Whilst it is possible that the geological composition of Mars varies immensely from region to region the researchers believe that it is more likely that the differences arise through a process known as subduction — in which material is recycled into the interior. They suggest that the Martian surface was oxidised very early in the history of the planet and that, through subduction, this oxygen-rich material was drawn into the shallow interior and recycled back to the surface during eruptions 4000 million years ago. The meteorites, by contrast, are much younger volcanic rocks that emerged from deeper within the planet and so were less influenced by this process.Professor Wood said: ‘The implication is that Mars had an oxygen-rich atmosphere at a time, about 4000 million years ago, well before the rise of atmospheric oxygen on earth around 2500 million years ago. As oxidation is what gives Mars its distinctive colour it is likely that the ‘red planet’ was wet, warm and rusty billions of years before Earth’s atmosphere became oxygen rich.’Read more
May 30, 2013 — Leading world climate change experts have thrown cold water on the idea that planting trees can offset carbon dioxide emissions from fossil fuels.
Professor Brendan Mackey of Griffith University Climate Change Response Program is the lead author of an international study involving researchers from Australia and the U.K. Their findings are reported in “Untangling the confusion around land carbon science and climate change mitigation policy,” published in the scientific journal Nature Climate Change.
“While protecting and restoring natural forests is part of the solution, the reality is that for all practical purposes fossil fuel CO2 emissions are irreversible,” Professor Mackey said.
The findings highlight the urgent need for policy-makers worldwide to re-think the issue as many decision-makers, national and internationally, assume that fossil fuel emissions can be offset through sequestering carbon by planting trees and other land management practices.
“There is a danger in believing that land carbon sinks can solve the problem of atmospheric carbon emissions because this legitimises the ongoing use of fossil fuels,” Professor Mackey said.
The study found that protecting natural forests avoids emissions that would otherwise result from logging and land clearing while also conserving biodiversity. Restoring degraded ecosystems or planting new forests helps store some of the carbon dioxide that was emitted from past land use activities.
“These land management actions should be rewarded as they are an important part of the solution,” Professor Mackay said.
“However, no amount of reafforestation or growing of new trees will ultimately off-set continuing CO2 emissions due to environmental constraints on plant growth and the large amounts of remaining fossil fuel reserves.
“Unfortunately there is no option but to cut fossil fuel emissions deeply as about a third of the CO2 stays in the atmosphere for 2 to 20 millennia.”Read more