ScienceDaily 18 Oct 2017 excerpt
…Results highlight the possibility of a strong precipitation reduction in the northern edge of the monsoon in the southwestern US in response to warming, with consequences for regional water resources, agriculture and ecosystems.
“Monsoon rains are critical for the southwest U.S. and northwest Mexico, yet the fate of the North American monsoon is quite uncertain,” said Pascale, the lead author on the paper. “The future of the monsoon will have direct impacts on agriculture, on livelihoods.”
Previous general circulation models have suggested that the monsoons were simply shifting later, with decreased rains through July but increased precipitation in September and October.
“The consensus had been that global warming was delaying the monsoon … which is also what we found with the simulation if you didn’t correct the SST biases,” Pascale said. “Uncontrolled, the SST biases can considerably change the response. They can trick us, introducing artefacts that are not real.”
Once those biases were corrected for, the researchers discovered that the monsoon is not simply delayed, but that the total precipitation is facing a dramatic reduction.
That has significant implications for regional policymakers, explained Kapnick. “Water infrastructure projects take years to a decade to plan and build and can last decades. They require knowledge of future climate … to ensure water supply in dry years. We had known previously that other broadly used global models didn’t have a proper North American monsoon. This study addresses this need and highlights what we need to do to improve models for the North American monsoon and understanding water in the southwest.”
The new model also suggests that the region’s famous thunderstorms may become less common, as the decreased rain is associated with increased stability in the lower-to-middle troposphere and weakened atmospheric convection.
“The North American monsoon is also related to extreme precipitation events that can cause flash floods and loss of life,” Kapnick said. “Knowing when the monsoon will start and predicting when major events will happen can be used for early warnings and planning to avoid loss of life and property damage. This paper represents the first major step towards building better systems for predicting the monsoon rains.”
The researchers chose to tackle the region in part because previous, coarser-resolution models had shown that this area would be drying out, a prediction that has been borne out in the droughts and wildfires of recent years. But most of those droughts are attributed to the change in winter storms, said Pascale.
“The storm track is projected to shift northward, so these regions might get less rain in winter, but it was very uncertain what happens to the monsoon, which is the other contributor to the rains of the region. We didn’t know, and it’s crucial to know,” he said.
In their model, the researchers were able to tease out the impacts of one factor at a time, which allowed them to investigate and quantify the monsoon response to the doubling of atmospheric carbon dioxide, increased temperatures and other individual changes.
Pascale stressed the limits of this or any other climate model. “They need to be used with an understanding of their shortcomings and utilized to their expected potential but no further. They can give us quite reliable information about the large scale atmospheric circulation, but if you want to look at the regional, small-scale effects, you have to be very careful,” he said. “Models are critical but they are not perfect, and small imperfections can lead to big misunderstandings.”
He continued: “We are not saying, ‘We are sure that this is what will be,’ but we wanted to point out some mechanisms which are key, and have to be taken into account in future research on the North American monsoon. This is a difficult region, so future research will point out if we were right, and to what extent.”
Salvatore Pascale, William R. Boos, Simona Bordoni, Thomas L. Delworth, Sarah B. Kapnick, Hiroyuki Murakami, Gabriel A. Vecchi, Wei Zhang. Weakening of the North American monsoon with global warming. Nature Climate Change, 2017; DOI: 10.1038/nclimate3412
- The land under our feet and the plant matter it contains could offset a significant amount of carbon emissions if managed properly. More research is needed to unlock soil’s potential to mitigate global warming, improve crop yields and increase resilience, say researchers.
The work, published in two overlapping studies Oct. 5 in Annual Review of Ecology, Evolution and Systematics and Global Change Biology, emphasizes the need for more research into how soil — if managed well — could mitigate a rapidly changing climate.
“Dirt is not exciting to most people,” said earth system science professor Rob Jackson, lead author of the Annual Review of Ecology, Evolution and Systematics article and coauthor of the Global Change Biology paper. “But it is a no-risk climate solution with big cobenefits. Fostering soil health protects food security and builds resilience to droughts, floods and urbanization.”
Humble, yet mighty
Organic matter in soil, such as decomposing plant and animal residues, stores more carbon than do plants and the atmosphere combined. Unfortunately, the carbon in soil has been widely lost or degraded through land use changes and unsustainable forest and agricultural practices, fires, nitrogen deposition and other human activities. The greatest near-term threat comes from thawing permafrost in Earth’s northern reaches, which could release massive amounts of carbon into the atmosphere.
Despite these risks, there is also great promise, according to Jackson and Jennifer Harden, a visiting scholar in Stanford’s School of Earth, Energy & Environmental Sciences and lead author of the Global Change Biology paper.
Improving how the land is managed could increase soil’s carbon storage enough to offset future carbon emissions from thawing permafrost, the researchers find. Among the possible approaches: reduced tillage, year-round livestock forage and compost application. Planting more perennial crops, instead of annuals, could store more carbon and to reduce erosion by allowing roots to reach deeper into the ground.
Jackson, Harden and their colleagues also found that about 70 percent of all sequestered carbon in the top meter of soil is in lands directly affected by agriculture, grazing or forest management — an amount that surprised the authors.
“I think if beer bets were involved, we all would have lost,” Harden said of her coauthors.
Jackson and his coauthors found a number of other surprises in their analysis. For example, plant roots are ?ve times more likely than leaves to turn into soil organic matter for the same mass of material. The study also provides the most complete estimate yet of carbon in peatland and permafrost — almost half of the world’s estimated soil carbon.
“Retaining and restoring soil organic matter helps farmers grow better crops, purifies our water and keeps the atmosphere cleaner,” said Jackson, Michelle and Kevin Douglas Provostial Professor in the School of Earth, Energy & Environmental Sciences.
The Jackson-led study describes an unexpectedly large stock of potentially vulnerable carbon in the northern taiga, an ecosystem that is warming more rapidly than any other. These carbon stocks are comparatively poorly mapped and understood.
The study warns of another danger: overestimating how the organic matter in soil is distributed. Jackson and his coauthors calculate there may be 25-30 percent less than currently estimated due to constraints from bedrock, a factor previously not analyzed in published scientific research.
While scientists are now able to remotely map and monitor environmental changes on Earth’s surface, they still don’t have a strong understanding of the interactions among biological, chemical and physical processes regulating carbon in soils. This knowledge is critical to understanding and predicting how the carbon cycle will respond to changes in the ecosystem, increasing food production and safeguarding natural services we depend on, such as crop pollination and underground water storage.
A rapidly changing climate — and its effects on soil — make these scientific advances all the more urgent.
“Soil has changed under our feet,” Harden said. “We can’t use the soil maps made 80 years ago and expect to find the same answers.”
However, funding pressures such as federal cuts to climate science, combined with turnover in science staff and a lack of systematic data threaten progress on soil carbon research. Jackson, Harden and their colleagues call for a renewed push to gather significantly more data on carbon in the soil and learn more about the role it plays in sequestering carbon. They envision an open, shared network for use by farmers, ranchers and other land managers as well as policymakers and organizations that need good data to inform land investments and conservation.
“If we lose momentum on carbon research, it will stifle our momentum for solving both climate and land sustainability problems,” Harden said.
Robert B. Jackson, Kate Lajtha, Susan E. Crow, Gustaf Hugelius, Marc G. Kramer, Gervasio Piñeiro. The Ecology of Soil Carbon: Pools, Vulnerabilities, and Biotic and Abiotic Controls. Annual Review of Ecology, Evolution, and Systematics, 2014; 48 (1) DOI: 10.1146/annurev-ecolsys-112414-054234
Over the past decade, increasing temperatures across much of Africa and decreasing rainfall across East Africa have come to represent an alarming climate trend. Chief among concerns is the impact such conditions have on human health.
A team of scientists from UC Santa Barbara’s Climate Hazards Group (CHG), the University of Minnesota and the U.S. Geological Survey’s Early Warning and Environmental Monitoring Program are exploring potential links between these climate effects and two health outcome indicators: malnutrition and low birth weights. Their findings — some good news, some bad — appear in the journal Global Environmental Change.
Combining temperature and rainfall data from the CHG InfraRed Precipitation with Stations, a satellite-based rainfall monitoring network, with socioeconomic household-level data, the team modeled future scenarios of climate impacts on health outcomes in 13 countries in sub-Saharan Africa.
“Our models indicate that vulnerable areas continuing to get warmer and drier could see more malnourished children and lower birth weights,” said lead author Frank Davenport, a CHG researcher. “However, that scenario potentially could be mitigated by positive development trends such as access to electricity, clean water and education.” With regard to child malnutrition, the data revealed much bigger changes resulting from warming and drying, yet greater potential for alleviating childhood stunting — a measure of malnutrition
“We found the widest variation of results among what are called ‘pastoralists,’ for a couple of reasons. One is that pastoralists tend to be the most vulnerable and the most food-insecure and, because they live in hot, dry, remote areas and have to purchase a great deal of their food, they have limited resources to fall back on in times of adversity. Second, pastoralists often are nomads who graze their herds over extended territories, so they’re notoriously difficult to sample in household surveys, where we get much of our socioeconomic data, so they tend to be underrepresented.”
Along with two previous, related papers, this research demonstrates that climate effects carry the same weight as economic indicators — showing that climate can have first-order effects on nutrition and health. Potential scenarios suggest increased wealth and better education can offset these effects. “The good news is that we can build up the resilience and the livelihoods of these populations,” said USGS Early Warning and Environmental Monitoring Program scientist Chris Funk.
CHG researcher and co-author Shraddhanand Shukla pointed out that despite the potential for long-term positive changes, setbacks such as drought or conflict can make situations worse. “The issue is that even as an entire country gets better, there are certain very vulnerable populations that tend to get marginalized or left behind,” he said. “We’re trying to model fairly complex social phenomena based on assumptions about what might happen in the future. So, no matter what, there’s still a lot we don’t know.”
The researchers’ ultimate goal is to provide useful information to guide interventions and resilience-building activities of aid agencies. “Even though some of our findings are disturbing, I think there’s a lot about this work that is hopeful,” Funk said.
Frank Davenport, Kathryn Grace, Chris Funk, Shraddhanand Shukla. Child health outcomes in sub-Saharan Africa: A comparison of changes in climate and socio-economic factors. Global Environmental Change, 2017; 46: 72 DOI: 10.1016/j.gloenvcha.2017.04.009