The result complements the team’s previous finding that what had looked like an “AMO” occurring during the period since industrialization is instead the result of a competition between steady human-caused warming from greenhouse gases and cooling from more time-variable industrial sulphur pollution.

“It is somewhat ironic, I suppose,” said Michael E. Mann, distinguished professor of atmospheric science and director, Earth System Science Center, Penn State. “Two decades ago, we brought the AMO into the conversation, arguing that there was a long-term natural, internal climate oscillation centered in the North Atlantic based on the limited observations and simulations that were available then, and coining the term ‘AMO.’ Many other scientists ran with the concept, but now we’ve come full circle. My co-authors and I have shown that the AMO is very likely an artifact of climate change driven by human forcing in the modern era and natural forcing in pre-industrial times.”

The researchers previously showed that the apparent AMO cycle in the modern era was an artifact of industrialization-driven climate change, specifically the competition between warming over the past century from carbon pollution and an offsetting cooling factor, industrial sulphur pollution, that was strongest from the 1950s through the passage of the Clean Air Acts in the 1970s and 1980s. But they then asked, why do we still see it in pre-industrial records?

Their conclusion, reported today (Mar. 5) in Science, is that the early signal was caused by large volcanic eruptions in past centuries that caused initial cooling and a slow recovery, with an average spacing of just over half a century. The result resembles an irregular, roughly 60-year AMO-like oscillation.

“Some hurricane scientists have claimed that the increase in Atlantic hurricanes in recent decades is due to the uptick of an internal AMO cycle,” said Mann. “Our latest study appears to be the final nail in the coffin of that theory. What has in the past been attributed to an internal AMO oscillation is instead the result of external drivers, including human forcing during the industrial era and natural volcanic forcing during the pre-industrial era.”

The researchers looked at state-of-the-art climate models both for preindustrial times over the past thousand years where external factors such as solar and volcanic drivers were used, and unforced, “control” simulations where no external drivers were applied and any changes that happen are internally generated. When they looked at simulations for the short, 3- to 7-year El Niño Southern Oscillation (ENSO) cycles, they found that these cycles occurred in the models without adding forcing by climate change, volcanic activity, or anything else.

However, when they looked for the AMO, it did not occur in the unforced model and only appeared in modern times using climate change variables as forcing and in preindustrial times with forcing by volcanic eruptions.

“The models do show intrinsic internal oscillations on a 3- to 7-year time scale characteristic of the established El Niño phenomenon, but nothing on the multi-decadal scale that would be the AMO,” said Byron A. Steinman, associate professor of Earth and environmental sciences, University of Minnesota Duluth, who was also on the project. “What we know is an oscillation like El Niño is real, but the AMO is not.”

Mann suggested that while some influential scientists continue to dismiss certain climate change trends as the result of a supposed internal AMO climate cycle, the best available scientific evidence does not support the existence of such a cycle.

Other researchers from Penn State on this project were Daniel J. Brouillette and Sonya K. Miller, both researchers in meteorology.

The National Science Foundation partially funded this research.

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Materials provided by Penn State. Original written by A’ndrea Elyse Messer. Note: Content may be edited for style and length.

Dr. Lin Shao, professor in the Department of Nuclear Engineering, worked alongside research scientists at the Los Alamos National Laboratory and Hokkaido University to create the next generation of high-performance ODS alloys, and so far they are some of the strongest and best-developed metals in the field.

ODS alloys consist of a combination of metals interspersed with small, nanometer-sized oxide particles and are known for their high creep resistance. This means that as temperatures rise, the materials keep their shape instead of deforming. Many ODS alloys can withstand temperatures up to 1,000 C and are typically used in power generation and engines within aerospace engineering, as well as cutlery.

The nuclear community has a high need for reliable and durable materials to make up the core components of nuclear reactors. The material must be high strength, radiation tolerant and resistant to void swelling (materials develop cavities when subjected to neutron radiation, leading to mechanical failures).

Nuclear researchers like Shao are consistently seeking to identify quality creep-resistant and swelling-resistant materials for their use in high-temperature reactors.

“In general, ODS alloys should be resistant to swelling when exposed to extreme neutron irradiation,” said Shao. “However, the majority of commercial ODS alloys are problematic from the beginning.”

This is because almost all commercial ODS alloys are based on the ferritic phase. Ferritic alloys, classified by their crystalline structure and metallurgical behavior, have good ductility and reasonable high-temperature strength. However, the ferritic phase is the weakest phase when judged by its swelling resistance, therefore making the majority of commercial ODS alloys fail in the first line of defense.

Shao, known internationally for his pioneering work in radiation materials science, directs the accelerator laboratory for testing alloys under extreme irradiation conditions. Shao and his research team collaborated with the Japanese research group at Hokkaido University led by Dr. Shigeharu Ukai to develop various new ODS alloys.

“We decided to explore a new design principle in which oxide particles are embedded in the martensitic phase, which is best to reduce void swelling, rather than the ferritic phase,” said Shao.

The resulting ODS alloys are able to survive up to 400 displacements per atom and are some of the most successful alloys developed in the field, both in terms of high-temperature strength and superior-swelling resistance.

Details of the complete project were published in the Journal of Nuclear Materials along with the most recent study. The team has since conducted multiple studies and attracted the attention from the U.S. Department of Energy and nuclear industry. The project resulted in a total of 18 journal papers and two doctoral degree dissertations.

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Materials provided by Texas A&M University. Original written by Laura Simmons. Note: Content may be edited for style and length.

The survey was conducted among more than 300 Tanzanians, some of whom live in the city of Moshi and some in the countryside. The team found that immune cells from participants from Moshi produced more inflammatory proteins. The people surveyed had no health problems and were not ill, but an activated immune system may increase the risk for lifestyle diseases, such as cardiovascular disease.

The researchers used new techniques to investigate the function of the immune system and the factors that influence its activity. Quirijn de Mast, internist-infectious diseases specialist at Radboud university medical center explains: “We looked at active RNA molecules in the blood — known as the transcriptome — and the composition of metabolic products in the blood.”

Major differences in diet

These analyses showed that metabolites derived from food had an effect on the immune system. Participants from rural areas had higher levels of flavonoids and other anti-inflammatory substances in their blood. The traditional rural Tanzanian diet, which is rich in whole grains, fibre, fruits and vegetables, contains high amounts of these substances. In people with an urban diet, which contains more saturated fats and processed foods, increased levels of metabolites that are involved in cholesterol metabolism were found. The team also found a seasonal change in the activity of the immune system. In the dry season, which is the time of harvest in the study area, the urban people had a less activated immune system.

Migration to the cities of Africa

It has been known for some time that a Western lifestyle and eating habits lead to chronic diseases. According to de Mast, two important findings have emerged from this study. “First of all, we showed that a traditional Tanzanian diet has a beneficial effect on inflammation and the functioning of the immune system. This is important because rapid urbanization is ongoing, not only in Tanzania, but also in other parts of Africa. The migration from the countryside to the city is leading to dietary changes and is accompanied by a rapid increase in the number of lifestyle diseases, which puts a heavy burden on the local healthcare systems. That is why prevention is essential, and diet can be very important for this.”

Western countries can learn from the results Second, these findings from Africa are also relevant for Western countries. Urbanization took place a long time ago in most western countries. By studying populations at different stages of urbanization, researchers therefore have unique opportunities to improve their understanding of how diet and lifestyle affect the human immune system.

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Materials provided by Radboud University Medical Center. Note: Content may be edited for style and length.