Explanation for formation of abundant features on Europa bodes well for search for extraterrestrial life

Europa is a prime candidate for life in our solar system, and its deep saltwater ocean has captivated scientists for decades. But it's enclosed by an icy shell that could be miles to tens of miles thick, making sampling it a daunting prospect. Now, increasing evidence reveals the ice shell may be less of a barrier and more of a dynamic system -- and site of potential habitability in its own right.

Ice-penetrating radar observations that captured the formation of a "double ridge" feature in Greenland suggest the ice shell of Europa may have an abundance of water pockets beneath similar features that are common on the surface. The findings, which appear in Nature Communications April 19, may be compelling for detecting potentially habitable environments within the exterior of the Jovian moon.

"Because it's closer to the surface, where you get interesting chemicals from space, other moons and the volcanoes of Io, there's a possibility that life has a shot if there are pockets of water in the shell," said study senior author Dustin Schroeder, an associate professor of geophysics at Stanford University's School of Earth, Energy & Environmental Sciences (Stanford Earth). "If the mechanism we see in Greenland is how these things happen on Europa, it suggests there's water everywhere."

A terrestrial analog

On Earth, researchers analyze polar regions using airborne geophysical instruments to understand how the growth and retreat of ice sheets might impact sea-level rise. Much of that study area occurs on land, where the flow of ice sheets is subject to complex hydrology -- such as dynamic subglacial lakes, surface melt ponds and seasonal drainage conduits -- that contributes to uncertainty in sea-level predictions.

Because a land-based subsurface is so different from Europa's subsurface ocean of liquid water, the study co-authors were surprised when, during a lab group presentation about Europa, they noticed that formations that streak the icy moon looked extremely similar to a minor feature on the surface of the Greenland ice sheet -- an ice sheet that the group has studied in detail.

"We were working on something totally different related to climate change and its impact on the surface of Greenland when we saw these tiny double ridges -- and we were able to see the ridges go from 'not formed' to 'formed,'?" Schroeder said.

Upon further examination, they found that the "M"-shaped crest in Greenland known as a double ridge could be a miniature version of the most prominent feature on Europa.

Prominent and prevalent

Double ridges on Europa appear as dramatic gashes across the moon's icy surface, with crests reaching nearly 1000 feet, separated by valleys about a half-mile wide. Scientists have known about the features since the moon's surface was photographed by the Galileo spacecraft in the 1990s but have not been able to conceive a definitive explanation of how they were formed.

Through analyses of surface elevation data and ice-penetrating radar collected from 2015 to 2017 by NASA's Operation IceBridge, the researchers revealed how the double ridge on northwest Greenland was produced when the ice fractured around a pocket of pressurized liquid water that was refreezing inside of the ice sheet, causing two peaks to rise into the distinct shape.

"In Greenland, this double ridge formed in a place where water from surface lakes and streams frequently drains into the near-surface and refreezes," said lead study author Riley Culberg, a PhD student in electrical engineering at Stanford. "One way that similar shallow water pockets could form on Europa might be through water from the subsurface ocean being forced up into the ice shell through fractures -- and that would suggest there could be a reasonable amount of exchange happening inside of the ice shell."

Snowballing complexity

Rather than behaving like a block of inert ice, the shell of Europa seems to undergo a variety of geological and hydrological processes -- an idea supported by this study and others, including evidence of water plumes that erupt to the surface. A dynamic ice shell supports habitability since it facilitates the exchange between the subsurface ocean and nutrients from neighboring celestial bodies accumulated on the surface.

"People have been studying these double ridges for over 20 years now, but this is the first time we were actually able to watch something similar on Earth and see nature work out its magic," said study co-author Gregor Steinbrügge, a planetary scientist at NASA's Jet Propulsion Laboratory (JPL) who started working on the project as a postdoctoral researcher at Stanford. "We are making a much bigger step into the direction of understanding what processes actually dominate the physics and the dynamics of Europa's ice shell."

The co-authors said their explanation for how the double ridges form is so complex, they couldn't have conceived it without the analog on Earth.

"The mechanism we put forward in this paper would have been almost too audacious and complicated to propose without seeing it happen in Greenland," Schroeder said.

The findings equip researchers with a radar signature for quickly detecting this process of double ridge formation using ice-penetrating radar, which is among the instruments currently planned for exploring Europa from space.

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No glacial fertilization effect in the Antarctic Ocean

Changes in the concentration of atmospheric carbon dioxide (CO2) are considered to be the main cause of past and future climate change. A long-standing debate centers on whether the roughly 30 percent lower CO2 content of the ice-age atmosphere was caused by iron fertilization. It is argued that iron-rich dust is carried into the ocean by wind and water, where it stimulates the growth of algae that absorb more CO2. As the algae die and then sink permanently into the depths of the ocean, the CO2 also remains there like in a trap. Although there is clear evidence that dust input increased during the ice ages, the fertilization effect is controversial, at least for the Antarctic Ocean.

In a recent study, an international team of 38 researchers from 13 countries led by Dr. Michael Weber from the Institute for Geosciences at the University of Bonn investigated this question. As part of the Integrated Ocean Discovery Program (IODP), the team traveled to the Scotia Sea on the drillship "JOIDES Resolution" and spent two months in 2019 bringing up cores from the seafloor at depths of 3,000 to 4,000 meters. Weber: "We collected the highest-resolution and longest climate archive ever obtained near Antarctica and its main dust source, Patagonia."

1.5 million years of climate history

In the 200-meter-long deep-sea core U1537, the climate history of the last 1.5 million years was recorded in detail. This allows the reconstruction of the dust input to be nearly doubled, since Antarctic ice cores only cover the last 800,000 years. Current records from the deep ocean show that dust deposition during the ice ages was actually five to 15 times higher. This is also reflected in the ice cores.

However, the researchers found no evidence of a fertilization effect from dust in the Antarctic Ocean during the ice ages. Rather, the production of algae, for example, and thus carbon CO2 sequestration, was high only during warm periods when dust input into the Scotia Sea was low. This means that during cold periods, other processes prevented the CO2 captured in the ocean from escaping into the atmosphere and triggering warming. The main factors here are much more extensive sea ice cover, more intense stratification in the ocean, and reduced dynamics of the current systems, which contributed to a reduction in the CO2 content of the atmosphere during cold periods.

The opposing trends in dust deposition and oceanic productivity during the ice ages and interglacial periods of the Pleistocene are accompanied by long-term, gradual changes in the climate system in the southern polar region. Bioproductivity was particularly high during the interglacial periods of the last 400,000 years, but during the mid-Pleistocene transition 1.2 million to 700,000 years ago, it differed little from that during cold periods. As the transition progressed, the dust input covered larger and larger areas in the Southern Hemisphere. Abrupt changes continued to occur 900,000 years ago, indicating greater glaciation of Antarctica.

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How air pollution alters lung tissue, increasing cancer susceptibility

Scientists have identified a mechanism that explains how fine air pollution particles might cause lung cancer, according to a study published today in eLife.

The findings could lead to new approaches for preventing or treating the initial lung changes that lead to the disease.

Tiny, inhalable fine particulate matter (FPM) found in air pollutants has been recognised as a Group 1 carcinogen and a substantial threat to global health. However, the cancer-causing mechanism of FPM remains unclear.

"Despite its potential to cause mutations, recent research suggests that FPM does not directly promote -- and may even inhibit -- the growth of lung cancer cells," explains first author Zhenzhen Wang, an associate researcher at Nanjing University (NJU), Nanjing, China, who carried out the study between labs at NJU and the University of Macau where she was sponsored by a University of Macau Fellowship. "This suggests that FPM might lead to cancer through indirect means that support tumour growth. For example, some studies suggest FPM can prevent immune cells from moving to where they are needed."

To explore this possibility, Wang and the team collected FPM from seven locations in China and studied its effects on the main immune cells that defend against tumour growth -- called cytotoxic T-cells (CTLs). In mice administered with lung cancer cells that were not exposed to FPM, CTLs were recruited to the lung to destroy the tumour cells. By contrast, in the mice whose lungs were exposed to FPM, the infiltration of CTLs was delayed -- potentially allowing the tumour cells to establish in lung tissue.

To investigate why the CTLs did not enter the lung as quickly in the FPM-exposed lungs, the team studied both the CTLs themselves and the lung tissue structure. They found that CTLs exposed to FPM still retained their migratory ability, but that FPM exposure dramatically compressed the lung tissue structure and the spaces that immune cells move between. There were also much higher levels of collagen -- a protein that provides biomechanical support for cells and tissues. When the team studied the movement of CTLs in the mice, in lung tissue exposed to FPM, CTLs struggled to move, whereas those in the untreated tissue were able to move freely.

Further analysis of the tissue showed that the structural changes were caused by increases in a collagen subtype called collagen IV, but the team still did not know how FPM triggered this. They found the answer when they looked more closely at the structural changes to collagen IV and the enzyme responsible for making them -- called peroxidasin. This enzyme drives a specific type of cross-linking that exposure to FPM was found to cause and aggravate in the lung tissue.

"The most surprising find was the mechanism by which this process occurred," Wang says. "The peroxidasin enzyme stuck to the FPM in the lung, which increased its activity. Taken together, this means that wherever FPM lands in the lung, increased peroxidasin activity leads to structural changes in the lung tissue that can keep immune cells out and away from growing tumour cells."

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Bioengineers visualize fat storage in fruit flies

For the first time, researchers have visually monitored, in high resolution, the timing and location of fat storage within the intact cells of fruit flies. The new optical imaging tool from the lab of bioengineering professor Lingyan Shi at the University of California San Diego is already being used to untangle often discussed, yet mysterious, links between diet and things like obesity, diabetes and aging.The work from bioengineers at the UC San Diego Jacobs School of Engineering is published in the journal Aging Cell.

The optical microscopy platform developed by the UC San Diego bioengineers is unique. It allows the researchers to visually track, in high resolution within fat cells, how specific dietary changes affect the way flies turn the energy from their food into fat. The tool also allows the researchers to monitor the reverse process of changing fat back into energy. In addition, the researchers can now visually monitor changes in size in individual fat-storage "containers" within the class of fruit fly cells that is analogous to mammalian fat (adipose) cells.

In the new paper in Aging Cell, the researchers demonstrated the ability to visually track changes in fat (lipid) metabolism in flies after they were put on a wide range of different diets. The diets included calorie-restricted diets, high protein diets, and diets with twice, four-times, and ten-times the sugar of a standard diet.

"With our new optical microscopy system, we can see both where and when fats are being put into storage and taken out of storage," said Shi, the bioengineering professor at UC San Diego who is the corresponding senior author on the new paper. "This is the first imaging technology that can visualize fat metabolism at high resolution in both space and time within individual fat cells. We have demonstrated that we can see both where and when lipid metabolism changes within individual fruit fly fat body cells in response to dietary changes."

"Interest in optimizing the human diet is intense," Shi continued. "People want answers to questions like, 'What are the best diets to slow aging? What are the best diets for losing weight? What are the best diets for extending health span?' I don't yet have answers to these questions, but in my lab, we develop new technologies that are getting us closer to answering some of the big dietary questions out there."

In the new work in Aging Cell, for example, the researchers report a new way to answer questions like:

How much does a specific diet, such as a high-protein diet, or a high-sugar diet, or a calorie-restricted diet, alter a fruit fly's process of turning energy from food into fat? And how much do these same diets affect a fruit fly's process of turning fat back into energy?

"We developed this tool to help us untangle the relationships between diet and phenomena like obesity, diabetes, aging, and longevity," said Shi.

Tracking the size of fat droplets within intact fruit fly cells is one example of what's possible with the new visualization platform.

"Droplet size is a way to track how much of the stored fat is 'turning over' or getting converted back into energy. This is an important aspect of lipid metabolism, and we now have a tool that allows us to track changes in the size of specific lipid droplets within individual cells of fruit flies," said Yajuan Li, MD. PhD, who is a postdoctoral researcher in the Shi lab at UC San Diego and the first author on the paper in Aging Cell.

Heavy water

The new visualization platform builds on some of Shi's earlier work using a variation on regular water, called heavy water or (D2O). Heavy water is, literally, heavier than regular water. Heavy water molecules contain one oxygen atom like regular water. But in place of the pair of hydrogen atoms -- the "H2" in "H20" -- heavy water contains a pair of heavier deuterium atoms.

Like "regular" water, heavy water is freely incorporated into cells in living organisms. So when the researchers provide heavy water to a fruit fly, and then that fruit fly begins to convert energy from its food into fat molecules to be stored, some of those fat molecules contain deuterium. In this way, the prevalence of deuterium atoms in lipids stored within the fat cells of fruit flies provides a way to measure how much fat that fly has stored.

By changing a fly's diet at the same time that you introduce heavy water, you have a way to monitor how the diet changes lipid turnover. More details on how the system works are in this 2021 profile, in which Shi said, "When we are developing a new technology, a new tool, it will definitely inspire us to ask new biological questions."

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With dwindling water supplies, the timing of rainfall matters

A new UC Riverside study shows it's not how much extra water you give your plants, but when you give it that counts.

This is especially true near Palm Springs, where the research team created artificial rainfall to examine the effects on plants over the course of two years. This region has both winter and summer growing seasons, both of which are increasingly impacted by drought and, occasionally, extreme rain events.

Normally, some desert wildflowers and grasses begin growing in December, and are dead by June. A second community of plants sprouts in July and flowers in August. These include the wildflowers that make for an extremely popular tourist attraction in "super bloom" years.

"We wanted to understand whether one season is more sensitive to climate change than another," said Marko Spasojevic, UCR plant ecologist and lead study author. "If we see an increase or decrease in summer rains, or winter rains, how does that affect the ecosystem?"

The team observed that in summer, plants grow more when given extra water, in addition to any natural rainfall. However, the same was not true in winter.

"Essentially, adding water in summer gets us more bang for our buck," Spasojevic said.

Their findings are described in a paper published in the University of California journal Elementa.

Over the course of the study, the team observed 24 plots of land at the Boyd Deep Canyon Desert Research Center, in the Palm Desert area. Some of the plots got whatever rain naturally fell. Others were covered and allowed to receive rain only in one season. A third group of plots received additional collected rainwater.

While adding water in summer resulted in higher plant biomass, it generally did not increase the diversity of plants that grew, the researchers noted. Decreasing rainfall, in contrast, had negative effects on plants across both summer and winter, but may lead to some increased growth in the following off-seasons.

Implications of the work extend beyond learning when additional water resources might be applied simply to help plants grow. Whole communities of animals depend on these plants. They are critical for pollinators such as bees and butterflies, and they play a big role in controlling erosion and movement of soils by wind.

"Studies like this one are critical for understanding the complex effects of climate change to dryland ecosystems," said Darrel Jenerette, UCR landscape ecologist and study co-author.

Desert plants also play an important role in removing carbon dioxide and nitrogen from the atmosphere to use as fuel for growth. Microbes that live in the soil can use the carbon and nitrogen released by plant roots, then send it back into the atmosphere where it can affect the climate.

"Drylands cover roughly a third of the land surface, so even small changes in the way they take in and emit carbon or nitrogen could have a big impact on our atmosphere," said Peter Homyak, UCR environmental scientist and study co-author.

As the team continues this research over the next few years, they expect to see changes in soil carbon and nitrogen cycling, given that plants are already being affected by changes in seasonal rainfall, as this study shows.

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Neural network model helps predict site-specific impacts of earthquakes

In disaster mitigation planning for future large earthquakes, seismic ground motion predictions are a crucial part of early warning systems and seismic hazard mapping. The way the ground moves depends on how the soil layers amplify the seismic waves (described in a mathematical site "amplification factor"). However, geophysical explorations to understand soil conditions are costly, limiting characterization of site amplification factors to date.

A new study by researchers from Hiroshima University published on April 5 in the Bulletin of the Seismological Society of America introduced a novel artificial intelligence (AI)-based technique for estimating site amplification factors from data on ambient vibrations or microtremors of the ground.

Subsurface soil conditions, which determine how earthquakes affect a site, vary substantially. Softer soils, for example, tend to amplify ground motion from an earthquake, while hard substrates may dampen it. Ambient vibrations of the ground or microtremors that occur all over the Earth's surface caused by human or atmospheric disturbances can be used to investigate soil conditions. Measuring microtremors provides valuable information about the amplification factor (AF) of a site, thus its vulnerability to damage from earthquakes due to its response to tremors.

The recent study from Hiroshima University researchers introduced a new way to estimate site effects from microtremor data. "The proposed method would contribute to more accurate and more detailed seismic ground motion predictions for future earthquakes," says lead author and associate professor Hiroyuki Miura in the Graduate School of Advanced Science and Engineering. The study investigated the relationship between microtremor data and site amplification factors using a deep neural network with the goal of developing a model that could be applied at any site worldwide.

The researchers looked into a common method known as Horizontal-to-vertical spectral ratios (MHVR) which is usually used to estimate the resonant frequency of the seismic ground. It can be generated from microtremor data; ambient seismic vibrations are analyzed in three dimensions to figure out the resonant frequency of sediment layers on top of bedrock as they vibrate. Previous research has shown, however, that MHVR cannot reliably be used directly as the site amplification factor. So, this study proposed a deep neural network model for estimating site amplification factors from the MHVR data.

The study used 2012-2020 microtremor data from 105 sites in the Chugoku district of western Japan. The sites are part of Japan's national seismograph network that contains about 1700 observation stations distributed in a uniform grid at 20 km intervals across Japan. Using a generalized spectral inversion technique, which separates out the parameters of source, propagation, and site, the researchers analyzed site-specific amplifications.

Data from each site were divided into a training set, a validation set, and a test set. The training set were used to teach a deep neural network. The validation set were used in the network's iterative optimization of a model to describe the relationship between the microtremor MHVRs and the site amplification factors. The test data were a completely unknown set used to evaluate the performance of the model.

The model performed well on the test data, demonstrating its potential as a predictive tool for characterizing site amplification factors from microtremor data. However, notes Miura, "the number of training samples analyzed in this study (80) sites is still limited," and should be expanded before assuming that the neural network model applies nationwide or globally. The researchers hope to further optimize the model with a larger dataset.

Rapid and cost-effective techniques are needed for more accurate seismic ground motion prediction since the relationship is not always linear. Explains Miura, "By applying the proposed method, site amplification factors can be automatically and accurately estimated from microtremor data observed at arbitrary site." Going forward, the study authors aim to continue to refine advanced AI techniques to evaluate the nonlinear responses of the ground to earthquakes.

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Extract from a common kitchen spice could be key to greener, more efficient fuel cells

Turmeric, a spice found in most kitchens, has an extract that could lead to safer, more efficient fuel cells.

Researchers at the Clemson Nanomaterials Institute (CNI) and their collaborators from the Sri Sathya Sai Institute of Higher Learning (SSSIHL) in India discovered a novel way to combine curcumin -- the substance in turmeric -- and gold nanoparticles to create an electrode that requires 100 times less energy to efficiently convert ethanol into electricity.

While the research team must do more testing, the discovery brings replacing hydrogen as a fuel cell feedstock one step closer.

"Of all the catalysts for alcohol oxidation in alkaline medium, the one we prepared is the best so far," said Apparao Rao, CNI's founding director and the R. A. Bowen Professor of Physics in the College of Science's.

Fuel cells generate electricity through a chemical reaction instead of combustion. They are used to power vehicles, buildings, portable electronic devices and backup power systems.

Hydrogen fuel cells are highly efficient and do not produce greenhouse gases. While hydrogen is the most common chemical element in the universe, it must be derived from substances such as natural gas and fossil fuels because it occurs naturally on Earth only in compound form with other elements in liquids, gases or solids. The necessary extraction adds to hydrogen fuel cells' cost and environmental impact.

In addition, hydrogen used in fuel cells is a compressed gas, creating challenges for storage and transportation. Ethanol, an alcohol made from corn or other agricultural-based feeds, is safer and easier to transport than hydrogen because it is a liquid.

"To make it a commercial product where we can fill our tanks with ethanol, the electrodes have to be highly efficient," said Lakshman Ventrapragada, a former student of Rao's who worked as a research assistant at the CNI and is an alumnus of SSSIHL. "At the same time, we don't want very expensive electrodes or synthetic polymeric substrates that are not eco-friendly because that defeats the whole purpose. We wanted to look at something green for the fuel cell generation process and making the fuel cell itself."

The researchers focused on the fuel cell's anode, where the ethanol or other feed source is oxidized.

Fuel cells widely use platinum as a catalyst. But platinum suffers from poisoning because of reaction intermediates such as carbon monoxide, Ventrapragada said. It is also costly.

The researchers used gold as a catalyst. Instead of using conducting polymers, metal-organic frameworks, or other complex materials to deposit the gold on the surface of the electrode, the researchers used curcumin because of its structural uniqueness. Curcumin is used to decorate the gold nanoparticles to stabilize them, forming a porous network around the nanoparticles. Researchers deposited the curcumin gold nanoparticle on the surface of the electrode at a 100 times lower electric current than in previous studies.

Without the curcumin coating, the gold nanoparticles agglomerate, cutting down on the surface area exposed to the chemical reaction, Ventrapragada said.

"Without this curcumin coating, the performance is poor," Rao said. "We need this coating to stabilize and create a porous environment around the nanoparticles, and then they do a super job with alcohol oxidation.

"There's a big push in the industry for alcohol oxidation. This discovery is an excellent enabler for that. The next step is to scale the process up and work with an industrial collaborator who can actually make the fuel cells and build stacks of fuel cells for the real application," he continued.

But the research could have broader implications than improved fuel cells. The electrode's unique properties could lend itself to future applications in sensors, supercapacitors and more, Ventrapragada said.

In collaboration with the SSSIHL research team, Rao's team is testing the electrode as a sensor that could help identify changes in the level of dopamine. Dopamine has been implicated in disorders such as Parkinson's disease and attention deficit hyperactivity disorder. When members of the research team tested urine samples obtained from healthy volunteers, they could measure dopamine to the approved clinical range with this electrode using a cost-effective method compared to standard ones used today, Rao said.

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Tumors partially destroyed with sound don't come back

Noninvasive sound technology developed at the University of Michigan breaks down liver tumors in rats, kills cancer cells and spurs the immune system to prevent further spread -- an advance that could lead to improved cancer outcomes in humans.

By destroying only 50% to 75% of liver tumor volume, the rats' immune systems were able to clear away the rest, with no evidence of recurrence or metastases in more than 80% animals.

"Even if we don't target the entire tumor, we can still cause the tumor to regress and also reduce the risk of future metastasis," said Zhen Xu, professor of biomedical engineering at U-M and corresponding author of the study in Cancers.

Results also showed the treatment stimulated the rats' immune responses, possibly contributing to the eventual regression of the untargeted portion of the tumor and preventing further spread of the cancer.

The treatment, called histotripsy, noninvasively focuses ultrasound waves to mechanically destroy target tissue with millimeter precision. The relatively new technique is currently being used in a human liver cancer trial in the United States and Europe.

In many clinical situations, the entirety of a cancerous tumor cannot be targeted directly in treatments for reasons that include the mass' size, location or stage. To investigate the effects of partially destroying tumors with sound, this latest study targeted only a portion of each mass, leaving behind a viable intact tumor. It also allowed the team, including researchers at Michigan Medicine and the Ann Arbor VA Hospital, to show the approach's effectiveness under less than optimal conditions.

"Histotripsy is a promising option that can overcome the limitations of currently available ablation modalities and provide safe and effective noninvasive liver tumor ablation," said Tejaswi Worlikar, a doctoral student in biomedical engineering. "We hope that our learnings from this study will motivate future preclinical and clinical histotripsy investigations toward the ultimate goal of clinical adoption of histotripsy treatment for liver cancer patients."

Liver cancer ranks among the top 10 causes of cancer related deaths worldwide and in the U.S. Even with multiple treatment options, the prognosis remains poor with five-year survival rates less than 18% in the U.S. The high prevalence of tumor recurrence and metastasis after initial treatment highlights the clinical need for improving outcomes of liver cancer.

Where a typical ultrasound uses sound waves to produce images of the body's interior, U-M engineers have pioneered the use of those waves for treatment. And their technique works without the harmful side effects of current approaches such as radiation and chemotherapy.

"Our transducer, designed and built at U-M, delivers high amplitude microsecond-length ultrasound pulses -- acoustic cavitation -- to focus on the tumor specifically to break it up," Xu said. "Traditional ultrasound devices use lower amplitude pulses for imaging."

The microsecond long pulses from UM's transducer generate microbubbles within the targeted tissues -- bubbles that rapidly expand and collapse. These violent but extremely localized mechanical stresses kill cancer cells and break up the tumor's structure.

Since 2001, Xu's laboratory at U-M has pioneered the use of histotripsy in the fight against cancer, leading to the clinical trial #HOPE4LIVER sponsored by HistoSonics, a U-M spinoff company. More recently, the group's research has produced promising results on histotripsy treatment of brain therapy and immunotherapy.

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Changes in vegetation shaped global temperatures over last 10,000 years

Follow the pollen. Records from past plant life tell the real story of global temperatures, according to research from a climate scientist at Washington University in St. Louis.

Warmer temperatures brought plants -- and then came even warmer temperatures, according to new model simulations published April 15 in Science Advances.

Alexander Thompson, a postdoctoral research associate in earth and planetary sciences in Arts & Sciences, updated simulations from an important climate model to reflect the role of changing vegetation as a key driver of global temperatures over the last 10,000 years.

Thompson had long been troubled by a problem with models of Earth's atmospheric temperatures since the last ice age. Too many of these simulations showed temperatures warming consistently over time.

But climate proxy records tell a different story. Many of those sources indicate a marked peak in global temperatures that occurred between 6,000 and 9,000 years ago.

Thompson had a hunch that the models could be overlooking the role of changes in vegetation in favor of impacts from atmospheric carbon dioxide concentrations or ice cover.

"Pollen records suggest a large expansion of vegetation during that time," Thompson said.

"But previous models only show a limited amount of vegetation growth," he said. "So, even though some of these other simulations have included dynamic vegetation, it wasn't nearly enough of a vegetation shift to account for what the pollen records suggest."

In reality, the changes to vegetative cover were significant.

Early in the Holocene, the current geological epoch, the Sahara Desert in Africa grew greener than today -- it was more of a grassland. Other Northern Hemisphere vegetation including the coniferous and deciduous forests in the mid-latitudes and the Arctic also thrived.

Thompson took evidence from pollen records and designed a set of experiments with a climate model known as the Community Earth System Model (CESM), one of the best-regarded models in a wide-ranging class of such models. He ran simulations to account for a range of changes in vegetation that had not been previously considered.

"Expanded vegetation during the Holocene warmed the globe by as much as 1.5 degrees Fahrenheit," Thompson said. "Our new simulations align closely with paleoclimate proxies. So this is exciting that we can point to Northern Hemisphere vegetation as one potential factor that allows us to resolve the controversial Holocene temperature conundrum."

Understanding the scale and timing of temperature change throughout the Holocene is important because it is a period of recent history, geologically speaking. The rise of human agriculture and civilization occurred during this time, so many scientists and historians from different disciplines are interested in understanding how early and mid-Holocene climate differed from the present day.

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Pollution from cooking emissions hangs in the air

Organic aerosols -- such as those released in cooking -- may stay in the atmosphere for several days, because of nanostructures formed by fatty acids as they are released into the air.

By identifying the processes which control how these aerosols are transformed in the atmosphere, scientists will be able to better understand and predict their impact on the environment and the climate.

Experts at the Universities of Birmingham and Bath have used instruments at the Diamond Light Source and the Central Laser Facility, both based at the Harwell Campus in Oxford, to probe the behaviour of thin films of oleic acid -- an unsaturated fatty acid commonly released when cooking.

In the study, published in Atmospheric Chemistry and Physics, they were able to analyse the particular molecular properties that control how rapidly aerosol emissions can be broken down in the atmosphere.

Then, using a theoretical model combined with experimental data the team was able to predict the amount of time aerosols generated from cooking may hang around in the environment.

These types of aerosols have long been associated with poor air quality in urban areas, but their impact on human-made climate change is hard to gauge. That's because of the diverse range of molecules found within aerosols, and their varying interactions with the environment.

By identifying the nanostructure of molecules emitted during cooking that slows down the break-up of organic aerosols, it becomes possible to model how they are transported and dispersed into the atmosphere.

Lead author Dr Christian Pfrang, of the University of Birmingham's School of Geography, Earth and Environmental Sciences, said: "Cooking aerosols account for up to 10 per cent of particulate matter (PM) emissions in the UK. Finding accurate ways to predict their behaviour will give us much more precise ways to also assess their contribution to climate change."

Co-author Dr Adam Squires, of the University of Bath, said: "We're increasingly finding out how molecules like these fatty acids from cooking can organise themselves into bilayers and other regular shapes and stacks within aerosol droplets that float in the air, and how this completely changes how fast they degrade, how long they persist in the atmosphere, and how they affect pollution and weather."

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