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.
Thompson conducted this research work as a graduate student at the University of Michigan. He is continuing his research in the laboratory of climate scientist Bronwen Konecky at Washington University.
“Overall, our study emphasizes that accounting for vegetation change is critical,” Thompson said. “Projections for future climate change are more likely to produce more trustworthy predictions if they include changes in vegetation.”
Alexander J. Thompson, Northern Hemisphere vegetation change drives a Holocene thermal maximum, Science Advances (2022). DOI: 10.1126/sciadv.abj6535. www.science.org/doi/10.1126/sciadv.abj6535
Washington University in St. Louis
Changes in vegetation shaped global temperatures over last 10,000 years (2022, April 15)
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NASA Moves Forward With Next-Gen Solar Sail Project – ExtremeTech
Getting from point A to point B in the solar system is no simple feat, and inefficient, heavy rockets aren’t always the best way. Therefore, NASA has announced it is moving ahead with a new solar sail concept that could make future spacecraft more efficient and maneuverable. The Diffractive Solar Sailing project is now entering phase III development under the NASA Innovative Advanced Concepts (NIAC) program, which could eventually lead to probes that use solar radiation to coast over the sun’s polar regions.
The concept of solar sails is an old one — they were first proposed in the 1980s. The gist is that you equip a vessel with a lightweight sail that translates the pressure from solar radiation into propulsion. The problem is that a solar sail has to be much larger than the spacecraft it’s dragging along. Even a low-thrust solar sail would need to be almost a square kilometer, and you need to keep it intact over the course of a mission. Plus, you have little choice but to fly in the direction of sunlight, so you have to make tradeoffs for either power or navigation. Futuristic diffractive light sails could address these shortcomings.
This work is being undertaken at the Johns Hopkins University Applied Physics Laboratory under the leadership of Amber Dubill and co-investigator Grover Swartzlander. The project progressed through phase I and II trials, which had the team developing concept and feasibility studies on diffractive light sails. The phase III award ensures $2 million in funding over the next two years to design and test the materials that could make diffractive light propulsion a reality.
A diffractive light sail, as the name implies, takes advantage of a property of light known as diffraction. When light passes through a small opening, it spreads out on the other side. This could be used to make a light sail more maneuverable so it doesn’t need to go wherever the solar winds blow.
The team will design its prototypes with several possible mission applications in mind. This technology most likely won’t have an impact on missions to the outer solar system where sunlight is weaker and the monumental distances require faster modes of transportation. However, heliophysics is a great use case for diffractive lightsailing as it would allow visiting the polar regions of the sun, which are difficult to access with current technology.
A lightsail with the ability to essentially redirect thrust from a continuous stream of sunlight would be able to enter orbit over the poles. It may even be possible to maneuver a constellation of satellites into this difficult orbit to study the sun from a new angle. In a few years, NASA may be able to conduct a demonstration mission. Until then, it’s all theoretical.
Tau Herculid meteor shower will happen Monday night, Tuesday morning – USA TODAY
461 new objects discovered at the edge of our solar system
It increases our knowledge of what’s floating in the Kuiper Belt by a significant margin.
- The meteor shower, known as the tau Herculids, could be spectacular, or it could be a total dud.
- If it does reach thousands of meteors per hour, it would be a “meteor storm.”
- Maximum activity is expected around 1 a.m. EDT Tuesday morning, May 31.
Sky watchers could be in for a memorable spectacle Monday night and early Tuesday morning as the Earth passes through debris from a disintegrating comet, leading to a potential meteor shower with thousands of shooting stars per hour.
The meteor shower, known as the tau Herculids, could be spectacular, or it could be a total dud, astronomers said.
“This is going to be an all or nothing event,” NASA meteor expert Bill Cooke said in a statement. If it does reach thousands of meteors per hour, it would be a “meteor storm,” as opposed to a shower.
There is “a small chance of something extraordinary – perhaps one of the most dramatic meteor displays since the spectacular Leonid meteor showers of more than 20 years ago,” said Joe Rao of Space.com.
Maximum activity is expected around 1 a.m. EDT Tuesday, the Space Weather Archive blog said.
The comet is known as 73P/Schwassmann-Wachmann 3 (SW3), named after the two German astronomers who discovered it in 1930. The comet is breaking into dozens of pieces as it orbits the sun, which it does every 5.4 years, NASA said.
EYE TO THE SKY: How to watch every meteor shower in 2022
In all, SW 3 has broken into more than 68 fragments. At its most recent appearance in March 2017, it showed signs that it sheds pieces in each return through the inner solar system, Rao said.
If it makes it to us this year, the debris from the comet will strike Earth’s atmosphere at 10 miles per second, which is on the slow side for a good meteor shower.
Stargazers will pay attention this year because meteors should be high in the night sky at the forecast peak time, NASA said. The higher the radiant point is in the sky, the more meteors you are likely to see.
Even better, the moon is new, so there will be no moonlight to wash out the faint meteors.
For ideal viewing of this or any meteor shower, find a spot away from city lights. Your eyes will need to adjust to the darkness, which could take 15 to 20 minutes. Watching meteor showers can take time, so be patient, experts advise. It could be worth the wait!
Toward customizable timber, grown in a lab – EurekAlert
Each year, the world loses about 10 million hectares of forest — an area about the size of Iceland — because of deforestation. At that rate, some scientists predict the world’s forests could disappear in 100 to 200 years.
In an effort to provide an environmentally friendly and low-waste alternative, researchers at MIT have pioneered a tunable technique to generate wood-like plant material in a lab, which could enable someone to “grow” a wooden product like a table without needing to cut down trees, process lumber, etc.
These researchers have now demonstrated that, by adjusting certain chemicals used during the growth process, they can precisely control the physical and mechanical properties of the resulting plant material, such as its stiffness and density.
They also show that, using 3D bioprinting techniques, they can grow plant material in shapes, sizes, and forms that are not found in nature and that can’t be easily produced using traditional agricultural methods.
“The idea is that you can grow these plant materials in exactly the shape that you need, so you don’t need to do any subtractive manufacturing after the fact, which reduces the amount of energy and waste. There is a lot of potential to expand this and grow three-dimensional structures,” says lead author Ashley Beckwith, a recent PhD graduate.
Though still in its early days, this research demonstrates that lab-grown plant materials can be tuned to have specific characteristics, which could someday enable researchers to grow wood products with the exact features needed for a particular application, like high strength to support the walls of a house or certain thermal properties to more efficiently heat a room, explains senior author Luis Fernando Velásquez-García, a principal scientist in MIT’s Microsystems Technology Laboratories.
Joining Beckwith and Velásquez-García on the paper is Jeffrey Borenstein, a biomedical engineer and group leader at the Charles Stark Draper Laboratory. The research is published today in Materials Today.
To begin the process of growing plant material in the lab, the researchers first isolate cells from the leaves of young Zinnia elegans plants. The cells are cultured in liquid medium for two days, then transferred to a gel-based medium, which contains nutrients and two different hormones.
Adjusting the hormone levels at this stage in the process enables researchers to tune the physical and mechanical properties of the plant cells that grow in that nutrient-rich broth.
“In the human body, you have hormones that determine how your cells develop and how certain traits emerge. In the same way, by changing the hormone concentrations in the nutrient broth, the plant cells respond differently. Just by manipulating these tiny chemical quantities, we can elicit pretty dramatic changes in terms of the physical outcomes,” Beckwith says.
In a way, these growing plant cells behave almost like stem cells — researchers can give them cues to tell them what to become, Velásquez-García adds.
They use a 3D printer to extrude the cell culture gel solution into a specific structure in a petri dish, and let it incubate in the dark for three months. Even with this incubation period, the researchers’ process is about two orders of magnitude faster than the time it takes for a tree to grow to maturity, Velásquez-García says.
Following incubation, the resulting cell-based material is dehydrated, and then the researchers evaluate its properties.
They found that lower hormone levels yielded plant materials with more rounded, open cells that have lower density, while higher hormone levels led to the growth of plant materials with smaller, denser cell structures. Higher hormone levels also yielded plant material that was stiffer; the researchers were able to grow plant material with a storage modulus (stiffness) similar to that of some natural woods.
Another goal of this work is to study what is known as lignification in these lab-grown plant materials. Lignin is a polymer that is deposited in the cell walls of plants which makes them rigid and woody. They found that higher hormone levels in the growth medium causes more lignification, which would lead to plant material with more wood-like properties.
The researchers also demonstrated that, using a 3D bioprinting process, the plant material can be grown in a custom shape and size. Rather than using a mold, the process involves the use of a customizable computer-aided design file that is fed to a 3D bioprinter, which deposits the cell gel culture into a specific shape. For instance, they were able to grow plant material in the shape of a tiny evergreen tree.
Research of this kind is relatively new, Borenstein says.
“This work demonstrates the power that a technology at the interface between engineering and biology can bring to bear on an environmental challenge, leveraging advances originally developed for health care applications,” he adds.
The researchers also show that the cell cultures can survive and continue to grow for months after printing, and that using a thicker gel to produce thicker plant material structures does not impact the survival rate of the lab-grown cells.
“Amenable to customization”
“I think the real opportunity here is to be optimal with what you use and how you use it. If you want to create an object that is going to serve some purpose, there are mechanical expectations to consider. This process is really amenable to customization,” Velásquez-García says.
Now that they have demonstrated the effective tunability of this technique, the researchers want to continue experimenting so they can better understand and control cellular development. They also want to explore how other chemical and genetic factors can direct the growth of the cells.
They hope to evaluate how their method could be transferred to a new species. Zinnia plants don’t produce wood, but if this method were used to make a commercially important tree species, like pine, the process would need to be tailored to that species, Velásquez-García says.
Ultimately, he is hopeful this work can help to motivate other groups to dive into this area of research to help reduce deforestation.
“Trees and forests are an amazing tool for helping us manage climate change, so being as strategic as we can with these resources will be a societal necessity going forward,” Beckwith adds.
This research is funded, in part, by the Draper Scholars Program.
Written by Adam Zewe, MIT News Office
Paper: “Physical, mechanical, and microstructural characterization of novel, 3D-printable, tunable, lab-grown plant materials generated from Zinnia elegans cell cultures”
“Physical, mechanical, and microstructural characterization of novel, 3D-printable, tunable, lab-grown plant materials generated from Zinnia elegans cell cultures”
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