How to tackle the global deforestation crisis

Imagine if France, Germany, and Spain were completely blanketed in forests -- and then all those trees were quickly chopped down. That's nearly the amount of deforestation that occurred globally between 2001 and 2020, with profound consequences.

Deforestation is a major contributor to climate change, producing between 6 and 17 percent of global greenhouse gas emissions, according to a 2009 study. Meanwhile, because trees also absorb carbon dioxide, removing it from the atmosphere, they help keep the Earth cooler. And climate change aside, forests protect biodiversity.

"Climate change and biodiversity make this a global problem, not a local problem," says MIT economist Ben Olken. "Deciding to cut down trees or not has huge implications for the world."

But deforestation is often financially profitable, so it continues at a rapid rate. Researchers can now measure this trend closely: In the last quarter-century, satellite-based technology has led to a paradigm change in charting deforestation. New deforestation datasets, based on the Landsat satellites, for instance, track forest change since 2000 with resolution at 30 meters, while many other products now offer frequent imaging at close resolution.

"Part of this revolution in measurement is accuracy, and the other part is coverage," says Clare Balboni, an assistant professor of economics at the London School of Economics (LSE). "On-site observation is very expensive and logistically challenging, and you're talking about case studies. These satellite-based data sets just open up opportunities to see deforestation at scale, systematically, across the globe."

Balboni and Olken have now helped write a new paper providing a road map for thinking about this crisis. The open-access article, "The Economics of Tropical Deforestation," appears this month in the Annual Review of Economics. The co-authors are Balboni, a former MIT faculty member; Aaron Berman, a PhD candidate in MIT's Department of Economics; Robin Burgess, an LSE professor; and Olken, MIT's Jane Berkowitz Carlton and Dennis William Carlton Professor of Microeconomics. Balboni and Olken have also conducted primary research in this area, along with Burgess.

So, how can the world tackle deforestation? It starts with understanding the problem.

Replacing forests with farms

Several decades ago, some thinkers, including the famous MIT economist Paul Samuelson in the 1970s, built models to study forests as a renewable resource; Samuelson calculated the "maximum sustained yield" at which a forest could be cleared while being regrown. These frameworks were designed to think about tree farms or the U.S. national forest system, where a fraction of trees would be cut each year, and then new trees would be grown over time to take their place.

But deforestation today, particularly in tropical areas, often looks very different, and forest regeneration is not common.

Indeed, as Balboni and Olken emphasize, deforestation is now rampant partly because the profits from chopping down trees come not just from timber, but from replacing forests with agriculture. In Brazil, deforestation has increased along with agricultural prices; in Indonesia, clearing trees accelerated as the global price of palm oil went up, leading companies to replace forests with palm tree orchards.

All this tree-clearing creates a familiar situation: The globally shared costs of climate change from deforestation are "externalities," as economists say, imposed on everyone else by the people removing forest land. It is akin to a company that pollutes into a river, affecting the water quality of residents.

"Economics has changed the way it thinks about this over the last 50 years, and two things are central," Olken says. "The relevance of global externalities is very important, and the conceptualization of alternate land uses is very important." This also means traditional forest-management guidance about regrowth is not enough. With the economic dynamics in mind, which policies might work, and why?

The search for solutions

As Balboni and Olken note, economists often recommend "Pigouvian" taxes (named after the British economist Arthur Pigou) in these cases, levied against people imposing externalities on others. And yet, it can be hard to identify who is doing the deforesting.

Instead of taxing people for clearing forests, governments can pay people to keep forests intact. The UN uses Payments for Environmental Services (PES) as part of its REDD+ (Reducing Emissions from Deforestation and forest Degradation) program. However, it is similarly tough to identify the optimal landowners to subsidize, and these payments may not match the quick cash-in of deforestation. A 2017 study in Uganda showed PES reduced deforestation somewhat; a 2022 study in Indonesia found no reduction; another 2022 study, in Brazil, showed again that some forest protection resulted.

"There's mixed evidence from many of these [studies]," Balboni says. These policies, she notes, must reach people who would otherwise clear forests, and a key question is, "How can we assess their success compared to what would have happened anyway?"

Some places have tried cash transfer programs for larger populations. In Indonesia, a 2020 study found such subsidies reduced deforestation near villages by 30 percent. But in Mexico, a similar program meant more people could afford milk and meat, again creating demand for more agriculture and thus leading to more forest-clearing.

At this point, it might seem that laws simply banning deforestation in key areas would work best -- indeed, about 16 percent of the world's land overall is protected in some way. Yet the dynamics of protection are tricky. Even with protected areas in place, there is still "leakage" of deforestation into other regions.

Still more approaches exist, including "nonstate agreements," such as the Amazon Soy Moratorium in Brazil, in which grain traders pledged not to buy soy from deforested lands, and reduced deforestation without "leakage."

Also, intriguingly, a 2008 policy change in the Brazilian Amazon made agricultural credit harder to obtain by requiring recipients to comply with environmental and land registration rules. The result? Deforestation dropped by up to 60 percent over nearly a decade.

Politics and pulp

Overall, Balboni and Olken observe, beyond "externalities," two major challenges exist. One, it is often unclear who holds property rights in forests. In these circumstances, deforestation seems to increase. Two, deforestation is subject to political battles.

For instance, as economist Bard Harstad of Stanford University has observed, environmental lobbying is asymmetric. Balboni and Olken write: "The conservationist lobby must pay the government in perpetuity … while the deforestation-oriented lobby need pay only once to deforest in the present." And political instability leads to more deforestation because "the current administration places lower value on future conservation payments."

Even so, national political measures can work. In the Amazon from 2001 to 2005, Brazilian deforestation rates were three to four times higher than on similar land across the border, but that imbalance vanished once the country passed conservation measures in 2006. However, deforestation ramped up again after a 2014 change in government. Looking at particular monitoring approaches, a study of Brazil's satellite-based Real-Time System for Detection of Deforestation (DETER), launched in 2004, suggests that a 50 percent annual increase in its use in municipalities created a 25 percent reduction in deforestation from 2006 to 2016.

How precisely politics matters may depend on the context. In a 2021 paper, Balboni and Olken (with three colleagues) found that deforestation actually decreased around elections in Indonesia. Conversely, in Brazil, one study found that deforestation rates were 8 to 10 percent higher where mayors were running for re-election between 2002 and 2012, suggesting incumbents had deforestation industry support.

"The research there is aiming to understand what the political economy drivers are," Olken says, "with the idea that if you understand those things, reform in those countries is more likely."

Looking ahead, Balboni and Olken also suggest that new research estimating the value of intact forest land intact could influence public debates. And while many scholars have studied deforestation in Brazil and Indonesia, fewer have examined the Democratic Republic of Congo, another deforestation leader, and sub-Saharan Africa.

Deforestation is an ongoing crisis. But thanks to satellites and many recent studies, experts know vastly more about the problem than they did a decade or two ago, and with an economics toolkit, can evaluate the incentives and dynamics at play.

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Satellite security lags decades behind the state of the art

Thousands of satellites are currently orbiting the Earth, and there will be many more in the future. Researchers from Ruhr University Bochum and the CISPA Helmholtz Center for Information Security in Saarbrücken have assessed the security of these systems from an IT perspective. They analysed three current low-earth orbit satellites and found that, from a technical point of view, hardly any modern security concepts were implemented. Various security mechanisms that are standard in modern mobile phones and laptops were not to be found: for example, there was no separation of code and data. Interviews with satellite developers also revealed that the industry relies primarily on security through obscurity.

The results were presented by a team headed by Johannes Willbold, a PhD student from Bochum, Dr. Ali Abbasi, a researcher from Saarbrücken, and Professor Thorsten Holz, formerly in Bochum, now in Saarbrücken, at the IEEE Symposium on Security and Privacy, which took place in San Francisco from 22 to 25 May 2023. The paper was awarded a Distinguished Paper Award at the conference.

Research satellites and commercial satellite put to the test

The examined satellites were two small models and one medium-sized model -- research satellites as well as a satellite of a commercial company -- which orbit the Earth at a short distance and are used to observe the Earth. Gaining access to satellites and their software was a challenge for the team, as commercial providers in particular rarely wish to reveal any details. The researchers eventually gained access through cooperation with the European Space Agency (ESA), various universities involved in the construction of satellites, and a commercial enterprise.

The team from Bochum and Saarbrücken conducted a thorough security analysis of the three models. They looked in detail at what the software running on the devices does and which communication protocols are used. They emulated the systems, i.e., rebuilt them virtually, so that they could test the software as if it were in a real satellite. "It was a very different world from the systems we usually study. For example, completely different communication protocols were used," as Thorsten Holz outlines the process.

Systems with specific requirements

Satellites orbiting the Earth can only be reached by their ground station on Earth within a time window of a few minutes. The systems must be robust against the radiation in space, and, since they can only consume a small amount of energy, they have a low power output. "The data rates are like those of modems in the 1990s," as Holz elaborates the challenges satellite developers face.

Based on the findings gained from the software analysis, the researchers worked out various attack scenarios. They showed that they could cut off the satellites from ground control and seize control of the systems, for example in order to take pictures with the satellite camera. "We were surprised that the technical security level is so low," points out Thorsten Holz, adding the following caveat with regard to potential ramifications: "It wouldn't be all that easy to steer the satellite to another location, for example, to crash it or have it collide with other objects."

Survey among developers

To find out how the people who develop and build satellites approach security, the research team compiled a questionnaire and submitted it to research institutions, the ESA, the German Aerospace Centre and various enterprises. Nineteen developers participated anonymously in the survey. "The results show us that the understanding of security in the industry is different than in many other areas, specifically that it's security by obscurity," concludes Johannes Willbold. Many of the respondents therefore assumed that satellites could not be attacked because there is no documentation of the systems, i.e., nothing is known about them. Only a few said that they encrypt data when communicating with satellites or use authentication in order to ensure that only the ground station is allowed to communicate with the satellite.

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Eruption of Tonga underwater volcano found to disrupt satellite signals halfway around the world

An international team has used satellite- and ground-based ionospheric observations to demonstrate that an air pressure wave triggered by volcanic eruptions could produce an equatorial plasma bubble (EPB) in the ionosphere, severely disrupting satellite-based communications. Their findings were published in the journal Scientific Reports.

The ionosphere is the region of the Earth's upper atmosphere where molecules and atoms are ionized by solar radiation, creating positively charged ions. The area with the highest concentration of ionized particles is called the F-region, an area 150 to 800 km above the Earth's surface. The F-region plays a crucial role in long-distance radio communication, reflecting and refracting radio waves used by satellite and GPS tracking systems back to the Earth's surface.

These important transmissions can be disrupted by irregularities in the F-region. During the day, the ionosphere is ionized by the Sun's ultraviolet radiation, creating a density gradient of electrons with the highest density near the equator. However, disruptions to this, such as the movement of plasma, electric fields, and neutral winds, can cause the formation of a localized irregularity of enhanced plasma density. This region can grow and evolve, creating a bubble-like structure called an EPB. EPB can delay radio waves and degrade the performance of GPS.

Since these density gradients can be affected by atmospheric waves, it has long been hypothesized that they are formed by terrestrial events such as volcanic activity. For an international team led by Designated Assistant Professor Atsuki Shinbori (he, him) and Professor Yoshizumi Miyoshi (he, him) of the Institute for Space-Earth Environmental Research (ISEE), Nagoya University, in collaboration with NICT, The University of Electro-Communications, Tohoku University, Kanazawa University, Kyoto University and ISAS, the Tonga volcano eruption offered them a perfect opportunity to test this theory.

The Tonga volcano eruption was the biggest submarine eruption in history. This allowed the team to test their theory using the Arase satellite to detect EPB occurrences, the Himawari-8 satellite to check the initial arrival of air pressure waves and ground-based ionospheric observations to track the motion of the ionosphere. They observed an irregular structure of the electron density across the equator that occurred after the arrival of pressure waves generated by the volcanic eruption.

"The results of this study showed EPBs generated in the equatorial to low-latitude ionosphere in Asia in response to the arrival of pressure waves caused by undersea volcanic eruptions off Tonga," Shinbori said.

The group also made a surprising discovery. For the first time, they showed that ionospheric fluctuations start a few minutes to a few hours earlier than the atmospheric pressure waves involved in the generation of plasma bubbles. This could have important implications because it suggests that the long-held model of geosphere-atmosphere-cosmosphere coupling, which states that ionospheric disturbances only happen after the eruption, needs revision.

"Our new finding is that the ionospheric disturbances are observed several minutes to hours before the initial arrival of the shock waves triggered by the Tonga volcanic eruption," Shinbori said. "This suggests that the propagation of the fast atmospheric waves in the ionosphere triggered the ionospheric disturbances before the initial arrival of the shock waves. Therefore, the model needs to be revised to account for these fast atmospheric waves in the ionosphere."

They also found that the EPB extended much further than predicted by the standard models. "Previous studies have shown that the formation of plasma bubbles at such high altitudes is a rare occurrence, making this a very unusual phenomenon," Shinbori said. "We found that the EPB formed by this eruption reached space even beyond the ionosphere, suggesting that we should pay attention to the connection between the ionosphere and the cosmosphere when extreme natural phenomenon, such as the Tonga event, occur."

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Underused satellite, radar data may improve thunderstorm forecasts

Tens of thousands of thunderstorms may rumble around the world each day, but accurately predicting the time and location where they will form remains a grand challenge of computer weather modeling. A new technique combining underused satellite and radar data in weather models may improve these predictions, according to a Penn State-led team of scientists.

"Thunderstorms are so ubiquitous it's hard to count how many you get in Pennsylvania, or the United States or globally every day," said Keenan Eure, doctoral student in the Department of Meteorology and Atmospheric Science at Penn State. "A lot of our challenges, even today, are figuring out how to correctly predict the time and location of the initiation of thunderstorms."

The scientists found that by combining data from the geostationary weather satellite GOES-16 and ground-based Doppler radar they could capture a more accurate picture of initial conditions in the boundary layer, the lowest part of the atmosphere, where storms form.

"There's value in improving thunderstorm predictions from both Doppler radar observations and satellite observations that are currently underused and we showed that not only can they be used to improve predictions but putting them together has lots of benefits," said Eure, lead author on the study. "The sum is greater than the individual parts."

The technique showed promise in improving forecasts of convection initiation, the conditions that spawn storms, several hours before the thunderstorms occurred in a case study from May 2018 in the Texas panhandle. The scientists reported their findings in the journal Monthly Weather Review.

"Keenan focused on using satellite observations to better define the environment in which the storms would later form, and on using radar observations to improve the low-level wind fields that eventually helped to create the storms," said David Stensrud, professor of meteorology at Penn State and Eure's advisor and co-author on the study. "This observation combination had not been studied previously and ended up adding significant value to the model forecasts on this day."

The scientists used data assimilation, a statistical method that can paint the most accurate possible picture of current weather conditions in the weather model, important because even small changes in the atmosphere can lead to large discrepancies in forecasts over time.

Understanding conditions in the boundary layer is particularly important because it strongly influences the ingredients for convection -- near-surface moisture, lift and instability -- a process that causes warm air near the Earth's surface to rise and form clouds.

"We obviously can't model every molecule in the atmosphere, but we want to get as close as possible," Eure said. We really believe this work adds a lot of valuable information that models currently don't have and that we can help the depiction of the lowest part of the atmosphere."

The team assimilated satellite and radar data separately and simultaneously and found the best results came from combining infrared brightness temperature observations from the satellite and radial wind velocity and boundary height observations from the radar.

The work uses all-sky satellite data assimilation, developed by Penn State's Center for Advanced Data Assimilation and Predictability Techniques, that assimilates satellite data from all weather conditions, including cloudy and clear skies. Forecasting previously relied on clear-sky observations, due to challenges in diagnosing the complex physical processes within clouds, the scientists said.

"While more cases need to be explored, these observations are currently available and could be used to improve thunderstorm prediction over the coming decade as NOAA continues to advance its Warn-on-Forecast paradigm in which computer model predictions help to make severe weather warnings more accurate and timely," Stensrud said.

Other Penn State researchers on the project were Matthew Kumjian and Steven Greybush, associate professors, Yunji Zhang, assistant professor and Paul Mykolajtchuk, former graduate student, in the Department of Meteorology and Atmospheric Science.

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Scientists call for global push to eliminate space junk

Scientists have called for a legally-binding treaty to ensure Earth's orbit isn't irreparably harmed by the future expansion of the global space industry.

In the week that nearly 200 countries agreed to a treaty to protect the High Seas after a 20-year process, the experts believe society needs to take the lessons learned from one part of our planet to another.

The number of satellites in orbit is expected to increase from 9,000 today to over 60,000 by 2030, with estimates suggesting there are already more than 100 trillion untracked pieces of old satellites circling the planet.

While such technology is used to provide a huge range of social and environmental benefits, there are fears the predicted growth of the industry could make large parts of Earth's orbit unusable.

Writing in the journal Science, an international collaboration of experts in fields including satellite technology and ocean plastic pollution say this demonstrates the urgent need for global consensus on how best to govern Earth's orbit.

They acknowledge that a number of industries and countries are starting to focus on satellite sustainability, but say this should be enforced to include any nation with plans to use Earth's orbit.

Any agreement, they add, should include measures to implement producer and user responsibility for satellites and debris, from the time they launch onwards. Commercial costs should also be considered when looking at ways to incentivise accountability. Such considerations are consistent with current proposals to address ocean plastic pollution as countries begin negotiations for the Global Plastics Treaty.

The experts also believe that unless action is taken immediately, large parts of our planet's immediate surroundings risk the same fate as the High Seas where insubstantial governance has led to overfishing, habitat destruction, deep-sea mining exploration, and plastic pollution.

The article was co-authored by researchers from the University of Plymouth, Arribada Initiative, The University of Texas at Austin, California Institute of Technology, NASA Jet Propulsion Laboratory, Spaceport Cornwall, and ZSL (Zoological Society of London).

They include the academic who led the first ever study into marine microplastics, also published in Science almost 20 years ago, and scientists who contributed to the commitment to develop a Global Plastics Treaty signed by 170 world leaders at the United Nations Environment Assembly in March 2022.

Dr Imogen Napper, Research Fellow at the University of Plymouth, led the newly-published study with funding from the National Geographical Society. She said: "The issue of plastic pollution, and many of the other challenges facing our ocean, is now attracting global attention. However, there has been limited collaborative action and implementation has been slow. Now we are in a similar situation with the accumulation of space debris. Taking into consideration what we have learnt from the high seas, we can avoid making the same mistakes and work collectively to prevent a tragedy of the commons in space. Without a global agreement we could find ourselves on a similar path."

Heather Koldewey, ZSL's Senior Marine Technical Advisor, said: "To tackle planetary problems, we need to bring together scientists from across disciplines to identify and accelerate solutions. As a marine biologist I never imagined writing a paper on space, but through this collaborative research identified so many parallels with the challenges of tackling environmental issues in the ocean. We just need to get better at the uptake of science into management and policy."

Dr Moriba Jah, Associate Professor of Aerospace Engineering and Engineering Mechanics at The University of Texas at Austin, said: "Ancient TEK (traditional ecological knowledge) informs us how we must embrace stewardship because our lives depend on it. I'm excited to work with others in highlighting the links and interconnectedness amongst all things and that marine debris and space debris are both an anthropogenic detriment that is avoidable."

Dr Kimberley Miner, Scientist at the NASA Jet Propulsion Laboratory, said: "Mirroring the new UN ocean initiative, minimizing the pollution of the lower Earth orbit will allow continued space exploration, satellite continuity, and the growth of life-changing space technology."

Melissa Quinn, Head of Spaceport Cornwall, said: "Satellites are vital to the health of our people, economies, security and Earth itself. However, using space to benefit people and planet is at risk. By comparing how we have treated our seas, we can be proactive before we damage the use of space for future generations. Humanity needs to take responsibility for our behaviours in space now, not later. I encourage all leaders to take note, to recognise the significance of this next step and to become jointly accountable."

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How a 3 cm glass sphere could help scientists understand space weather

Solar flares and other types of space weather can wreak havoc with spaceflight and with telecommunications and other types of satellites orbiting the Earth. But, to date, scientists' ability to research ways to overcome that challenge has been severely limited. That's because experiments they conduct in laboratories here on Earth are affected by gravity in ways that are so different from conditions in space.

But a new study by UCLA physicists could, at last, help conquer that issue -- which could be a big step toward safeguarding humans (and equipment) during space expeditions, and to ensuring the proper functioning of satellites. The paper is published in Physical Review Letters.

The UCLA researchers effectively reproduced the type of gravity that exists on or near stars and other planets inside of a glass sphere measuring 3 centimeters in diameter (about 1.2 inches). To do so, they used sound waves to create a spherical gravitational field and generate plasma convection -- a process in which gas cools as it nears the surface of a body and then reheats and rises again as it nears the core -- creating a fluid current that in turn generates a magnetic current.

The achievement could help scientists overcome the limiting role of gravity in experiments that are intended to model convection that occurs in stars and other planets.

"People were so interested in trying to model spherical convection with laboratory experiments that they actually put an experiment in the space shuttle because they couldn't get a strong enough central force field on the ground," said Seth Putterman, a UCLA physics professor and the study's senior author. "What we showed is that our system of microwave-generated sound produced gravity so strong that Earth's gravity wasn't a factor. We don't need to go into space to do these experiments anymore."

UCLA researchers used microwaves to heat sulfur gas to 5,000 degrees Fahrenheit inside the glass sphere. The sound waves inside the ball acted like gravity, constraining movement of the hot, weakly ionized gas, known as plasma, into patterns that resemble the currents of plasma in stars.

"Sound fields act like gravity, at least when it comes to driving convection in gas," said John Koulakis, a UCLA project scientist and the study's first author. "With the use of microwave-generated sound in a spherical flask of hot plasma, we achieved a gravity field that is 1,000 times stronger than Earth's gravity."

On Earth's surface, hot gas rises because gravity holds denser, colder gas closer to the planet's center.

Indeed, the researchers found that hot, bright gas near the outer half of the sphere also moved outward toward the walls of the sphere. The strong, sustained gravity generated turbulence that resembled that seen near the Sun's surface. In the inner half of the sphere, the acoustic gravity changed direction and pointed outward, which causes hot gas to sink to the center. In the experiment, acoustic gravity naturally held the hottest plasma at the center of the sphere, where it also occurs in stars.

The ability to control and manipulate plasma in ways that mirror solar and planetary convection will help researchers understand and predict how solar weather affects spacecraft and satellite communications systems. Last year, for example, a solar storm knocked out 40 SpaceX satellites. The phenomenon has also been problematic for military technology: the formation of turbulent plasma around hypersonic missiles, for example, can interfere with weapons systems communications.

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Stars disappear before our eyes

A startling analysis from Globe at Night -- a citizen science program run by NSF's NOIRLab -- concludes that stars are disappearing from human sight at an astonishing rate. The study finds that, to human eyes, artificial lighting has dulled the night sky more rapidly than indicated by satellite measurements. The study published in the journal Science showcases the unique contributions that citizen scientists can make in essential fields of research.

From the glowing arc of the Milky Way to dozens of intricate constellations, the unaided human eye should be able to perceive several thousand stars on a clear, dark night. Unfortunately, growing light pollution has robbed about 30% of people around the globe and approximately 80% of people in the United States of the nightly view of their home galaxy. A new paper published in the journal Science concludes that the problem is getting rapidly worse.

New citizen-science-based research sheds alarming light on the problem of 'skyglow' -- the diffuse illumination of the night sky that is a form of light pollution. The data for this study came from crowd-sourced observations collected from around the world as part of Globe at Night, a program run by NSF's NOIRLab and developed by NRAO astronomer Connie Walker. The research reveals that skyglow is increasing more rapidly than shown in satellite measurements of Earth's surface brightness at night.

"At this rate of change, a child born in a location where 250 stars were visible would be able to see only abound100 by the time they turned 18," said Christopher Kyba, a researcher at the German Research Centre for Geosciences and lead author of the paper detailing these results.

Light pollution is a familiar problem that has many detrimental effects, not only on the practice of astronomy. It also has an impact on human health and wildlife, since it disrupts the cyclical transition from sunlight to starlight that biological systems have evolved alongside. Furthermore, the loss of visible stars is a poignant loss of human cultural heritage. Until relatively recently, humans throughout history had an impressive view of the starry night sky, and the effect of this nightly spectacle is evident in ancient cultures, from the myths it inspired to the structures that were built in alignment with celestial bodies.

Despite being a well-recognized issue, however, the changes in sky brightness over time are not well documented, particularly on a global scale.

Globe at Night has been gathering data on stellar visibility every year since 2006.* Anyone can submit observations through the Globe at Night web application on a desktop or smartphone. After entering the relevant date, time and location, participants are shown a number of star maps. They then record which one best matches what they can see in the sky without any telescopes or other instruments.

This gives an estimate of what is called the naked eye limiting magnitude, which is a measure of how bright an object must be in order to be seen. This can be used to estimate the brightness of skyglow, because as the sky brightens, the fainter objects disappear from sight.

The authors of the paper analyzed more than 50,000 observations submitted to Globe at Night between 2011 and 2022, ensuring consistency by omitting entries that were affected by factors including cloud cover and moonlight. They focused on data from Europe and North America, since these regions had a sufficient distribution of observations across the land area as well as throughout the decade studied. The paper notes that the sky is likely brightening more quickly in developing countries, where satellite observations indicate the prevalence of artificial lighting is growing at a higher rate.

After devising a new method to convert these observations into estimates of the change in skyglow, the authors found that the loss of visible stars reported by Globe at Night indicates an increase in sky brightness of 9.6% per year over the past decade. This is much greater than the roughly 2% per year global increase in surface brightness measured by satellites.

"This shows that existing satellites aren't sufficient to study how Earth's night is changing," said Kyba. "We've developed a way to 'translate' Globe at Night observations of star visibility made at different locations from year to year into continent-wide trends of sky brightness change. That shows that Globe at Night isn't just an interesting outreach activity, it's an essential measurement of one of Earth's environmental variables."

Existing satellites are not well suited to measuring skyglow as it appears to humans, because there are no current instruments monitoring the whole Earth that can detect wavelengths shorter than 500 nanometers, which corresponds to the color cyan, or greenish blue. Shorter wavelengths, however, contribute disproportionately to skyglow, because they scatter more effectively in the atmosphere. White LEDs, now increasingly commonly used in high-efficiency outdoor lighting, have a peak in emission between 400 and 500 nanometers.

"Since human eyes are more sensitive to these shorter wavelengths at nighttime, LED lights have a strong effect on our perception of sky brightness," said Kyba. "This could be one of the reasons behind the discrepancy between satellite measurements and the sky conditions reported by Globe at Night participants."

Beyond wavelength differences, space-based instruments do not measure light emitted horizontally very well, such as from illuminated signs or windows, but these sources are significant contributors to skyglow as seen from the ground. Crowd-sourced observations will therefore always be invaluable for investigating the direct human effects of sky brightness.

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Loon stratospheric balloons confirm wind data from Aeolus

ESA's novel Aeolus satellite reliably measures wind speed also in higher air layers and thus in a region of the atmosphere where other direct global wind measurements are relatively sparse. This is the result of a study for which data from the satellite were compared with wind observations from stratospheric balloons. Stratospheric balloons would provide highly accurate data on the horizontal wind speed and are therefore also suitable for the validation of future satellite missions. Future wind satellites should increase the vertical resolution to better resolve gravity waves in the tropics, writes the team of researchers from the Leibniz Institute for Tropospheric Research (TROPOS), the European Space Agency (ESA), the European Centre for Medium-Range Weather Forecasts (ECMWF), the University of Hamburg and the Google company Loon. The study has now been published in the Quarterly Journal of the Royal Meteorological Society.

The quality of numerical weather prediction models and thus of weather forecasts depends heavily on the available data. In recent decades, a global observation system has therefore been built up which also includes wind profiles from weather balloons, aircraft data or wind profiler radar systems. However, most of this data comes from the densely populated northern hemisphere. In the southern hemisphere, over the oceans and especially in the tropics, the network of direct measurements is still relatively sparse.

The launch of the European Space Agency's (ESA) first wind satellite Aeolus on 22 August 2018 was therefore a major step towards global wind measurements. This novel satellite has a powerful laser on board, the Atmospheric Laser Doppler Instrument (ALADIN). ALADIN is the first Doppler wind lidar in space to provide profiles of horizontal wind speed from the Earth's surface or from the top of thick clouds up to a height of about 30 km on a global scale. To do this, the satellite emits short ultraviolet laser pulses as it orbits the Earth. A small part of these light pulses is scattered back to the satellite by air molecules, aerosols and clouds and collected and processed in the detector there. For one circumnavigation of the globe Aeolus takes 90 minutes, within a week the satellite collects wind data around the entire globe. This data is assimilated by weather forecasting centres around the world to improve their forecasts. Since there have been no comparable satellite missions so far, the data are checked particularly critically and compared with other wind measurements.

A study recently published used data from 229 stratospheric balloons of the Loon project between July 2019 and December 2020 from tropical Latin America, Atlantic Ocean, Africa and Indian Ocean for comparison. Loon was a commercial project that had provided remote regions with internet access via helium balloons in the stratosphere. The balloons, which were about 12 metres in diameter, acted as floating mobile phone stations at altitudes of 16 to 20 kilometres above the ground. For maintaining the network, the balloons had to automatically correct the wind direction by changing the altitude. This created an extensive data set on wind speeds in these atmospheric layers, which partially fills the gap in wind data at this altitude in the global observation system. The Loon project was discontinued in 2021 for economic reasons, but a highly interesting data set remains for atmospheric research.

"Our analysis confirms that the Aeolus satellite provides almost bias-free wind measurements in the upper troposphere and lower stratosphere. In contrast, the current ECWMF weather model systematically underestimates the wind speed there by about 1 metre per second, which could be demonstrated by the Aeolus and Loon data. These results are important to better understand dynamical processes in the upper troposphere and lower stratosphere and to further improve the weather models," emphasises Dr. Sebastian Bley from TROPOS, who worked for the study at ESA in Frascati, Italy. Another recommendation of the researchers is to carry out more vertical measurements to be able to provide more wind information in the atmospheric layers. This could further improve the accuracy of upcoming wind satellites. In addition to wind speed, Aeolus also provides information about aerosols and clouds, but only via a portion of the backscattered light. "We hope that future wind missions will also be able to measure depolarisation, the rotation of light when it is reflected. That would be a milestone because the satellite could then also provide more information about aerosols," explains Bley.

Aeolus was developed as an explorer mission with an expected lifetime of 3 years to demonstrate the technology of a Doppler wind lidar in space. However, expectations have been exceeded and Aeolus has now been providing valuable data for over 4 years. The wind data are now used in the weather forecasts of several weather services throughout Europe, such as the German Weather Service (DWD), and have been convincing due to their positive influence on the quality of weather forecasts. The way forward for the follow-on mission Aeolus-2 has been recently decided in the ESA ministerial and will be jointly developed by ESA and EUMETSAT.

In September, researchers from the USA had integrated Aeolus data into the hurricane model (HWRF) of the US weather and oceanography agency NOAA on a trial basis in order to better predict tropical storms. Their conclusion is that the use of Aeolus wind data is most effective where there are no reconnaissance flights into the hurricanes and could therefore have the greatest positive impact on tropical cyclone forecasting in the Pacific and Indian Oceans.

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Researchers 3D print sensors for satellites

MIT scientists have created the first completely digitally manufactured plasma sensors for orbiting spacecraft. These plasma sensors, also known as retarding potential analyzers (RPAs), are used by satellites to determine the chemical composition and ion energy distribution of the atmosphere.

The 3D-printed and laser-cut hardware performed as well as state-of-the-art semiconductor plasma sensors that are manufactured in a cleanroom, which makes them expensive and requires weeks of intricate fabrication. By contrast, the 3D-printed sensors can be produced for tens of dollars in a matter of days.

Due to their low cost and speedy production, the sensors are ideal for CubeSats. These inexpensive, low-power, and lightweight satellites are often used for communication and environmental monitoring in Earth's upper atmosphere.

The researchers developed RPAs using a glass-ceramic material that is more durable than traditional sensor materials like silicon and thin-film coatings. By using the glass-ceramic in a fabrication process that was developed for 3D printing with plastics, there were able to create sensors with complex shapes that can withstand the wide temperature swings a spacecraft would encounter in lower Earth orbit.

"Additive manufacturing can make a big difference in the future of space hardware. Some people think that when you 3D-print something, you have to concede less performance. But we've shown that is not always the case. Sometimes there is nothing to trade off," says Luis Fernando Velásquez-García, a principal scientist in MIT's Microsystems Technology Laboratories (MTL) and senior author of a paper presenting the plasma sensors.

Joining Velásquez-García on the paper are lead author and MTL postdoc Javier Izquierdo-Reyes; graduate student Zoey Bigelow; and postdoc Nicholas K. Lubinsky. The research is published in Additive Manufacturing.

Versatile sensors

An RPA was first used in a space mission in 1959. The sensors detect the energy in ions, or charged particles, that are floating in plasma, which is a superheated mix of molecules present in the Earth's upper atmosphere. Aboard an orbiting spacecraft like a CubeSat, the versatile instruments measure energy and conduct chemical analyses that can help scientists predict the weather or monitor climate change.

The sensors contain a series of electrically charged meshes dotted with tiny holes. As plasma passes through the holes, electrons and other particles are stripped away until only ions remain. These ions create an electric current that the sensor measures and analyzes.

Key to the success of an RPA is the housing structure that aligns the meshes. It must be electrically insulating while also able to withstand sudden, drastic swings in temperature. The researchers used a printable, glass-ceramic material that displays these properties, known as Vitrolite.

Pioneered in the early 20th century, Vitrolite was often used in colorful tiles that became a common sight in art deco buildings.

The durable material can also withstand temperatures as high as 800 degrees Celsius without breaking down, whereas polymers used in semiconductor RPAs start to melt at 400 degrees Celsius.

"When you make this sensor in the cleanroom, you don't have the same degree of freedom to define materials and structures and how they interact together. What made this possible is the latest developments in additive manufacturing," Velásquez-García says.

Rethinking fabrication

The 3D printing process for ceramics typically involves ceramic powder that is hit with a laser to fuse it into shapes, but this process often leaves the material coarse and creates weak points due to the high heat from the lasers.

Instead, the MIT researchers used vat polymerization, a process introduced decades ago for additive manufacturing with polymers or resins. With vat polymerization, a 3D structure is built one layer at a time by submerging it repeatedly into a vat of liquid material, in this case Vitrolite. Ultraviolet light is used to cure the material after each layer is added, and then the platform is submerged in the vat again. Each layer is only 100 microns thick (roughly the diameter of a human hair), enabling the creation of smooth, pore-free, complex ceramic shapes.

In digital manufacturing, objects described in a design file can be very intricate. This precision allowed the researchers to create laser-cut meshes with unique shapes so the holes lined up perfectly when they were set inside the RPA housing. This enables more ions to pass through, which leads to higher-resolution measurements.

Because the sensors were cheap to produce and could be fabricated so quickly, the team prototyped four unique designs.

While one design was especially effective at capturing and measuring a wide range of plasmas, like those a satellite would encounter in orbit, another was well-suited for sensing extremely dense and cold plasmas, which are typically only measurable using ultraprecise semiconductor devices.

This high precision could enable 3D-printed sensors for applications in fusion energy research or supersonic flight. The rapid prototyping process could even spur more innovation in satellite and spacecraft design, Velásquez-García adds.

"If you want to innovate, you need to be able to fail and afford the risk. Additive manufacturing is a very different way to make space hardware. I can make space hardware and if it fails, it doesn't matter because I can make a new version very quickly and inexpensively, and really iterate on the design. It is an ideal sandbox for researchers," he says.

While Velásquez-García is pleased with these sensors, in the future he wants to enhance the fabrication process. Reducing the thickness of layers or pixel size in glass-ceramic vat polymerization could create complex hardware that is even more precise. Moreover, fully additively manufacturing the sensors would make them compatible with in-space manufacturing. He also wants to explore the use of artificial intelligence to optimize sensor design for specific use cases, such as greatly reducing their mass while ensuring they remain structurally sound.

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Satellite monitoring of biodiversity moves within reach

Internationally comparable data on biodiversity is needed to protect threatened ecosystems, restore destroyed habitats and counteract the negative effects of global biodiversity loss. Current biodiversity monitoring, however, is labor-intensive and costly. In addition, many places around the world are difficult to access.

Biodiversity monitoring from space possible via satellite

Anna Schweiger from the Remote Sensing Laboratories at the Department of Geography, University of Zurich (UZH), and Etienne Laliberté from the University of Montréal, have now shown that plant biodiversity across ecosystems ranging from Arctic tundra to tropical forests can be reliably assessed using image spectrometry. "With our study, we hope to contribute to the future detection of changes in species composition of our Earth's ecosystems from space. The goal is to provide evidence-based guidance for policy measures to protect species and mitigate negative consequences of biodiversity loss," says first author Anna Schweiger.

Imaging spectrometers measure the reflectance of light from the visible to the shortwave infrared range of the electromagnetic spectrum. The reflectance of plants is determined by their chemical, anatomical and morphological characteristics, which are important for interactions among plants and with their environment. "Plants with similar traits, as well as closely related species, therefore tend to have similar reflectance spectra," explains Schweiger.

Using reflected light to assess the characteristics of individual plants and plant communities

The current study is a continuation of the researchers' work on spectral diversity metrics. Their indices calculate spectral variation among individual plants within communities, and among communities within a region. The diversity within communities is called alpha-diversity, while the diversity among communities is called beta-diversity.

Data for the study came from the National Ecological Observatory Network (NEON). The network uses standardized methods to collect biodiversity and Earth observation data across the United States which are then made publicly available. NEON imaging spectrometer data collected from research flights have a pixel size of 1x1 meter.

Spectral diversity calculations showed that the detection of alpha-diversity depends on plant size. Spectral diversity calculated in forests with closed canopies and large individual trees matched plant diversity determined on the ground better than spectral diversity calculated in open landscapes dominated by small herbaceous plants and grasses. Spectral beta-diversity, however, captured differences in plant community composition across all ecosystems studied based on a spatial resolution of 20x20 meters. This pixel size corresponds to the size of NEON's vegetation inventory plots.

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Researchers discover source of super-fast electron 'rain'

UCLA scientists have discovered a new source of super-fast, energetic electrons raining down on Earth, a phenomenon that contributes to the colorful aurora borealis but also poses hazards to satellites, spacecraft and astronauts.

The researchers observed unexpected, rapid "electron precipitation" from low-Earth orbit using the ELFIN mission, a pair of tiny satellites built and operated on the UCLA campus by undergraduate and graduate students guided by a small team of staff mentors.

By combining the ELFIN data with more distant observations from NASA's THEMIS spacecraft, the scientists determined that the sudden downpour was caused by whistler waves, a type of electromagnetic wave that ripples through plasma in space and affects electrons in the Earth's magnetosphere, causing them to "spill over" into the atmosphere.

Their findings, published March 25 in the journal Nature Communications, demonstrate that whistler waves are responsible for far more electron rain than current theories and space weather models predict.

"ELFIN is the first satellite to measure these super-fast electrons," said Xiaojia Zhang, lead author and a researcher in UCLA's department of Earth, planetary and space sciences. "The mission is yielding new insights due to its unique vantage point in the chain of events that produces them."

Central to that chain of events is the near-Earth space environment, which is filled with charged particles orbiting in giant rings around the planet, called Van Allen radiation belts. Electrons in these belts travel in Slinky-like spirals that literally bounce between the Earth's north and south poles. Under certain conditions, whistler waves are generated within the radiation belts, energizing and speeding up the electrons. This effectively stretches out the electrons' travel path so much that they fall out of the belts and precipitate into the atmosphere, creating the electron rain.

One can imagine the Van Allen belts as a large reservoir filled with water -- or, in this case, electrons, said Vassilis Angelopolous, a UCLA professor of space physics and ELFIN's principal investigator. As the reservoir fills, water periodically spirals down into a relief drain to keep the basin from overflowing. But when large waves occur in the reservoir, the sloshing water spills over the edge, faster and in greater volume than the relief drainage. ELFIN, which is downstream of both flows, is able to properly measure the contributions from each.

The low-altitude electron rain measurements by ELFIN, combined with the THEMIS observations of whistler waves in space and sophisticated computer modeling, allowed the team to understand in detail the process by which the waves cause rapid torrents of electrons to flow into the atmosphere.

The findings are particularly important because current theories and space weather models, while accounting for other sources of electrons entering the atmosphere, do not predict this extra whistler wave-induced electron flow, which can affect Earth's atmospheric chemistry, pose risks to spacecraft and damage low-orbiting satellites.

The researchers further showed that this type of radiation-belt electron loss to the atmosphere can increase significantly during geomagnetic storms, disturbances caused by enhanced solar activity that can affect near-Earth space and Earth's magnetic environment.

"Although space is commonly thought to be separate from our upper atmosphere, the two are inextricably linked," Angelopoulos said. "Understanding how they're linked can benefit satellites and astronauts passing through the region, which are increasingly important for commerce, telecommunications and space tourism."

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Fast changes between the solar seasons resolved by new sun clock

Violent activity on our Sun leads to some of the most extreme space weather events on Earth, impacting systems such as satellites, communications systems, power distribution and aviation. The roughly 11 year cycle of solar activity has three 'seasons', each of which affects the space weather felt at Earth differently: (i) solar maximum, the sun is active and disordered, when space weather is stormy and events are irregular (ii) the declining phase, when the sun and solar wind becomes ordered, and space weather is more moderate and (iii) solar minimum, when activity is quiet.

In a new study led by the University of Warwick and published in The Astrophysical Journal, scientists found that the change from solar maximum to the declining phase is fast, happening within a few (27 day) solar rotations. They also showed that the declining phase is twice as long in even-numbered solar cycles as it is in odd-numbered cycles.

No two solar cycles are the same in amplitude or duration. To study the solar seasons, the scientists built a sun clock from the daily sunspot number record available since 1818. This maps the irregular solar cycles onto a regular clock. The magnetic polarity of the sun reverses after each roughly 11 year solar cycle giving a roughly 22 year magnetic cycle (named after George Ellery Hale) and to explore this, a 22 year clock was constructed. The effect on space weather at earth can be tracked back using the longest continuous records of geomagnetic activity over the past 150 years, and once the clock is constructed, it can be used to study multiple observations of seasonal solar activity which affect the earth.

With the greater detail afforded by the sun clock, the scientists could see that the switch from solar maximum to the declining phase is fast, occurring within a few (27 day) solar rotations. There was also a clear difference in the duration of the declining phase when the sun's magnetic polarity is 'up' compared to 'down': in even-numbered cycles it is around twice as long as odd-numbered cycles. As we are about to enter cycle 25, the scientists anticipate that the next declining phase will be short.

Lead author Professor Sandra Chapman of the University of Warwick Department of Physics said: "By combining well known methods in a new way, our clock resolves changes in the Sun's climate to within a few solar rotations. Then you find the changes between some phases can be really sharp.

"If you know you've had a long cycle, you know the next one's going to be short, we can estimate how long it's going to last. Knowing the timing of the climate seasons helps to plan for space weather. Operationally it is useful to know when conditions will be active or quiet, for satellites, power grids, communications."

The results also provide a clue to understanding how the Sun reverses polarity after every cycle.

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Satellite unexpectedly detects a unique exoplanet

The exoplanet-hunting satellite CHEOPS of the European Space Agency (ESA), in which the Instituto de Astrofísica de Canarias (IAC) is participating along with other European institutions, has unexpectedly detected a third planet passing in front of its star while it was exploring two previously known planets around the same star. This transit, according to researchers, will reveal exciting details about a strange planet "without a known equivalent."

The discovery is one of the first results of CHEOPS (CHaracterising ExOPlanet Satellite) and the first time that an exoplanet has been seen with a period longer than 100 days transiting a star which is sufficiently bright to be seen with the naked eye. The discovery was published today in the journal Nature Astronomy.

This bright star similar to the sun, called Nu2 Lupi, is a little more than 50 light years from Earth, in the constellation of Lupus. In 2019, HARPS (High Accuracy Radial velocity Planet Searcher) of the European Southern Observatory (ESO) in Chile discovered three exoplanets in this system (called b, c, and d) with masses between those of the Earth and Neptune, and with orbital periods of 11.6, 27.6 and 107.6 days respectively. Afterwards NASA's TESS satellite, designed to detect transiting planets, found that the two interior planets, b and c, transit Nu2 Lupi, making it one of the only three naked eye stars which have more than one transiting planet.

"Transiting systems such as Nu2 Lupi are of great importance in our understanding of how planets form and evolve, because we can compare several planets around the same bright star in detail," explains Laetitia Delrez, a researcher at the University of Liege (Belgium) and first author of the article.

"Our idea was to follow up previous studies of Nu2 Lupi and to observe planets b and c passing in front of Nu2 Lupi with CHEOPS, but during a transit of planet c we were amazed to see an unexpected transit of planet d, which is further out within the system," she adds.

Transits of planets give a valuable opportunity to study their atmospheres, their orbits, their sizes and their compositions. A transiting planet block out a tiny but detectable proportion of the light of its star when it passes in front of it, and it was this tiny drop in the light which led the researchers to their discovery. Because exoplanets with long periods orbit far away from their stars, the possibility of detecting a planet during transit is very small indeed, which makes the finding with CHEOPS a real surprise.

Using the high precision techniques of CHEOPS planet d was found to have some 2.5 times the radius of the Earth, and its orbital period around its star of a little over 107 days, was confirmed. In addition, using archive observations from terrestrial telescopes its mass could be estimated at 8.8 times that of the Earth.

"The amount of radiation from the star which falls onto planet d is quite small compared to many other known exoplanets. If it were in our own solar system Nu2 Lupi d would orbit between Mercury and Venus," says Mahmoudreza Oshagh, a senior postdoctoral researcher at the IAC, and a co-author of the paper. "Combined with its bright parent star, its long orbital period and its ideal situation for follow-up, this means that planet d is very exciting: it is an exceptional object, with no known equivalent, and it will certainly be a fundamental object for future studies."

The majority of long period transiting exoplanets discovered until now are orbiting stars which are too faint to allow detailed follow-up observations, which means that we know little about their properties. Nu2 Lupi is, however, sufficiently bright to be an attractive object for other powerful space telescopes such as the NASA/ESA Hubble Space Telescope, the future James Webb Space Telescope, as well as major observatories on the ground. "Given its general properties and its orbit, planet d will be an exceptionally favourable objective to study an exoplanet with a moderate atmospheric temperature around a star similar to the Sun," adds Laetitia Delrez.

Combining the new data from CHEOPS with archive data from other observatories, the researchers found that planet b is mainly rocky, while planets c and d appear to have large quantities of water surrounded by hydrogen and helium gas. In fact, planets c and d contain much more water than the Earth, a quarter of the mass of each of them is water, in comparison with less than 0.1% on Earth. But this water is not liquid, it is high pressure ice, or high temperature water vapour.

"Although none of these planets would be habitable, their diversity makes the system very exciting and a great future perspective to show how these bodies formed and how they have changed with time," explains Enric Pallé, an IAC researcher and a co-author of the article. "We can also look for rings or moons within the Nu2 Lupi system, because the extreme accuracy and stability of CHEOPS could allow us to detect bodies close to the size of Mars."

CHEOPS is designed to gather high precision data of individual stars known to harbour planets, rather than to make a more general survey of possible exoplanets around many stars. This approach and accuracy are proving exceptionally useful to understand the planetary systems around the stars around us.

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Understanding of invisible but mighty particles in Earth's radiation belts

Tiny charged electrons and protons which can damage satellites and alter the ozone have revealed some of their mysteries to University of Otago scientists.

In a study, published in Geophysical Research Letters, the group looked at charged particles interacting with a type of radio wave called 'EMIC' -- a wave generated in Earth's radiation belts (invisible rings of charged particles orbiting the Earth).

Lead author Dr Aaron Hendry, of the Department of Physics, says it is important to understand how these waves affect the belts -- which are filled with expensive and important satellites -- and Earth's climate.

"Much like the Earth's atmosphere, the Earth's magnetosphere -- the region around the Earth where our magnetic field is stronger than the Sun's -- sometimes experiences strong 'storms', or periods of high activity. These storms can cause significant changes to the number of particles in the radiation belts and can accelerate some of them to very high speeds, making them a danger to our satellites. Knowing how many of these particles there are, as well as how fast they're moving, is very important to us, so that we can make sure our satellites keep working.

"Activity within the radiation belts can sometimes cause the orbits of these particles to change. If these changes bring the particles low enough to reach the Earth's upper atmosphere, they can hit the dense air, lose all of their energy and fall out of orbit.

"EMIC waves are known to be able to cause these changes and drive the loss of particles from the radiation belts. As well as causing beautiful light displays that we call aurora, this rain of particles can also cause complex chemical changes to the upper atmosphere that can in turn cause small, but important, changes the amount of ozone present in atmosphere.

"Although these changes are small, understanding them is very important to properly understanding how the chemistry of the atmosphere works, how it is changing over time, and the impact it is having on the climate," Dr Hendry says.

For their latest study, the researchers used data from GPS satellites to look at how many electrons EMIC waves can knock into the Earth's atmosphere.

A general rule in the radiation belts is that at slower speeds, you have many more electrons. So, if the minimum speed of the EMIC wave interaction is lowered, there are a lot more electrons around to interact with waves.

By looking at data from satellites that monitor how many electrons there are in the radiation belts and how fast they're going, the researchers have been able to show that you can see the number of electrons in the radiation belts go down significantly when EMIC waves are around.

"Excitingly, we have also seen changes in the number of electrons at speeds significantly lower than the current 'accepted' minimum speed. This means that EMIC can affect much larger numbers of electrons than we previously thought possible. Clearly, we need to rethink how we're modelling this interaction, and the impact it has on the radiation belts. There are a lot of electrons in the radiation belts, so being able to knock enough of them into the atmosphere to make a noticeable change is quite remarkable.

"This has shown that we need to take these EMIC waves into account when we're thinking about how the radiation belts change over time, and how these changes in the radiation belt affect the climate on Earth."

Dr Hendry says the impact of EMIC-driven electrons on atmospheric chemistry is not currently being included by major climate models, which try to predict how the Earth's climate will change over time, so making sure this process is understood and included in these models is very important.

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Saturn's tilt caused by its moons, researchers say

 

Saturn illustration.

Two scientists from CNRS and Sorbonne University working at the Institute of Celestial Mechanics and Ephemeris Calculation (Paris Observatory -- PSL/CNRS) have just shown that the influence of Saturn's satellites can explain the tilt of the rotation axis of the gas giant. Their work, published on 18 January 2021 in the journal Nature Astronomy, also predicts that the tilt will increase even further over the next few billion years.

Rather like David versus Goliath, it appears that Saturn's tilt may in fact be caused by its moons. This is the conclusion of recent work carried out by scientists from the CNRS, Sorbonne University and the University of Pisa, which shows that the current tilt of Saturn's rotation axis is caused by the migration of its satellites, and especially by that of its largest moon, Titan.

Recent observations have shown that Titan and the other moons are gradually moving away from Saturn much faster than astronomers had previously estimated. By incorporating this increased migration rate into their calculations, the researchers concluded that this process affects the inclination of Saturn's rotation axis: as its satellites move further away, the planet tilts more and more.

The decisive event that tilted Saturn is thought to have occurred relatively recently. For over three billion years after its formation, Saturn's rotation axis remained only slightly tilted. It was only roughly a billion years ago that the gradual motion of its satellites triggered a resonance phenomenon that continues today: Saturn's axis interacted with the path of the planet Neptune and gradually tilted until it reached the inclination of 27° observed today.

These findings call into question previous scenarios. Astronomers were already in agreement about the existence of this resonance. However, they believed that it had occurred very early on, over four billion years ago, due to a change in Neptune's orbit. Since that time, Saturn's axis was thought to have been stable. In fact, Saturn's axis is still tilting, and what we see today is merely a transitional stage in this shift. Over the next few billion years, the inclination of Saturn's axis could more than double.

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Counting elephants from space

 For the first time, scientists have successfully used satellite cameras coupled with deep learning to count animals in complex geographical landscapes, taking conservationists an important step forward in monitoring populations of endangered species.

For this research, the satellite Worldview 3 used high-resolution imagery to capture African elephants moving through forests and grasslands. The automated system detected animals with the same accuracy as humans are able to achieve.

The algorithm that enabled the detection process was created by Dr Olga Isupova, a computer scientist at the University of Bath in the UK. The project was a collaboration with the UK's University of Oxford and the University of Twente in the Netherlands.

Dr Isupova said the new surveying technique allows vast areas of land to be scanned in a matter of minutes, offering a much-needed alternative to human observers counting individual animals from low-flying airplanes. As it sweeps across the land, a satellite can collect over 5,000 km² of imagery every few minutes, eliminating the risk of double counting. Where necessary (for instance, when there is cloud coverage), the process can be repeated the next day, on the satellite's next revolution of Earth.

The population of African elephants has nose-dived over the past century, mainly due to poaching and habitat fragmentation. With only 40,000-50,000 elephants left in the wild, the species is classified as endangered.

"Accurate monitoring is essential if we're to save the species," said Dr Isupova. "We need to know where the animals are and how many there are."

Satellite monitoring eliminates the risk of disturbing animals during data collection and ensures humans are not hurt in the counting process. It also makes it simpler to count animals moving from country to country, as satellites can orbit the planet without regard for border controls or conflict.

This study was not the first to use satellite imagery and algorithms to monitor species, but it was the first to reliably monitor animals moving through a heterogeneous landscape -- that is, a backdrop that includes areas of open grassland, woodland and partial coverage.

"This type of work has been done before with whales, but of course the ocean is all blue, so counting is a lot less challenging," said Dr Isupova. "As you can imagine, a heterogeneous landscape makes it much hard to identify animals."

The researchers believe their work demonstrates the potential of technology to support conservationists in their plight to protect biodiversity and to slow the progress of the sixth mass extinction -- the ongoing extinction event triggered by human activity.

"We need to find new state-of-the-art systems to help researchers gather the data they need to save species under threat," said Dr Isupova.

African elephants were chosen for this study for good reason -- they are the largest land animal and therefore the easiest to spot. However, Dr Isupova is hopeful that it will soon be possible to detect far smaller species from space.

"Satellite imagery resolution increases every couple of years, and with every increase we will be able to see smaller things in greater detail," she said, adding: "Other researchers have managed to detect black albatross nests against snow. No doubt the contrast of black and white made it easier, but that doesn't change the fact that an albatross nest is one-eleventh the size of an elephant."

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Breakthrough method for predicting solar storms

Extensive power outages and satellite blackouts that affect air travel and the internet are some of the potential consequences of massive solar storms. These storms are believed to be caused by the release of enormous amounts of stored magnetic energy due to changes in the magnetic field of the sun's outer atmosphere -- something that until now has eluded scientists' direct measurement. Researchers believe this recent discovery could lead to better "space weather" forecasts in the future.

"We are becoming increasingly dependent on space-based systems that are sensitive to space weather. Earth-based networks and the electrical grid can be severely damaged if there is a large eruption," says Tomas Brage, Professor of Mathematical Physics at Lund University in Sweden.

Solar flares are bursts of radiation and charged particles, and can cause geomagnetic storms on Earth if they are large enough. Currently, researchers focus on sunspots on the surface of the sun to predict possible eruptions. Another and more direct indication of increased solar activity would be changes in the much weaker magnetic field of the outer solar atmosphere -- the so-called Corona.

However, no direct measurement of the actual magnetic fields of the Corona has been possible so far.

"If we are able to continuously monitor these fields, we will be able to develop a method that can be likened to meteorology for space weather. This would provide vital information for our society which is so dependent on high-tech systems in our everyday lives," says Dr Ran Si, post-doc in this joint effort by Lund and Fudan Universities.

The method involves what could be labelled a quantum-mechanical interference. Since basically all information about the sun reaches us through "light" sent out by ions in its atmosphere, the magnetic fields must be detected by measuring their influence on these ions. But the internal magnetic fields of ions are enormous -- hundreds or thousands of times stronger than the fields humans can generate even in their most advanced labs. Therefore, the weak coronal fields will leave basically no trace, unless we can rely on this very delicate effect -- the interference between two "constellations" of the electrons in the ion that are close -- very close -- in energy.

The breakthrough for the research team was to predict and analyze this "needle in the haystack" in an ion (nine times ionized iron) that is very common in the corona.

The work is based on state-of-the art calculations performed in the Mathematical Physics division of Lund University and combined with experiments using a device that could be thought of as being able to produce and capture small parts of the solar corona -- the Electron Beam Ion Trap, EBIT, in Professor Roger Hutton's group in Fudan University in Shanghai.

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New research supports previous studies on global sea level rise

As a result of global warming, the world's oceans have risen by an average of around 3 mm a year since the early 1990s. But how much they have risen year on year has been a matter of some debate among experts, for instance in the UN's climate panel IPCC. Is the rise constant, or is it accelerating every year?

Now, in a new study, a Danish student has shown that the rise is accelerating. In other words, the oceans are rising faster every year. The new research supports previous studies and has been published in the scientific journal Advances in Space Research.

The calculations were done by Tadea Veng , who studies Earth and Space Physics and Engineering at DTU Space under the supervision of Professor Ole Baltazar Andersen.

"Using data from independent European satellites, our results show the same rate of acceleration in sea level rise used by the UN Climate Panel, which they based on data from American satellites," says Tadea Veng.

According to the new calculations, the average acceleration between 1991 and 2019 was 0.1 mm/year2 (or to be more precise, 0.095 mm/year2). This means that if, for example, the oceans rose by 2 mm in 2000, by 2010 they would have risen by 3 mm, and around 2020 by almost 4 mm.

The new findings have just been published in the scientific journal Advances in Space Research. In december, 25-year-old Tadea presented her research at the annual meeting of the American Geophysical Union, the world's largest conference on space and geophysics research.

The calculations are based on data from a number of European remote-sensing satellites in orbit around Earth (the European Space Agency's ERS1, ERS2, Envisat and Cryosat missions).

Tadea Veng compared her own results to calculations based on the US satellite data used in the climate change reports regularly published by the IPCC. (The US satellites are NASA's Topex/Poseidon, Jason-1, Jason-2 and Jason-3.) Based on data from the US satellites, the acceleration has been calculated as 0.084 mm/year2.

But unlike the US satellites, European satellites also take measurements in the Arctic region. Therefore, the new research provides a more comprehensive picture of the global rise in sea levels.

"In recent years, there's been a good deal of debate about the acceleration due to inaccuracies in the satellite measurements from Topex/Poseidon, the oldest of the US satellites. That's why it's important that we now also have results using data from European satellites. Acceleration is an important factor in modelling future sea level rise," says Professor Ole Baltazar Andersen, who co-authored the article.

"Tadea has presented an important and very useful contribution to the research and to the UN Climate Panel. It's a solid piece of scientific work, which is why Advances in Space Research chose to publish it."

In other words, there is now no doubt that the world's oceans are rising, and that this has happened at an increasing rate over the past 30 years. Overall, the world's oceans are estimated to have risen by approximately 75 mm from 1991 to 2019.

Satellites in orbit around Earth measure the distance to the oceans' surface over time and across very large areas using radar signals, among other things. This data can then be used, for example, to calculate the acceleration of sea level rise. The European Space Agency launched the CryoSat satellite in 2010. It measures sea levels and changes in ice cover in the Arctic and Antarctic.

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Red alert as Arctic lands grow greener

New research techniques are being adopted by scientists tackling the most visible impact of climate change -- the so-called greening of Arctic regions.

The latest drone and satellite technology is helping an international team of researchers to better understand how the vast, treeless regions called the tundra is becoming greener.

As Arctic summer temperatures warm, plants are responding. Snow is melting earlier and plants are coming into leaf sooner in spring. Tundra vegetation is spreading into new areas and where plants were already growing, they are now growing taller.

Understanding how data captured from the air compare with observations made on the ground will help to build the clearest picture yet of how the northern regions of Europe, Asia and North America are changing as the temperature rises.

Now a team of 40 scientists from 36 institutions, led by two National Geographic Explorers, have revealed that the causes of this greening process are more complex -- and variable -- than was previously thought.

Researchers from Europe and North America are finding that the Arctic greening observed from space is caused by more than just the responses of tundra plants to warming on the ground. Satellites are also capturing other changes including differences in the timing of snowmelt and the wetness of landscapes.

Lead author Dr Isla Myers-Smith, of the University of Edinburgh's School of GeoSciences, said: "New technologies including sensors on drones, planes and satellites, are enabling scientists to track emerging patterns of greening found within satellite pixels that cover the size of football fields."

Professor Scott Goetz of the School of Informatics, Computing and Cyber Systems at Northern Arizona University, says this research is vital for our understanding of global climate change. Tundra plants act as a barrier between the warming atmosphere and huge stocks of carbon stored in frozen ground.

Changes in vegetation alter the balance between the amount of carbon captured and its release into the atmosphere. Small variations could significantly impact efforts to keep warming below 1.5 degrees centigrade -- a key target of the Paris Agreement. The study will help scientists to figure out which factors will speed up or slow down warming.

Co-lead author Dr Jeffrey Kerby, who was a Neukom Fellow at Dartmouth College while conducting the research, said: "Besides collecting new imagery, advances in how we process and analyse these data -- even imagery that is decades old -- are revolutionising how we understand the past, present, and future of the Arctic."

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TESS satellite uncovers 'first nearby super-Earth'

An international team of astronomers led by Cornell's Lisa Kaltenegger has characterized the first potentially habitable world outside of our own solar system.

Located about 31 light-years away, the super-Earth planet -- named GJ 357 d -- was discovered in early 2019 owing to NASA's Transiting Exoplanet Survey Satellite (TESS), a mission designed to comb the heavens for exoplanets, according to their new modeling research in the Astrophysical Journal Letters.

"This is exciting, as this is humanity's first nearby super-Earth that could harbor life -- uncovered with help from TESS, our small, mighty mission with a huge reach," said Kaltenegger, associate professor of astronomy, director of Cornell's Carl Sagan Institute and a member of the TESS science team.

The exoplanet is more massive than our own blue planet, and Kaltenegger said the discovery will provide insight into Earth's heavyweight planetary cousins. "With a thick atmosphere, the planet GJ 357 d could maintain liquid water on its surface like Earth, and we could pick out signs of life with telescopes that will soon be online," she said.

Astronomers from the Institute of Astrophysics of the Canary Islands and the University of La Laguna, both in Spain, announced the discovery of the GJ 357 system July 31 in the journal Astronomy & Astrophysics. They showed that the distant solar system -- with a diminutive M-type dwarf sun, about one-third the size of our own sun -- harbors three planets, with one of those in that system's habitable zone: GJ 357 d.

Last February, the TESS satellite observed that the dwarf sun GJ 357 dimmed very slightly every 3.9 days, evidence of a transiting planet moving across the star's face. That planet was GJ 357 b, a so-called "hot Earth" about 22% larger than Earth, according to the NASA Goddard Space Flight Center, which guides TESS.

Follow-up observations from the ground led to the discovery of two more exoplanetary siblings: GJ 357 c and GJ 357 d. The international team of scientists collected Earth-based telescopic data going back two decades -- to reveal the newly found exoplanets' tiny gravitational tugs on its host star, according to NASA.

Exoplanet GJ 357 c sizzles at 260 degrees Fahrenheit and has at least 3.4 times Earth's mass. However, the system's outermost known sibling planet -- GJ 357 d, a super-Earth -- could provide Earth-like conditions and orbits the dwarf star every 55.7 days at a distance about one-fifth of Earth's distance from the sun. It is not yet known if this planet transits its sun.

Kaltenegger, doctoral candidate Jack Madden and undergraduate student Zifan Lin '20 simulated light fingerprints, climates and remotely detectable spectra for a planet that could range from a rocky composition to a water world.

Madden explained that investigating new discoveries provides an opportunity to test theories and models. "We built the first models of what this new world could be like," he said. "Just knowing that liquid water can exist on the surface of this planet motivates scientists to find ways of detecting signs of life."

Lin described the work from an undergraduate perspective: "Working on a newly discovered planet is something of a dream come true. I was among the first group of people to model its spectra, and thinking about this still overwhelms me."

In a nod to her institute's namesake, the late Cornell professor Carl Sagan, Kaltenegger said: "If GJ 357 d were to show signs of life, it would be at the top of everyone's travel list -- and we could answer a 1,000-year-old question on whether we are alone in the cosmos."

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