8 in 10 lizards could be at risk due to deforestation

In Colorado, people flock to the Rocky Mountains when the summer heat gets unbearable. Animals seek shelter too when temperatures become extreme, and forests serve as critical sanctuaries for small tree-dwelling animals like lizards.

In a new study published March 5 in the journal Nature Climate Change, scientists from the University of Colorado Boulder and Tel Aviv University in Israel revealed that deforestation combined with climate change could negatively impact 84% of North America's lizards by the end of the century. Nearly one in five could face population decline.

Unlike mammals that can maintain their body temperatures in a variety of ways -- sweating when it gets too hot and relying on warm fur when it gets too cold -- cold-blooded animals like lizards have limited strategies to thermoregulate. Tree-climbing lizards move around tree trunks to bask in the sun for warmth. When the ground gets too hot, they climb higher or move into the shade.

"What's really interesting about lizards is that they just need to be able to move a short distance around the tree trunk to get to a very different climate and habitat environment," said Keith Musselman, an assistant professor in the Department of Geography and CU Boulder's Institute of Arctic and Alpine Research. "These microhabitats are particularly important when we think about how we modify our natural environment and make conservation decisions."

Using computer simulations, the team showed that global warming can actually benefit lizards living in colder regions or at higher latitudes in North America. Warmer weather increases the animals' activity time, meaning they have more time to look for food or mates during the day. However, deforestation would largely reverse these positive effects by reducing opportunities for shade in hotter climates that help them cool down.

The team simulated lizard models for different climate regions across North America. They found that tree loss could decrease lizards' activity time by an average of 34% by the end of the century. Without trees, the animals would have to hide under rocks or in caves to avoid overheating. The impact would be especially prominent for species that already live in warmer regions, where future summers will become too warm for activity on the ground.

The team estimated that deforestation would accelerate population declines for 18% of lizards in North America.

"Our work provides new insights into the mechanisms by which deforestation may cause population declines in the face of climate change," said Ofir Levy, a zoologist and Musselman's collaborator at Tel Aviv University. "The decline in lizards can lead to a cascading effect as they are an important part of almost every ecological system."

Despite international pledges to halt deforestation, tree clearing continues to happen globally. From 2001 to 2022, about 459 million hectares, or 12%, of global tree cover disappeared.

"Deforestation is a worldwide problem, and our conclusions can help decision-makers on other continents in designing conservation and habitat restoration programs that consider climate change," said Omer Zlotnick, the paper's first author and a Ph.D. student at Tel Aviv University.

Lizard populations are already at risk because of climate change. In one study, scientists estimated that 54% of lizard populations in Mexico would go extinct by 2080 because of their inability to adapt to the rapidly warming planet.

Deforestation would further exacerbate the threat by taking away these animals' refuges.

Read more at Science Daily

NASA analysis confirms 2023 as warmest year on record

Earth's average surface temperature in 2023 was the warmest on record, according to an analysis by NASA. Global temperatures last year were around 2.1 degrees Fahrenheit (1.2 degrees Celsius) above the average for NASA's baseline period (1951-1980), scientists from NASA's Goddard Institute for Space Studies (GISS) in New York reported.

"NASA and NOAA's global temperature report confirms what billions of people around the world experienced last year; we are facing a climate crisis," said NASA Administrator Bill Nelson. "From extreme heat, to wildfires, to rising sea levels, we can see our Earth is changing. There's still more work to be done, but President Biden and communities across America are taking more action than ever to reduce climate risks and help communities become more resilient -- and NASA will continue to use our vantage point of space to bring critical climate data back down to Earth that is understandable and accessible for all people. NASA and the Biden-Harris Administration are working to protect our home planet and its people, for this generation -- and the next."

In 2023, hundreds of millions of people around the world experienced extreme heat, and each month from June through December set a global record for the respective month. July was the hottest month ever recorded. Overall, Earth was about 2.5 degrees Fahrenheit (or about 1.4 degrees Celsius) warmer in 2023 than the late 19th-century average, when modern record-keeping began.

"The exceptional warming that we're experiencing is not something we've seen before in human history," said Gavin Schmidt, director of GISS. "It's driven primarily by our fossil fuel emissions, and we're seeing the impacts in heat waves, intense rainfall, and coastal flooding."

Though scientists have conclusive evidence that the planet's long-term warming trend is driven by human activity, they still examine other phenomena that can affect yearly or multi-year changes in climate such as El Niño, aerosols and pollution, and volcanic eruptions.

Typically, the largest source of year-to-year variability is the El Niño -- Southern Oscillation ocean climate pattern in the Pacific Ocean. The pattern has two phases -- El Niño and La Niña -- when sea surface temperatures along the equator switch between warmer, average, and cooler temperatures. From 2020-2022, the Pacific Ocean saw three consecutive La Niña events, which tend to cool global temperatures. In May 2023, the ocean transitioned from La Niña to El Niño, which often coincides with the hottest years on record.

However, the record temperatures in the second half of 2023 occurred before the peak of the current El Niño event. Scientists expect to see the biggest impacts of El Niño in February, March, and April.

Scientists have also investigated possible impacts from the January 2022 eruption of the Hunga Tonga-Hunga Ha'apai undersea volcano, which blasted water vapor and fine particles, or aerosols, into the stratosphere. A recent study found that the volcanic aerosols -- by reflecting sunlight away from Earth's surface -- led to an overall slight cooling of less than 0.2 degrees Fahrenheit (or about 0.1 degrees Celsius) in the Southern Hemisphere following the eruption.

"Even with occasional cooling factors like volcanoes or aerosols, we will continue to break records as long as greenhouse gas emissions keep going up," Schmidt said. "And, unfortunately, we just set a new record for greenhouse gas emissions again this past year."

"The record-setting year of 2023 underscores the significance of urgent and continued actions to address climate change," said NASA Deputy Administrator Pam Melroy. "Recent legislation has delivered the U.S. government's largest-ever climate investment, including billions to strengthen America's resilience to the increasing impacts of the climate crisis. As an agency focused on studying our changing climate, NASA's fleet of Earth observing satellites will continue to provide critical data of our home planet at scale to help all people make informed decisions."

Open Science in Action

NASA assembles its temperature record using surface air temperature data collected from tens of thousands of meteorological stations, as well as sea surface temperature data acquired by ship- and buoy-based instruments. This data is analyzed using methods that account for the varied spacing of temperature stations around the globe and for urban heating effects that could skew the calculations.

Independent analyses by NOAA and the Hadley Centre (part of the United Kingdom Met Office) concluded the global surface temperatures for 2023 were the highest since modern record-keeping began. These scientists use much of the same temperature data in their analyses but use different methodologies. Although rankings can differ slightly between the records, they are in broad agreement and show the same ongoing long-term warming in recent decades.

Building on a half century of research, observations, and models, the Biden-Harris Administration including NASA and several federal partners recently launched the U.S. Greenhouse Gas Center to make critical climate data readily available to decisionmakers and citizens. The center supports collaboration across U.S. government agencies and the non-profit and private sectors to make air-, ground-, and space-borne data and resources available online.

Read more at Science Daily

Scientists discover places on the moon where it's always 'sweater weather'

Future human explorers on the moon might have 99 problems but staying warm or cool won't be one. A team led by planetary scientists at UCLA has discovered shady locations within pits on the moon that always hover around a comfortable 63 degrees Fahrenheit.

The pits, and caves to which they may lead, would make safer, more thermally stable base camps for lunar exploration and long-term habitation than the rest of the moon's surface, which heats up to 260 degrees during the day and drops to 280 degrees below zero at night.

Pits were first discovered on the moon in 2009, and since then, scientists have wondered if they led to caves that could be explored or used as shelters. About 16 of the more than 200 pits are probably collapsed lava tubes, said Tyler Horvath, a UCLA doctoral student in planetary science, who led the new research. Two of the most prominent pits have visible overhangs that clearly lead to some sort of cave or void, and there is strong evidence that another's overhang may also lead to a large cave.

Lava tubes, also found on Earth, form when molten lava flows beneath a field of cooled lava or a crust forms over a river of lava, leaving a long, hollow tunnel. If the ceiling of a solidified lava tube collapses, it opens a pit that can lead into the rest of the cavelike tube.

Horvath processed images from the Diviner Lunar Radiometer Experiment -- a thermal camera and one of six instruments on NASA's robotic Lunar Reconnaissance Orbiter -- to find out if the temperature within the pits diverged from those on the surface.

Focusing on a roughly cylindrical 100-meter-deep depression about the length and width of a football field in an area of the moon known as the Mare Tranquillitatis, Horvath and his colleagues used computer modeling to analyze the thermal properties of the rock and lunar dust and to chart the pit's temperatures over a period of time.

The results, recently published in the journal Geophysical Research Letters, revealed that temperatures within the permanently shadowed reaches of the pit fluctuate only slightly throughout the lunar day, remaining at around 63 degrees. If a cave extends from the bottom of the pit, as images taken by the Lunar Reconnaissance Orbiter Camera suggest, it too would have this relatively comfortable temperature.

The research team, which also included UCLA professor of planetary science David Paige and Paul Hayne of the University of Colorado Boulder, believes the shadowing overhang is responsible for the steady temperature, limiting how hot things get during the day and preventing heat from radiating away at night. Meanwhile, the sunbaked part of the pit floor hits daytime temperatures close to 300 degrees, some 40 degrees hotter than the moon's surface.

"Because the Tranquillitatis pit is the closest to the lunar equator, the illuminated floor at noon is probably the hottest place on the entire moon," said Horvath.

A day on the moon lasts nearly 15 Earth days, during which the surface is constantly bombarded by sunlight and is frequently hot enough to boil water. Unimaginably cold nights also last about 15 Earth days. Inventing heating and cooling equipment that can operate under these conditions and producing enough energy to power it nonstop could prove an insurmountable barrier to lunar exploration or habitation. Solar power -- NASA's most common form of power generation -- doesn't work at night, after all. (NASA currently has no plans to establish an exploration base camp or habitations on the moon.)

Building bases in the shadowed parts of these pits allows scientists to focus on other challenges, like growing food, providing oxygen for astronauts, gathering resources for experiments and expanding the base. The pits or caves would also offer some protection from cosmic rays, solar radiation and micrometeorites.

"Humans evolved living in caves, and to caves we might return when we live on the moon," said Paige, who leads the Diviner Lunar Radiometer Experiment.

Diviner has been mapping the moon continuously since 2009, producing NASA's second largest planetary dataset and providing the most detailed and comprehensive thermal measurements of any object in our solar system, including Earth. The team's current work on lunar pits has improved data from the Diviner experiment.

"Because nobody else had looked at things this small with Diviner, we found that it had a bit of double vision, causing all of our maps to a be a bit blurry," said Horvath. The team worked to align the many images taken by the instrument until they could achieve an accurate thermal reading down to the level of single pixel. This process yielded much higher resolution maps of the moon's surface.

Data from the early stages of this lunar pit thermal modeling project were used to help develop the thermal management system of the rover for NASA's proposed Moon Diver mission. Horvath and Hayne were part of the science team for this mission, which aims to have the rover rappel into the Tranquillitatis pit to research the layers of lava flows seen in its walls and to explore any existing cave.

Read more at Science Daily

Dinosaurs took over amid ice, not warmth, says a new study of ancient mass extinction

Many of us know the conventional theory of how the dinosaurs died 66 million years ago: in Earth's fiery collision with a meteorite, and a following global winter as dust and debris choked the atmosphere. But there was a previous extinction, far more mysterious and less discussed: the one 202 million years ago, which killed off the big reptiles who up until then ruled the planet, and apparently cleared the way for dinosaurs to take over. What caused the so-called Triassic-Jurassic Extinction, and why did dinosaurs thrive when other creatures died?

We know that the world was generally hot and steamy during the Triassic Period, which preceded the extinction, and during the following Jurassic, which kicked off the age of dinosaurs. However, a new study turns the idea of heat-loving dinosaurs on its head: It presents the first physical evidence that Triassic dinosaur species -- then a minor group largely relegated to the polar regions -- regularly endured freezing conditions there. The telltale indicators: dinosaur footprints along with odd rock fragments that only could have been deposited by ice. The study's authors say that during the extinction, cold snaps already happening at the poles spread to lower latitudes, killing off the coldblooded reptiles. Dinosaurs, already adapted, survived the evolutionary bottleneck and spread out. The rest is ancient history.

"Dinosaurs were there during the Triassic under the radar all the time," said Paul Olsen, a geologist at Columbia University's Lamont-Doherty Earth Observatory, and lead author of the study. "The key to their eventual dominance was very simple. They were fundamentally cold-adapted animals. When it got cold everywhere, they were ready, and other animals weren't."

The study, based on recent excavations in the remote desert of northwest China's Junggar Basin, was just published in the journal Science Advances.

Dinosaurs are thought to have first appeared during the Triassic Period in temperate southerly latitudes about 231 million years ago, when most of the planet's land was joined together in one giant continent geologists call Pangaea. They made it to the far north by about 214 million years ago. Until the mass extinction at 202 million years, the more expansive tropical and subtropical regions in between were dominated by reptiles including relatives of crocodiles and other fearsome creatures.

During the Triassic, and for most of the Jurassic, atmospheric concentrations of carbon dioxide ranged at or above 2000 parts per million -- five times today's levels -- so temperatures must have been intense. There is no evidence of polar ice caps then, and excavations have shown that deciduous forests grew in polar regions. However, some climate models suggest that the high latitudes were chilly some of the time; even with all that CO2, they would have received little sunlight much of the year, and temperatures would decline at least seasonally. But until now, no one has produced any physical evidence that they froze.

At the end of the Triassic, a geologically brief period of perhaps a million years saw the extinction of more than three quarters of all terrestrial and marine species on the planet, including shelled creatures, corals and all sizable reptiles. Some animals living in burrows, such as turtles, made it through, as did a few early mammals. It is unclear exactly what happened, but many scientists connect it to a series of massive volcanic eruptions that could have lasted hundreds of years at a stretch. At this time, Pangaea started to split apart, opening what is now the Atlantic Ocean, and separating what are now the Americas from Europe, Africa and Asia. Among other things, the eruptions would have caused atmospheric carbon dioxide to skyrocket beyond its already high levels, causing deadly temperatures spikes on land, and turning ocean waters too acid for many creatures to survive.

The authors of the new study cite a third factor: During the eruptions' fiercest phases, they would have belched sulfur aerosols that deflected so much sunlight, they caused repeated global volcanic winters that overpowered high greenhouse-gas levels. These winters might have lasted a decade or more; even the tropics may have seen sustained freezing conditions. This killed uninsulated reptiles, but cold-adapted, insulated dinosaurs were able to hang on, say the scientists.

The researchers' evidence: fine-grained sandstone and siltstone formations left by sediments in shallow ancient lake bottoms in the Junggar Basin. The sediments formed 206 million years ago during the late Triassic, through the mass extinction and beyond. At that time, before landmasses rearranged themselves, the basin lay at about 71 degrees north, well above the Arctic Circle. Footprints found by the authors and others show that dinosaurs were present along shorelines. Meanwhile, in the lakes themselves, the researchers found abundant pebbles up to about 1.5 centimeters across within the normally fine sediments. Far from any apparent shoreline, the pebbles had no business being there. The only plausible explanation for their presence: they were ice-rafted debris (IRD).

Briefly, IRD is created when ice forms against a coastal landmass and incorporates bits of underlying rock. At some point the ice becomes unmoored and drifts away into the adjoining water body. When it melts, the rocks drop to the bottom, mixing with normal fine sediments. Geologists have extensively studied ancient IRD in the oceans, where it is delivered by glacial icebergs, but rarely in lake beds; the Junggar Basin discovery adds to the scant record. The authors say the pebbles were likely picked up during winter, when lake waters froze along pebbly shorelines. When warm weather returned, chunks of that ice floated off with samples of the pebbles in tow, and later dropped them.

"This shows that these areas froze regularly, and the dinosaurs did just fine," said study co-author Dennis Kent, a geologist at Lamont-Doherty.

How did they do it? Evidence has been building since the 1990s that many if not all non-avian dinosaurs including tyrannosaurs had primitive feathers. If not for flight, some coverings could have used for mating display purposes, but the researchers say their main purpose was insulation. There is also good evidence that, unlike the cold-blooded reptiles, many dinosaurs possessed warm-blooded, high-metabolism systems. Both qualities would have helped dinosaurs in chilly conditions.

"Severe wintery episodes during volcanic eruptions may have brought freezing temperatures to the tropics, which is where many of the extinctions of big, naked, unfeathered vertebrates seem to have occurred," said Kent. "Whereas our fine feathered friends acclimated to colder temperatures in higher latitudes did OK."

The findings defy the conventional imagery of dinosaurs, but some prominent specialists say they are convinced. "There is a stereotype that dinosaurs always lived in lush tropical jungles, but this new research shows that the higher latitudes would have been freezing and even covered in ice during parts of the year," said Stephen Brusatte, a professor of paleontology and evolution at the University of Edinburgh. "Dinosaurs living at high latitudes just so happened to already have winter coats [while] many of their Triassic competitors died out."

Randall Irmis, curator of paleontology at the Natural History Museum of Utah, and specialist in early dinosaurs, agrees. "This is the first detailed evidence from the high paleolatitudes, the first evidence for the last 10 million years of the Triassic Period, and the first evidence of truly icy conditions," he said. "People are used to thinking of this as being a time when the entire globe was hot and humid, but that just wasn't the case."

Olsen says the next step to better understand this period is for more researchers to look for fossils in former polar areas like the Junggar Basin. "The fossil record is very bad, and no one is prospecting," he said. "These rocks are gray and black, and it is much harder to prospect [for fossils] in these strata. Most paleontologists are attracted to the late Jurassic, where it's known there are many big skeletons to be had. The paleo-Arctic is basically ignored."

Read more at Science Daily

196 lasers help scientists recreate the conditions inside gigantic galaxy clusters

Galaxies rarely live alone. Instead, dozens to thousands are drawn together by gravity, forming vast clusters that are the largest objects in the universe.

"Galaxy clusters are one of the most awe-inspiring things in the universe," said Prof. Emeritus Don Lamb, a University of Chicago astrophysicist and co-author on a new paper published March 9 -- one that may point the way towards solving a decades-long mystery.

Scientists have long known that the hydrogen gas in galaxy clusters is searingly hot -- about 10 million degrees Kelvin, or roughly the same temperature as the center of the sun -- which is so hot that hydrogen atoms cannot exist. Instead the gas is a plasma consisting of protons and electrons.

But a puzzle persists: There is no straightforward explanation for why or how the gas stays so hot. According to the normal rules of physics, it should have cooled within the age of the universe. But it hasn't.

The challenge for anyone trying to solve this puzzle is that you can't exactly create these kinds of powerfully hot and magnetic conditions in your backyard.

However, there is now one place on Earth where you can: the most energetic laser facility in the world. The National Ignition Facility at Lawrence Livermore National Laboratory is able to create such extreme conditions -- though only for a tiny fraction of a second in a volume the size of a dime.

Scientists from UChicago, the University of Oxford, and the University of Rochester worked together to use the National Ignition Facility -- located in Livermore, California -- to create conditions similar to the hot gas in gigantic galaxy clusters. "The experiments conducted at the NIF are literally out of this world," said Jena Meinecke, who was the first author on the paper.

The scientists focused 196 lasers onto a single tiny target, creating a white-hot plasma with intense magnetic fields that exists for a few billionths of a second.

This was long enough for them to determine that instead of a uniform temperature, there were hot and cold spots in the plasma.

This dovetails with one of the theories that has been proposed for how heat is trapped inside galaxy clusters. Normally, heat would be easily distributed as electrons collide with each other. But the tangled magnetic fields inside the plasma can affect these electrons, causing them to spiral along the direction of magnetic fields -- which can prevent them from evenly distributing and dispersing their energy.

In fact, in the experiment they saw that the conduction of energy was suppressed by more than a factor of 100.

"This is an incredibly exciting result because we've been able to show that what astrophysicists have proposed is on the right track," said Lamb, the Robert A. Millikan Distinguished Service Professor Emeritus in Astronomy and Astrophysics.

"This is indeed an astonishing result," added study co-author University of Rochester Prof. Petros Tzeferacos, who oversaw computer simulations of the complicated experiment. "The simulations were key to untangling the physics at play in the turbulent, magnetized plasma, but the level of thermal transport suppression was beyond what we expected."

The simulations were done with a computer code called the FLASH codes, which was developed at the University of Chicago and is now hosted at the University of Rochester's Flash Center for Computational Science, which is led by Tzeferacos. The code allows scientists to simulate their laser experiments in exquisite detail before they do them, so that they can achieve the results they seek.

This is critical because the scientists only get a precious few shots at the facility -- if something goes wrong, there's no redo. And because the experiment conditions only last nanoseconds, the scientists have to make sure they make the measurements they need at exactly the right time. This means everything has to be precisely plotted out far ahead of time.

"It's a challenge when you're at the very extremes of what can be done, but that's where the frontier is," said Lamb.

More questions remain about the physics of galaxy clusters, however. Though the hot and cold spots are solid evidence for the impact of magnetic fields on the cooling of the hot gas in galaxy clusters, further experiments are needed to understand exactly what is happening. The group is planning its next round of experiments at NIF later this year.

For the moment, though, they're happy to have shed light on why the gas in galaxy clusters is still hot even after billions of years.

Galaxies rarely live alone. Instead, dozens to thousands are drawn together by gravity, forming vast clusters that are the largest objects in the universe.

"Galaxy clusters are one of the most awe-inspiring things in the universe," said Prof. Emeritus Don Lamb, a University of Chicago astrophysicist and co-author on a new paper published March 9 -- one that may point the way towards solving a decades-long mystery.

Scientists have long known that the hydrogen gas in galaxy clusters is searingly hot -- about 10 million degrees Kelvin, or roughly the same temperature as the center of the sun -- which is so hot that hydrogen atoms cannot exist. Instead the gas is a plasma consisting of protons and electrons.

But a puzzle persists: There is no straightforward explanation for why or how the gas stays so hot. According to the normal rules of physics, it should have cooled within the age of the universe. But it hasn't.

The challenge for anyone trying to solve this puzzle is that you can't exactly create these kinds of powerfully hot and magnetic conditions in your backyard.

However, there is now one place on Earth where you can: the most energetic laser facility in the world. The National Ignition Facility at Lawrence Livermore National Laboratory is able to create such extreme conditions -- though only for a tiny fraction of a second in a volume the size of a dime.

Scientists from UChicago, the University of Oxford, and the University of Rochester worked together to use the National Ignition Facility -- located in Livermore, California -- to create conditions similar to the hot gas in gigantic galaxy clusters. "The experiments conducted at the NIF are literally out of this world," said Jena Meinecke, who was the first author on the paper.

The scientists focused 196 lasers onto a single tiny target, creating a white-hot plasma with intense magnetic fields that exists for a few billionths of a second.

This was long enough for them to determine that instead of a uniform temperature, there were hot and cold spots in the plasma.

This dovetails with one of the theories that has been proposed for how heat is trapped inside galaxy clusters. Normally, heat would be easily distributed as electrons collide with each other. But the tangled magnetic fields inside the plasma can affect these electrons, causing them to spiral along the direction of magnetic fields -- which can prevent them from evenly distributing and dispersing their energy.

In fact, in the experiment they saw that the conduction of energy was suppressed by more than a factor of 100.

"This is an incredibly exciting result because we've been able to show that what astrophysicists have proposed is on the right track," said Lamb, the Robert A. Millikan Distinguished Service Professor Emeritus in Astronomy and Astrophysics.

"This is indeed an astonishing result," added study co-author University of Rochester Prof. Petros Tzeferacos, who oversaw computer simulations of the complicated experiment. "The simulations were key to untangling the physics at play in the turbulent, magnetized plasma, but the level of thermal transport suppression was beyond what we expected."

The simulations were done with a computer code called the FLASH codes, which was developed at the University of Chicago and is now hosted at the University of Rochester's Flash Center for Computational Science, which is led by Tzeferacos. The code allows scientists to simulate their laser experiments in exquisite detail before they do them, so that they can achieve the results they seek.

This is critical because the scientists only get a precious few shots at the facility -- if something goes wrong, there's no redo. And because the experiment conditions only last nanoseconds, the scientists have to make sure they make the measurements they need at exactly the right time. This means everything has to be precisely plotted out far ahead of time.

"It's a challenge when you're at the very extremes of what can be done, but that's where the frontier is," said Lamb.

More questions remain about the physics of galaxy clusters, however. Though the hot and cold spots are solid evidence for the impact of magnetic fields on the cooling of the hot gas in galaxy clusters, further experiments are needed to understand exactly what is happening. The group is planning its next round of experiments at NIF later this year.

Read more at Science Daily

Sauropod dinosaurs were restricted to warmer regions of Earth

Giant, long-necked sauropods, thought to include the largest land animals ever to have existed, preferred to live in warmer, more tropical regions on Earth, suggesting they may have had a different physiology from other dinosaurs, according to a new study led by researchers at UCL and the University of Vigo.

The study, published in the journal Current Biology, investigated the enigma of why sauropod fossils are only found at lower latitudes, while fossils of other main dinosaur types seem ubiquitously present, with many located in the polar regions.

The researchers analysed the fossil record across the Mesozoic era (the time of the dinosaurs), lasting from around 230 to 66 million years ago, looking at occurrences of fossils of the three main dinosaur types: sauropods, which include the Brontosaurus and the Diplodocus, theropods ("lizard-hipped"), which include velociraptors and Tyrannosaurus rex, and ornithischians ("bird-hipped") such as the Triceratops.

Combining this fossil data with data about climate throughout the period, along with information about how continents have moved across the globe, the researchers concluded that sauropods were restricted to warmer, drier habitats than other dinosaurs. These habitats were likely to be open, semi-arid landscapes, similar to today's savannahs.

Co-author Dr Philip Mannion (UCL Earth Sciences) said: "Our research shows that some parts of the planet always seemed to be too cold for sauropods. They seem to have avoided any temperatures approaching freezing. Other dinosaur types, in contrast, could thrive in Earth's polar regions, from innermost Antarctica to polar Alaska -- which, due to the warmer climate, were ice-free, with lush vegetation.

"This suggests sauropods had different thermal requirements from other dinosaurs, relying more on their external environment to heat their bodies -- slightly closer to being 'cold-blooded', like modern-day reptiles. Their grand size hints that this physiology may have been unique."

First author Dr Alfio Alessandro Chiarenza, formerly of UCL who is now based at the University of Vigo, Spain, said: "It may be that sauropods were physiologically incapable of thriving in colder regions, or that they thrived less well in these areas than their dinosaurian cousins and were outcompeted.

"A mix of features may have helped sauropods shed heat more easily than mammals do today. Their long necks and tails would have given them a larger surface area, and they may have had a respiratory system more akin to birds, which is much more efficient.

"Some species of theropods and ornithischians are known to have had feathers or downy fur helping them retain body warmth. This suggests they may have generated their own body heat. For sauropods, however, there is no evidence of this kind of insulation.

"Sauropods' strategies for keeping their eggs warm may also have differed from the other dinosaurs. Theropods probably warmed eggs by sitting on them, whereas ornithischians seem to have used heat generated by decaying plants. Sauropods, meanwhile, may have buried their eggs, relying on heat from the sun and the ground."

In their paper, the researchers noted that the fossil record showed zero occurrences of sauropods above a latitude of 50 degrees north -- an area encompassing most of Canada, Russia, northern Europe and the UK -- or below 65 degrees south, encompassing Antarctica. In contrast, there are rich records for theropods and ornithischians living above 50 degrees north in later periods (from 145 million years ago).

To test if this was a true reflection of where sauropods lived, researchers used a statistical technique to adjust for gaps in the fossil record, and also analysed where the highest diversities of dinosaur types were in different periods throughout the Mesozoic era.

They combined fossil data with climate data, allowing an estimate of the temperature ranges of the dinosaur types' habitats, finding that sauropods' range across the latitudes was more restricted during colder periods.

They then used habitat modelling to infer which regions of the globe would likely be suitable for sauropods and the other dinosaur types to live.

While in the past it was believed that dinosaurs were ectothermic ("cold-blooded"), like reptiles today, relying on the external environment to heat their bodies, it is now thought they were closer to "warm-blooded" mammals, generating some of their own body heat (endothermic).

Read more at Science Daily

Warmer soil stores less carbon

Global warming will cause the world's soil to release carbon, new research shows.

Scientists used data on more than 9,000 soil samples from around the world, and found that carbon storage "declines strongly" as average temperatures increase.

This is an example of a "positive feedback," where global warming causes more carbon to be released into the atmosphere, further accelerating climate change.

Importantly, the amount of carbon that could be released depends on the soil type, with coarse-textured (low-clay) soils losing three times as much carbon as fine-textured (clay-rich) soils.

The researchers, from the University of Exeter and Stockholm University, say their findings help to identify vulnerable carbon stocks and provide an opportunity to improve Earth System Models (ESMs) that simulate future climate change.

"Because there is more carbon stored in soils than there is in the atmosphere and all the trees on the planet combined, releasing even a small percentage could have a significant impact on our climate," said Professor Iain Hartley of Exeter's College of Life and Environmental Sciences.

"Our analysis identified the carbon stores in coarse-textured soils at high-latitudes (far from the Equator) as likely to be the most vulnerable to climate change.

"Such stores, therefore, may require particular attention given the high rates of warming taking place in cooler regions.

"In contrast, we found carbon stores in fine-textured soils in tropical areas to be less vulnerable to climate warming."

The data on the 9,300 soil profiles came from the World Soil Information database, with the study focusing on the top 50cm of soil.

By comparing carbon storage in places with different average temperatures, the researchers estimated the likely impact of global warming.

For every 10°C of increase in temperature, average carbon storage (across all soils) fell by more than 25%.

"Even bleak forecasts do not anticipate this level of warming, but we used this scale to give us confidence that the effects we observed were caused by temperature rather than other variables," Professor Hartley said.

"Our results make it clear that, as temperatures rise, more and more carbon is release from soil.

"It's important to note that our study did not examine the timescales involved, and further research is needed to investigate how much carbon could be released this century."

The researchers found that their results could not be represented by an established ESM.

"This suggests that there is an opportunity to use the patterns we have observed to improve how models represent soils, and further reduce uncertainty in their projections," Professor Hartley said.

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