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      Climate change helped some dinosaurs migrate to Greenland

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      A drop in carbon dioxide levels may have helped sauropodomorphs, early relatives of the largest animal to ever walk the earth, migrate thousands of kilometers north past once-forbidding deserts around 214 million years ago.
      Scientists pinpointed the timing of the dinosaurs’ journey from South America to Greenland by correlating rock layers with sauropodomorph fossils to changes in Earth’s magnetic field. Using that timeline, the team found that the creatures’ northward push coincides with a dramatic decrease in CO2, which may have removed climate-related barriers, the team reports February 15 in Proceedings of the National Academy of Sciences.
      The sauropodomorphs were a group of long-necked, plant-eating dinosaurs that included massive sauropods such as Seismosaurus as well as their smaller ancestors (SN: 11/17/20). About 230 million years ago, sauropodomorphs lived mainly in what is now northern Argentina and southern Brazil. But at some point, these early dinosaurs picked up and moved as far north as Greenland.
      Exactly when they could have made that journey has been a puzzle, though. “In principle, you could’ve walked from where they were to the other hemisphere, which was something like 10,000 kilometers away,” says Dennis Kent, a geologist at Columbia University. Back then, Greenland and the Americas were smooshed together into the supercontinent Pangea. There were no oceans blocking the way, and mountains were easy to get around, he says. If the dinosaurs had walked at the slow pace of one to two kilometers per day, it would have taken them approximately 20 years to reach Greenland.

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      But during much of the Late Triassic Epoch, which spans 233 million to 215 million years ago, Earth’s carbon dioxide levels were incredibly high — as much as 4,000 parts per million. (In comparison, CO2 levels currently are about 415 parts per million.) Climate simulations have suggested that level of CO2 would have created hyper-arid deserts and severe climate fluctuations, which could have acted as a barrier to the giant beasts. With vast deserts stretching north and south of the equator, Kent says, there would have been few plants available for the herbivores to survive the journey north for much of that time period.
      Previous estimates suggested that these dinosaurs migrated to Greenland around 225 million to 205 million years ago. To get a more precise date, Kent and his colleagues measured magnetic patterns in ancient rocks in South America, Arizona, New Jersey, Europe and Greenland — all locales where sauropodomorphs fossils have been discovered. These patterns record the orientation of Earth’s magnetic field at the time of the rock’s formation. By comparing those patterns with previously excavated rocks whose ages are known, the team found that sauropodomorphs showed up in Greenland around 214 million years ago.
      Vertebrate fossils from the Late Triassic have been found at a number of sites around the world, some of which are marked (black dots) on this map showing how the continents were arranged about 220 million years ago. New dating of rocks at sites in South America and Greenland pinpoint when long-necked dinosaurs known as sauropodomorphs migrated north.Dennis Kent and Lars Clemmensen
      That more precise date for the sauropodomorphs’ migration may explain why it took them so long to start the trek north — and how they survived journey: Earth’s climate was changing rapidly at that time.
      Around the time that sauropodomorphs appeared in Greenland, carbon dioxide levels plummeted within a few million years to 2,000 parts per million, making the climate more travel-friendly to herbivores, the team reports. The reason for this drop in carbon dioxide — which appears in climate records from South America and Greenland — is unknown, but it allowed for an eventual migration northward.
      “We have evidence for all of these events, but the confluence in timing is what is remarkable here,” says Morgan Schaller, a geochemist at Rensselaer Polytechnic Institute in Troy, N.Y., who was not involved with this study. These new findings, he says, also help solve the mystery of why plant eaters stayed put during a time that meat eaters roamed freely.
      “This study reminds us that we can’t understand evolution without understanding climate and environment,” says Steve Brusatte, a vertebrate paleontologist and evolutionary biologist at the University of Edinburgh, also not involved with the study. “Even the biggest and most awesome creatures that ever lived were still kept in check by the whims of climate change.” More

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      A drop in CFC emissions puts the hole in the ozone layer back on track to closing

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      Good news for the ozone layer: After a recent spike in CFC-11 pollution, emissions of this ozone-destroying chemical are on the decline.
      Emissions of trichlorofluoromethane, or CFC-11, were supposed to taper off after the Montreal Protocol banned CFC-11 production in 2010 (SN: 7/7/90). But 2014 to 2017 saw an unexpected bump. About half of that illegal pollution was pegged to eastern China (SN: 5/22/19). Now, atmospheric data show that global CFC-11 emissions in 2019 were back down to the average levels seen from 2008 to 2012, and about 60 percent of that decline was due to reduced emissions in eastern China, two teams report online February 10 in Nature. 
      These findings suggest that the hole in Earth’s ozone layer is still on track to close up within the next 50 years — rather than being delayed, as it would have been if CFC-11 emissions had remained at the levels seen from 2014 to 2017 (SN: 12/14/16).
      One group analyzed the concentration of CFC-11, used to make insulating foams for buildings and household appliances, in the air above atmospheric monitoring stations around the globe. The team found that the world emitted about 52,000 metric tons of CFC-11 in 2019 — a major drop from the annual average of 69,000 metric tons from 2014 to 2018. The 2019 emissions were comparable to the average annual emissions from 2008 to 2012, Stephen Montzka, an atmospheric chemist at the U.S. National Oceanic and Atmospheric Administration in Boulder, Colo., and colleagues report.

      The new measurements imply that there has been a significant decrease in illicit CFC-11 production within the last couple of years, the researchers say, probably thanks to more rigorous regulation enforcement in China and elsewhere.
      Another group confirmed that emissions from eastern China have diminished since 2018 by analyzing air samples from Hateruma, Japan and Gosan, South Korea. The region emitted about 5,000 metric tons of CFC-11 in 2019, which was about 10,000 metric tons less than its average annual emissions from 2014 to 2017 and was similar to the 2008 to 2012 average. That analysis was led by Sunyoung Park, a geochemist at Kyungpook National University in Daegu, South Korea.

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      The recent downturn in CFC-11 pollution shows that “the Montreal Protocol is working,” says A.R. “Ravi” Ravishankara, an atmospheric scientist at Colorado State University in Fort Collins not involved in either study. When someone violates the treaty, “atmospheric sleuthing” can uncover the culprits and spur countries to take action, he says. “China clearly took action, because you can see the result of that action in the atmosphere.” 
      Montzka cautions that it might not always be so easy to point the finger at rogue emitters. “I think we got lucky this time,” he says, because atmospheric monitoring sites in Asia were able to trace the bulk of illegal emissions to eastern China and monitor the situation over several years. Many places around the world, such as in Africa and South America, lack atmospheric monitoring stations — so it’s still a mystery which countries besides China were responsible for the recent rise and fall of CFC-11 emissions. More

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      Three things to know about the disastrous flood in India

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      A flash flood surged down a river in India’s Himalayan Uttarakhand state on February 7, killing at least 30 people and washing away two hydroelectric power stations.
      As rescue workers search for more than 100 people who are still missing, officials and scientists are trying to unravel the causes of the sudden flood. Did a glacier high up in the mountains collapse, releasing a huge plug of frigid meltwater that spilled into the river? Or was the culprit a landslide that then triggered an avalanche? And what, if any, link might these events have to a changing climate?
      Here are three things to know about what might have caused the disaster in Uttarakhand.
      1. One possible culprit was the sudden break of a glacier high in the mountains.
      News reports in the immediate wake of the disaster suggested that the floodwaters were caused by the sudden overflow of a glacial lake high up in the mountain, an event called a glacial lake outburst flood.
      “It’s likely too early to know what exactly happened,” says Anjal Prakash, the research director of the Bharti Institute of Public Policy at the Indian School of Business in Hyderabad. Satellite images show that a section of a glacier broke off, but how that break relates to the subsequent floods is still unknown. One possibility is that the glacier was holding back a lake of meltwater, and that heavy snowfall in the region two days earlier added enough volume to the lake that the water forced its way out, breaking the glacier and surging into nearby rivers.
      This scenario is certainly in line with known hazards for the region. “These mountains are very fragile,” says Prakash, who was also a lead author on the Intergovernmental Panel on Climate Change’s 2019 special report on oceans and the cryosphere, Earth’s icy places. But, he notes, there isn’t yet much on-the-ground data to help clarify events. “The efforts are still focused on relief at the moment.”
      2. A landslide may be to blame instead.
      Other researchers contend that the disaster wasn’t caused by a glacial lake outburst flood at all. Instead, says Daniel Shugar, a geomorphologist at the University of Calgary in Canada, satellite images snapped during the disaster show the telltale marks of a landslide: a dark scar snaking through the white snow and clouds of dust clogging the air above. “You could see this train of dust in the valley, and that’s common for a very large landslide,” Shugar says.
      “WOW,” he wrote on Twitter the morning of February 7, posting side-by-side satellite shots of a dark area of possible “massive dust deposition,” contrasted against the same snowy, pristine region just the day before.

      Landslides — the sudden failure of a slope, sending a rush of rocks and sediment downhill — can be triggered by anything from an earthquake to an intense deluge of rain. In high, snowy mountains, cycles of freezing and thawing and refreezing again can also begin to break the ground apart; the ice-filled cracks can slowly widen over time, setting the stage for sudden failure, and then, disaster.
      The satellite images seem to point clearly to such a landslide, rather than a typical glacial lake overflow, Shugar says. The force of the landslide may have actually broken off that piece of hanging glacier, he says. Another line of evidence against a sudden lake burst is that “there were no lakes of any size visible” in the satellite images taken over the region.
      However, an outlying question for this hypothesis is where the floodwaters came from. It might be that one of the rivers draining down the mountain was briefly dammed by the rockfall; a sudden release of that dam could send a large plug of water from the river swiftly and disastrously downhill. “But that’s a pure guess at the moment,” Shugar says.
      3. It’s not yet clear whether climate change played a role in the disaster.
      The risk of both glacial lake outburst floods and freeze-thaw-related landslides in Asia’s high mountains has increased due to climate change. At first glance, “it was a climate event,” Prakash says. “But the data are still coming.”
      The region, which includes the Hindu Kush Himalayan mountains and the Tibetan Plateau, “has been a climate change hot spot for a pretty long time,” Prakash says. The region is often called Earth’s third pole, because the stores of ice and snow in the Himalayan watershed amount to the largest reserves of freshwater outside of the polar regions. The region is the source of 10 major river systems that provide water to almost 2 billion people.
      Climate change reports have warned that warming is not only threatening this water supply, but also increasing the likelihood of natural hazards (SN: 5/29/19). In the Intergovernmental Panel on Climate Change’s 2019 special report on oceans and the cryosphere, scientists noted that glacier retreat, melting snow and thawing permafrost are making mountain slopes more unstable and also increasing the number of glacial lakes, upping the likelihood of a sudden, catastrophic failure (SN: 9/25/19).
      A 2019 comprehensive assessment focusing on climate change’s impacts in Asia’s high mountains found that the glaciers in the region have retreated much more quickly in the last decade than was anticipated, Prakash says, “and that is alarming for us.” Here’s another way to look at it: Glaciers are retreating twice as fast as they were at the end of the 20th century (SN: 6/19/19).
      Glacier-related landslides in the region have also become increasingly common in the last decade, as the region warms and destabilizing freeze-thaw cycles within the ground occur higher and higher up on the slopes.
      But in the case of this particular disaster, Shugar says, it’s just hard to say conclusively at this point what role climate change might have played, or even what specific event might have triggered a landslide. “Sometimes there is no trigger; sometimes it’s just time,” he says. “Or it’s that we just don’t understand the trigger.”

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      Ship exhaust studies overestimate cooling from pollution-altered clouds

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      Among the biggest questions for climate change forecasters is how atmospheric aerosols shape clouds, which can help cool the planet. Now, a new study finds that one promising strategy for understanding how aerosols and clouds interact can overestimate the cooling ability of pollution-generated clouds by up to 200 percent, researchers report in the Jan. 29 Science.
      “Clouds in general, and how aerosols interact with the climate, are a big uncertainty in climate models,” says Franziska Glassmeier, an atmospheric scientist at Delft University of Technology in the Netherlands. Scientists know that aerosols — both natural, as from volcanoes, and human-caused, as from pollution — can change a cloud’s thickness, ability to scatter sunlight or how much rainfall it produces. But these complicated physical effects are difficult to simulate, so scientists have sought real-world examples to study these effects.
      Enter ship tracks. Exhaust belched out of massive cargo ships crossing the oceans can form these bright lines of clouds. The tiny exhaust particles act as cloud nuclei: Water vapor condenses on the particles to form cloud droplets, the watery stuff of clouds. Ship tracks are “this prime example where we can see this cause and effect,” Glassmeier says. “Put in particles, and you can see the clouds get brighter.” Brighter clouds means that they are reflecting even more sunlight back into space.
      Visible and measurable by satellite, the tracks offer a potential window into how larger-scale industrial pollution around the globe might be altering the planet’s cloudscape — and perhaps how such clouds might affect the climate. Satellite-derived analyses of ship tracks involve measuring the density of the water droplets in the clouds from the images, and calculating how the brightness of the clouds changes over time.

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      To assess how well ship tracks actually represent the overall impact of pollution on clouds, Glassmeier and her colleagues compared the cooling effect of ship track clouds with that of simulated pollution-derived clouds, such as might occur over a city. In particular, the researchers wanted to simulate how both the thickness and the brightness of the clouds — and therefore their cooling effect — might evolve over time, as a result of processes like rainfall and evaporation.
      The problem, the team found, is that the ship tracks don’t tell the whole story. Ship tracks are short-lived, because the source of pollution is always on the move. But industrial pollution doesn’t tend to happen in a brief pulse: Instead, there is a steady influx of particles to the atmosphere. And that difference in inputs affects how natural clouds respond over time.
      In both the ship track studies and the simulations of industrial pollution, clouds initially brighten and produce a cooling effect. That’s because, in both cases, the addition of abundant aerosol particles to the atmosphere gives water vapor numerous surfaces on which to condense, creating many small water droplets that form this brighter cloud and reflect incoming radiation.
      After a few hours, however, as a ship moves on, the ship track goes away, and the pulse of pollution ceases, Glassmeier says. The initial brief bit of cooling subsides as the preexisting natural clouds return to their original, nonpolluted state.
      But in the case of industrial pollutants, the natural clouds don’t return to their original state, the simulations show. Rather, the pollutants hasten the clouds’ demise. That’s because the tinier aerosol-seeded droplets begin to evaporate more quickly than larger, natural cloud droplets would. This increased evaporation thins the original cloud, allowing more heat through than if the pollutants never arrived. And that can ultimately have an overall warming, rather than cooling, effect on the climate, the team says.
      “There is this timescale effect that needs to be taken into account,” Glassmeier says. Relying solely on ship track data to understand all sources of pollution misses this gradual thinning effect. “I wouldn’t throw all the ship track data away; we just need to interpret it in a new way.” Current climate models tend to omit this thinning effect, she says.
      The new study is “really useful for helping to interpret aerosol-cloud relationships in satellite data,” says Edward Gryspeerdt, an atmospheric physicist at Imperial College London who was not involved in the study. It “demonstrates that the cloud response to aerosols is not instant, but evolves over time.”
      Scientists have been aware that ship tracks may not lead to cooling, says Graeme Stephens, an atmospheric scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. For example, Stephens notes that he and others have previously found that ship tracks can speed up cloud thinning by increasing the rate of evaporation at the tops of the clouds, while at the same time suppressing rainfall, which maintains some of the cloud’s thickness. These two competing responses make determining a cloud’s ultimate fate tricky.
      But what ship tracks can do is act as “a controlled laboratory of sorts,” Stephens says. They “offer us a way to examine aerosol influences on clouds in a direct, concrete way.” More

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      Some bacteria are suffocating sea stars, turning the animals to goo

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      The mysterious culprit behind a deadly sea star disease is not an infection, as scientists once thought.
      Instead, multiple types of bacteria living within millimeters of sea stars’ skin deplete oxygen from the water and effectively suffocate the animals, researchers report January 6 in Frontiers in Microbiology. Such microbes thrive when there are high levels of organic matter in warm water and create a low oxygen environment that can make sea stars melt in a puddle of slime.
      Sea star wasting disease — which causes lethal symptoms like decaying tissue and loss of limbs — first gained notoriety in 2013 when sea stars living off the U.S. Pacific Coast died in massive numbers. Outbreaks of the disease had also occurred before 2013, but never at such a large scale.
      Scientists suspected that a virus or bacterium might be making sea stars sick. That hypothesis was supported in a 2014 study that found unhealthy animals may have been infected by a virus (SN: 11/19/14). But the link vanished when subsequent studies found no relationship between the virus and dying sea stars, leaving researchers perplexed (SN: 5/5/16). 

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      The new finding that a boom of nutrient-loving bacteria can drain oxygen from the water and cause wasting disease “challenges us to think that there might not always be a single pathogen or a smoking gun,” says Melissa Pespeni, a biologist at the University of Vermont in Burlington who was not involved in the work. Such a complex environmental scenario for killing sea stars “is a new kind of idea for [disease] transmission.”  
      There were certainly many red herrings during the hunt for why sea stars along North America’s Pacific Coast were melting into goo, says Ian Hewson, a marine biologist at Cornell University. In addition to the original hypothesis of a viral cause for sea star wasting disease — which Hewson’s team reported in 2014 in Proceedings of the National Academy of Sciences but later disproved — he and colleagues analyzed a range of other explanations, from differences in water temperature to exposing the animals to bacteria. But nothing reliably triggered wasting.   
      Then the researchers examined the types of bacteria living with healthy sea stars compared with those living among the animals with wasting disease. “That was when we had our aha moment,” says Hewson.
      Not all sea stars are susceptible to sea star wasting disease. Species that have more structures on their surface, and therefore more surface area for bacteria to deplete oxygen, appear more likely to get severely sick compared with flatter sea stars. In this photo, an ochre sea star (Pisaster ochraceus) succumbs to the disease in Davenport, Calif., in June 2018.Ian Hewson
      Types of bacteria known as copiotrophs, which thrive in environments with lots of nutrients, were present around the sea stars at higher levels than normal either shortly before the animals developed lesions or as they did so, Hewson and colleagues found. Bacterial species that survive only in environments with little to no oxygen were also thriving. In the lab, the sea stars began wasting when the researchers added phytoplankton or a common bacterial-growth ingredient to the warm water tubs those microbes and sea stars were living in.  
      Experimentally depleting oxygen from the water had a similar effect, causing lesions in 75 percent of the animals, while none succumbed in the control group. Sea stars breathe by diffusing oxygen over small external projections called skin gills, so the lack of oxygen in the wake of flourishing copiotrophs leaves sea stars struggling for air, the data show. It’s unclear how the animals degrade in low oxygen conditions, but it could be due to massive cell death.
      Although the disease isn’t caused by a contagious pathogen, it is transmissible in the sense that dying sea stars generate more organic matter that spur bacteria to grow on healthy animals nearby. “It’s a bit of a snowball effect,” Hewson says.
      The team also analyzed tissues from sea stars that had succumbed in the 2013 mass die-off — which followed a large algal bloom on the U.S. West Coast — to see if such environmental conditions might explain that outbreak. In fast-growing appendages that help them move, the sea stars that perished had high amounts of a form of nitrogen found in low oxygen conditions — a sign that those animals may have died from a lack of oxygen.
      The problem may get worse with climate change, Hewson says. “Warmer waters can’t have as much oxygen [compared with colder water] just by physics alone.” Bacteria, including copiotrophs, also flourish in warm water.  
      But pinpointing the likely cause could help experts better treat sick sea stars in the lab, Hewson says. Some techniques include increasing the oxygen levels in a water tank to make the gas more easily available to sea stars or getting rid of extra organic matter with ultraviolet light or water exchange.
      “There’s still a lot to figure out with this disease, but I think [this new study] gets us a long way to understanding how it comes about,” Pespeni says. More

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      ‘The New Climate War’ exposes tactics of climate change ‘inactivists’

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      The New Climate WarMichael E. MannPublic Affairs, $29
      Sometime around the fifth century B.C., the Chinese general and military strategist Sun Tzu wrote in his highly quotable treatise The Art of War, “If you know the enemy and know yourself, you need not fear the result of a hundred battles.”
      In The New Climate War, climate scientist Michael Mann channels Sun Tzu to demystify the myriad tactics of “the enemy” — in this case, “the fossil fuel companies, right-wing plutocrats and oil-funded governments” and other forces standing in the way of large-scale action to combat climate change. “Any plan for victory requires recognizing and defeating the tactics now being used by inactivists as they continue to wage war,” he writes.
      Mann is a veteran of the climate wars of the 1990s and early 2000s, when the scientific evidence that the climate is changing due to human emissions of greenhouse gases was under attack. Now, with the effects of climate change all around us (SN: 12/21/20), we are in a new phase of those wars, he argues. Outright denial has morphed into “deception, distraction and delay.”
      Such tactics, he says, are direct descendants of earlier public relations battles over whether producers or consumers must bear ultimate responsibility for, say, smoking-related deaths. When it comes to the climate, Mann warns, an overemphasis on individual actions could eclipse efforts to achieve the real prize: industrial-scale emissions reductions.

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      He pulls no punches, calling out sources of “friendly fire” from climate advocates who he says divide the climate community and play into the “enemy’s” hands. These advocates include climate purists who lambaste scientists for flying or eating meat; science communicators who push fatalistic visions of catastrophic futures; and idealistic technocrats who advocate for risky, pie-in-the-sky geoengineering ideas. All, Mann says, distract from what we can do in the here and now: regulate emissions and invest in renewable energy.
      The New Climate War’s main focus is to combat psychological warfare, and on this front, the book is fascinating and often entertaining. It’s an engrossing mix of footnoted history, acerbic political commentary and personal anecdotes. As far as what readers can do to assist in the battle, Mann advocates four strategies: Disregard the doomsayers; get inspired by youth activists like Greta Thunberg; focus on educating the people who will listen; and don’t be fooled into thinking it’s too late to take action to change the political system.
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      2020 and 2016 tie for the hottest years on record

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      2020 is in a “dead heat” with 2016 for the hottest year on record, scientists with NASA and the National Oceanic and Atmospheric Administration announced January 14.
      Based on ocean temperature data from buoys, floats and ships, as well as temperatures measured over land at weather stations around the globe, the U.S. agencies conducted independent analyses and arrived at a similar conclusion.
      NASA’s analysis showed 2020 to be slightly hotter, while NOAA’s showed that 2016 was still slightly ahead. But the differences in those assessments are within margins of error, “so it’s effectively a statistical tie,” said NASA climatologist Gavin Schmidt of the Goddard Institute for Space Studies in New York City at a Jan. 14 news conference.
      NOAA climate scientist Russell Vose, who is also based in New York City, described in the news conference the extreme warmth that occurred over land last year, including a months-long heat wave in Siberia (SN: 12/21/20). Europe and Asia recorded their hottest average temperatures on record in 2020, with South America recording its second warmest.
      It’s possible that 2020’s temperatures in some areas might have been even higher if not for massive wildfires. Vose noted that smoke lofted high into the stratosphere as a result of Australia’s intense fires in early 2020 may have slightly decreased temperatures in the Northern Hemisphere, though this is not yet known (SN: 12/15/20).
      The ocean-climate pattern known as the El Niño Southern Oscillation can boost or decrease global temperatures, depending on whether it’s in an El Niño or La Niña phase, respectively, Schmidt said (SN: 5/2/16). The El Niño phase was waning at the start of 2020, and a La Niña was starting, so the overall impact of this pattern was muted for the year. 2016, on the other hand, got a large temperature boost from El Niño. Without that, “2020 would have been by far the warmest year on record,” he said.
      But placed in the bigger picture, these rankings “don’t tell the whole story,” Vose said. “The last six to seven years really stand out above the rest of the record, suggesting the kind of rapid warming we’re seeing. [And] each of the past four decades was warmer than the one preceding it.” More