The ice told a story of Earth's climate history. The frozen soil was examined, set aside and then forgotten.
Half a century later, scientists rediscovered that soil in a Danish freezer. It is now revealing its secrets.
Using lab techniques unimaginable in the 1960s when the core was drilled, we and an international team of fellow scientists were able to show that Greenland's massive ice sheet had melted to the ground there within the past million years. Radiocarbon dating shows that it would have happened more than 50,000 years ago. It most likely happened during times when the climate was warm and sea level was high, possibly 400,000 years ago.
And there was more. As we explored the soil under a microscope, we were stunned to discover the remnants of a tundra ecosystem – twigs, leaves and moss. We were looking at northern Greenland as it existed the last time the region was ice-free. Our peer-reviewed study was published on March 15 in Proceedings of the National Academy of Sciences.
Engineers pull up a section of the 4,560-foot-long ice core at Camp Century in the 1960s. U.S. Army Corps of Engineers
With no ice sheet, sunlight would have warmed the soil enough for tundra vegetation to cover the landscape. The oceans around the globe would have been more than 10 feet higher, and maybe even 20 feet. The land on which Boston, London and Shanghai sit today would have been under the ocean waves.
All of this happened before humans began warming Earth's climate. The atmosphere at that time contained far less carbon dioxide than it does today, and it wasn't rising as quickly. The ice core and the soil below are something of a Rosetta Stone for understanding how durable the Greenland ice sheet has been during past warm periods – and how quickly it might melt again as the climate heats up.
Secret Military Bases and Danish Freezers
The story of the ice core begins during the Cold War with a military mission dubbed Project Iceworm. Starting around 1959, the U.S. Army hauled hundreds of soldiers, heavy equipment and even a nuclear reactor across the ice sheet in northwest Greenland and dug a base of tunnels inside the ice. They called it Camp Century.
It was part of a secret plan to hide nuclear weapons from the Soviets. The public knew it as an Arctic research laboratory. Walter Cronkite even paid a visit and filed a report.
Workers build the snow tunnels at the Camp Century research base in 1960. U.S. Army Corps of Engineers
Camp Century didn't last long. The snow and ice began slowly crushing the buildings inside the tunnels below, forcing the military to abandon it in 1966. During its short life, however, scientists were able to extract the ice core and begin analyzing Greenland's climate history. As ice builds up year by year, it captures layers of volcanic ash and changes in precipitation over time, and it traps air bubbles that reveal the past composition of the atmosphere.
One of the original scientists, glaciologist Chester Langway, kept the core and soil samples frozen at the University at Buffalo for years, then he shipped them to a Danish archive in the 1990s, where the soil was soon forgotten.
A few years ago, our Danish colleagues found the soil samples in a box of glass cookie jars with faded labels: "Camp Century Sub-Ice."
Geomorphologist Paul Bierman (right) and geochemist Joerg Schaefer of Columbia University examine the jars holding Camp Century sediment for the first time. They were in a Danish freezer set at -17 F. Paul Bierman / CC BY-ND
A Surprise Under the Microscope
On a hot July day in 2019, two samples of soil arrived at our lab at the University of Vermont frozen solid. We began the painstaking process of splitting the precious few ounces of frozen mud and sand for different analyses.
First, we photographed the layering in the soil before it was lost forever. Then we chiseled off small bits to examine under the microscope. We melted the rest and saved the ancient water.
Then came the biggest surprise. While we were washing the soil, we spotted something floating in the rinse water. Paul grabbed a pipette and some filter paper, Drew grabbed tweezers and turned on the microscope. We were absolutely stunned as we looked down the eyepiece.
Staring back at us were leaves, twigs and mosses. This wasn't just soil. This was an ancient ecosystem perfectly preserved in Greenland's natural deep freeze.
Dating Million-Year-Old Moss
How old were these plants?
Over the last million years, Earth's climate was punctuated by relatively short warm periods, typically lasting about 10,000 years, called interglacials, when there was less ice at the poles and sea level was higher. The Greenland ice sheet survived through all of human history during the Holocene, the present interglacial period of the last 12,000 years, and most of the interglacials in the last million years.
But our research shows that at least one of these interglacial periods was warm enough for a long enough period of time to melt large portions of the Greenland ice sheet, allowing a tundra ecosystem to emerge in northwestern Greenland.
We used two techniques to determine the age of the soil and the plants. First, we used clean room chemistry and a particle accelerator to count atoms that form in rocks and sediment when exposed to natural radiation that bombards Earth. Then, a colleague used an ultra-sensitive method for measuring light emitted from grains of sand to determine the last time they were exposed to sunlight.
Maps of Greenland show the speed of the ice sheet as it flows (left) and the landscape hidden beneath it (right). BedMachine v3; Copernicus Climate Change Service (C3S) / CC BY-ND
The concentration of carbon dioxide in the atmosphere today is well beyond past levels determined from ice cores. On March 14, 2021, the CO2 level was about 417 ppm. NASA Jet Propulsion Laboratory / CC BY-ND
The million-year time frame is important. Previous work on another ice core, GISP2, extracted from central Greenland in the 1990s, showed that the ice had also been absent there within the last million years, perhaps about 400,000 years ago.
Losing the Greenland ice sheet would be catastrophic to humanity today. The melted ice would raise sea level by more than 20 feet. That would redraw coastlines worldwide.
About 40% of the global population lives within 60 miles of a coast, and 600 million people live within 30 feet of sea level. If warming continues, ice melt from Greenland and Antarctica will pour more water into the oceans. Communities will be forced to relocate, climate refugees will become more common, and costly infrastructure will be abandoned. Already, sea level rise has amplified flooding from coastal storms, causing hundreds of billions of dollars of damage every year.
Tundra near the Greenland ice sheet today. Is this what Camp Century looked like before the ice came back sometime in the last million years? Paul Bierman / CC BY-ND
The story of Camp Century spans two critical moments in modern history. An Arctic military base built in response to the existential threat of nuclear war inadvertently led us to discover another threat from ice cores – the threat of sea level rise from human-caused climate change. Now, its legacy is helping scientists understand how Earth responds to a changing climate.
Andrew Christ is a postdoctoral fellow and lecturer in geology at the University of Vermont.
Paul Bierman is a fellow of the Gund Institute for Environment and professor of geology and natural resources at the University of Vermont.
Disclosure statement: Andrew Christ receives funding from the Gund Institute for Environment and the National Science Foundation. Paul Bierman receives funding from the U.S. National Science Foundation and UVM Gund Institute for Environment.
Reposted with permission from The Conversation.
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Eye-Catching Designs Made from Recycled Plastic Bottles
The company sells a range of eco-friendly items like leggings, rash guards, and board shorts that are made using recycled post-consumer plastic bottles. There are currently 16 causes represented by distinct marine-life patterns, from whale shark research and invasive lionfish removal to sockeye salmon monitoring and abalone restoration.
One such organization is Get Inspired, a nonprofit that specializes in ocean restoration and environmental education. Get Inspired founder, marine biologist Nancy Caruso, says supporting on-the-ground efforts is one thing that sets Waterlust apart, like their apparel line that supports Get Inspired abalone restoration programs.
"All of us [conservation partners] are doing something," Caruso said. "We're not putting up exhibits and talking about it — although that is important — we're in the field."
Waterlust not only helps its conservation partners financially so they can continue their important work. It also helps them get the word out about what they're doing, whether that's through social media spotlights, photo and video projects, or the informative note card that comes with each piece of apparel.
"They're doing their part for sure, pushing the information out across all of their channels, and I think that's what makes them so interesting," Caruso said.
And then there are the clothes, which speak for themselves.
Advocate Apparel to Start Conversations About Conservation
Waterlust's concept of "advocate apparel" encourages people to see getting dressed every day as an opportunity to not only express their individuality and style, but also to advance the conversation around marine science. By infusing science into clothing, people can visually represent species and ecosystems in need of advocacy — something that, more often than not, leads to a teaching moment.
"When people wear Waterlust gear, it's just a matter of time before somebody asks them about the bright, funky designs," said Waterlust's CEO, Patrick Rynne. "That moment is incredibly special, because it creates an intimate opportunity for the wearer to share what they've learned with another."
The idea for the company came to Rynne when he was a Ph.D. student in marine science.
"I was surrounded by incredible people that were discovering fascinating things but noticed that often their work wasn't reaching the general public in creative and engaging ways," he said. "That seemed like a missed opportunity with big implications."
Waterlust initially focused on conventional media, like film and photography, to promote ocean science, but the team quickly realized engagement on social media didn't translate to action or even knowledge sharing offscreen.
Rynne also saw the "in one ear, out the other" issue in the classroom — if students didn't repeatedly engage with the topics they learned, they'd quickly forget them.
"We decided that if we truly wanted to achieve our goal of bringing science into people's lives and have it stick, it would need to be through a process that is frequently repeated, fun, and functional," Rynne said. "That's when we thought about clothing."
Support Marine Research and Sustainability in Style
To date, Waterlust has sold tens of thousands of pieces of apparel in over 100 countries, and the interactions its products have sparked have had clear implications for furthering science communication.
For Caruso alone, it's led to opportunities to share her abalone restoration methods with communities far and wide.
"It moves my small little world of what I'm doing here in Orange County, California, across the entire globe," she said. "That's one of the beautiful things about our partnership."
Check out all of the different eco-conscious apparel options available from Waterlust to help promote ocean conservation.
Melissa Smith is an avid writer, scuba diver, backpacker, and all-around outdoor enthusiast. She graduated from the University of Florida with degrees in journalism and sustainable studies. Before joining EcoWatch, Melissa worked as the managing editor of Scuba Diving magazine and the communications manager of The Ocean Agency, a non-profit that's featured in the Emmy award-winning documentary Chasing Coral.
The Big Idea
Permafrost – frozen soil in the far north – is thawing, releasing greenhouse gases and long-lost microbes. But one thing that scientists have not studied extensively is whether permafrost contains certain kinds of particles that could affect clouds and weather.
As atmospheric scientists, we found in a recent study that thawing permafrost contains lots of microscopic ice-nucleating particles. These particles make it easier for water droplets to freeze; and if the ones in permafrost get airborne, they could affect Arctic clouds.
In the summer of 2018, one of us, Jessie Creamean, went to Fairbanks, Alaska, and collected samples of permafrost from a research tunnel deep underground. These samples ranged from 18,000 to 30,000 years old, and our team tested them to see how many ice-nucleating particles are hiding in permafrost.
It turns out permafrost contains a ton of them – up to 100 million highly active individual particles per gram of mostly dead microbes and pieces of plants. This density is on par with what is found in fertile soils, which are some of the most concentrated sources of ice-nucleating particles on Earth. Everywhere in the world, ice-nucleating particles typically play a major role in cloud behavior, and the strength of that effect is still being studied.
This 18,000-year-old permafrost sample contains millions of ice-nucleating particles per gram. Thomas Hill / CC BY-ND
Why It Matters
No one yet knows whether ice-nucleating particles from permafrost are getting into the atmosphere and affecting clouds. But the theory of how ice-nucleating particles change clouds is understood.
Clouds are made up of billions of tiny water droplets or ice crystals, often a mix of both. A cloud is like a forest of trees: All water droplets of the cloud require a seed – a tiny aerosol particle – to form and grow on. Almost any little speck of material from the land or the ocean can be the seed of a liquid cloud droplet. Because of their unique ability to line up water molecules into an icelike grid, they help supercooled liquid in a cloud to freeze at warmer temperatures.
Ice-nucleating particles are extremely good at forming small ice crystals – a rare skill found in less than 1 in a million of all the particles floating around in the air. Ice-nucleating particles can be mineral dust from deserts, specks of soil from farm fields or – like what we found in the permafrost – bacteria and bits of biological material from oceans or plants.
The ability to easily form ice has big consequences for clouds and weather.
Most of the time, airborne water droplets need to freeze before they can fall to the ground as snow or rain. Ice-nucleating particles allow cloud ice to form at warmer air temperatures than normal, up to around 28 degrees Fahrenheit. Without these particles, a water droplet can supercool to about negative 36 F before freezing. When ice-nucleating particles are in a cloud, water droplets freeze more easily. This can cause the cloud to rain or snow and disappear earlier, and reflect less sunlight.
As permafrost thaws, ice-nucleating particles are getting into rivers, lakes and eventually the ocean. National Park Service / C.Ciancibelli / Wikimedia Commons
What Still Isn’t Known
Our work found there are a lot of these ice-nucleating particles in thawing permafrost, which is important because permafrost covers 24% of the exposed land surface in the Northern Hemisphere. The question now is whether these particles are getting into the atmosphere or not. No other researchers that we're aware of have looked at permafrost's effect on cloud formation, or the mechanisms by which ice-nucleating particles from permafrost become airborne.
We hypothesize that ice-nucleating particles from thawing permafrost could get into lakes and rivers, make their way to coastal Arctic Ocean waters and spread over large areas. Then, winds could eject these ice-nucleating particles into the air, where they could enhance the freezing of clouds and affect weather.
There are still many unknowns and a lot of work to do.
What’s Next
This summer, we are teaming up with colleagues from the Cold Regions Research and Engineering Laboratory in Fairbanks and the National Center for Atmospheric Research in Boulder, Colorado, to set out for a six-week expedition to the Alaskan Arctic tundra. We will collect hundreds of samples of permafrost, lake water, river water, coastal ocean water and air samples to see whether ice-nucleating particles from permafrost are present, and in what amounts. Our goal is to use these findings in models to predict how thawing permafrost could alter the region's clouds.
Jessie Creamean is a research scientist at Colorado State University. Thomas Hill is a research scientist at Colorado State University.
Disclosure statement: Jessie Creamean receives funding for this work from the National Science Foundation (Award OPP-1946657). Thomas Hill receives funding for this work from the National Science Foundation (Award OPP-1946657).
Reposted with permission from The Conversation.
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NASA and the European Copernicus Climate Change Service rated 2020 as tied with 2016 as the warmest year on record (NASA rates the margin of error at .05 degrees C); the Japan Meteorological Agency rated 2020 as the warmest year on record. Minor differences in rankings often occur among various research groups, the result of different ways they handle data-sparse regions such as the Arctic.
Global ocean temperatures in 2020 were the third-warmest on record, global land temperatures the warmest on record. Global satellite-measured temperatures in 2020 for the lowest eight kilometers of the atmosphere were the second-warmest or warmest in the 42-year record, according to the University of Alabama, Huntsville and Remote Sensing Solutions, respectively.
The Northern Hemisphere had its warmest year on record in 2020 and the Southern Hemisphere its fifth-warmest. By continent, here are the 2020 temperature rankings:
Europe: first warmest
Asia: first warmest
South America: second warmest
Africa: fourth warmest
Australia (and Oceania): fourth warmest
North America: 10th warmest
As detailed in a January 12 post at this site by Bob Henson, 2020 for the U.S. was the fifth-warmest year in history going back to 1895. Ten states had their second-warmest year on record and four had their third-warmest year. None of the contiguous 48 states was below-average in temperature in 2020.
Figure 1. Departure of temperature from average for 2020, the second-warmest year the globe has seen since record-keeping began in 1880, according to NOAA. Record-high annual temperatures over land and ocean surfaces were measured across parts of Europe, Asia, southern North America, South America, and across parts of the Atlantic, Indian, and Pacific oceans. No land or ocean areas were record cold for the year. NOAA National Centers for Environmental Information
The remarkable global warmth of 2020 means that the seven warmest years on record since 1880 were the most recent seven years — 2014 through 2020. The near-record global warmth in 2020 is all the more striking since it occurred during the minimum of the weakest solar cycle in more than 100 years and during a year without a strong El Niño. Record-warm global temperatures typically occur during strong El Niño events and when the solar cycle is near its maximum. The warmth of 2020 is a testament to how significantly human-caused global warming is heating the planet.
Figure 2. Total ocean heat content (OHC) in the top 2000 meters from 1958-2020. Cheng et al., Upper Ocean Temperatures Hit Record High in 2020, Advances in Atmospheric Sciences
Warmest Year on Record for Total Ocean Heat Content
Despite the presence of a prominent La Niña event that began in August, the total heat content of the world's oceans in 2020 was the warmest in recorded human history, according to a January 13, 2021 paper by Cheng et al., Upper Ocean Temperatures Hit Record High in 2020, published in Advances in Atmospheric Sciences. In the uppermost 2,000 meters of the oceans, there were 211 to 234 zettajoules more heat in 2020 than the 1981-2010 average, and 2020 had 1 to 20 zettajoules more ocean heat content than in 2019 (a zettajoule is one sextillion joules — ten to the 21st power). For comparison, in 2010, humans used a total of 0.5 zettajoules of energy.
More than 90% of the increasing heat from human-caused global warming accumulates in the ocean because of its large heat capacity. The remaining heating manifests as atmospheric warming, a drying and warming landmass, and melting land and sea ice. Increasing ocean heat content causes sea-level rise through thermal expansion of the water and melting of glaciers in contact with the ocean. It also produces stronger and more rapidly intensifying hurricanes; causes more intense precipitation events that can lead to destructive flooding; contributes to "marine heat waves" that damage or destroy coral reefs; and disrupts atmospheric circulation patterns.
A Slew of Heat Records in 2020
International records researcher Maximiliano Herrera keeps the pulse of the planet in remarkable detail, and he logged 11 nations or territories that set or tied their all-time heat records in 2020. That total fell far short of the record of 24 such records in 2019. No nations or territories set or tied an all-time cold record in 2020. Here are the all-time heat records set in 2020:
Colombia: 42.6°C (108.7°F) at Jerusalem, February 19 (tie);
Ghana: 44.0°C (111.2°F) at Navrongo, April 6;
Cuba: 39.2°C (102.6°F) at Palo Seco, April 10; broken again April 11 with 39.3°C (102.7°F) at Veguitas, and again on April 12 with 39.7°C (103.5°F) at Veguitas;
Mayotte, France department: 36.4°C (97.5°F) at Trevani, April 14;
Taiwan: 40.5°C (104.9°F) at Taimali Research Center, July 16;
Lebanon: 45.4°C (113.7°F) at Houche Al Oumara, July 27;
United States: 54.4°C (129.9°F) at Death Valley, California, August 16;
Japan: 41.1°C (106.0°F) at Hamamatsu, August 17;
Dominica: 35.7°C (96.3°F) at Canefield Airport, September 15;
Puerto Rico (U.S. territory): 37.8°C (100.0°F ) at Aguirre, September 17; and
Paraguay: 45.5°C (113.9°F ) at Pozo Hondo, September 26.
Among global weather stations having at least 40 years of record-keeping, Herrera documented 348 that exceeded their all-time heat record in 2020; only eight stations with a long-term period of record set an all-time cold record in 2020. For comparison, 632 stations set their all-time heat record in 2019 and 11 their all-time cold record.
Notable Global Heat and Cold Records for 2020
Hottest temperature in the Northern Hemisphere: 54.4°C (129.9°F) at Death Valley, U.S., August 16;
Coldest temperature in the Northern Hemisphere: -66.0°C (-86.8°F) at Summit, Greenland, January 2;
Hottest temperature in the Southern Hemisphere: 48.9°C (120.0°F) at Penrith Lakes, Australia, January 4;
Coldest temperature in the Southern Hemisphere: -80.8°C (-113.4°F) at Dome Fuji, Antarctica, August 16;
Highest 2020 average temperature worldwide: 31.5°C (88.7°F) at Yelimane, Mali, and Matam, Senegal; and
Highest 2020 average temperature in the Southern Hemisphere: 29.8°C (85.6°F) at Surabaya Airport, Indonesia, and Wyndham, Australia.
Earth's record for hottest yearly average temperature was 32.9°C (91.2°F) at Makkah, Saudi Arabia, in 2010 and 2016.
126 Additional Monthly National/Territorial Heat Records Beaten or Tied
In addition to the 11 all-time national heat records, 126 other national monthly heat records were set in 2020, for a total of 137 national monthly heat records:
– January (13): Norway, South Korea, Angola, Congo Brazzaville, Dominica, Mexico, Indonesia, Guinea Bissau, Gambia, Sao Tome and Principe, Cuba, British Indian Ocean Territory, Singapore;
– February (12): Spain, Antarctica, Azerbaijan, Costa Rica, The Bahamas, Switzerland, Maldives, Gambia, Russia, Seychelles, Dominican Republic, U.S. Virgin Islands;
– March (7): Paraguay, Cabo Verde, Mozambique, Seychelles, United States, Thailand, Northern Mariana Islands;
– April (14): Paraguay, Niger, St. Barthelemy, Honduras, Guernsey, Haiti, Congo Brazzaville, Kyrgyzstan, Mongolia, China, Saba, Northern Mariana Islands, U.S. Virgin Islands, Dominican Republic;
– May (10): Niger, Greece, Saba, Cyprus, Solomon Islands, Turkey, Haiti, Kazakhstan, Chile, Uzbekistan;
– June (6): Maldives, Thailand, U.S. Virgin Islands, Saba, Kenya, Ghana;
– July (7): Mozambique, U.S. Virgin Islands, Laos, Myanmar, Iran, Saudi Arabia, Northern Mariana Islands;
– August (6): Solomon Islands, Mexico, Australia, Cocos Islands, Paraguay, U.S. Virgin Islands;
– September (18): Laos, Taiwan, Japan, Turkey, Lebanon, Israel, Jordan, Cyprus, Mexico, Belgium, Netherlands, Luxembourg, Botswana, St. Barthelemy, Mayotte, Argentina, Brazil, British Indian Ocean Territory;
– October (11): Algeria, Brazil, Tunisia, Turkey, Cyprus, Jordan, Peru, Myanmar, Northern Marianas Islands, Botswana, Maldives;
– November (11): Luxembourg, Finland, Nepal, Mexico, Aland Islands, Sweden, Maldives, Northern Marianas, Taiwan, Swaziland, Sudan; and
– December (11): Mexico, Ghana, Pakistan, Algeria, Qatar, Maldives, Niger, Taiwan, Dominica, Falkland Islands, South Georgia and the Sandwich Islands.
One Monthly National/Territorial Cold Record Beaten or Tied in 2020
– April: St. Eustatius.
An October monthly record reported in Aruba was judged to be unreliable.
Hemispherical and Continental Temperature Records in 2020
– Highest minimum temperature ever recorded in the Northern Hemisphere in January: 29.1°C (84.4°F) at Bonriki, Kiribati, January 17;
– Highest maximum temperature ever recorded in North America in January: 42.0°C (107.6°F) at Vicente Guerrero, Mexico, January 21;
– Highest temperature ever recorded in continental Antarctica and highest February temperature ever recorded in Antarctica plus the surrounding islands: 18.4°C (65.1°F) at Base Esperanza, February 6;
– Highest minimum temperature ever recorded in February in Antarctica: 7.6°C (45.7°F) at Base Marambio, February 9;
– Highest minimum temperature ever recorded in February in the Northern Hemisphere: 32.0°C (89.6°F) at Yelimane, Mali, February 23;
– Highest minimum temperature ever recorded in April in the Southern Hemisphere: 31.1°C (88.0°F) at Argyle, Australia, April 2;
– Highest minimum temperature ever recorded in May in Europe: 30.1°C (86.2°F) at Emponas, Greece, May 17;
– Highest minimum temperature ever recorded in May in North America: 35.0°C (95.0°F) at Death Valley, California (U.S.), May 28;
– Highest temperature ever recorded in the polar regions: 38.0°C (100.4°F) at Verkhoyansk, Russia, June 20;
– Highest reliable temperature ever recorded on Earth: 54.4°C (129.9°F) at Death Valley, California, August 16;
– Highest reliable minimum temperature ever recorded in August in North America: 40.0°C (104.0°F) at Death Valley, California (U.S.), August 17;
– Highest temperature ever recorded in Australia and Oceana in August: 40.7°C (105.3°F) at Yampi Sound, Australia, August 22; beaten again with 41.2°C (106.2°F) at West Roebuck, Australia, on August 23; and
– Highest temperature ever recorded in the Northern Hemisphere in November: 44.8°C (112.6°F) at San Francisco and Tubares, Mexico, November 5.
December 2020: Earth's Eighth-Warmest December on Record
December 2020 was the eighth-warmest December since global record-keeping began in 1880, NOAA's National Centers for Environmental Information reported January 14. NASA and the European Copernicus Climate Change Service rated the month as the sixth-warmest December on record, and the Japan Meteorological Agency rated it as the tenth-warmest. Again: Minor differences in rankings often occur among various research groups, the result of different ways they handle data-sparse regions such as the Arctic.
Figure 3. Departure of sea surface temperature from average in the benchmark Niño 3.4 region of the eastern tropical Pacific (5°N-5°S, 170°W-120°W). Sea surface temperature were approximately one degree Celsius below average over the past month, characteristic of moderate La Niña conditions. Tropical Tidbits
A Moderate La Niña Event Continues
La Niña conditions remained in the moderate range during December and early January, prompting NOAA to continue its La Niña advisory in a January 14 monthly discussion of the state of the El Niño/Southern Oscillation, or ENSO.
Over the past month, sea surface temperatures in the benchmark Niño 3.4 region of the eastern tropical Pacific (5°N-5°S, 170°W-120°W) have been approximately 1 degree Celsius below average. The threshold for "strong" La Niña conditions is 1.5 degrees Celsius below average; "moderate" La Niña conditions are 1.0-1.5 degrees below average.
Forecasters at NOAA and at Columbia University's International Research Institute for Climate and Society expect La Niña conditions will continue through the winter (95% chance during January-February-March), and potentially transition to "neutral" during the spring (55% chance during April-May-June). About half of all La Niña events continue into a second year, but fewer than 20% of the ENSO models predicted that La Niña conditions would last into the summer of 2021.
Arctic Sea Ice: Third-Lowest December Extent on Record
Arctic sea ice extent during December 2020 was the third-lowest in the 42-year satellite record, behind 2016 and 2017, according to the National Snow and Ice Data Center. Antarctic sea ice extent in December 2020 was near-average.
Notable Global Heat and Cold Marks for December 2020
– Hottest temperature in the Northern Hemisphere: 41.5°C (106.7°F) at Matam, Senegal, December 2;
– Coldest temperature in the Northern Hemisphere: -57.5°C (-71.5°F) at Oymykon, Russia, December 29;
– Hottest temperature in the Southern Hemisphere: 48.7°C (119.7°F) at Birdsville, Australia, December 5; and
– Coldest temperature in the Southern Hemisphere: -44.9°C (-48.8°F) at Dome A, Antarctica, December 3.
Major Weather Stations' New All-Time Heat or Cold Records in December 2020
Among global stations with a record of at least 40 years, two stations set all-time cold records in December, and no stations set an all-time heat record:
Hamamasu (Japan) min. -21.5°C (-6.7°F), December 31; and
Bibai (Japan) min. -26.5°C (-15.7°F), December 31.
Statistics courtesy of Maximiliano Herrera.
Reposted with permission from Yale Climate Connections.
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