State of the climate in 2020

Jessica Blunden, T. Boyer, Robert J.H. Dunn, Jessicca Allen, Andrea Andersen, Gregory Hammer, S. Elizabeth Love-Brotak, Deborah J. Misch, Deborah B. Riddle, Sara W. Veasey, M. Ades, Robert Adler, F. Aldred, Richard P. Allan, Rob Allan, J. Anderson, Anthony Argüez, C. Arosio, John A. Augustine, C. Azorin-MolinaJ. Barichivich, H. E. Beck, Andreas Becker, Nicolas Bellouin, Angela Benedetti, David I. Berry, Stephen Blenkinsop, Olivier Bock, X. Bodin, Michael G. Bosilovich, Olivier Boucher, S. A. Buehler, B. Calmettes, Laura Carrea, Laura Castia, Hanne H. Christiansen, John R. Christy, E. S. Chung, Melanie Coldewey-Egbers, Owen R. Cooper, Richard C. Cornes, Curt Covey, M. F. McCabe, T. Park, S. Sharma, Lei Shi, Hui Wang, John E. Walsh, Lei Wang, Wei Wang

Research output: Contribution to journalReview articlepeer-review

58 Scopus citations

Abstract

In 2020, the dominant greenhouse gases stored in Earth’s atmosphere continued to increase. The annual global average carbon dioxide (CO2) concentration at Earth’s surface was 412.5 ± 0.1 ppm, an increase of 2.5 ± 0.1 ppm over 2019, and the highest in the modern instrumental record and in ice core records dating back 800,000 years. While anthropogenic CO2 emissions were estimated to decrease around 6%–7% globally during the year due to reduced human activities during the COVID-19 pandemic, the reduction did not materially affect atmospheric CO2 accumulation as it is a relatively small change, less even than interannual variability driven by the terrestrial biosphere. The net global uptake of ~3.0 petagrams of anthropogenic carbon by oceans in 2020 was the highest in the 39-year record and almost 30% higher than the 1999–2019 average. Weak El Niño-like conditions in the eastern equatorial Pacific Ocean in early 2020 cooled and transitioned to a moderate La Niña later in the year. Even so, the annual global surface temperature across land and oceans was among the three highest in records dating to the mid- to late 1800s. In Europe, 17 countries reported record high annual mean temperatures, contributing to the warmest year on record for the European continent. Elsewhere, Japan, Mexico, and Seychelles also experienced record high annual mean temperatures. In the Caribbean, Aruba, Martinique, and St. Lucia reported their all-time monthly maximum temperatures. In the United States, Furnace Creek in Death Valley, California, reached 54.4°C on 16 August—the hottest temperature measured on Earth since 1931, pending confirmation. North of 60°N, the annual mean temperature over Arctic land areas was 2.1°C above the 1981–2010 average, the highest in the 121-year record. On 20 June, a temperature of 38°C was observed at Verkhoyansk, Russia (67.6°N), provisionally the highest temperature ever measured within the Arctic Circle. Near the opposite pole, an atmospheric river—a long, narrow region in the atmosphere that transports heat and moisture from sub-tropical and midlatitudes—brought extreme warmth from sub-tropical and midlatitudes to parts of Antarctica during austral summer. On 6 February, Esperanza Station recorded a temperature of 18.3°C, the highest temperature recorded on the continent, surpassing the previous record set in 2015 by 1.1°C. The warmth also led to the largest late-summer surface melt event in the 43-year record, affecting more than 50% of the Antarctic Peninsula. In August, daily sea ice extent in the waters surrounding Antarctica shifted from below to above average, marking the end of persistent below-average sea ice extent since austral spring 2016. In the Arctic, when sea ice reached its annual maximum extent in March, thin, first-year ice comprised ~70% of the ice; the thickest ice, which is usually more than four years old, had declined by more than 86% since 1985 to make up just 2% of total ice in 2020. When the minimum sea ice extent was reached in September, it was the second smallest except for 2012 in the 42-year satellite record. The Northern Sea Route along the Siberian coast was open for about 2.5 months, from late July through mid-October, compared to less than a month typically. Glaciers across the global cryosphere lost mass for the 33rd consecutive year, and permafrost temperatures continued to reach record highs at many high latitude and mountain locations. In the Northern Hemisphere, lakes froze three days later and thawed 5.5 days earlier on average. In Finland, the average duration of lake ice was 42 days shorter. Record high spring temperatures in central Siberia drove rapid snow melt that contributed to the lowest June snow cover extent across Eurasia in the 54-year record. As is typical, some areas around the world were notably dry in 2020 and some were notably wet. The Middle East experienced an extreme drought during autumn, with most places reporting no precipitation in October. In South America, the Bolivian lowlands suffered one of its most severe droughts on record during autumn. Drought also spanned the Chaco and Pantanal in Bolivia, Paraguay, and southern Brazil. The Paraguay River shrank to its lowest levels in half a century. A decadal “mega drought” in south-central Chile continued through its 11th year, with extreme conditions in the most populated areas. Argentina reported its driest year since 1995. In North America, drought continued to prevail in the West. The lack of moisture in drought-stricken regions often provide ideal conditions for fire. Total fire emissions in the western United States in 2020 were almost three times higher than the 2003–10 mean. The Arctic experienced its highest fire year in terms of carbon emitted into the atmosphere, surpassing the record set in 2019 by 34%, with most of the fires occurring in Arctic Asia. In the tropics, the Amazon saw its highest fire activity since 2012, while fire activity in tropical Asia—including Indonesia—was one of the lowest on record, related to wet conditions as La Niña evolved during the fire season. The 2020 Southwest Asian Monsoon season (June–September) was the wettest since 1981, also coincident with the emergence of La Niña. The Meiyu rainy season, which usually occurs between July and August over the Yangtze and Huaihe River Valleys of China, was extended by two months in 2020. The May–October total rainfall averaged over the area was the most since the start of the record in 1961. Associated severe flooding affected about 45.5 million people. A widespread desert locust infestation during 2019–20 impacted equatorial and northern East Africa, as heavy rains and prevailing winds were favorable for breeding and movement of swarms across Kenya, Ethiopia, northeastern Somalia, Uganda, South Sudan, and northern Tanzania. The massive infestation destroyed thousands of square kilometers of cropland and pasture lands, resulting in one million people in need of food aid in Ethiopia alone. Extremely heavy rains in April also triggered widespread flooding and landslides in Ethiopia, Somalia, Rwanda, and Burundi. The Lake Victoria region was the wettest in its 40-year record. Across the global oceans, the average ocean heat content reached a record high in 2020 and the sea surface temperature was the third highest on record, surpassed only by 2016 and 2019. Approximately 84% of the ocean surface experienced at least one marine heatwave (MHW) in 2020. For the second time in the past decade, a major MHW developed in the northeast Pacific, covering an area roughly six times the size of Alaska in September. Global mean sea level was record high for the ninth consecutive year, reaching 91.3 mm above the 1993 average when satellite measurements began, an increase of 3.5 mm over 2019. Melting of the Greenland Ice Sheet accounted for about 0.8 mm of the sea level rise, with an overall loss of 293 ± 66 gigatons of ice. A total of 102 named tropical storms were observed during the Northern and Southern Hemisphere storm seasons, well above the 1981–2010 average of 85. In the North Atlantic, a record 30 tropical cyclones formed, surpassing the previous record of 28 in 2005. Major Hurricanes Eta and Iota made landfall along the eastern coast of Nicaragua in nearly the same location within a two-week period, impacting over seven million people across Central America. In the western North Pacific, Super Typhoon Goni was the strongest tropical cyclone to make landfall in the historical record and led to the evacuation of almost 1 million people in the Philippines. Very Severe Cyclonic Storm Gati was the strongest recorded cyclone to make landfall over Somalia. Bosaso, in northeast Somalia, received 128 mm of rainfall in a 24-hour period, exceeding the city’s average annual total of 100 mm. Above Earth’s surface, the annual lower troposphere temperature equaled 2016 as the highest on record, while stratospheric temperatures continued to decline. In 2020, the stratospheric winter polar vortices in both hemispheres were unusually strong and stable. Between December 2019 and March 2020, the Arctic polar vortex was the strongest since the beginning of the satellite era, contributing to record low stratospheric ozone levels in the region that lasted into spring. The anomalously strong and persistent Antarctic polar vortex was linked to the longest-lived, and 12th-largest, ozone hole over the region, which lasted to the end of December.

Original languageEnglish (US)
Pages (from-to)1-481
Number of pages481
JournalBulletin of the American Meteorological Society
Volume102
Issue number8
DOIs
StatePublished - Aug 2021

Bibliographical note

Funding Information:
Ted Scambos was supported under NASA grant NN1X 4AM54G, the Arctic Sea Ice News and Analysis project and NSF ANT 1738992, the NSF-NERC International Thwaites Glacier Collaboration TARSAN project.

Funding Information:
• Walt Meier’s contribution was supported by the NASA Snow and Ice Distributed Active Archive Center (DAAC) at NSIDC, part of the NASA Earth Science Data and Information System (ESDIS) Project.

Funding Information:
• R. E. Killick is supported by the Met Office Hadley Centre Climate Programme funded by BEIS and Defra. PMEL contribution numbers 5214, 5215, 5216, 5217, and 5247.

Funding Information:
Richard Cornes, David Berry, and Elizabeth Kent were funded by the NERC CLASS programme (NE/R015953/1), the NERC GloSAT project (NE/S015647/2), and the Copernicus Climate Change Service (C3S_311a_Lot2). The UAHNMATv1 work was supported by the U.S. Department of Energy (DE-SC0005330 and DE-SC0019296.

Funding Information:
• The material is based upon work supported in part by the National Science Foundation award #OIA-1753748, by the State of Alaska, by the Joint Fire Science Program award #20-3-01-1, by the NOAA Climate Program Office through Grant NA16OAR4310162 with the Alaska Center for Climate Assessment and Policy at the University of Alaska at Fairbanks, and by the NASA Weather and Data Analysis program.

Funding Information:
• L. Cheng is supported by National Natural Science Foundation of China (42076202) and Strategic Priority Research Program of the Chinese Academy of Sciences (XDB42040402.

Funding Information:
• Thomas Ballinger was supported by the Experimental Arctic Prediction Initiative at the University of Alaska Fairbanks. • Melinda Webster was supported by NASA’s Weather and Atmospheric Dynamics program under 80NS-SC20K0922.

Funding Information:
• Max Holmes and coauthors acknowledge National Science Foundation support for the Arctic Great Rivers Observatory (NSF 1913888, 1914081, 1914215, 1913962). • Shiklomanov and Tretiakov acknowledge support from the Russian Foundation for Basic Research (grants 18-05-60192 and 18-05-60240).

Funding Information:
We would like to acknowledge the national and/or hydrometeorological services/bureaus of Morocco, Algeria, Egypt, Senegal (National Aviation and Meteorology Agency), Nigeria, Ethiopia, Kenya, Tanzania, Burundi, Rwanda, South Africa, Madagascar, Seychelles, Comoros Mayotte (France), Reunion (France), and Mauritius. • We acknowledge support by the NOAA-CPC International Desk. Global data sets from NCEP./NCAR and GPCP are acknowledged. • Samson Hagos and Zhe Feng are supported by the U.S. Department of Energy Office of Science Biological and Environmental Research as part of the Atmospheric Systems Research (ASR) Program.

Funding Information:
Work at the Jet Propulsion Laboratory, California Institute of Technology, was done under contract with the National Aeronautics and Space Administration (NASA). The authors would like to acknowledge Margit Aun from University of Tartu, Servicio Meteorológico Nacional (SMN) in Argentina, Spanish Agencia Estatal de Meteorología (AEMET), Argentinian Dirección Nacional del Antártico-Instituto Antártico Argentino (DNA-IAA), and Academy of Finlands' projects FARPOCC and SAARA for Marambio data. Kaisa Lakkala is supported by the CHAMPS project (grant no. 329225) of the Academy of Finland under the CLIHE programme. We are indebted to the many NOAA Corps Officers and GML technical personnel who spend the winters at the South Pole Station to obtain the ongoing balloon and ground-based datasets. We also acknowledge the logistics support in Antarctica provided by the National Science Foundation Office of Polar Programs.

Funding Information:
• Data from the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) were provided by the Geological Survey of Denmark and Greenland (GEUS) at http://www.promice.dk. • Twila Moon was supported by the University of Colorado Boulder Cooperative Institute for Research in Environmental Sciences. • Marco Tedesco was supported by National Science Foundation ANS #1713072, National Science Foun - dation PLR-1603331, NASA MAP #80NSSC17K0351, NASA #NN1X 7AH04G, and the Heising-Simons foundation. • Thomas Mote was supported by National Science Foundation #1900324.

Funding Information:
• Germar Bernhard and coauthors acknowledge the support of Biospherical Instruments, San Diego; the Research Council of Norway through its Centres of Excellence funding scheme, project number 223268/ F50; the Academy of Finland for supporting UV measurements through the FARPOCC, SAARA, and CHAMPS (grant no. 329225) projects; the European Space Agency for supporting the DACES project; the Norwegian Environment Agency for funding UV measurements at Andøya and Ny-Ålesund; and the European Union for supporting e-shape. The authors also thank the Microwave Limb Sounder team at NASA’s Jet Propulsion Laboratory for data-processing and analysis support, and Juha M. Karhu, Tomi Karppinen, and Markku Ahponen from the Finnish Meteorological Institute for operating the Brewer UV spectroradiometer at Sodankylä .

Funding Information:
Phil Reid and Jan Lieser were supported through the Australian Bureau of Meteorology, and Rob Massom by the Australian Antarctic Division. The work of Phil Reid and Rob Massom was also supported by the Australian Government’s Australian Antarctic Partnership Program and contributes to AAS Project 4116.

Funding Information:
Veronica Tamsitt acknowledges support of CSHOR; CSHOR is a joint research Centre for Southern Hemisphere Ocean Research between QNLM and CSIRO. Air–sea heat flux data and code used in section 6g can be accessed online from doi:10.5281/zenodo.4595930. This is PMEL contribution number 5218.

Funding Information:
• Valuable climate information was provided by National Meteorological and Hydrological Services of the WMO RA VI Region, either by direct submission to the authors or via the web. • Valentina Khan acknowledges the support of Ministry of Science and Higher Education of the Russian Federation (Agreement No.075-15-2021-577 with A.M. Obukhov Institute of Atmospheric Physics RAS).

Funding Information:
Sandra Barreira was supported by the Argentine Naval Hydrographic Service.

Funding Information:
Sharon Stammerjohn was supported under NSF PLR 1440435 she also thanks the Institute of Arctic and Alpine Research and the National Snow and Ice Data Center, both at the University of Colorado Boulder, for institutional and data support.

Funding Information:
• Hazel Shapiro was supported by the Interagency Arctic Research Policy Committee and the Arctic Research Consortium of the United States (NSF grant #PLR-1928794). • Sandy Starkweather appreciates support from NOAA’s Arctic Research Program. • All the authors appreciate the support of the subject matter experts who contributed their time and expertise, and the Arctic Data Center for their partnership in creating a searchable online catalog of the 2020 data products referenced in this study.

Funding Information:
Wouter A. Dorigo, L. Moesinger, and R. M. Zotta acknowledge the TU Wien Wissenschaftspreis 2015, a personal grant awarded to Wouter Dorigo.

Publisher Copyright:
© 2021 American Meteorological Society.

ASJC Scopus subject areas

  • Atmospheric Science

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