September 2020 Global Climate Report

Introduction

Temperature anomalies and percentiles are shown on the gridded maps below. The anomaly map on the left is a product of a merged land surface temperature (Global Historical Climatology Network, GHCN) and sea surface temperature (ERSST version 5) anomaly analysis. Temperature anomalies for land and ocean are analyzed separately and then merged to form the global analysis. For more information, please visit NCEI's Global Surface Temperature Anomalies page. The percentile map on the right provides additional information by placing the temperature anomaly observed for a specific place and time period into historical perspective, showing how the most current month, season or year compares with the past.

Temperature

In the atmosphere, 500-millibar height pressure anomalies correlate well with temperatures at the Earth's surface. The average position of the upper-level ridges of high pressure and troughs of low pressure—depicted by positive and negative 500-millibar height anomalies on the September 2020 map—is generally reflected by areas of positive and negative temperature anomalies at the surface, respectively.

Monthly Temperature: September 2020

During September 2020, warmer-than-average temperatures were present across much of the globe. Temperature departures of +1.5°C (+2.7°F) or higher were observed across parts of the North Pacific Ocean, western parts of Canada and the U.S., the North Atlantic Ocean, South America, Europe, Asia, Australia, and Antarctica. Record-warm September temperatures departures were present across the Middle East and Mediterranean Sea, northern and southern parts of Asia, Kara Sea, the north and western Pacific Ocean, Indian Ocean, northwestern Australia, as well as parts of South America and the western contiguous U.S. Overall, about 8.49% of the world's land and ocean surfaces had a record-warm September temperature. This was the second highest September percentage since records began in 1951, behind September 2015. Cooler-than-average conditions were limited to parts of Greenland and adjacent portions of the North Atlantic Ocean, eastern Canada, the eastern U.S., the tropical eastern and central Pacific Ocean, the southern Indian Ocean, and the western part of Asia and northern Africa. However, no land or ocean areas had record-cold September temperatures.

Regionally, Europe had its warmest September with a temperature departure of +2.33°C (+4.19°F), exceeding the now second warmest September set in 2015, 2017, and 2018 by 0.22°C (0.40°F). Europe's five warmest Septembers have occurred since 2006. Meanwhile, South America, Asia, and Oceania had their second-warmest September since regional records began in 1910.

September 2020 Blended Land and Sea Surface Temperature Anomalies in degrees Celsius

September 2020 Blended Land and Sea Surface Temperature Percentiles

Averaged as a whole, the September 2020 global land and ocean surface temperature was the highest for September in the 141-year record at 0.97°C (1.75°F) above the 20th century average of 15.0°C (59.0°F). This value surpassed the previous record set in 2015 and, again in 2016, by only 0.02°C (0.04°F). The month of September 2020 marked the 44th consecutive September and the 429th consecutive month with temperatures, at least nominally, above the 20th century average. The ten warmest Septembers have occurred since 2005, while the seven warmest Septembers have occurred in the last seven years (2014–2020).

The global land-only surface temperature for September was also the highest on record at 1.47°C (2.65°F) above average. The previous record of 1.40°C (2.52°F) was set in September 2016. Record warm September temperatures across the global land encompassed 12.55% of the global land surface—the highest on record. This was also the sixth highest percentage for record warm land temperatures for any month in the 837-monthly record. Meanwhile, the global ocean-only surface temperature for September 2020 was 0.77°C (1.39°F) and the fourth highest since global records began in 1880. Only Septembers of 2015, 2016, and 2019 were warmer.

The Southern Hemisphere land and ocean surface temperature departure from average for September 2020 was also the highest on record at 0.70°C (1.26°F) above average. This value exceeded the previous record set in September 2015, 2017, and 2018 by 0.01°C (0.02°F). The Southern Hemisphere's five warmest Septembers have occurred since 2014. Meanwhile, the Northern Hemisphere had its third-warmest September on record with a combined land and ocean surface temperature departure from average of 1.21°C (2.18°F).

September Global Land and Ocean Plot

September Global Hemisphere Plot

The most current data can be accessed via the Global Surface Temperature Anomalies page.

Select national information is highlighted below. Please note that different countries report anomalies with respect to different base periods. The information provided here is based directly upon these data:

• The Netherlands observed its warmest September day on record when the temperatures rose to 35.1°C (95.2°F) on September 15, 2020 in the municipality of Gilze-Rijen. The previous record of 34.2°C (93.6°F) was set on September 4, 1929 in Maastricht.
• The Kingdom of Bahrain's September 2020 mean temperature was 2.4°C (4.3°F) above average and the highest for September since national records began in 1902. The previous record was set in September 2017 (+2.2°C / +4.0°F). The national maximum temperature was also the highest for September on record. According to the Kingdom of Bahrain's Ministry of Transportation and Telecommunications, Bahrain had 10 days where the maximum (daytime) temperature was over 40.0°C (104.0°F). On September 9, the Bahrain International Airport had a maximum temperature of 43.7°C (110.7°F)—the fifth highest maximum temperature in the 75-year record for September.
• Warmer-than-average temperatures engulfed much of Australia during September 2020, resulting in a national mean temperature departure of 2.55°C (4.59°F) above the 1981–2010 average and the second warmest September in the 111-year national record. Only September of 2013 was warmer at +2.84°C (+5.11°F). The national maximum temperature was also the second highest on record, while the minimum temperature for Australia was the highest for September on record. Regionally, Queensland, South Australia, Western Australia, and the Northern Territory had a September mean temperature that ranked among the top two highest for September on record.

Year-to-date Temperature: January–September 2020

The January–September global land and ocean surface temperature was 1.02°C (1.84°F) above average and the second highest such period in the 141-year record. This was only 0.04°C (0.07°F) shy of tying the record set in 2016. According to NCEI's temperature ranking outlook, there is nearly a 65% chance of 2020 ending as the warmest year on record and about 35% chance of it being the second warmest year on record.

During the first nine months of the year, warmer-than-average temperatures were present across much of the global land and ocean surfaces. The most notable warm temperature departures were observed across northern Asia, where temperatures were at least 3.0°C (5.4°F) above average. Record-warm January–September temperatures were observed across much of northern Asia and across parts of southeastern China, Europe, northern Africa, northern South America, Central America as well as the Atlantic, Indian, and Pacific oceans. Meanwhile, cooler-than-average temperatures were limited to Alaska, western Canada, northern India, and across the southern oceans. However, no land or ocean areas had a record-cold January–September temperature.

January–September 2020 Blended Land and Sea Surface Temperature Anomalies in degrees Celsius

January–September 2020 Blended Land and Sea Surface Temperature Percentiles

Regionally, Europe, Asia, and the Gulf of Mexico had their warmest January–September period on record. Europe's year-to-date temperature of 2.12°C (3.82°:F) marked the first time the January–September temperature was over 2.0°C (3.6°F) and bested the previous record set in 2018 by 0.16°C (0.29°F). Similarly, Asia's year-to-date temperature departure was +2.30°C (+4.14°F), marking only the second time Asia's January–September temperature departure surpassed 2.0°C (3.6°F). This value was also 0.30°C (0.54°F) higher than the now second warmest such period set in 2016. Also, the Gulf of Mexico's 2020 year-to-date temperature was 0.92°C (1.66°F) above average and exceeded the previous record set in 2017 by 0.13°C (0.23°F).

Meanwhile, South America and the Caribbean region had a January–September temperature departure that ranked as the second highest on record.

According to Spain's Agencia Estatal de Meteorología, the January–September 2020 national temperature is the highest since national records began in 1961 and exceeding the previous record set in 2017 by 0.1°C (0.2°F).

January–September Global Land and Ocean Plot

January–September Global Hemisphere Plot

Precipitation

September Precipitation

September 2020 Land-Only Precipitation Anomalies

September 2020 Land-Only Precipitation Percent of Normal

The maps shown above represent precipitation percent of normal (left, using a base period of 1961–1990) and precipitation percentiles (right, using the period of record) based on the GHCN dataset of land surface stations. As is typical, precipitation anomalies during September 2020 varied significantly around the world. September 2020 precipitation was generally drier than normal across parts of the southwestern and northern contiguous U.S., central and southern South America, western and northern Europe, western and northern Russia, northern Asia, and western and eastern parts of Australia. Wetter-than-average conditions were present across parts of the southeastern contiguous U.S., central Europe, Scandinavia, central and southeastern Asia, and southern and northern parts of Australia.

Global Precipitation Climatology Project (GPCP)

The following analysis is based upon the Global Precipitation Climatology Project (GPCP) Interim Climate Data Record. It is provided courtesy of the GPCP Principal Investigator team at the University of Maryland.

The Global Precipitation Climatology Project (GPCP) monthly data set is a long-term (1979-present) analysis (Adler et al., 2018) using a combination of satellite and gauge information. An interim GPCP analysis completed within ~10 days of the end of the month allows its use in climate monitoring.

September 2020 GPCP precipitation anomalies

April-September 2020 GPCP precipitation percent anomalies

As the globe slides into the transition seasons of Fall in the Northern Hemisphere and Spring in the Southern Hemisphere, the summer monsoon in Asia is still active with significant rains, and the tropical cyclone season across the Pacific and Atlantic basins is well underway. A weak La Niña in the central/western Pacific is also evident. These and other large-scale (and smaller-scale) processes provide the drive for the precipitation patterns observed this month. Overlying these effects are trends in the precipitation patterns associated with global warming.

Figure 1 (top panel) presents the typical features of the summer monsoon over southeast Asia providing its usual heavy rainfall over the area. The ITCZ stretches across the Pacific and Atlantic above the Equator. Additional peaks are over Africa and South America, again north of the Equator, and at middle latitudes over ocean and land.

Over North America the anomaly chart (Fig. 1, middle panel) shows a few positive anomalies along the Gulf coast related partially to tropical cyclone activity, but a large negative area across the western part of the continent. This region has been undergoing a long-term drought and an especially intense wildfire season this year. This rainfall deficit over land is connected to the larger sub-tropical dry zone to the west extending from the U.S. west coast to past Hawaii (see all panels in Fig. 1). To the south of this feature the ITCZ is evident with a narrow east-west positive anomaly (middle and bottom panels) with a break and then another positive anomaly in the far eastern Pacific associated with tropical cyclone tracks from the ITCZ to the northwest. To the south of the ITCZ another east-west band of negative anomalies is evident. This anomaly pattern in the eastern Pacific has been persistent as can be seen in Fig. 2, which shows results from the last six months and is a classic wet-getting-wetter (in the ITCZ), dry-getting-drier (in the sub-tropics) scenario in this region. Even rainfall trend maps in this region (not shown) show this type of feature over the last 40 years.

In relation to these rainfall features, Lau and Tao (2020) have explored circulation and other changes that are related to sub-tropical drying in certain regions as seen in the Figs. 1 and 2. One feature of these changes is a shrinking and intensification of the ITCZ indicating increasing upward motion there and an associated drying to the north of the that zone indicating increased subsidence there, essentially an intensification of the north-south Hadley circulation in this area. In this context, the GPCP monthly precipitation data were examined over the last few months and for the entire record of GPCP?back to 1979.

June-September Percentage change difference

A summary result is shown in Fig. 3, where an index based on rainfall anomalies in the eastern Pacific and western North America zone is shown for the combined months of June-September. The index is the gradient between the ITCZ and the sub-tropics, in percentage rainfall anomaly terms because of the large mean rainfall differences between the two areas. Two things are immediately evident: 1) there is a gradual trend indicating a strengthening of the Hadley circulation over the 40-year period; and 2) that for the last few years, especially 2020, the north-south circulation was very strong, and was likely associated with drying over the mid-latitude zone. The trend may reflect a circulation trend associated with increased drying and increases in wildfire occurrences in the western U.S. The very high values for this year may be related to the harsh wildfire season this year. The trend, likely related to global warming (with possible influence from a Pacific Decadal Oscillation (PDO) shift around 1998), shows changes happening over the last 40 years related to circulation changes which result in rainfall distribution changes, not just over land, but over the ocean. Further examination of these relations is needed, but the results clearly indicate the value of precipitation information over both land and ocean to understand regional changes.

Elsewhere, strong positive anomalies exist over much of eastern China in September (Fig. 1, middle panel), where repetitive flooding has occurred through the summer season. Floods also occurred in Korea, both North and South and in western Japan this month due to tropical cyclones. A strip of positive anomalies running across southern India and the Bay of Bengal ends up in the Maritime Continent (MC). To the east of there, along the Equator over the western to central Pacific a negative anomaly of rainfall exists, just to the south of the ITCZ position this month. In actuality, the ITCZ is shifted northward from its normal position. The positive anomaly over the MC and this negative anomaly along the Equator is a likely result of the current weak La Niña, with negative SST anomalies along the central Pacific Equator. Over Australia positive rainfall anomalies cover a majority of the country, typical of La Niña conditions there in spring. These regional rainfall anomaly features may strengthen over the coming months if the La Niña persists, as forecasted.

Over Africa the ITCZ over land is strong this month with positive anomalies running east-west across the continent at 10 N. The rainfall features are related to flooding, especially in Sudan where flooding has been persistent during this rainy season, especially along the White Nile. Further west, flooding in Chad and along the west coast occurred. Even further to the west into the eastern Atlantic, tropical systems have been active, but often turning toward the extra-tropics as can be seen from the pattern of mean rainfall and anomalies (Fig. 1) through the central Atlantic affecting the Bermuda area, the Canadian maritime provinces and even further north towards Europe. The Gulf of Mexico was also active in September, with landfalling storms affecting coastal areas from Florida to Texas as seen in the positive anomalies.

In South America the continent is dominated by precipitation deficits in September, especially in southeast Brazil. The negative rainfall anomalies have persisted for months in this general area as part of a long-term drought that is also related to continuing wildfire issues in the Amazon.

Background discussion of long-term means, variations and trends of global precipitation can be found in Adler et al. (2017).

Ocean Heat Content

Ocean Heat Content (OHC) is essential for understanding and modeling global climate since > 90% of excess heat in the Earth's system is absorbed by the ocean. Further, expansion due to increased ocean heat contributes to sea level rise. Change in OHC is calculated from the difference of observed temperature profiles from the long-term mean.

Global OHC for July–September 2020 tied with July–September 2018 for the second highest July–September OHC in our records, which extend back to 1955. Overall, the latest quarterly OHC reveals widespread warmer than normal conditions relative to the 1955–2006 mean, a situation observed since the end of 2016. However, a significant drop in the global OHC since January–March 2020 has occurred, which concides with the development in the last six months of a La Niña event. Warmer than normal conditions, > 10x10⁵ J/m³, in the tropical and subtropical Western Pacific Ocean extend into the Central Pacific Ocean south of the Equator. In contrast, cool conditions, < -10x10⁵ J/m³, in the tropical and subtropical Eastern Pacific Ocean extend westward around the Equator from the South America coast to about 170E. Much higher, > 30x10⁵ J/m³, than normal OHC conditions continue to exist in the Gulf Stream/North Atlantic Current, the Southwestern Atlantic Ocean, and the Tasman Sea. Cool conditions, < -10x10⁵ J/m³, still appear along the south and west coast of Australia. Similarly, cooler than normal conditions persist in the subpolar North Atlantic Ocean south of Greenland and Iceland, and in the Norwegian Sea. Much warmer than normal conditions, > 30x10⁵ J/m³, exist along the Kuroshio Current/Kuroshio Extension/North Pacific Current, the Scotia Sea, and Northwestern Weddell Sea. Warm conditions dominate the North Indian Ocean.

References

• Adler, R., G. Gu, M. Sapiano, J. Wang, G. Huffman 2017. Global Precipitation: Means, Variations and Trends During the Satellite Era (1979-2014). Surveys in Geophysics 38: 679-699, doi:10.1007/s10712-017-9416-4
• Adler, R., M. Sapiano, G. Huffman, J. Wang, G. Gu, D. Bolvin, L. Chiu, U. Schneider, A. Becker, E. Nelkin, P. Xie, R. Ferraro, D. Shin, 2018. The Global Precipitation Climatology Project (GPCP) Monthly Analysis (New Version 2.3) and a Review of 2017 Global Precipitation. Atmosphere. 9(4), 138; doi:10.3390/atmos9040138
• Gu, G., and R. Adler, 2022. Observed Variability and Trends in Global Precipitation During 1979-2020. Climate Dynamics, doi:10.1007/s00382-022-06567-9
• Huang, B., Peter W. Thorne, et. al, 2017: Extended Reconstructed Sea Surface Temperature version 5 (ERSSTv5), Upgrades, validations, and intercomparisons. J. Climate, doi: 10.1175/JCLI-D-16-0836.1
• Huang, B., V.F. Banzon, E. Freeman, J. Lawrimore, W. Liu, T.C. Peterson, T.M. Smith, P.W. Thorne, S.D. Woodruff, and H-M. Zhang, 2016: Extended Reconstructed Sea Surface Temperature Version 4 (ERSST.v4). Part I: Upgrades and Intercomparisons. J. Climate, 28, 911-930, doi:10.1175/JCLI-D-14-00006.1.
• Menne, M. J., C. N. Williams, B.E. Gleason, J. J Rennie, and J. H. Lawrimore, 2018: The Global Historical Climatology Network Monthly Temperature Dataset, Version 4. J. Climate, in press. https://doi.org/10.1175/JCLI-D-18-0094.1.
• Peterson, T.C. and R.S. Vose, 1997: An Overview of the Global Historical Climatology Network Database. Bull. Amer. Meteorol. Soc., 78, 2837-2849.
• Vose, R., B. Huang, X. Yin, D. Arndt, D. R. Easterling, J. H. Lawrimore, M. J. Menne, A. Sanchez-Lugo, and H. M. Zhang, 2021. Implementing Full Spatial Coverage in NOAA's Global Temperature Analysis. Geophysical Research Letters 48(10), e2020GL090873; doi:10.1029/2020gl090873.

Citing This Report

Metadata