September 2020 Temperature Update

The following is a summary of global temperature conditions in Berkeley Earth’s analysis of September 2020.

  • September 2020 was the warmest September since records began in 1850.
  • This includes the warmest September in land areas and the fourth warmest in ocean areas.
  • Record-setting warmth occurred over parts of the Arctic Ocean, coincident with the second-lowest Arctic sea ice extent on record.
  • A weak to moderate La Niña continues in the Pacific.
  • With 9 months completed, 2020 is approximately tied with 2016 as the warmest year since instrumental measurements began.
  • We estimate a 57% chance that 2020 ends as the warmest year.

Global Summary

Globally, September 2020 is found to have been the warmest September since records began in 1850, slightly exceeding the record set in 2019. Previously in 2020, April, May, June, and July have each been record warm or tied the previous record.

The global mean temperature in September 2020 was 0.91 ± 0.06 °C (1.64 ± 0.10 °F) above the 1951 to 1980 average.

This is equivalent to being 1.26 ± 0.08 °C (2.27 ± 0.14 °F) above the 1850 to 1900 average, which is frequently used as a benchmark for the preindustrial period.

The global mean temperature anomaly in September 2020 was a tick upward from July and August, though still cooler than in the first six months of the year. The current values are close to the long-term trend line associated with recent global warming.

Spatial Variation

September 2020 continues the ongoing pattern of wide-spread warmth. Particularly warm conditions were present in parts of Asia, the Middle East, South America, and Australia. Record setting warmth was also present in parts of the Arctic Ocean and North Pacific. Significantly cool temperatures occurred in central Pacific and central Asia.

The extreme warmth in the Arctic Ocean was associated with sea ice declining to the second lowest sea ice extent on record. Subsequently, the refreezing of the Arctic Ocean has also been extremely slow. This has led to the longest period of open seaways in the Arctic Ocean observed in the satellite era.

We estimate that 5.5% of the Earth’s surface experienced their locally warmest September average, and 72% of the Earth’s surface was significantly warmer when compared to their local average during the period 1951 to 1980. No locations had their locally coldest September.

The continuing development of a cool area in the Eastern Pacific, first observed in June, is indicative of moderate La Niña conditions.

Over land regions, 2020 was the warmest September, coming in as 1.54 ± 0.03 °C (2.77 ± 0.05 °F) above the 1951 to 1980 average. This is, by a considerable margin, the warmest September ever observed over land. Somewhat remarkably, this record-setting warmth can not tied to extreme values in any specific region but occurred due to warm temperatures present in many locations.

September 2020 was nominally the fourth warmest September in the oceans, recorded as 0.56 ± 0.07 °C (1.01 ± 0.11 °F) above the 1951 to 1980 average, though 2020 is essentially tied with 2019 and 2016 for the second warmest September in the oceans.  However, all of these years are below the record warm September in the oceans set in 2015.

La Niña

September 2020 demonstrates weak to moderate La Niña conditions in the Pacific Ocean. This weather phenomenon is characterized by the emergence of relatively cool ocean water in the Eastern Central Pacific and would be expected to have a significant impact on global weather patterns over the next several months. La Niña is expected to peak this winter.

La Niña conditions this fall and winter would be expected to reduce global mean temperature towards the end of 2020 and in early 2021. Such conditions also tend to reduce the likelihood that 2020 becomes a record warm year, though that effect has been muted so far.

September model forecast from IRI/CPC showing the likely evolution of La Niña conditions during the latter half of 2020 and first half of 2021.

2020 January to September Summary

After 9 months, the Earth in 2020 has been marked by above average temperatures nearly everywhere, with especially extreme conditions across Asia. We estimate that the January to September average has been record warm for 10.3% of the Earth, and appreciably above the 1951 to 1980 average for 91% of the Earth. Only, 1.0% of the Earth’s surface was significantly cooler than the 1951 to 1980 average during the current January to September period, and no locations were record cool.

In addition, the January to September averages for Asia and Europe have set new record highs.

Looking at regions where January to September temperature averages were either the top 5 warmest or the top 5 coldest observed, we note extensive regions with record or near-record warmth during the first nine months of 2020 and no regions of near-record cold.

Rest of 2020

Of the first nine months of 2020, April, May, June, July, and September each set or tied a record for warmth. Other months were each no lower than the fourth warmest. Overall, the January to September average is essentially tied with 2016 as the warmest start to a year. In 2016 temperatures were boosted due to a massive El Niño event. It is remarkable that 2020 is approaching the same level of warmth despite the emergence of La Niña conditions this year.

The projected warmth during the second half of the year remains quite high. However, the emergence of a cool pattern over the Eastern Central Pacific and a moderate La Niña event expected to peak this winter suggests that temperatures at the end of 2020 may be cooler than otherwise expected. By contrast, the persistent low sea ice in the Arctic may further contribute to relative warmth. If 2020 sets a new record for warmest year, the extraordinary conditions over Eurasia this year will have played a prominent role.

The statistical approach that we use now believes that 2020 has an 57% likelihood of surpassing 2016 and becoming the warmest year that has been directly measured. This is an increase from the previous forecast that placed the odds of a new record at 36%. This increase in probability is driven by the surprising warmth in September in spite of the ongoing La Niña.

Regardless of whether a new record is set, it remains highly likely that 2020 will be either the warmest or second warmest year since 1850.

Likelihood of final 2020 ranking, based on January to July:

  • 1st place (57%)
  • 2nd place (42%)
  • 3rd place (1%)
  • Top 3 overall (>99%)

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