Antarctica's 18.3°C Record at Esperanza Base, Explained

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Originally published 2020-02-10.

The highest temperature ever officially recorded on the Antarctic continent is 18.3°C (64.9°F). It was measured on 6 February 2020 at Esperanza, an Argentine research base near the northern tip of the Antarctic Peninsula, and the World Meteorological Organization (WMO) confirmed it as the continental record in July 2021. A warm, dry downslope wind known as a föhn did most of the work that day, on top of a peninsula that has warmed sharply over the past half century.

Antarctica's 18.3°C Reading at Esperanza in February 2020

The red buildings above are Esperanza Base, on Hope Bay. It is one of the few places in Antarctica where families live year-round, which makes it an unusual setting for a weather record.

The record in numbers

  • New continental record: 18.3°C at Esperanza on 6 February 2020.
  • Previous record: 17.5°C (63.5°F), also at Esperanza, on 24 March 2015. The new reading beat it by 0.8°C, or about 1.4°F.
  • Record for the wider Antarctic region: 19.8°C (67.6°F) on Signy Island in January 1982. Signy is a small island in the South Orkneys, so it counts for the region south of 60°S but not for the continent itself.
  • A reading that was rejected: 20.75°C reported on 9 February 2020 from a Brazilian permafrost monitoring station on Seymour Island.

The Argentine research base Esperanza, on the northern tip of #Antarctic Peninsula, saw a new record temperature of 18.3°C today (old one 17.5°C on 24 March 2015), per @SMN_Argentina.
Details of previous record at https://t.co/19Un83mmHn#ClimateChange pic.twitter.com/ZKvzr765Am

— WMO | OMM (@WMO) February 6, 2020

(This post is no longer available on X.)

Argentina's national weather service (SMN) reported the reading the same day, and the WMO shared the news while noting that it would need to be checked. That caution was standard practice: every extreme of this kind goes before a WMO committee of climate scientists, who look at the instrument, its housing, its calibration and the weather situation before anything enters the official archive.

Antarctica's 18.3°C Reading at Esperanza in February 2020

The raw station report above, decoded from the international "synop" weather code, lists Esperanza's observations every few hours. The temperature column shows 18.3°C in the 15:00 UTC observation on 6 February, and the maximum-temperature group sent at midnight logs 18.4°C. Notice too the strong south-westerly winds and the very dry air: at the warmest hour the dew point was under 2°C. Both are signatures of a föhn.

How the WMO verified it

The WMO's evaluation committee announced its verdict on 1 July 2021. It accepted Esperanza's 18.3°C as the new record for the Antarctic continent. It also turned down the higher Seymour Island figure. That station's original radiation shield, the louvred housing that keeps sunlight off the sensor, had been lost, and the improvised replacement let the sensor heat up. With that bias, the reading could not count as an official observation.

WMO Secretary-General Petteri Taalas said the Esperanza record was "consistent with the climate change we are observing." The committee's rapporteur, Randall Cerveny, added a broader lesson: the Seymour Island case showed why media should be careful with unverified extremes.

Antarctica's 18.3°C Reading at Esperanza in February 2020

This map of station readings for 6 February shows how isolated the spike was. Esperanza, circled, stands out against much cooler values elsewhere on the peninsula and the surrounding islands.

The record spread fast. Climate activist Greta Thunberg posted the figure the next day, and the Reuters news agency reported Antarctica's "hottest temperature ever" on 8 February. Much of the coverage came before verification, which is part of why the WMO later urged care.

Where Esperanza is, and why location matters

Esperanza sits at Hope Bay on the Trinity Peninsula, the very northern end of the Antarctic Peninsula, at about 63°24′S. That is far closer to South America than to the South Pole, and summers there are mild by Antarctic standards. The base has kept weather records since 1961.

Antarctica's 18.3°C Reading at Esperanza in February 2020

The map above marks the three places that matter for the record books: Signy Island, offshore and north of 60°S, Esperanza on the peninsula tip, and a third station, marked Station D-80, far inland for contrast. The distinction between "continent" and "region" explains why two different records exist.

Argentina founded Esperanza on 17 December 1953. Today it houses around 55 people in winter, including about ten families and two teachers who run a small school. In 1978 Emilio Palma was born there, the first person known to have been born on the Antarctic continent.

The photo shared by The Antarctic Report, credited to Néstor Franco, shows the base on the day. The post also notes the station's latitude and that records there began in 1961.

The föhn effect: why the peninsula can suddenly get warm

A föhn (also spelled foehn) is a warm, dry, often gusty wind that blows down the lee side of a mountain range. The Antarctic Peninsula has a high mountain spine, and when strong westerly winds push air over it, the air reaching the eastern side, where Esperanza sits, can be much warmer than air at the same height on the windward side.

Several processes combine to produce that warmth:

  • Losing moisture on the way up. Air rising over the mountains cools, its water vapour condenses and falls as snow, and the condensation releases heat into the air. Because the moisture is gone, that heat is not used up again on the descent.
  • Drawing down warmer air from aloft. When low-level air cannot cross the barrier, air from nearer the ridge top flows over and down the lee slope, warming as it is compressed.
  • Mixing and sunshine. Turbulence mixes warm air down into the valleys, and the clear, dry skies on the lee side allow more solar heating.

Föhn winds can lift local temperatures by more than ten degrees within hours. Because the air is so dry, they also melt and evaporate snow quickly, and scientists have linked them to surface melting on the peninsula's ice shelves.

Antarctica's 18.3°C Reading at Esperanza in February 2020

This global map from Climate Reanalyzer (University of Maine) shows daily average temperature anomalies for 6 February 2020 against a 1979–2000 baseline. The deep red patch over the Antarctic Peninsula, with Esperanza labelled, marks how far above normal the area was that day.

Antarctica's 18.3°C Reading at Esperanza in February 2020

Meteorologist Andrej Flis of Severe Weather Europe produced a series of maps from the American GFS forecast model. This one, for 00 UTC on 7 February, shows near-surface temperature anomalies across Antarctica, with the strongest warmth concentrated over the peninsula.

Antarctica's 18.3°C Reading at Esperanza in February 2020

Zooming in, the GFS temperature analysis at 80 metres above ground for 18 UTC on 6 February shows a pool of warm air on the eastern, lee side of the peninsula's mountains and much colder air on the western side. Models smooth out local peaks, so the exact maximum is not shown, but the pattern is the classic föhn shape.

Antarctica's 18.3°C Reading at Esperanza in February 2020

The relief map explains why. The peninsula's mountain spine, in orange and brown, acts as the barrier that air must climb before it plunges down towards Hope Bay.

Antarctica's 18.3°C Reading at Esperanza in February 2020

The wind analysis for the same time completes the picture. Strong flow crosses the mountains, and the fastest winds, shown in dark red, run down the lee slopes, exactly where the warming appeared.

Weather event or climate signal?

A single hot day does not prove a trend on its own, and the föhn was the immediate trigger. Still, the record did not happen in a vacuum. According to the WMO, the Antarctic Peninsula has warmed by almost 3°C over the past 50 years, making it one of the fastest-warming regions on Earth. A warmer starting point makes it easier for a föhn event to push temperatures past old records.

The record also fell during an unusually warm period worldwide. Copernicus, the European climate service, reported that January 2020 was the warmest January in its global record at that time, and that Europe was 3.1°C warmer than the 1981–2010 average for the month.

A useful rule when reading about extremes is to keep three things separate: one station's maximum on one day, the continent's average conditions, and the long-term trend. Mixing them leads to both alarmism and denial. The Esperanza record is best read as a striking weather event that fits a well-documented regional warming pattern.

Still the coldest place on Earth

None of this changes Antarctica's status as the coldest continent. Most of it is a high ice plateau where summer temperatures stay far below freezing. The lowest reliably measured natural temperature on Earth, −89.2°C (−128.6°F), was recorded at the Soviet, now Russian, Vostok Station on 21 July 1983. Vostok lies about 3,488 metres above sea level in the interior of East Antarctica. Satellite measurements have since suggested even colder pockets on the high ridge between Dome A and Dome F, but those are surface estimates rather than standard air-temperature readings.

Antarctica's 18.3°C Reading at Esperanza in February 2020

Vostok's climate table shows how extreme the interior is: average highs below −30°C even in summer and record lows near −90°C in winter.

Antarctica's 18.3°C Reading at Esperanza in February 2020

The map marks Vostok Station deep inside East Antarctica, far from the warm, maritime tip of the peninsula where Esperanza sits. The two records, hot and cold, come from places that might as well be different worlds.

Sources: World Meteorological Organization, 1 July 2021: WMO verifies one temperature record for Antarctic continent and rejects another; Wikipedia: Esperanza Base; Wikipedia: Foehn wind; Wikipedia: Vostok Station. Maps: Ogimet, Climate Reanalyzer (University of Maine), Andrej Flis / Severe Weather Europe (GFS model).

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