A Te Herenga Waka—Victoria University of Wellington researcher is part of the 12-person World Meteorological Organization (WMO) evaluation team whose extensive review led to WMO confirmation of a new record high temperature for the Antarctic continent.

Climate change expert Professor James Renwick, who heads the University’s Te Kura Tātai Aro Whenua—School of Geography, Environment and Earth Sciences, and colleagues from Brazil, Argentina, the United Kingdom, the United States and Spain verified the temperature of 18.3° Celsius recorded at Argentina’s Esperanza station on 6 February 2020.

However, they rejected a temperature of 20.75°C reported at a Brazilian automated permafrost monitoring station on Seymour Island on 9 February 2020.

The previous record for the continent was 17.5°C recorded at Esperanza station on 24 March 2015. The record for the Antarctic region as a whole, including all ice and land south of 60° latitude, is 19.8°C, taken at the UK’s Signy Island station in January 1982.

“Verification of this maximum temperature record is important because it helps us to build up a picture of the weather and climate in one of Earth’s final frontiers,” said WMO Secretary-General Professor Petteri Taalas.

“Even more so than the Arctic, the Antarctic is poorly covered in terms of continuous and sustained weather and climate observations and forecasts, even though both play an important role in driving climate and ocean patterns and in sea level rise.

“The Antarctic Peninsula [the northwest tip near to South America] is among the fastest warming regions of the planet, almost 3°C over the last 50 years. This new temperature record is therefore consistent with the climate change we are observing. WMO is working in partnership with the Antarctic Treaty System to help conserve this pristine continent.”

The team of which Professor Renwick was a member was commissioned by WMO’s Weather and Climate Extremes Archive to review the weather situation on the Antarctic Peninsula at the time of the two latest reported records.

It determined that a large high-pressure system over the area created ‘föhn’ conditions (downslope winds producing significant surface warming) and resulted in local warming at both Esperanza and Seymour Island stations. Past evaluations have demonstrated that such meteorological conditions are conducive for producing record temperature scenarios.

The team also examined the two observations’ instrumental setups. The examination of the data and metadata of the Esperanza station revealed no major concerns. However, a detailed analysis of data and metadata of the Seymour Island station indicated an improvised radiation shield led to a demonstrable thermal bias error for the temperature sensor.

The new record will now be added to the WMO Archive of Weather and Climate Extremes, which includes the world’s highest and lowest temperatures, rainfall, heaviest hailstone, longest dry period, maximum gust of wind, longest lightning flash, and weather-related mortalities.

Professor Renwick said föhn conditions also caused Aotearoa New Zealand’s highest recorded temperatures.

“The hottest day ever recorded in Aotearoa is still 42°C in Rangiora and Christchurch, and other places in Canterbury, on 7 February 1973. That happened in a big nor’westerly event just like the one that caused the new record for the Antarctic.

“The Antarctic Peninsula has mountains running down its length, perpendicular to the flow of the north-west winds, so places on the eastern side of the Peninsula can experience very warm days, just like in Canterbury, which lies downwind of the Southern Alps.”

Full details of the WMO assessment are given in the online issue of the Bulletin of the American Meteorological Society.

Professor Renwick and his colleagues stressed the need for increased caution on the part of both scientists and the media in releasing early announcements of record temperatures before they have been thoroughly investigated and properly validated.

In a proactive act, WMO has decided to undertake ‘rapid response’ team analysis of new purported records. This will provide initial guidance to global media and the general public before a formal in-depth investigation, which often takes many months.

“This investigation highlights an important ‘teachable moment,’ particularly with regard to media dissemination of this type of information,” said Professor Randall Cerveny, Rapporteur of Climate and Weather Extremes for WMO and a member of the investigating team.

“When news of these observations became known, global media quickly disseminated them with headlines of temperatures exceeding 20°C for the first time ever in Antarctica. The examples presented here illustrate why media should be cautious in reporting temperature extremes.

“To achieve the level of absolute accuracy needed for our official WMO Archive of Extremes requires a great deal of attention to many factors, such as instrument maintenance, placement and type—factors that are often not appreciated by the media and the public and that are time-consuming to investigate.”

Professor Renwick is also one of four Te Herenga Waka—Victoria University of Wellington researchers who are lead authors for next year’s Sixth Assessment Report from the Intergovernmental Panel on Climate Change (IPCC).

He, Professor David Frame, director of the New Zealand Climate Change Research Institute, and Professor Nicholas Golledge from the Antarctic Research Centre are members of the working group on the physical science basis of climate change, whose contribution to the report is due to be released early next month.

Dr Judy Lawrence from the New Zealand Climate Change Research Institute is a member of another IPCC working group.