New Study Reveals Surprising Insights into Climate Data Accuracy

In a context of increasingly rapid climate change, the accuracy of scientific data plays a vital role. Meteorological observations are used in a wide range of studies, enabling us to better understand the complex interactions taking place within the Earth’s climate system. With this in mind, a team including researchers from the institut des géosciences de l’environnement (IGE- OSUG, CNRS / IRD / INRAE / Grenoble INP / Université Grenoble Alpes), examined in detail the precipitation records for Ny-Ålesund, a locality in the Norwegian archipelago of Svalbard in the Arctic Ocean. They succeeded in reducing a measurement bias that had distorted the data over a recent forty-year period.

In a study published on May 24, 2024 in the Journal of Hydrometeorology, titled "Artificial Trends or Real Changes? Investigating Precipitation Records in Ny-Ålesund, Svalbard," researchers delve into the complexities of precipitation measurement in one of the world’s most challenging climates. The Svalbard archipelago, situated in the Atlantic-Arctic region, has witnessed a notable surge in precipitation over recent decades, posing significant implications for various environmental processes related to the cryosphere, bio-geochemical cycles, and ecosystems.

The study, led by Olivier Champagne and Hans-Werner Jacobi from IGE, focuses on Ny-Ålesund, located at 79°N in the northwest region of Svalbard, which serves as a critical site for meteorological observations in the Arctic. Over the years, precipitation data collected from Ny-Ålesund have been heavily relied upon by researchers worldwide. However, the accuracy of these records has been subject to debate due to well-documented issues with precipitation gauges, particularly their undercatch during windy conditions.
The researchers aimed to ascertain whether the observed trend of precipitation in Ny-Ålesund between 1975 and 2022 was genuine and to what extent it was influenced by the so-called gauge undercatch, which leads to biases in the collection of snow. Employing several correction factors developed over decades based on local wind speed and temperature, the team meticulously analyzed 12-hourly precipitation data from the Ny-Ålesund weather station.

The findings revealed intriguing insights. Like the temperature, the precipitation record shows a clear increasing trend during the observational period. For the entire 1975-2022 period, the observed increase was +3.8 mm/year in the raw data, which increased even to +4.5 mm/year (±0.2) after applying corrections. This corresponds to an increase of approximately 50 % of today’s annual accumulation compared to the annual accumulation at the beginning of the observational period. However, by analyzing only the most recent 40-year period (1983-2022), the observed trend remains at +3.8 mm/year in the raw data, while it decreased to +2.6 mm/year (±0.5) after corrections. Key to these adjustments was the discovery that the recent rise in precipitation was predominantly attributed to an increase in wet snowfall and rainfall, which are measured more accurately by the precipitation gauge. This underscores the necessity of applying correction factors, particularly in regions like Svalbard where significant inter-annual variations in weather conditions are commonplace.

Hans-Werner Jacobi says,

"Our research underscores the importance of meticulous data analysis and correction methodologies in climate studies, particularly in regions where weather conditions fluctuate significantly. By accurately accounting for gauge undercatch, we can obtain more reliable insights into long-term precipitation trends, thereby enhancing our understanding of climate dynamics and facilitating informed decision-making."

This study not only sheds light on the intricacies of climate data interpretation but also underscores the imperative of employing rigorous methodologies to ensure the accuracy of environmental observations.

Référence

Champagne, O., O. Zolina, J.-P. Dedieu, M. Wolff, and H.-W. Jacobi, Artificial trends or real changes? Investigating precipitation records in Ny-Ålesund, Svalbard, J.Hydrometeorol. 25 (6), 809-825, 2024.DOI : 10.1175/JHM-D-23-0182.1

This article was published in french by CNRS-INSU.

Updated on 12 February 2025