Climate change is increasing the need for accurate climate information. To understand how the climate has developed – and how it will change in the future – researchers use what are known as reanalyses. A reanalysis is a comprehensive dataset created by combining historical observations with advanced numerical models, providing a comprehensive picture of past weather and ocean conditions. The Nansen Center has led the development of a new and unique reanalysis that provides new insights into the last 160 years of our recent climate history.
The Earth’s climate is constantly changing, and the ocean plays a key role in this development. The ocean is the Earth’s largest heat reservoir, and changes in ocean currents and the transport of warm or cold water are important for both regional and global temperature variations. The oceans can therefore amplify or dampen global warming, leading to large differences in temperature from year to year or from decade to decade. This affects evaporation and precipitation and has major societal consequences.
We rely on reanalyses to gain insight into how such processes have developed over time. Using data assimilation, where available observations are combined with climate models, we can obtain a comprehensive picture of how the climate has developed. We gain knowledge about conditions from the depths of the ocean to the upper atmosphere, and not just for the relatively few places where actual observations have been made.
The Nansen Center has collaborated with researchers from the University of Bergen and the European Centre for Medium-Range Weather Forecasts (ECMWF) in the UK to develop the longest coupled reanalysis to date. Using the NorCPM climate model and historical sea surface temperature measurements, a reanalysis has been produced covering the period from 1860 to 2022. This analysis provides valuable insight into how the ocean affects the atmosphere and sea ice, leading to natural variations in climate around the globe. The length of the reanalysis makes it possible to identify slow changes in the climate system and provides new insight into how the ocean contributes to such changes.
The reanalysis opens up a number of practical and socially beneficial applications. A deeper understanding of natural climate variations can contribute to the development of more accurate climate policy and better climate adaptation. In the field of renewable energy, the data can be used to plan both energy production and infrastructure. The fishing and aquaculture industries will gain a stronger knowledge base for sustainable resource management, while the insurance industry can use the new climate data to map future risks and the extent of damage. At the same time, the reanalysis provides research communities with valuable insights for improving climate models and increasing understanding of both past and future climate change.
Key researchers: Yiguo Wang, François Counillon, Noel Keenlyside
