Preprints
https://doi.org/10.5194/essd-2025-127
https://doi.org/10.5194/essd-2025-127
19 Mar 2025
 | 19 Mar 2025
Status: a revised version of this preprint was accepted for the journal ESSD and is expected to appear here in due course.

An ensemble-based coupled reanalysis of the climate from 1860 to the present (CoRea1860+)

Yiguo Wang, François Counillon, Lea Svendsen, Ping-Gin Chiu, Noel Keenlyside, Patrick Laloyaux, Mariko Koseki, and Eric de Boisseson

Abstract. Climate reanalyses are essential for studying climate variability, understanding climate processes, and initializing climate predictions. We present CoRea1860+ (Wang and Counillon, 2025, https://doi.org/10.11582/2025.00009), a 30-member coupled reanalysis spanning from 1860 to the present, produced using the Norwegian Climate Prediction Model (NorCPM) and assimilating sea surface temperature (SST) observations. NorCPM combines the Norwegian Earth System Model with the ensemble Kalman filter data assimilation method. SST, available throughout the entire period, serves as the primary source of instrumental oceanic measurements prior to the 1950s. CoRea1860+ belongs to the category of sparse-input reanalyses, designed to minimize artifacts arising from changes in the observation network over time. By exclusively assimilating oceanic data, this reanalysis offers valuable insights into the ocean’s role in driving climate system variability, including its influence on the atmosphere and sea ice. This study first describes the numerical model, SST dataset, and assimilation implementation used to produce CoRea1860+. It then provides a comprehensive evaluation of the reanalysis across four key areas: reliability, ocean variability, sea ice variability, and atmospheric variability, benchmarked against more than ten independent reanalyses and observational datasets. Overall, CoRea1860+ demonstrates strong reliability, particularly in observation-rich periods, and provides a reasonable representation of climate variability. It successfully captures key features such as multidecadal variability and long-term trends in ocean heat content, the Atlantic meridional overturning circulation, and sea ice variability in both hemispheres. Furthermore, CoRea1860+ aligns well with the other datasets for surface air temperature, precipitation, sea level pressure, and 500 hPa geopotential height, especially in the tropics where air-sea interactions are most pronounced.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
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Yiguo Wang, François Counillon, Lea Svendsen, Ping-Gin Chiu, Noel Keenlyside, Patrick Laloyaux, Mariko Koseki, and Eric de Boisseson

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2025-127', Anonymous Referee #1, 29 Apr 2025
    • RC2: 'Reply on RC1', Anonymous Referee #1, 29 Apr 2025
    • AC1: 'Reply on RC1', Yiguo Wang, 27 May 2025
  • RC3: 'Comment on essd-2025-127', Anonymous Referee #2, 08 May 2025
    • AC2: 'Reply on RC3', Yiguo Wang, 27 May 2025

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2025-127', Anonymous Referee #1, 29 Apr 2025
    • RC2: 'Reply on RC1', Anonymous Referee #1, 29 Apr 2025
    • AC1: 'Reply on RC1', Yiguo Wang, 27 May 2025
  • RC3: 'Comment on essd-2025-127', Anonymous Referee #2, 08 May 2025
    • AC2: 'Reply on RC3', Yiguo Wang, 27 May 2025
Yiguo Wang, François Counillon, Lea Svendsen, Ping-Gin Chiu, Noel Keenlyside, Patrick Laloyaux, Mariko Koseki, and Eric de Boisseson

Data sets

CoRea1860+: a coupled reanalysis of the climate from 1860 to the present Yiguo Wang and Francois Counillon https://doi.org/10.11582/2025.00009

Yiguo Wang, François Counillon, Lea Svendsen, Ping-Gin Chiu, Noel Keenlyside, Patrick Laloyaux, Mariko Koseki, and Eric de Boisseson

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Short summary
CoRea1860+ is a new climate dataset that reconstructs past climate conditions from 1860 to today. By using advanced modeling techniques and incorporating sea surface temperature observations, it provides a consistent picture of long-term climate variability. The dataset captures key ocean, sea ice and atmosphere changes, helping scientists understand past climate changes and variability.
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