Reindert J. Haarsma

Bio: Reindert J. Haarsma is an academic researcher from Royal Netherlands Meteorological Institute. The author has contributed to research in topics: Climate model & Sea surface temperature. The author has an hindex of 36, co-authored 65 publications receiving 3953 citations.

High Resolution Model Intercomparison Project (HighResMIP v1.0) for CMIP6

Abstract: . Robust projections and predictions of climate variability and change, particularly at regional scales, rely on the driving processes being represented with fidelity in model simulations. The role of enhanced horizontal resolution in improved process representation in all components of the climate system is of growing interest, particularly as some recent simulations suggest both the possibility of significant changes in large-scale aspects of circulation as well as improvements in small-scale processes and extremes. However, such high-resolution global simulations at climate timescales, with resolutions of at least 50 km in the atmosphere and 0.25° in the ocean, have been performed at relatively few research centres and generally without overall coordination, primarily due to their computational cost. Assessing the robustness of the response of simulated climate to model resolution requires a large multi-model ensemble using a coordinated set of experiments. The Coupled Model Intercomparison Project 6 (CMIP6) is the ideal framework within which to conduct such a study, due to the strong link to models being developed for the CMIP DECK experiments and other model intercomparison projects (MIPs). Increases in high-performance computing (HPC) resources, as well as the revised experimental design for CMIP6, now enable a detailed investigation of the impact of increased resolution up to synoptic weather scales on the simulated mean climate and its variability. The High Resolution Model Intercomparison Project (HighResMIP) presented in this paper applies, for the first time, a multi-model approach to the systematic investigation of the impact of horizontal resolution. A coordinated set of experiments has been designed to assess both a standard and an enhanced horizontal-resolution simulation in the atmosphere and ocean. The set of HighResMIP experiments is divided into three tiers consisting of atmosphere-only and coupled runs and spanning the period 1950–2050, with the possibility of extending to 2100, together with some additional targeted experiments. This paper describes the experimental set-up of HighResMIP, the analysis plan, the connection with the other CMIP6 endorsed MIPs, as well as the DECK and CMIP6 historical simulations. HighResMIP thereby focuses on one of the CMIP6 broad questions, “what are the origins and consequences of systematic model biases?”, but we also discuss how it addresses the World Climate Research Program (WCRP) grand challenges.

ECBILT: a dynamic alternative to mixed boundary conditions in ocean models

Abstract: As an alternative to the frequently used mixed boundary conditions in ocean GCM’s, we presenta dynamic atmospheric model (ECBILT) that is simple and yet describes the relevant dynamicand thermodynamic feedback processes to the ocean. This provides the possibility of studyingatmosphere/ocean dynamics on very long time-scales of the order of a thousand years. Themodel is two orders of magnitude faster than AGCMs. We have been running ECBILT withprescribed SSTs for a period of 500 years with seasonal cycle included both in the solar forcingand in the climatological SSTs. The mean state and the variability properties of ECBILT arereasonably realistic. The simulation of the surface fluxes is quite realistic and justifies couplingECBILT to an ocean GCM. We have done two SST anomaly experiments, one with a tropicalSST anomaly as observed during January 1983 and one with an SST anomaly in the northernextra-tropical Atlantic ocean. For the tropical SST anomaly experiment the amount of anomalousprecipitation agrees well with what has been found with atmospheric GCM’s, but theresulting extra-tropical teleconnection pattern is very weak. The atmospheric response patternto extra-tropical SST anomalies agrees well with similar SST anomaly experiments performedwith atmospheric GCM’s. We have tested the performance of ECBILT in coupled mode bycoupling it to a simple ocean GCM and thermodynamic sea-ice model and integrating thecoupled system for a period of thousand years after a spin up of 6000 years. The simulation ofthe mean water mass distribution and the mean circulation of the ocean resembles the observedocean circulation. It has a warm and fresh bias and the circulation and associated transportsare too diffuse and too weak. The ocean’s variability is realistic, considering the simplicity ofthe ocean model, although a bit too weak. We have explored the covariability between theatmosphere and ocean over the Northern Atlantic ocean by performing a singular value decompositionof SST anomalies and 800 hPa geopotential height anomalies. The 2nd mode showsa peak in both spectra at a timescale of about 18 years. The time scale of this mode is set bythe ocean but the physical mechanisms that are operating are not yet unambiguously identified.The simulation of this coupled extra tropical decadal mode of variability, which also shows upin the observations and in much more complex coupled models provides strong evidence forthe potential usefullness of ECBILT when studying atmosphere/ocean interaction and the associatedocean variability on time scales ranging from decades to many thousands of years. DOI: 10.1034/j.1600-0870.1998.t01-1-00007.x

Western Europe is warming much faster than expected

Abstract: . The warming trend of the last decades is now so strong that it is discernible in local temperature observations. This opens the possibility to compare the trend to the warming predicted by comprehensive climate models (GCMs), which up to now could not be verified directly to observations on a local scale, because the signal-to-noise ratio was too low. The observed temperature trend in western Europe over the last decades appears much stronger than simulated by state-of-the-art GCMs. The difference is very unlikely due to random fluctuations, either in fast weather processes or in decadal climate fluctuations. In winter and spring, changes in atmospheric circulation are important; in spring and summer changes in soil moisture and cloud cover. A misrepresentation of the North Atlantic Current affects trends along the coast. Many of these processes ontinue to affect trends in projections for the 21st century. This implies that climate predictions for western Europe probably underestimate the effects of anthropogenic climate change.

Description of the Earth system model of intermediate complexity LOVECLIM version 1.2

Abstract: . The main characteristics of the new version 1.2 of the three-dimensional Earth system model of intermediate complexity LOVECLIM are briefly described. LOVECLIM 1.2 includes representations of the atmosphere, the ocean and sea ice, the land surface (including vegetation), the ice sheets, the icebergs and the carbon cycle. The atmospheric component is ECBilt2, a T21, 3-level quasi-geostrophic model. The ocean component is CLIO3, which consists of an ocean general circulation model coupled to a comprehensive thermodynamic-dynamic sea-ice model. Its horizontal resolution is of 3° by 3°, and there are 20 levels in the ocean. ECBilt-CLIO is coupled to VECODE, a vegetation model that simulates the dynamics of two main terrestrial plant functional types, trees and grasses, as well as desert. VECODE also simulates the evolution of the carbon cycle over land while the ocean carbon cycle is represented by LOCH, a comprehensive model that takes into account both the solubility and biological pumps. The ice sheet component AGISM is made up of a three-dimensional thermomechanical model of the ice sheet flow, a visco-elastic bedrock model and a model of the mass balance at the ice-atmosphere and ice-ocean interfaces. For both the Greenland and Antarctic ice sheets, calculations are made on a 10 km by 10 km resolution grid with 31 sigma levels. LOVECLIM1.2 reproduces well the major characteristics of the observed climate both for present-day conditions and for key past periods such as the last millennium, the mid-Holocene and the Last Glacial Maximum. However, despite some improvements compared to earlier versions, some biases are still present in the model. The most serious ones are mainly located at low latitudes with an overestimation of the temperature there, a too symmetric distribution of precipitation between the two hemispheres, and an overestimation of precipitation and vegetation cover in the subtropics. In addition, the atmospheric circulation is too weak. The model also tends to underestimate the surface temperature changes (mainly at low latitudes) and to overestimate the ocean heat uptake observed over the last decades.

Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change

Abstract: Drafting Authors: Neil Adger, Pramod Aggarwal, Shardul Agrawala, Joseph Alcamo, Abdelkader Allali, Oleg Anisimov, Nigel Arnell, Michel Boko, Osvaldo Canziani, Timothy Carter, Gino Casassa, Ulisses Confalonieri, Rex Victor Cruz, Edmundo de Alba Alcaraz, William Easterling, Christopher Field, Andreas Fischlin, Blair Fitzharris, Carlos Gay García, Clair Hanson, Hideo Harasawa, Kevin Hennessy, Saleemul Huq, Roger Jones, Lucka Kajfež Bogataj, David Karoly, Richard Klein, Zbigniew Kundzewicz, Murari Lal, Rodel Lasco, Geoff Love, Xianfu Lu, Graciela Magrín, Luis José Mata, Roger McLean, Bettina Menne, Guy Midgley, Nobuo Mimura, Monirul Qader Mirza, José Moreno, Linda Mortsch, Isabelle Niang-Diop, Robert Nicholls, Béla Nováky, Leonard Nurse, Anthony Nyong, Michael Oppenheimer, Jean Palutikof, Martin Parry, Anand Patwardhan, Patricia Romero Lankao, Cynthia Rosenzweig, Stephen Schneider, Serguei Semenov, Joel Smith, John Stone, Jean-Pascal van Ypersele, David Vaughan, Coleen Vogel, Thomas Wilbanks, Poh Poh Wong, Shaohong Wu, Gary Yohe

Climate Change 2007: The Physical Science Basis.

Abstract: Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

Chapter 12 - Long-term climate change: Projections, commitments and irreversibility

Abstract: This chapter assesses long-term projections of climate change for the end of the 21st century and beyond, where the forced signal depends on the scenario and is typically larger than the internal variability of the climate system. Changes are expressed with respect to a baseline period of 1986-2005, unless otherwise stated.