Numerical climate models use quantitative methods to simulate the interactions of the important drivers of climate, including atmosphere, oceans, land surface and ice. They are used for a variety of purposes from study of the dynamics of the climate system to projections of future climate. Climate models may also be qualitative models and also narratives, largely descriptive, of possible futures.
A general circulation model (GCM) is a type of climate model. It employs a mathematical model of the general circulation of a planetary atmosphere or ocean. It uses the Navier–Stokes equations on a rotating sphere with thermodynamic terms for various energy sources. These equations are the basis for computer programs used to simulate the Earth's atmosphere or oceans. Atmospheric and oceanic GCMs are key components along with sea ice and land-surface components.
The Community Climate System Model (CCSM) is a coupled general circulation model (GCM) developed by the University Corporation for Atmospheric Research (UCAR) with funding from the National Science Foundation (NSF), the Department of Energy (DoE), and the National Aeronautics and Space Administration (NASA). The coupled components include an atmospheric model, a land-surface model, an ocean model, and a sea ice model. CCSM is maintained by the National Center for Atmospheric Research (NCAR).
In climatology, the Coupled Model Intercomparison Project (CMIP) is a collaborative framework designed to improve knowledge of climate change. It was organized in 1995 by the Working Group on Coupled Modelling (WGCM) of the World Climate Research Programme (WCRP). It is developed in phases to foster the climate model improvements but also to support national and international assessments of climate change. A related project is the Atmospheric Model Intercomparison Project (AMIP) for global coupled ocean-atmosphere general circulation models (GCMs).
A Heinrich event is a natural phenomenon in which large groups of icebergs break off from the Laurentide Ice Sheet and traverse the Hudson Strait into the North Atlantic. First described by marine geologist Hartmut Heinrich, they occurred during five of the last seven glacial periods over the past 640,000 years. Heinrich events are particularly well documented for the last glacial period but notably absent from the penultimate glaciation. The icebergs contained rock mass that had been eroded by the glaciers, and as they melted, this material was dropped to the sea floor as ice rafted debris forming deposits called Heinrich layers.
The Atlantic meridional overturning circulation (AMOC) is the "main current system in the South and North Atlantic Oceans". As such, it is a component of Earth's oceanic circulation system and plays an important role in the climate system. If the strength of the AMOC changes this could have impacts on some elements of the climate system. The AMOC includes currents at the surface as well as at great depths in the Atlantic Ocean. These currents are driven by changes in the atmospheric weather as well as by changes in temperature and salinity. They collectively make up one half of the global thermohaline circulation that encompasses the flow of major ocean currents. The other half is the Southern Ocean overturning circulation.
In climate science, a tipping point is a critical threshold that, when crossed, leads to large, accelerating and often irreversible changes in the climate system. If tipping points are crossed, they are likely to have severe impacts on human society and may accelerate global warming. Tipping behavior is found across the climate system, for example in ice sheets, mountain glaciers, circulation patterns in the ocean, in ecosystems, and the atmosphere. Examples of tipping points include thawing permafrost, which will release methane, a powerful greenhouse gas, or melting ice sheets and glaciers reducing Earth's albedo, which would warm the planet faster.
An atmospheric reanalysis is a meteorological and climate data assimilation project which aims to assimilate historical atmospheric observational data spanning an extended period, using a single consistent assimilation scheme throughout.
DIVA allows the spatial interpolation/gridding of data (analysis) in an optimal way, comparable to optimal interpolation (OI), taking into account uncertainties on observations. In comparison to standard OI, used in Data assimilation, DIVA, when applied to ocean data, takes into account coastlines, sub-basins and advection because of its variational formulation on the real domain. Calculations are highly optimized and rely on a finite element resolution. Tools to generate the finite element mesh are provided as well as tools to optimize the parameters of the analysis. Quality control of data can be performed and error fields can be calculated. Also detrending of data is possible. Finally 3D and 4D extensions are included with emphasis on direct computations of climatologies from ODV spreadsheet files.
Regional Ocean Modeling System (ROMS) is a free-surface, terrain-following, primitive equations ocean model widely used by the scientific community for a diverse range of applications. The model is developed and supported by researchers at the Rutgers University, University of California Los Angeles and contributors worldwide.
Ocean general circulation models (OGCMs) are a particular kind of general circulation model to describe physical and thermodynamical processes in oceans. The oceanic general circulation is defined as the horizontal space scale and time scale larger than mesoscale. They depict oceans using a three-dimensional grid that include active thermodynamics and hence are most directly applicable to climate studies. They are the most advanced tools currently available for simulating the response of the global ocean system to increasing greenhouse gas concentrations. A hierarchy of OGCMs have been developed that include varying degrees of spatial coverage, resolution, geographical realism, process detail, etc.
The Model for Prediction Across Scales (MPAS) is an Earth system modeling software that integrates atmospheric, oceanographic, and cryospheric modeling across scales from regional to planetary. It includes climate and weather modeling and simulations that were used initially by researchers in 2013. The atmospheric models were created by the Earth System Laboratory at the National Center for Atmospheric Research and the oceanographic models were created by the Climate, Ocean, and Sea Ice Modeling Group at Los Alamos National Laboratory. The software has been used to model real-time weather as well as seasonal forecasting of convection, tornadoes and tropical cyclones. The atmospheric modeling component of the software can be used with other atmospheric modeling software including the Weather Research and Forecasting Model, the Global Forecast System, and the Community Earth System Model.
Axel Timmermann is a German climate physicist and oceanographer with an interest in climate dynamics, human migration, dynamical systems' analysis, ice-sheet modeling and sea level. He served a co-author of the IPCC Third Assessment Report and a lead author of IPCC Fifth Assessment Report. His research has been cited over 18,000 times and has an h-index of 70 and i10-index of 161. In 2017, he became a Distinguished Professor at Pusan National University and the founding Director of the Institute for Basic Science Center for Climate Physics. In December 2018, the Center began to utilize a 1.43-petaflop Cray XC50 supercomputer, named Aleph, for climate physics research.
The Nucleus for European Modeling of the Ocean (NEMO) is a general model of ocean circulation developed by a European consortium and used in many countries of Europe.
Earth systems models of intermediate complexity (EMICs) form an important class of climate models, primarily used to investigate the earth's systems on long timescales or at reduced computational cost. This is mostly achieved through operation at lower temporal and spatial resolution than more comprehensive general circulation models (GCMs). Due to the nonlinear relationship between spatial resolution and model run-speed, modest reductions in resolution can lead to large improvements in model run-speed. This has historically allowed the inclusion of previously unincorporated earth-systems such as ice sheets and carbon cycle feedbacks. These benefits are conventionally understood to come at the cost of some model accuracy. However, the degree to which higher resolution models improve accuracy rather than simply precision is contested.
CICE is a computer model that simulates the growth, melt and movement of sea ice. It has been integrated into many coupled climate system models as well as global ocean and weather forecasting models and is often used as a tool in Arctic and Southern Ocean research. CICE development began in the mid-1990s by the United States Department of Energy (DOE), and it is currently maintained and developed by a group of institutions in North America and Europe known as the CICE Consortium. Its widespread use in Earth system science in part owes to the importance of sea ice in determining Earth's planetary albedo, the strength of the global thermohaline circulation in the world's oceans, and in providing surface boundary conditions for atmospheric circulation models, since sea ice occupies a significant proportion (4-6%) of Earth's surface. CICE is a type of cryospheric model.
Atlantification is the increasing influence of Atlantic water in the Arctic. Warmer and saltier Atlantic water is extending its reach northward into the Arctic Ocean. The Arctic Ocean is becoming warmer and saltier and sea-ice is disappearing as a result. The process can be seen on the figure on the far right, where the sea surface temperature change in the past 50 years is shown, which is up to 5 degrees in some places. This change in the Arctic climate is most prominent in the Barents Sea, a shallow shelf sea north of Scandinavia, where sea-ice is disappearing faster than in any other Arctic region, impacting the local and global ecosystem.
Rong Zhang is a Chinese-American physicist and climate scientist at the National Oceanic and Atmospheric Administration. Her research considers the impact of Atlantic meridional overturning circulation on climate phenomena. She was elected Fellow of the American Meteorological Society in 2018 and appointed their Bernhard Haurwitz Memorial Lecturer in 2020.
OceanParcels, “Probably A Really Computationally Efficient Lagrangian Simulator”, is a set of python classes and methods that is used to track particles like water, plankton and plastics. It uses the output of Ocean General Circulation Models (OGCM's). OceanParcels main goal is to process the increasingly large amounts of data that is governed by OGCM's. The flow dynamics are simulated using Lagrangian modelling and the geophysical fluid dynamics are simulated with Eulerian modelling or provided through experimental data. OceanParcels is dependent on two principles, namely the ability to read external data sets from different formats and customizable kernels to define particle dynamics.
Helene Hewitt is a British climate scientist who is a research fellow at the Met Office. Her research considers climate and ocean models. Hewitt serves on the CLIVAR Ocean Model Development Panel. She was awarded an Order of the British Empire in the 2022 Birthday Honours.
