Frequently Asked Questions

What data can be downloaded from this website?

This website provides climate change projections that have been generated for the 4th Assessment Report (AR4) of the IPCC by the Community Climate System Model (CCSM-3). Currently this portal distributes a subset of all variables produced by the CCSM-3, including monthly mean 2D variables from atmosphere and land component models . In addition, one can download statistically downscaled CCSM-3 projections of temperature and precipitation for the contiguous USA.

What data formats are available for download?

Currently, the datasets can be downloaded in a GIS Shapefile format or text file. Some of the products and anomalies are also available as a .PNG via a Web Map Service. If you would like access to the underlying netCDF data you may access this data via our Web Coverage Service.

What GIS software can I use to work with shapefiles?

Shapefiles are a common GIS format that can be used in Esri GIS software. Shapefiles can also be imported into other commercial and open source GIS software packages.

How do I cite the data from this site?

For detailed citation information please refer to this document.

Where can I get additional CCSM variables (not in a Shapefile format)?

All CCSM variables produced for the IPCC can be obtained from Earth System Grid portal. Data from Earth System Grid is available in netCDF format.

After registration I am still unable to login.

Once you register an email will be sent to the address you supplied in the registration process. You must click on the link in that email in order to complete the registration process.

I have forgotten my login/password.

Click the “Request new password" link on the login page. If you continue to have problems please contact us.

What are scenarios and why are they used?

Future greenhouse gas emissions are the product of very complex dynamic systems, determined by driving forces such as demographic development, socio-economic development, and technological change. Their future evolution is highly uncertain. Scenarios are not specific predictions or forecasts of future climate. Rather, scenarios are plausible alternative futures. Each scenario is an example of what can happen under particular assumptions about the use of fossil fuel and other human activities. Scenarios assist in climate modeling, help to examine potential climate change and explore vulnerabilities of humans and ecosystems under a changed climate. For more information, visit IPCC special report on Emissions scenarios.

What is the difference between 'Climate Change Commitment', '20th Century Freeze' and '20th Century Constant' scenarios?

The "Climate Change Commitment","20th Century Freeze" and "20th Century Constant" all represent the same scenario. Here terms "Freeze", "Commitment", and "Constant" are synonymous and used interchangeably.

What is gained by averaging all of the ensemble members of a given scenario?

An ensemble average is preferable to use for general analysis rather than a specific ensemble member. However, whether or not to use the ensemble average depends on the analysis being done. Climate models are statistical representations of the Earth's climate, and are not intended to replicate specific weather events, nor should they be used that way.

What is the projection and datum of the data?

When you download a shapefile there is an associated projection file (.prj). The climate model runs on a perfect sphere with a radius of 6371.22 KM. However all input data into the model is based on WGS-84. Therefore, it is appropriate to assume the output from the model is also WGS-84.

Does the CCSM portray El Nino/ENSO events?

Climate models are not like weather forecast models. Years in the Control Run do not go together with calendar years, therefore the control run of the CCSM-3 does not project specific events at the exact time these events occur (like the 1997 El Nino). The CCSM control runs are designed to illustrate internal model variability, by having fixed external forcings. Projections may show warming of the sea surface but in a generic sense. It is more random and is a statistical representation of such events rather than actual. Therefore, a specific event like an El Nino is present in the model only in a statistical sense. Sea surface temperatures for a specific time period will not necessarily be a replication of observed events. CCSM modelers may perform additional runs where they supply ocean observational data, which forces the system to incorporate interactions between ocean and atmosphere and pick out specific events like El Nino.

How good is the model's representation of the Earth's surface?

Elevation is an input in the model, however, it is not a Digital Elevation Model. The values are derived from the U.S. Navy 10' global topography dataset.

Would you consider making other global climate models available in GIS format?

Comparing outputs from different GCMs does indeed gives more comprehensive view of climate change predictions and the uncertainties. Even though we are looking into providing results from other GCMs in the future, currently our data distribution agreement is with the CCSM model only.

Where can I get climate change projections produced by other global climate models?

The IPCC Data Distribution Centre and Program for Climate Model Diagnosis and Intercomparison (PCMDI) provide IPCC multi-model data and documentation. All IPCC CCSM-3 experiments are also available in NetCDF format through the Earth System Grid data portal.

What is a climate anomaly?

A climate anomaly is the difference of a future climate compared to the present climate. We have provided four time period anomalies; Near Term (2020-2039), Mid-Term (2040-2059), End of Century (2080-2099), Last Decade (2090-2099) for our anomalies. The present day climate is computed from the 20th Century Experiment (1980-1999). We use a twenty-year average to compute our anomalies in order to filter out noise from the model and better see the climate signal.

What are long-term means?

Long-term means are the twenty year averages which were computed for our four time periods; Near Term (2020-2039), Mid-Term (2040-2059), End of Century (2080-2099), Last Decade (2090-2099). As well as our present day twenty-year average which is computed from the 20th Century Experiment (1980-1999). We use a twenty-year average to compute our anomalies in order to filter out noise from the model and better see the climate signal.

What is the CCSM?

The Community Climate System Model (CCSM) is a community-wide effort led by the National Center for Atmospheric Research (NCAR) and is a key component of the National Science Foundation program on Climate Modeling, Analysis and Prediction. Composed of four separate models simultaneously simulating the earth's atmosphere, ocean, land surface and sea-ice, and one central coupler component, the CCSM allows researchers to conduct fundamental research into the earth's past, present and future climate states. CCSM 3.0 was released in 2004. The CCSM project played a major role in the IPCC AR4 through the completion and analysis of an extensive series of emission scenario experiments. A subset of CCSM model runs is available through this portal.

What are the CCSM components?

CCSM software is based on framework that divides the complete climate system into component models connected by a coupler. Individual components - ocean, atmosphere, land, and sea-ice - can be exchanged for alternate models, thus allowing different configurations appropriate for different applications.

What is the spatial resolution of the climate change projections produced by the CCSM-3?

The spatial resolution of CCSM-3 climate change projections is approximately 1.4 x 1.4 degrees. However, the model outputs are generated on an irregular grid. The longitude range can be exactly specified - the center of the first grid box is at 0E and the spacing is precisely 1.40625°. The latitudes, however, vary in spacing from 1.389° to 1.400767°.

What is the spatial resolution of downscaled CCSM-3 temperature and precipitation projections?

Spatial resolution of downscaled CCSM-3 projections of temperature and precipitation for the contiguous USA is approximately 4.5 km.

What is downscaling?

Downscaling is the general name for a procedure to take information known at large scales to make predictions at local scales. The two main approaches to downscaling climate information are dynamical and statistical. Dynamical downscaling requires running high-resolution climate models on a regional sub-domain, using observational data or lower-resolution climate model output as a boundary condition.  These models use physical principles to reproduce local climates, but are computationally intensive.  Statistical downscaling is a two-step process consisting of i) the development of statistical relationships between local climate variables (e.g., surface air temperature and precipitation) and large-scale predictors (e.g., pressure fields), and ii) the application of such relationships to the output of global climate model experiments to simulate local climate characteristics in the future. More information about the method used to downscale CCSM-3 projections is available in this white paper.

Where can I learn more about climate change impacts research?

Much of information about climate change impacts can be found in IPCC Working Group II Report on Impacts, Adaptation and Vulnerability.

What is IPCC?

The Intergovernmental Panel on Climate Change (IPCC) was established by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess scientific, technical and socio-economic information relevant for the understanding of climate change, its potential impacts and options for adaptation and mitigation. IPCC produces assessment and special reports on climate change and related topics. The 4th Assessment Report (AR4) on Climate Change was released in 2007 and is available through the IPCC web site. In late 2007, participants in all the IPCC assessments since 1990 shared in the Nobel Peace Prize.

What are UCAR, NCAR and UCP?

The University Corporation for Atmospheric Research (UCAR), National Center for Atmospheric Research (NCAR) and UCAR Community Programs (UCP) are part of a collaborative community dedicated to understanding the atmosphere and the interconnected processes that make up the Earth system, from the ocean floor to the Sun's core. The National Center for Atmospheric Research and the UCAR Community Programs provide research, facilities, and services for the atmospheric and Earth sciences community. NCAR and UCP are managed by the nonprofit University Corporation for Atmospheric Research. To learn more about UCAR, NCAR and UCP visit UCAR's web site.

What is the NCAR GIS Program?

The NCAR GIS Program is an interdisciplinary effort to foster collaborative science, spatial data interoperability, and knowledge sharing with GIS. The main goal of the GIS Program is to promote and support the use of GIS as both an analysis, and an infrastructure tool in atmospheric research and to address broader issues of spatial data management, interoperability, and geoinformatics within the geosciences. Working in collaboration with other NCAR strategic initiatives, divisions, and UCAR programs, the program supports variety of science projects at NCAR, improves compatibility of atmospheric data sets with GIS tools, and creates bridges between atmospheric, geo- and social sciences. In 2004, the GIS Initiative launched “GIS Climate Change Scenarios” portal (this website) to serve a wide community of GIS users interested in global climate change. For more information about GIS Program or this portal, contact our staff.

What is NCAR's involvement in IPCC?

As one of the world’s leading climate modeling and research centers, NCAR is a strong supporter of the IPCC scientific assessment process. NCAR scientists have served as lead and contributing authors in each of the four full IPCC assessment reports (1990, 1995, 2001, and 2007) as well as a number of special reports and technical papers that have focused on more specific issues. NCAR climate modeling and process study research has contributed to the peer-reviewed scientific literature that forms the basis of the IPCC’s work. 40 NCAR staff served as coordinating lead authors, lead authors, reviewers, or contributors on the 2007 IPCC reports, with additional staff providing technical support. More information about NCAR's contribution to IPCC is available.