If you have worked with climate risk data, you have likely encountered NEX-GDDP-CMIP6 somewhere in the data pipeline. It powers climate risk platforms, feeds academic research, and supports TCFD-aligned scenario analysis. Yet most practitioners use it indirectly, through tools that abstract away the underlying data.
This guide explains what NEX-GDDP-CMIP6 actually contains, how to access it directly, which climate models and variables are included, and where the dataset has limitations that matter for risk analysis.
What Is NEX-GDDP-CMIP6?
NEX-GDDP-CMIP6 stands for NASA Earth Exchange Global Daily Downscaled Projections, built on the Coupled Model Intercomparison Project Phase 6 (CMIP6). It is a publicly available dataset that provides bias-corrected, statistically downscaled climate projections from global climate models.
The “downscaled” part matters. Raw CMIP6 climate model output operates at coarse resolution (100-300 km grid cells). NEX-GDDP-CMIP6 refines this to approximately 25 km resolution (0.25 degrees), making it usable for regional and location-level analysis rather than just continental-scale research.
NASA produces the dataset at the NASA Center for Climate Simulation (NCCS). It covers daily climate variables from 1950 through 2100, spanning both historical observations and future projections under different emission scenarios.
What Are CMIP6 Models Used For?
CMIP6 is the sixth generation of coordinated climate model experiments, organized by the World Climate Research Programme. Over 100 climate modeling centers worldwide contributed models to CMIP6, each simulating how the Earth’s climate system responds to greenhouse gas concentrations.
These models are used for:
- IPCC assessment reports (the AR6 report draws primarily from CMIP6 output)
- National climate adaptation planning (governments use CMIP6 projections to plan infrastructure)
- Corporate climate risk assessment (TCFD-aligned physical risk analysis relies on CMIP6 scenarios)
- Insurance and financial sector stress testing (central banks reference CMIP6 in climate scenario exercises)
NEX-GDDP-CMIP6 makes these models accessible without requiring supercomputer access or climate science expertise to process the raw outputs. For background on how these scenarios work, see our guides to SSP scenarios and RCP scenarios.
How Many Climate Models Are in CMIP6?
The full CMIP6 archive contains output from over 50 distinct climate models. NEX-GDDP-CMIP6 includes a curated subset, currently featuring 35 models that passed NASA’s quality and completeness requirements.
Not all models perform equally across regions. Each model has its own Equilibrium Climate Sensitivity (ECS), which measures how much the planet warms when CO₂ doubles. ECS values across the NEX-GDDP-CMIP6 models range from approximately 1.8°C to 5.6°C, meaning the same emission scenario can produce materially different warming outcomes depending on which model you select.
For practical risk analysis, most practitioners do not run all 35 models. Common approaches include:
- Single model with fallback: Select one well-validated model (such as ACCESS-CM2, MPI-ESM1-2-HR, or MIROC6) and use alternates if data gaps exist for a given scenario or time period
- Multi-model ensemble: Run 5-10 models and report the median and spread. Provides uncertainty bounds but requires 5-10x more computation
- Hot/cold bracketing: Select one high-ECS and one low-ECS model to show the range of plausible futures
The choice of approach depends on computational resources and whether uncertainty quantification is required. For screening-level risk assessment, a single well-chosen model delivers actionable results. For regulatory submissions or academic publications, multi-model ensembles are typically expected.
NEX-GDDP-CMIP6 Variables and Resolution
The dataset provides five core climate variables at daily temporal resolution:
| Variable | Full Name | Native Unit | Typical Use |
|---|---|---|---|
| tas | Daily Mean Temperature | Kelvin | Temperature change analysis |
| tasmax | Daily Maximum Temperature | Kelvin | Heat wave detection, wildfire risk |
| tasmin | Daily Minimum Temperature | Kelvin | Cold stress, frost days |
| pr | Precipitation | kg/m²/s | Drought, extreme rainfall, flood risk |
| sfcWind | Surface Wind Speed | m/s | Severe storms, wildfire spread |
Unit conversions practitioners need to know:
- Temperature: Celsius = Kelvin – 273.15
- Precipitation: mm/day = flux value × 86,400 (seconds per day)
- Annual precipitation: mm/year = mm/day × 365
Variables NOT Included (and Why It Matters)
Several climate variables that would be useful for risk analysis are absent from NEX-GDDP-CMIP6:
- Relative humidity (hurs) and specific humidity (huss): Available in raw CMIP6 output but excluded from NEX-GDDP because they show inconsistent bias patterns across models. This means heat index calculations and full Fire Weather Index (FWI) scoring cannot be derived from this dataset alone.
- Total runoff (mrro): Not available, forcing flood risk analyses to use precipitation as a proxy for river discharge. Actual catchment hydrology requires dedicated hydrological models.
These gaps are standard across most downscaled climate datasets, not specific to NEX-GDDP-CMIP6. Practitioners working on wildfire typically supplement with other humidity data sources or use simplified temperature-wind proxies.
Spatial Resolution: What 25 km Means in Practice
The 0.25-degree (~25 km) grid means each pixel represents the average climate signal across a 625 km² area. This resolution is sufficient for:
- Distinguishing coastal vs. inland climate signals
- Capturing regional precipitation patterns
- Identifying broad heat and drought exposure zones
But it cannot resolve:
- Urban heat island effects within a city
- Microclimates from local terrain (valley vs. hilltop within the same grid cell)
- Individual property-level exposure differences
For site-specific engineering decisions, higher-resolution downscaling or local weather station data should supplement NEX-GDDP-CMIP6 projections. For portfolio screening and TCFD disclosure, 25 km resolution is the standard accepted by regulators and rating agencies.
Scenarios Available in NEX-GDDP-CMIP6
The dataset provides projections under two main Shared Socioeconomic Pathways:
- SSP2-4.5: Moderate mitigation, approximately 2.7°C warming by 2100. Represents a “middle of the road” trajectory where some climate policies are implemented.
- SSP5-8.5: High emissions, approximately 4.4°C warming by 2100. Represents a fossil-fuel-intensive economy with limited climate policy.
The historical scenario covers 1950-2014, providing the observed baseline against which future changes are measured.
Notably, SSP1-2.6 (the optimistic, below-2°C pathway) is not available in most NEX-GDDP-CMIP6 models. This means the dataset cannot directly model the “best case” trajectory that Paris Agreement targets aspire to. For sea level rise analysis specifically, IPCC AR6 published SSP1-2.6 projections separately, and these are often hardcoded into risk platforms rather than derived from CMIP6 model output.
How to Access NEX-GDDP-CMIP6
The dataset is freely available through several channels, each suited to different technical capabilities:
Google Earth Engine
The most accessible option for analysts who want to query data without managing downloads. The GEE collection ID is NASA/GDDP-CMIP6. You can filter by model, scenario, date range, and variable, then extract values for specific coordinates or regions.
GEE handles the computational infrastructure, but has processing limits that may constrain batch analyses across thousands of locations or full model ensembles.
AWS S3 (Open Data Registry)
For large-scale or programmatic access, the full dataset is hosted on AWS S3 at s3://nex-gddp-cmip6. Files are in NetCDF4 format, organized by model, scenario, and variable. This is the preferred access method for data scientists building custom pipelines.
The total dataset size is substantial (multiple terabytes), so downloading everything is impractical. Most users write scripts that selectively pull the specific models, variables, and time periods they need.
NASA NCCS THREDDS Server
NASA’s own data server at NCCS provides OPeNDAP and HTTP access. This is useful for subsetting data remotely without downloading full files, but the server can be slower than AWS for heavy workloads.
Direct Download
NASA provides direct HTTP download links through the NCCS data portal. Suitable for one-off analyses but not scalable for production workflows.
Get a Climate Risk Assessment Using NEX-GDDP-CMIP6 Data
See CMIP6 projections applied to your location across multiple scenarios. Free, no commitment.
Strengths and Limitations of NEX-GDDP-CMIP6
Understanding what the dataset can and cannot do prevents misuse:
| Strengths | Limitations |
|---|---|
| Bias-corrected (not raw model output) | ~25 km resolution misses local microclimate |
| 35 models for uncertainty quantification | No SSP1-2.6 (optimistic pathway) for most variables |
| Daily temporal resolution | No humidity variables (hurs, huss excluded) |
| Free and publicly accessible | No runoff variable (mrro missing) |
| Multiple access methods (GEE, AWS, NASA) | Static archive (not updated with new observations) |
| Coverage through 2100 | Full ensemble requires terabytes of storage |
For most physical climate risk analysis applications, NEX-GDDP-CMIP6 provides the best balance of resolution, accessibility, and model coverage. Platforms like Continuuiti use it as the primary climate data layer, supplementing with WRI Aqueduct for water stress and IPCC AR6 for sea level rise where NEX-GDDP-CMIP6 has gaps.
For a comparison of how different climate data APIs expose this data, including rate limits and pricing, see our API comparison guide. And for a broader look at the climate models that feed NEX-GDDP-CMIP6, including how GCMs work, see our climate models explainer.
Frequently Asked Questions
What variables are in NEX-GDDP-CMIP6?
Five daily climate variables: tas (mean temperature), tasmax (maximum temperature), tasmin (minimum temperature), pr (precipitation), and sfcWind (surface wind speed). All temperature variables are in Kelvin and precipitation is in kg/m²/s. Humidity variables and runoff are not included due to reliability issues across CMIP6 models.
What is the difference between CMIP5 and CMIP6?
CMIP6 (2019-present) has more participating models (50+ vs ~40), uses SSP scenarios instead of RCPs, and features improved model physics. CMIP6 models generally show higher climate sensitivity, meaning they project more warming for the same emissions. NEX-GDDP-CMIP6 replaced the earlier NEX-GDDP dataset based on CMIP5.
What is the resolution of NEX-GDDP-CMIP6?
Approximately 25 km (0.25 degrees) spatial resolution, achieved through statistical downscaling of coarser CMIP6 output. Temporal resolution is daily. Suitable for regional risk screening and TCFD disclosure, but not for site-specific engineering analysis.
How do I access NEX-GDDP-CMIP6 data?
Four main channels: Google Earth Engine (collection NASA/GDDP-CMIP6) for interactive analysis, AWS S3 (s3://nex-gddp-cmip6) for programmatic access, NASA NCCS THREDDS server for remote subsetting, and direct HTTP download from NASA’s portal. GEE is easiest to start with; AWS S3 is best for production pipelines.
Why is SSP1-2.6 not available in NEX-GDDP-CMIP6?
Most models only provide projections for SSP2-4.5 and SSP5-8.5 scenarios. The optimistic SSP1-2.6 pathway was not included in the downscaling process. For sea level rise, IPCC AR6 published SSP1-2.6 projections separately, and risk platforms typically use these as hardcoded values.
How does CMIP6 change the picture for climate projections?
CMIP6 models show higher climate sensitivity (ECS range: 1.8-5.6°C) than CMIP5, projecting more warming for the same emissions. CMIP6 also introduced SSPs combining socioeconomic narratives with radiative forcing, replacing the simpler RCPs from CMIP5. For more on the differences, see our climate models guide.
