Supported Climate Scenarios
Climate scenarios are projections of future climate conditions based on different assumptions about greenhouse gas emissions, technological developments, socioeconomic factors, and policy decisions. Not all hazards are impacted by changing climate conditions; others may not yet show a clear impact due to general scientific uncertainty.
Current Scenario
Current scenarios represent conditions in the current time period based on historical, observed, or modeled data. We provide the potential risk for all hazards in the current scenario.
For some hazards, we also apply metrics from the current scenario, as described:
Earthquakes – Some physical hazard risks, such as earthquakes, aren't expected to change as the climate changes. These risks will continue to be a factor in the future at similar levels to today, so the current risk is the same as the future risk. We apply current metrics to future scenarios.
Strong winds and tornadoes – While it's possible that climate change could impact strong winds and tornadoes, the scientific community's current understanding of the magnitude and direction of these changes is inconclusive. Therefore, we also apply current metrics to future scenarios for strong winds and tornadoes.
Sea level rise – We report inundation depths given sea level rise of 0 ft, 1 ft, and 2 ft. Both 1 ft and 2 ft represent future sea level rise. However, different locations are expected to reach those levels at different times. In our current dataset, 1 ft broadly corresponds to 2030-2050 and 2 ft to 2050-2080, depending on local conditions. To explore local scenarios, you can use the NOAA Sea Level Rise Viewer.
FEMA flood and inland flood – We depend on FEMA data for these hazards, which only report current risks. Although climate change may impact inland flooding, we only report current risks based on FEMA. Metrics for future scenarios are reported as null.
Future Scenarios
We use Coupled Model Intercomparison Project Phase 5 (CMIP5) or Coupled Model Intercomparison Project Phase 6 (CMIP6) as the basis of our future hazard metrics whenever possible. Certain metrics, such as temperature and precipitation, are output directly by the models. However, climate models do not generally output many hazards, including hurricane probability or wildfire probability. Instead, we model these based on CMIP6 variables that drive these hazards, such as temperature, precipitation, soil moisture, and vegetation.
Overview of Climate Scenarios
A brief explanation of Representative Concentration (RCP) and Shared Socioeconomic Pathways (SSP) scenarios may help you understand our supported metrics.
Representative Concentration Pathways (RCP) Scenarios
CMIP5 models are based on Representative Concentration Pathways (RCP) used to project future greenhouse gas concentrations. Greenhouse gas concentration trajectory is used to model the potential impacts of different radiative forcing levels.
Radiative forcing describes the energy balance across the boundary of the earth's atmosphere caused by factors such as changes in greenhouse gases. Higher levels of radiative forcing mean that more net radiation is coming into the earth's atmosphere than being emitted, causing the earth to warm. It's measured in watts per square meter and used when describing Representative Concentration Pathways (RCPs), which are named according to the value forecast in 2100 relative to pre-industrial values. For example, RCP 4.5 predicts a radiative forcing of 4.5 Watts per square meter (W/m2) by 2100, and RCP 8.5 predicts 8.5.
Shared Socioeconomic Pathways (SSP) Scenarios
The SSPs were developed over the last several years as a community effort and describe global developments leading to different challenges for mitigation and adaptation to climate change.
The Shared Socioeconomic Pathways (SSP) Scenarios used in CMIP6 models were developed to help explain how different global societal trends, such as population, economic growth, education, urbanization, and the rate of technological development, might influence greenhouse gas emissions and climate change. Effectively, they're an extension of RCP and use the equivalent radiative forcing values in conjunction with societal trends.
Five SSP (1-5) scenarios represent changes in global societal trends. You can see the differentiation with these two examples:
SSP2 – indicates a path in which social, economic, and technological trends do not shift markedly from historical patterns and include moderate changes in development and a mixture of progress and challenges. Its projected radiative forcing aligns with RCP 4.5, resulting in the SSP2-4.5 climate scenario.
SSP5 – represents a continued dependency on fossil fuels, rapid economic growth, and global development. This path rapidly increases greenhouse gas emissions that align with RCP 8.5, resulting in the SSP5-8.5 climate scenario.
Supported Future Scenarios
For supported hazards, we provide metrics for these SSP scenarios (or their RCP-equivalents):
SSP2-4.5 2030 and 2050 (Moderate) – a middle-of-the-road scenario with a moderate reduction of greenhouse gas dependencies and continued historical, societal development patterns.
SSP5-8.5 2030 and 2050 (Severe) – a fossil-fuel-dependent scenario with increased greenhouse gas emissions and rapid economic growth and development.