Climate Data for Flood Model

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Learn more about the climate data that is included in the First Street Foundation flood model.

The First Street Foundation Flood Model is unique in the way it accounts for a changing climate. Typical flood models derive their flows based purely on statistical analyses of historical records of rainfall and stream gauges. The First Street Foundation Flood Model incorporates the output of an ensemble of 21 Global Climate Models (GCM) to account for the uncertainty of future climate scenarios as well as the current climate itself. Because extreme events occur infrequently by their nature, a long record of climate data is needed to attempt to characterize these extreme events. But by creating a long record, the analysis would cloud the changes in climate over time. 

The First Street Foundation Flood Model uses a baseline historical period of 1980-2010, creating a 30-year period of observed data. The Global Climate Model projections for 2020 allow for the creation of not only a new climate that accounts for changes since the historical data was recorded but also the potential spread of what the true climate actually is right now, as opposed to what a small sample has shown over the last few years. The 21 climate models create different outputs for several environmental factors. 

First Street has chosen to use the carbon emissions scenario represented by IPCC RCP 4.5. This represents a middle-ground scenario among the four primary emissions scenarios. Additionally, First Street chose to model low and high scenarios corresponding to the 25th and 75th percentiles of the distribution of the representation of environmental change values in the 21 GCM outputs. The climate models vary in the way they predict environmental changes, and this distribution is wide enough to encompass the range of change factors from the median representations of the other carbon emissions scenarios by 2050.


You can learn more about First Street’s Climate Model through the webinar that we hosted on the climate model. The slides for the presentation are here and the video is here.

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