Data for: Climate change increases evaporative and crop irrigation demand in North America

Across North America, warmer temperatures have increased reference evapotranspiration (ETo), taxing water resources. This problem is especially pronounced for semi-arid regions with large amounts of irrigated agriculture, such as California’s Central Valley. In this region, increased ETo has increased irrigation demand, but the role of anthropogenic climate change (ACC) in driving this increase has not yet been quantified. Here, we quantify the first-order influence of ACC on ETo and how these changes have translated into increased irrigation demand. We calculated observed and counterfactual ETo over North America using ERA5-Land data and 20 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6). At the scale of North America, we found that ACC accounted for all of the observed ETo increase (1.06 mm/yr) during 1980-2022. The largest observed increases in ETo were found in the southwestern and central regions, where ACC has likely exacerbated trends linked to natural clima..., , , # Data for: Climate change increases evaporative and crop irrigation demand in North America

[https://doi.org/10.5061/dryad.bcc2fqzpx](https://doi.org/10.5061/dryad.bcc2fqzpx)

## Description of the data and file structure

These data files accompany the manuscript, Climate Change Increases Reference Evapotranspiration and Crop Irrigation Demand in North America. Files included are observational ETo, CO2-adjusted observational ETo, and four estimates of counterfactual ETo (with forced contributions from T + RH, windspeed, solar radiation, and all variables removed). 

Observational and CO2-adjusted observational ETo were calculated from ERA5-Land using the Penman-Monteith Equation. Counterfactual ETo files were created by removing forced trends in each / variable from ERA5-Land; forced trends calculated using a low-pass filter on GCM data from CMIP6.

### Files and variables

#### File: ETo\_co2adj\_era5land\_obs.nc

**Description:** CO2-adjusted observational ETo (mm)

#### File: ETo\...,