| 17 Jul 2026
Overview of ParallelClim-WestUS-Daily – high-resolution observed and counterfactual daily climate data for the western United States, 1951–2025
Abstract. Extreme climate events and trends commonly elicit curiosity as to the role of anthropogenic climate change. In the western United States (US), severe droughts and heatwaves over the first quarter of the 21st century have strained water-management, agricultural, and ecological systems while also putting humans at risk from wildfires and hydrological hazards. Understanding whether and how climate change has promoted or intensified these processes requires estimating anthropogenic effects on a wide range of climate variables, including background mean conditions, higher-frequency variances, and how these changes have been distributed intra-annually and spatially. Here we introduce ParallelClim-WestUS-Daily, a new dataset of observed daily, high-resolution (~4 km) gridded climate data for the western US from 1951–2025 as well as a parallel, counterfactual realization of the observed sequence of climate but excluding anthropogenic changes in background mean climate or daily variances. Our dataset includes eight surface climate variables commonly used in hydrological, vegetation, and wildfire modeling: daily precipitation total, daily maximum and minimum temperature, and daily means of vapor pressure, wind velocity, downwelling shortwave and longwave radiation, and surface pressure. Anthropogenic climate change is estimated as the weighted mean change among 24 climate models relative to the second half of the 19th century according to the CMIP6 Historical experiment through 2014, extended with SSP2-4.5 for 2015–2025. Model weightings are based on agreement with global surface temperature trends, limiting the influence of models with likely unrealistic climate sensitivities to greenhouse-gas forcing. The ParallelClim-WestUS-Daily dataset will allow new opportunities to explore effects of anthropogenic climate change on western US hydroclimate and complex hydroclimatic impacts such as soil moisture, snowpack, streamflow, vegetation productivity, and wildfire.
Review of “Overview of ParallelClim-WestUS-Daily – high-resolution observed and counterfactual daily climate data for the western United States, 1951–2025” by Williams et al.
Overall recommendation: Minor revision
General comment:
This paper introduces a newly created dataset, named ParallelClim-WestUS-Daily. It includes 8 surface variables in daily frequency, which were generated for a virtual parallel world with an assumption with what if there was no anthropogenic climate change. To remove the anthropogenic changing signal from the real-world observation, the authors leveraged output of climate models that were conducted for the CMIP6. In particular, they used simulations from CMIP6’s Historical and SSP2-4.5 experiments to extract the change by subtracting the last half of the 19C mean. Model weightings were considered with their consistency in reproducing the observed temperature trend.
The newly created dataset has 4-km resolution and covers 1951-2025 over the western US (about half of CONUS). The dataset was created from the nClimGrid-daily dataset of NOAA, PRISM, dynamically downscaled ERA5, or other reanalysis datasets, depending on variables.
I find the dataset to be a very useful resource to the community. The manuscript is well prepared with detailed information on data production methodology, technical/scientific reasonings for choices that were made for the production, and validation. I only have a few minor comment and recommend accepting the manuscript.
Specific comments:
Line 271 ESGF: Please consider citing Williams et al. 2016 for ESGF.
Williams, D. N., Balaji, V., Cinquini, L., Denvil, S., Duffy, D., Evans, B., Ferraro, R., Hansen, R., Lautenschlager, M., and Trenham, C.: A Global Repository for Planet-Sized Experiments and Observations, B. Am. Meteorol. Soc., 97, 803–816, https://doi.org/10.1175/BAMS-D-15-00132.1, 2016.
Figure 2: For the left column, it looks like the panels are for anomaly time series of global surface temperature, that could be used to get trend from it, rather than trend itself. Some clarification would be helpful. For the CDF column, labels for dotted and red lines would be helpful as well. The similar comment applies to Figures 3 and 4.
Line 760-763, Data: I confirmed both datasets are available at the given links. I presume the second link is a temporary one and will be updated to https://doi.org/10.5281/zenodo.20261472 once the paper gets accepted. Code availability is also confirmed.