This dataset collection presents a global surface ozone compilation for long-term trends and ESM (Earth System Model) evaluation.

The project (Process Based Earth System Model Evaluation) brought together all publicly available surface ozone observations from online databases from the modern era to build a consistent dataset for the evaluation of chemical transport and chemistry-climate (Earth System) models for projects such as the Chemistry-Climate Model Initiative (CCMI) and Aer-Chem-MIP.

From a total dataset of approximately 6600 sites and 500 million hourly observations from 1971-2015, approximately 2200 sites and 200 million hourly observations pass screening as high-quality sites in regional background locations that are appropriate for use in global model evaluation. There was generally good data volume in the datasets since the start of air quality monitoring networks in 1990 through to 2013. Ozone observations are biased heavily toward North America and Europe with sparse coverage over the rest of the globe.

This dataset collection was made available for the purposes of model evaluation as a set of gridded metrics intended to describe the distribution of ozone concentrations on monthly and annual timescales. This collection currently holds version 2.4 data only, but future versions may follow.