Climate Change

Climate attribution examines the contribution of particular drivers to an observed climate change or event. Depending on the question, the analysis may compare observations with simulations representing anthropogenic and natural influences, assess physical mechanisms, or use several independent lines of evidence. The IPCC describes attribution methods that include model-based fingerprinting, process-based approaches, empirical methods, and counterfactual comparisons.

Historical observations can establish whether temperature, precipitation, sea level, or another climate variable changed over the period relevant to a dispute. An expert may compare station records, gridded datasets, reanalyses, satellite observations, and model simulations while considering changes in measurement coverage and uncertainty. The appropriate dataset depends on the variable, location, and timescale being examined.

A global or large-scale climate projection does not automatically establish conditions at a specific property, city, watershed, or project site. Regional analysis may require downscaling, local observations, multiple model simulations, and consideration of processes that operate below a global model's resolution. The expert can determine whether the available climate information supports the level of geographic specificity claimed in the dispute.