What is the purpose of calibrating and validating environmental models, and what are two common performance metrics?

• A. Calibration tests predictive ability; Validation tunes parameters; metrics: p-values and t-tests.
• B. Calibration tunes model parameters to fit observed data; Validation tests predictive ability on independent data; metrics: R^2 (or NSE), RMSE, MAE.
• C. Calibration and validation are the same; metrics: AIC and BIC.
• D. Calibration adjusts data collection frequency; validation calibrates instruments; metrics: correlation only.

Answer: (B)