Framework / Assessment California Forests and Rangelands: Proposed Indicators Summary Evaluate departure in air temperature by ecosystem units as a measure of climate warming. This will allow comparison of differing degrees of climate warming across forest ecosystems. Air Temperature is a direct indicator of climate change and can have impacts on forest and ecosystem health. Use climate data from downscaled Global Climate Models (GCM) to assess warming trends among ecosystem units. Indicator will evaluate both historic conditions and project future conditions.