This working group addresses the challenge of quantifying climate change and variability and its relationship to ecosystem response at long-term ecological research sites. We will examine the accumulated evidence of climate change and variability from selected long-term ecological research sites, which have been participating in intersite analysis of climate trends since 2009, and discuss implications for ecological responses to climate change. We will review state-of-the-art quantitative techniques to analyze trends and uncertainty in climate records at long-term ecological research sites. Participants will discuss the utility of long-term records as the basis for forecasts of future climate, and how climate model predictions can be downscaled to related to observed changes at long-term ecological research sites. The group will formulate a plan for continued intersite analysis of climate change and anticipated ecosystem responses at decadal to multi-decadal time scales at long-term ecological research sites.