Why

Climate models have similar inputs of solar variability, volcanic eruptions, anthropogenic forcings, but have internal variability that will not coincide directly with the weather. They are not a hindcast and will not mirror history (not decade specific). Additionally, natural variability can mask climate signals in any year or decade, but over time (multiple decades), projections do capture the overall trend from increased greenhouse gas emissions. Therefore, year-to-year or decade-to-decade comparisons can be confusing and misleading. Instead comparisons between longer periods that capture natural variability should be used.

This DON'T will provide details and examples of how to make comparisons that account for variability appropriately.