Temperature

Mean Annual Temperature

About this indicator: This indicator is the average of the last ten years' annual temperature in the Puget Sound lowlands as compared to the near term historical average temperature (the average from 1971 to 2000). This indicator is chosen as a rough proxy to track the impact of global warming and climate change at the regional level.

Drivers/influencing factors: Many regional climatic factors control changes in annual temperatures. For example, cyclic and natural changes in oceanic sea surface temperatures can result in persistent weather patterns such as El Nino and La Nina that can last from months to years. In King County, La Nina weather patterns, for example, usually result in cooler and wetter than average weather conditions. In addition to natural causes of climate variability, human caused climate change driven by greenhouse gas emissions (such as carbon dioxide) are a strong control on global and local climate. Because there is significant year to year natural variability in average temperature, and because this indicator is focused on measuring the human caused impact on regional climate, a 10 year average temperature is used.

Status: The ten year running average for the Puget Sound Lowlands (1999-2008) is 0.45ºF above the 1971-2000 average. Overall, five of the 10 warmest years on record for the contiguous U.S. have occurred since 1999, part of a five decade period in which mean temperatures for the contiguous U.S. have risen at a rate near 0.4ºF per decade. This data indicates that the trends observed for the region is consistent with U.S. and national trends of a warming and changing climate system.

Mean annual temperature
2007 Findings
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