Weather vs. Climate

Posted on January 16, 2009

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It’s winter, and just as ever summer brings out kooks claiming that a hot spell in Colorado is the result of global warming, so too does winter bring out the kooks claiming that record cold temperatures and snowfall in New England means global warming is bunk. In both cases people are confusing weather and climate. So, as an Official S&R Public Service Announcement™, here’s the definitions of weather and climate, as well as a number of easy to understand examples of each.

weather
climate
  • The slowly varying aspects of the atmosphere–hydrosphere–land surface system. (source : American Meteorology Society)
  • The average of weather over at least a 30-year period. Note that the climate taken over different periods of time (30 years, 1000 years) may be different. The old saying is climate is what we expect and weather is what we get. (source: NOAA Climate Prediction Center)
  • Climate in a narrow sense is usually defined as the “average weather,” or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands of years. (source: EPA Glossary of Climate Change Terms)
Weather is… Climate is…
…a thunderstorm. …a million thunderstorms in the same area over decades.
…a single tornado. …a region affected by seasonal tornadoes for decades or centuries at a time.
…a hot spell in the summer. …a hot spell that happens every at the same time and place every year for decades at a time.
…an extreme hurricane season. …decades of “extreme” hurricane seasons defining a new norm for hurricane intensity.
…India’s monsoon coming late one year. …the average date of the arrival of India’s monsoon averaged over the last 30+ years.
…the Amazon basin’s rain pattern today. …the Amazon basin’s rain coming every day in a given season for hundreds or thousands of years in a row.
…an unusually large amount of snowfall. …how much snow falls every year, on average, over multiple decades.
…an arctic cold snap causing record cold in Scotland. …arctic cold snaps happening at the same place at the same time for years or decades on end.

Any questions?

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