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2019-08-14. When Does Weather Become Climate?

posted Aug 21, 2019, 9:38 AM by Alan Gould
By Oliver Bothe, Eos/AGU. [https://eos.org/opinions/when-does-weather-become-climate] For GSS Energy Flow chapter 6 and Climate Change chapter 6. Excerpt: Individuals and political organizations alike often define “climate” as climate scientist John Kennedy did on Twitter: “Practically speaking: weather’s how you choose an outfit, climate’s how you choose your wardrobe.” Meanwhile, the scientific literature rarely defines climate more specifically than as the “statistics of weather.” ...Possibly the most common current definition is that from the Intergovernmental Panel on Climate Change’s (IPCC) Fifth Assessment Report, which distinguishes between “climate in a narrow sense…as the average weather…over a period of time ranging from months to…millions of years” and “climate in a wider sense” as “the state…of the climate system.” ...Earth’s climate system includes its atmosphere, hydrosphere, cryosphere, biosphere, and lithosphere. Besides statistics, descriptions of the climate system’s behavior may employ thermodynamics and fluid dynamics, along with chemistry, electromagnetism, rheology, and plasma physics. ...The American Meteorological Society defines weather as the “state of the atmosphere” at a specific time and emphasizes the minutes-to-days scale of its variations and how these variations influence life or a celestial body. ...If weather on Earth takes place over minutes to days and the shortest climate timescale is monthly, we need a conceptual definition of the transition between weather and climate. The IPCC separates climate variability from the scales of “individual weather events.”.... 
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