Climate
T h e c l i m a t e i s c o m m o n l y c o n s i d e r e d t o b e t h e w e a t h e r a v e r a g e d o v e r a l o n g p e r i o d o f t i m e , t y p i c a l l y 3 0 y e a r s . S o m e w h a t m o r e p r e c i s e l y , t h e c o n c e p t o f " c l i m a t e " a l s o i n c l u d e s t h e s t a t i s t i c s o f t h e w e a t her - s u c h a s t h e d e g r e e o f d a y - t o - d a y o r y e a r - t o - y e a r v a r i a t i o n e x p e c t e d . T h e I n t e r g o v e r n m e n t a l P a n e l o n C l i m a t e C h a n g e ( I P C C ) g l o s s a r y d e f i n i t i o n i s :
C l i m a t e i n a n a r r o w s e n s e i s u s u a l l y d e f i n e d a s t he a v e r a g e w e a t h e r , o r m o r e r i g o r o u s l y , a s t h e s t a t i s t i c a l d e s c r i p t i o n i n t e r m s o f t h e m e a n a n d v a r i a b i l i t y o f r e l e v a n t q u a n t i t i e s o v e r a p e r i o d o f t i m e r a n g i n g f r o m m o n t h s t o t h o u s a n d s o r m i l l i o n s o f y e a r s .
T h e c l a s s i c a l p e r i o d i s 3 0 y e a r s , a s d e f i n e d b y t h e W o r l d M e t e o r o l o g i c a l O r g a n i z a t i o n ( W M O ) . T h e s e q u a n t i t i e s a r e m o s t o f t e n s u r f a c e v a r i a b l e s s u c h a s t e m p e r a t u r e , p r e c i p i t a t i o n , a n d w i n d . C l i m a t e i n a w i d e r s e n s e i s t h e s t a t e , i n c l u d i n g a s t a t i s t i c a l d e s c r i p t i o n , o f t h e c l i m a t e s y s t e m .
Climate versus weather
Climate diagram of Bangkok, ThailandIn the most succinct words, weather is the combination of events in the atmosphere and climate is the overall accumulated weather in a certain location.
The exact boundaries of what is climate and what is weather are not well defined and depend on the application. For example, in some senses an individual El Niņo event could be considered climate; in others, as weather.
When the original conception of climate as a long-term average came to be considered, perhaps towards the end of the 19th century, the idea of climate change was not current, and a 30 year average seemed reasonable.
Given the current availability of data on long-term trends in the temperature record, it is harder to give a definition of climate to suit all purposes: over a 30 year period, averages may shift; over a shorter period, the statistics are less stable.
In a given geographical region, the climate generally does not vary over time on the scale of a human life span.
However, over geological time, climate can vary considerably for a given place on the Earth. For example, Scandinavia has been through a number of ice ages over hundreds of thousands of years (the last one ending about 10,000 years ago).
Paleoclimatology is the study of these past climates, their origin, and by extension, the origin of today's climate.
Classifications and Other Information Wikipedia
Ancient Warming Caused Huge Spike in Temps, Study Says National Geographic - December 20, 2007
Rising seas 'to beat predictions' BBC - December 17, 2007
11 Hottest Years Occurred in Past 13 Live Science - December 13, 2007
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