Weather is an all-encompassing term used to describe all of the many and varied phenomena that can occur in the atmosphere of a planet. The term is normally taken to mean the activity of these phenomena over short periods of time, usually no more than a few days in length. Average atmospheric conditions over significantly longer periods are known as climate. Usage of the two terms often overlaps and the concepts are obviously very closely related.

Basic mechanism

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Weather phenomena result from temperature differences around the globe, which arise mainly because areas closer to the tropics, around the equator, receive more energy from the Sun than more northern and southern regions, nearer to the Earth's poles.

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Weather & Natural Disasters Coverage | PBS NewsHour | PBS

News Wrap: Storm Pounds Midwest, New England
Wed, 09 Dec 2009 18:20:00 -0500
In other news, a major winter storm that rocked the midwest earlier this week has moved east to New England, and General David Petraeus warned the surge in Afghanistan may be tougher than the surge in Iraq.
Fact Sheet: Copenhagen Climate Summit
Mon, 07 Dec 2009 10:04:00 -0500
Representatives from 192 nations are converging on Copenhagen Monday for the opening day of the two-week United Nations Climate Change Conference, where the next steps are expected to be hashed out towards an international emissions agreement.
In Australia, Drought Threatens Natural Resources
Tue, 01 Dec 2009 18:33:00 -0500
Special correspondent Fred de Sam Lazaro takes an in-depth look into the drought plaguing Australia.
News Wrap: Iran May Not Send Uranium Abroad
Thu, 29 Oct 2009 18:15:00 -0500
In other news, Iran gave no indication it will agree to a U.N. plan to ship most of its nuclear fuel abroad for enrichment, and President Obama traveled to the military post at Dover, Del. to honor 18 American killed in Afghanistan earlier this week.
Cities Struggle With Access to Green Energy Sources
Wed, 28 Oct 2009 18:36:00 -0500
In cities across the country, officials are faced with the task of getting renewable energy from the outskirts of town to the urban centers where demand is greatest. NewsHour correspondent Spencer Michels reports from Los Angeles.
Obama Visits New Orleans to Gauge Recovery
Thu, 15 Oct 2009 18:03:00 -0500
President Obama flew to New Orleans on Thursday to assess the city's recovery efforts in the aftermath of Hurricane Katrina. Margaret Warner reports.

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