Climate and Global Change

Warm near the equator and cold at the poles, our planet is able to support a variety of living things because of its diverse regional climates. The average of all these regions makes up Earth's global climate. Climate has cooled and warmed throughout Earth history for various reasons. Rapid warming like we see today is unusual in the history of our planet. The scientific consensus is that climate is warming as a result of the addition of heat-trapping greenhouse gases which are increasing dramatically in the atmosphere as a result of human activities.

Roaming across Arctic <a
  href="/earth/polar/sea_ice.html&edu=high&dev=1">sea ice</a>, <a
  href="/earth/polar/polar_bears_jan07.html&edu=high&dev=1">polar
  bears</a> peer through cracks in the ice to look for ringed seals, their
  favorite food, in the water below. Almost all of a polar bear's food comes
  from the sea. The <a
  href="/earth/polar/sea_ice.html&edu=high&dev=1">floating sea
  ice</a> is a perfect vantage point for the bears as they hunt for food.
  Unfortunately, the amount of sea ice floating in the <a
  href="/earth/polar/polar_north.html&edu=high&dev=1">Arctic
  region</a> is shrinking each year, and getting farther apart.<p><small><em>Image courtesy of Ansgar Walk.  Creative Commons Attribution-Share Alike 2.5 Generic license.</em></small></p><a href="/earth/climate/cli_define.html&edu=high&dev=1">Regional climate</a> is
the average weather pattern in a place over more than thirty years,
including the variations in
<a href="/earth/climate/cli_seasons.html&edu=high&dev=1">seasons</a>.
The climate of a region depends on many factors including sunlight,
altitude, topography, and proximity to oceans. Since the equatorial regions
receive more sunlight than the poles, climate varies with
<a href="/earth/climate/cli_latitude.html&edu=high&dev=1">latitude</a>.
This image shows how sea surface temperatures change at different latitudes.<p><small><em>Image courtesy of NOAA.  Public domain.</em></small></p>Many forms of air pollution are human-made. Industrial plants, power plants
and vehicles with internal combustion engines produce <a href="/earth/climate/nitrogen_airpollution.html&edu=high&dev=1">nitrogen
oxides</a>,
<a href="/earth/Atmosphere/vocs.html&edu=high&dev=1">VOCs</a>,
<a href="/physical_science/chemistry/carbon_monoxide.html&edu=high&dev=1">carbon monoxide</a>,
<a href="/physical_science/chemistry/carbon_dioxide.html&edu=high&dev=1">carbon dioxide</a>,
<a href="/physical_science/chemistry/sulfur_oxides.html&edu=high&dev=1">sulfur dioxide</a> and
<a href="/earth/Atmosphere/particulates.html&edu=high&dev=1">particulates</a>.
Some of these gases are <a href="/earth/climate/cli_greengas.html&edu=high&dev=1">greenhouse
gases</a>,
meaning that they retain heat in the Earth's atmosphere, due to the Earth's
<a href="/earth/climate/earth_greenhouse.html&edu=high&dev=1">greenhouse effect</a>.<p><small><em>Image copyright UCAR</em></small></p>On November 7, 2013, Typhoon Haiyan (Yolanda in the Philippines) made landfall, with imated wind speeds of ~315 km/hr - the strongest <a href="/earth/Atmosphere/hurricane/intensity.html&edu=high&dev=1">tropical cyclone</a> to make landfall in recorded history.  As Haiyan moved across the Philippines before reaching Vietnam and China, its <a href="/earth/Atmosphere/wind.html&edu=high&dev=1">winds</a> and <a href="/earth/Atmosphere/hurricane/surge.html&edu=high&dev=1">storm surge</a> left devastation in its wake, leading to massive loss of life, destruction of homes, and hundreds of thousands of displaced inhabitants. <a href="http://www.cnn.com/2013/11/09/world/iyw-how-to-help-typhoon-haiyan/index.html">How to Help</a><p><small><em>Image courtesy of COMS-1, SSEC, University of Wisconsin-Madison</em></small></p>Scientists at the University of Michigan have found that <a href="/earth/polar/cryosphere_permafrost1.html&edu=high&dev=1">permafrost</a> in the <a href="/earth/polar/polar_north.html&edu=high&dev=1">Arctic</a> is extremely sensitive to sunlight.  Exposure to sunlight releases carbon gases trapped in the permafrost, including <a href="/earth/climate/earth_greenhouse.html&edu=high&dev=1">climate-warming</a> <a href="/physical_science/chemistry/carbon_dioxide.html&edu=high&dev=1">carbon dioxide</a>, to the <a href="/earth/Atmosphere/overview.html&edu=high&dev=1">atmosphere</a> much faster than previously thought.<p><small><em>George Kling, The University of Michigan</em></small></p>Scientists are concerned that melting Arctic sea ice will increase the amount of fresh water in the <a href="/earth/polar/arctic_currents.html&edu=high&dev=1">Beaufort Gyre</a>, which could spill out into the Atlantic and cause major climate shifts in North America and Western Europe. Watch the <a href="/earth/changing_planet/freshwater_arctic.html&edu=high&dev=1">Changing Planet: Fresh Water in the Arctic video</a>.<p><small><em> Courtesy of Jack Cook, WHOI (<a href="http://www.whoi.edu">Woods Hole Oceanographic Institute</a>)</em></small></p>

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