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&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">sea ice</a>, <a
  href="/earth/polar/polar_bears_jan07.html&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">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&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">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&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">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/polar/cryosphere_permafrost1.html&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">Permafrost</a> is
ground that is below the freezing point of water (0C or 32F) for two
or more years. Permafrost is found at high latitudes like the
<a href="/earth/polar/polar_north.html&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">Arctic</a> and
<a href="/earth/polar/polar_south.html&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">Antarctic</a>.
It is also common at high altitudes - like mountainous areas wherever the
<a href="/earth/climate/cli_define.html&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">climate</a> is
cold. 
Permafrost has been thawing relatively quickly in recent years. Scientists
have found that the rate of permafrost thaw has increased because of <a href="/earth/climate/cli_effects.html&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">global
warming</a>.<p><small><em>Image courtesy of the    USGS</em></small></p><a href="/earth/climate/cli_define.html&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">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&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">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&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">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>Greenland's <a href="http://www.windows2universe.org/earth/polar/cryosphere_glacier1.html">ice sheet</a> saw a record <a href="http://www.windows2universe.org/headline_universe/olpa/greenland_10dec07.html">melt</a> in July 2012.  Scientists studying this event have found that this melting event was triggered by an influx of unusually warm air and amplified by the presence of a blanket of thin low-level <a href="http://www.windows2universe.org/earth/Atmosphere/cloud.html">clouds</a> which pushed temperatures up above freezing.  For more information see the <a href="http://www.news.wisc.edu/21638">press release</a> from the University of Wisconsin Madison.<p><small><em>Image courtesy of University of Wisconsin-Madison</em></small></p>As temperatures rise and soil moisture decreases, plants are stressed, which can lead to <a href="/earth/climate/crops_withering.html&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">crop withering</a>. <a href="/teacher_resources/online_courses/health/events_health.html&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">Droughts</a> accompanied by increased temperatures can lead to famine, social and political disruptions. Scientists are  helping with early identification of drought that might trigger food shortages. Watch the NBC Learn video - <a href="/earth/changing_planet/withering_crops_intro.html&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">Changing Planet: Withering Crops</a> to find out more.<p><small><em>Image taken by Tomas Castelazo, Creative Commons <a href=&quot;http://creativecommons.org/licenses/by/3.0/deed.en&quot;>Attribution 3.0 Unported</a> license.</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&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">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&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">winds</a> and <a href="/earth/Atmosphere/hurricane/surge.html&dev=1/earth/Atmosphere/moons/=/earth/climate/cli_greengas.html">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>

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