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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">sea ice</a>, <a
  href="/earth/polar/polar_bears_jan07.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">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">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">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">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">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>Coral animals build reefs in warm, tropical seawater. However, <a href="/earth/changing_planet/ocean_temperatures_intro.html">seawater can be too warm</a> for their liking.  If waters get too warm, coral animals lose the algae that live within their little bodies, a process called coral bleaching. Without the algae, corals have less nutrition. Unless cooler temperatures return, allowing algae to
 return, the coral dies.<p><small><em>Credit: UNC</em></small></p>Scientists at the University of Michigan have found that <a href="/earth/polar/cryosphere_permafrost1.html">permafrost</a> in the <a href="/earth/polar/polar_north.html">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">climate-warming</a> <a href="/physical_science/chemistry/carbon_dioxide.html">carbon dioxide</a>, to the <a href="/earth/Atmosphere/overview.html">atmosphere</a> much faster than previously thought.<p><small><em>George Kling, The University of Michigan</em></small></p>Greenlandís <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>A <a href="http://iopscience.iop.org/1748-9326/8/2/024035/article">study</a> of over 40,000 written entries in Irish Annals and ice core measurements shows a strong correlation between <a href="http://www.windows2universe.org/earth/interior/eruptions.html">volcanic eruptions</a> and extreme cold weather in Ireland over a 1200 year period, from 431 to 1649.  During this time up to 48 volcanic eruptions were identified in Greenland ice core records through deposition of volcanic sulfate in annual layers of ice. Find out more about <a href="http://www.windows2universe.org/earth/climate/geosphere_volcanoes_influence_on_climate.html">volcanoes and climate</a>.<p><small><em>Image Courtesy of Marco Fulle</em></small></p>

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA