Anti-crepuscular rays are beams of sunlight that appear to converge on a point opposite the sun. They are similar to crepuscular rays, but are seen opposite the sun in the sky. Anti-crepuscular rays are most frequently visible near sunrise or sunset. This photo of anti-crepuscular rays was taken at sunset in Boulder, Colorado. Crepuscular rays are usually much brighter than anti-crepuscular rays.<p><small><em> Image Courtesy of Carlye Calvin</em></small></p>Scientists at the University of Michigan have found that <a href="/earth/polar/cryosphere_permafrost1.html&edu=elem&dev=1">permafrost</a> in the <a href="/earth/polar/polar_north.html&edu=elem&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=elem&dev=1">climate-warming</a> <a href="/physical_science/chemistry/carbon_dioxide.html&edu=elem&dev=1">carbon dioxide</a>, to the <a href="/earth/Atmosphere/overview.html&edu=elem&dev=1">atmosphere</a> much faster than previously thought.<p><small><em>George Kling, The University of Michigan</em></small></p>As temperatures rise and soil moisture decreases, plants are stressed, which can lead to <a href="/earth/climate/crops_withering.html&edu=elem&dev=1">crop withering</a>. <a href="/teacher_resources/online_courses/health/events_health.html&edu=elem&dev=1">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&edu=elem&dev=1">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 May 20, 2013, a massive EF5 <a href="http://www.windows2universe.org/earth/Atmosphere/tornado.html">tornado</a> hit Moore, Oklahoma, devastating communities and lives. The tornado, on the ground for 40 minutes, took a path through a subdivision of homes, destroying block after block of homes, and hitting two elementary schools just as school was ending as well as a hospital. Hundreds of people were injured, and 24 were killed.<p><small><em>Image courtesy of Ks0stm, Creative Commons Attribution-Share Alike 3.0 Unported license</em></small></p>A new study has found that <a href="/earth/Atmosphere/airpollution_intro.html&edu=elem&dev=1">pollution</a> from <a href="/earth/Atmosphere/particulates.html&edu=elem&dev=1">fine particles</a> in the air - mainly the result of burning coal or <a href="/earth/interior/eruptions.html&edu=elem&dev=1">volcanic eruptions</a> - can shade <a href="/earth/Life/cnidarian.html&edu=elem&dev=1">corals</a> from sunlight and cool the surrounding water resulting in reduced growth rates. Coral growth rates in the Caribbean were affected by volcanic aerosol emissions in the early 20th century and by aerosol emissions caused by humans in the later 20th century. For more information, see the <a href="http://www.exeter.ac.uk/news/featurednews/title_278202_en.html">press release</a>.<p><small><em>Image courtesy of Toby Hudson (Wikimedia Commons)</em></small></p>This image is a montage of high resolutions photographs of the Earth taken in January 2012 by the Visible/Infrared Imager Radiometer Suite (VIIRS) instrument on the Suomi NPP satellite. The image shows many stunning details of <a href="http://www.windows2universe.org/earth/earth.html">our home planet</a> - <a href="http://solarsystem.nasa.gov/multimedia/gallery/VIIRS_4Jan2012.jpg">particularly at high resolution</a>. The beauty of our planet is obvious from space - our blue <a href="http://www.windows2universe.org/earth/Water/overview.html">waters</a>, our white <a href="http://www.windows2universe.org/earth/Atmosphere/cloud.html">clouds</a>, and the green from <a href="http://www.windows2universe.org/earth/Life/life.html">life</a> abundant at the surface.<p><small><em>Image courtesy of NASA</em></small></p>


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