An increase in the average air temperature on the Earth's surface is called global warming. Global warming is part of a natural cycle and is not caused by increased human-caused carbon dioxide emissions. Humans are therefore not responsible for global warming. Global warming is part of a natural cycle of climate change. The Pleistocene describes the period from 1.8 million years ago to about 10,000 years ago. During the Pleistocene, significant advances of continental ice sheets occurred in North America and Europe. The Holocene Maximum is a period that occurred around 11,000 years ago and marked the end of the Ice Age. Temperatures then were much higher than today. The period between 900 and 1300 AD is known as the Medieval Warm Period, where higher temperatures were documented in historical accounts. The Little Ice Age took place between the 16th and mid-19th centuries. During this period, polar ice caps extended much further from the poles than they do now. Accordingly, it is acceptable to assert that climate change and therefore global warming are part of the Earth's natural cycle. Global warming is claimed to be “man-made” because it is caused by greenhouse gases (notably carbon dioxide) which contribute to the “greenhouse effect”. The sun emits shortwave radiation through the upper atmosphere to Earth. The Earth's surface is warmed and the Earth emits long-wave infrared rays into space. Greenhouse gases absorb infrared radiation from the sun and reflect it back to Earth. The Earth's surface is warmed by reflected heat, which consequently leads to global warming. Human-caused carbon dioxide emissions alone cannot be...... middle of paper ......lobalwarmingswindle.co.uk/temperature_record.html. [Accessed March 1, 2009].Anon. (2009). CO2 and temperature. The great global warming scam. (Online). Available: http://www.greatglobalwarmingswindle.co.uk/co2_temperature.html. [Accessed March 1, 2009].Anon. (2007). The Great Global Warming Swindle: Carbon Dioxide Is Not the Culprit!. Stranger than fiction. (Online). Available: http://www.mymultiplesclerosis.co.uk/stranger-than-fiction/global-warming.html. [Accessed March 1, 2009]. Hamilton, C.J. (2009). Sun. Views of the solar system. (Online). Available: http://www.solarviews.com/eng/sun.htm [Accessed: February 1, 2010] Gutmann, E. (2008). Investigation into “the great global warming scam.” Ars Technica. (Online). Available: http://arstechnica.com/science/news/2008/04/investigating-the-great-global-warming-swindle.ars. [Accessed: March 1 2009].