Global warming is an increase in the average temperature in the world. Scientists were able to trace the global climate and concluded that over the past ten thousand years, the Earth's climate has been relatively constant. In the 20th century, global temperature increased by 0.740°C. The change in warming and cooling of global average temperatures causes climate change, a change related to climate patterns such as temperatures, precipitation, wind, and humidity. This temperature flow is affected by multiple factors, making it difficult to determine the true source of the problem. The facts show that the warming of the Earth is natural; however, there is some evidence that the warming trend has increased due to human activity. Global warming due to human activity Every day, human activity has negative effects on the environment. The burning of fossil fuels has released large concentrations of carbon dioxide (CO2) into the atmosphere. Developing countries like China and developed countries like the United States are consuming more fossil fuels, thereby releasing more CO2 from their intakes (Vital Signs 42). This released CO2 is more evident in urban areas. Many activities such as driving, using gas stoves, and burning coal release different types of gases called greenhouse gases. A greenhouse gas is a gas that traps heat in the atmosphere and helps warm the Earth's temperature, known as the greenhouse effect. Heat is retained because gases prevent Earth's heat from being released into space. According to Mary E. Williams, editor of Writing the Critical Essay Global Warming: "CO2 concentrations are higher than they have ever been...The IPCC concluded in 2001...... middle of the article... ...Survey. Gallup poll. March 2010. Web. May 19, 2014..Pacharuri, Dr. RK “United Nations Climate Change Summit, September 22, 2009 STATEMENT BY DR. RK PACHAURI Chairman, Director General of the IPCC” Questions and answers on global warming and abrupt climate change. Worldwatch Institute. 2014. Web May 19, 2014. http://www.worldwatch.org/node/3949Resources Institute Director, Yale Climate and Energy Institute. IPCC, September 22, 2013. Web. May 19, 2014..Williams, Mary E. Writing the Critical Essay on Global Warming. Farmington Hills, MI 48331-3535: Greenhaven, 2006. Print. WorldWatch Institute Vital Signs 2007-2008 The trends shaping our future. New York, NY 10110: WW Norton & Company, Inc, 2007. Print.