Measurements of temperature take by instruments all over the world , on land and at sea have revealed that during the 20 century the Earth's surface and lowest part of the atmosphere warmed up on average by about 0.6 c. During this period, man-made emissions of greenhouse gases, including carbon dioxide, methane and nitrous oxide have increased , largely as a result of the burning of fossil fuels for energy and transportation, and land use changes including deforestation for agriculture