...6.4 °C (2.0 to 11.5 °F) during the twenty-first century. Subscribe to Government Jobs The past 200-plus years, mean global temperatures have been rising from natural environment and human activity is a significant contributing factor in changing mean global temperatures. Mainly from vehicles, and burning forests, smokestacks, are perhaps the leading power driving the fashion. Gases affect the green house, carbon dioxide, methane, nitrous oxide etc into the atmosphere. The major source of carbon ...