The global average temperature in 2011 was the ninth-warmest in the modern meteorological record that began in 1880, said National Aeronautics and Space Administration (NASA) scientists. NASA's Goddard Institute for Space Studies said the global average surface temperature for 2011 was 0.51 degrees C warmer than the mid-20th century baseline temperature. The current higher temperatures were largely attained by increased concentrations of greenhouse gases in the atmosphere, especially carbon dioxide. Carbon dioxide is emitted by human activities such as coal-fired power plants, fossil-fueled vehicles, and human breath. Currently carbon dioxide levels in the atmosphere exceed 390 parts per million (ppm), compared to 285 ppm in 1880 and 315 in 1960, said NASA.
