by William R. Cline, Peterson Institute for International
Economics Op-ed in the Omaha World-Herald April 13, 2008 © Omaha
World-Herald Global average temperatures rose about 1 degree
Fahrenheit during the 20th century, and most scientists
attribute the change primarily to man-made global warming.
Concentrations of carbon dioxide, the main greenhouse gas
trapping heat and causing global warming, are now about one-
fourth higher than their known average in the 19th century.
Under the more plausible scenarios for world growth and energy
use, global emissions of carbon dioxide would approximately
double by 2050 and quadruple by 2100. The rise would occur
partly because energy is estimated to shift increasingly from
natural gas and oil toward coal, which is more abundant and more
intensive in carbon dioxide emissions. The amount of carbon
dioxide in the atmosphere is estimated to double from its
present level by the end of this century. Average temperatures
would be about 5 degrees Fahrenheit higher than today, an