Global Climate Change Science
A large number of scientists believe that human activities, which have increased
atmospheric concentrations of carbon dioxide (CO2) by 35% from preindustrial values of 280
parts per million (ppm) to 378 ppm over the past 150 years, are leading to an increase in global
average temperatures. Global temperatures have already risen 0.6o
C (0.9o
F) in the last 100
years, and, according to model projections, might rise anywhere from as little as 1.8o
C to as
much as 7.1o
C (2.7o
F to 10.7o
F) over the next 100 years. However, the science of “global
warming” is not without challengers, who argue that scientific proof is incomplete or
contradictory, and that there remain many uncertainties about the nature and direction of Earth’s climate. Nevertheless, there is significant concern that human activities, such as the
burning of fossil fuels, industrial production, deforestation, and certain land-use practices are
increasing atmospheric concentrations of carbon dioxide (CO2) that, along with increasing
concentrations of other trace gases such as methane (CH4), nitrous oxide (N2O), hydrofluorocarbons
(HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6), may be leading to
changes in the chemical composition and physical dynamics of Earth’s atmosphere, including
how heat/energy is distributed between the land, ocean, atmosphere and space.