No Doubts Global Warming Is Real, U.S.
Experts Say
Industrial emissions are a leading cause, they say --
contradicting critics, already in the minority, who argue that
climate change could be caused by mostly natural forces.
"There is no doubt that the composition of the atmosphere is
changing because of human activities, and today greenhouse gases are
the largest human influence on global climate," wrote Thomas Karl,
director of the National Oceanic and Atmospheric Administration's
National Climatic Data Center, and Kevin Trenberth, head of the
Climate Analysis Section at the National Center for Atmospheric
Research.
"The likely result is more frequent heat waves, droughts, extreme
precipitation events, and related impacts, e.g., wildfires, heat
stress, vegetation changes, and sea-level rise," they added in a
commentary to be published in Friday's issue of the journal Science.
Karl and Trenberth estimate that, between 1990 and 2100, there is
a 90 percent probability that average global temperatures will rise
by between 3.1 and 8.9 degrees Fahrenheit (1.7 and 4.9 degrees
Celsius) because of human influences on climate.
Such dramatic warming will further melt already crumbling
glaciers, inundating coastal areas. Many other groups have already
shown that ice in Greenland, the Arctic and Antarctica is melting
quickly.
Karl and Trenberth noted that carbon dioxide levels in the
atmosphere have risen by 31 percent since preindustrial times.
Carbon dioxide is the No. 1 greenhouse gas, causing warming
temperatures by trapping the Sun's energy in the atmosphere.
Emissions of sulfate and soot particles have significant effects
too, but more localized, they said.
"Given what has happened to date and is projected in the future,
significant further climate change is guaranteed," they wrote.
The United States has balked at signing international treaties to
reduce climate-changing emissions, but the two experts said global
cooperation is key.
"Climate change is truly a global issue, one that may prove to be
humanity's greatest challenge," they wrote. "It is very unlikely to
be adequately addressed without greatly improved international
cooperation and action."
