Read the original story in The Oregonian here.
About 300 people gathered in a Portland State University ballroom Tuesday night to hear three Oregon climate scientists make their case that increases in manmade greenhouse gases are driving climate change.
The event hosted by the Oregon chapter of the American Meteorological Society, was open to the public. It came in response to aJanuary panel of global warming skeptics hosted by the chapter that event organizers estimated drew about 500 people.
The audience flip-flopped from January, when mostly skeptics attended. Chapter President Steve Pierce asked for a show of hands beforehand Tuesday evening, then estimated that at least 90 percent of the crowd favored the statement that human activities are the main cause of global warming.
The three panelists -- Christina Hulbe of Portland State and Phil Mote and Andreas Schmittner of Oregon State University -- focused on the science behind predictions of increased global warming, pointing to drops in the extent of Arctic sea ice since 1979, worldwide shrinking of glaciers, increased temperatures in the 20th century and increased water vapor consistent with rising temperatures.
Sun cycles, cosmic ray activity, increased urbanization and natural variability, including the El Niño-La Niña cycle, can't explain the measured temperature increases, they said.
The vast majority of published climate scientists and scientific bodies support the theory that rising greenhouse gases will drive significant temperature increases, though they acknowledge uncertainties about important climate variables, such as cloud formation.
"Many of us would like to believe that humans are not affecting the global climate," said Mote, director of the Oregon Climate Change Research Institute. "But it's not about what we want to believe, it's about what the evidence tells us."
The relative flattening of already high global temperatures in the last decade comes from natural climate influences, such as recent La Niñas, "temporarily overcoming the influence of rising greenhouse gases," he said. The late 20th and early 21st centuries "are likely the warmest period the Earth has seen in at least 1,200 years," NOAA says.
Skeptics in the audience, including two of the three speakers from January, asked most of the questions afterward. Among other points, they noted earlier projections of more rapid warming and earlier periods of heightened warming, including the Medieval Warm Period, when manmade emissions of carbon dioxide and other greenhouse gases were minimal.
In general, skeptics acknowledge 20th century warming but pin it to natural climate cycles and say the effect of increasing greenhouse gases is likely to be much more modest than projected.
The panelists Tuesday focused on potential increases in global average temperature of roughly 3 degrees to 7 degrees Fahrenheit by 2100. Ice Age climate reconstructions indicate increases in that range could have a dramatic effect on the planet, Schmittner said.
Pierce said the chapter will post the speakers' presentations on its Web site --ametsoc.org/chapters/oregon. As a national body, the American Meteorological Societyasserts that human activities are "a major contributor to climate change," while the Oregon chapter has decided to take "no formal position" on global warming.