| April 7, 2010 |  |
Setting the Record Straight on Colbert Report Debate
Last night on "The Colbert Report," Dr. Brenda Ekwurzel, a climate scientist with the Union of Concerned Scientists UCS), debated Joe Bastardi, an AccuWeather meteorologist, in what the show billed as a "Science Catfight."
Although the interview was primarily about Stephen Colbert getting laughs, Bastardi and Ekwurzel did discuss some serious scientific topics. During the debate, Bastardi made several claims at odds with mainstream climate science that Ekwurzel was not able to respond to directly during the brief time the segment was allotted in the program.
While some television weathercasters are skeptical about the role human activity plays in climate change, most meteorologists agree that human activity is driving global warming. According to an official statement of the American Meteorological Society, "strong observational evidence and results from modeling studies indicate that, at least over the last 50 years, human activities are a major contributor to climate change."
That statement is consistent with others from the National Academy of Sciences, the U.N. Intergovernmental Panel on Climate Change, NASA, the National Oceanic and Atmospheric Administration, the American Geophysical Union, the American Physical Society and other scientific institutions.
WHAT'S CAUSING GLOBAL WARMING?
Bastardi claimed: "The drivers that have been pushing this [global warming], the Pacific Ocean being warm, the Atlantic Ocean being warm, they're all going to come off. So if CO2 continues to rise and temperatures continue to flatten out, which they've done over the past five or 10 years starts falling, we'll know…. I think we're going to find out that global warming is basically natural."
It is true that natural cycles, such as the Arctic Oscillation, El Nino and La Nina will continue to play a significant role in affecting the climate over the course of years and decades. But global warming is raising the temperature baseline on which they all operate. Since 1880, the Earth has significantly warmed as carbon dioxide levels have continued to rise. Changes to natural climate drivers, including the sun, volcanic activity and the cycles Bastardi cites are not significant enough to explain the jump in global temperatures over the past several decades. In fact, climate scientists would be shocked if the increase in carbon dioxide levels—which have increased more than 40 percent since the pre-Industrial era—were not raising global temperatures.
Global temperatures have not "flattened out" over the past five or 10 years. Such claims focus on short-term climate shifts and use particularly hot years, such as 1998, as their starting point. In reality, the past 10 years have been the hottest decade on record.
IS ARCTIC SEA ICE SHRINKING?
Bastardi claimed that the "[Arctic sea] ice has just returned to normal…. If you look at today's Arctic ice sheet, it's back to where it was two, three, four, five years ago…."
Bastardi's statement is based on a short-term look at Arctic sea ice extent, a measure of the area encompassed by the furthest edges of ice coverage. This year's maximum winter sea ice extent was particularly late, thanks to a cold spring. But over the last six years or more, the maximum extent of sea ice has remained well below the 1979 to 2000 average extent, both in the winter and summer. This past winter was no exception. Sea ice extent is still below average.
In any case, a better measure of the stability of Arctic sea is sea ice thickness and its persistence over time. The new 2010 melt season is about to begin with more thin ice than usual. Thin ice likely will melt quickly in the summer.
One study found that the overall mean winter thickness of 3.64 meters in 1980 decreased to only 1.89 meters by 2008—a net decrease of 1.75 meters, or 48 percent. And by the end of February 2009, less than 10 percent of Arctic sea ice was more than two years old, down from the historic values of 30 percent (see page 31 in the linked report).
This season's annual winter increase in sea ice extent is not evidence of an Arctic recovery. The National Snow and Ice Data Center concludes that "a true recovery would continue over a longer time period than two years … but also [a] return to [sea ice extent] within the range of natural variation. In a recovery, scientists would also expect to see a return to an Arctic sea ice cover dominated by thicker, multiyear ice."
Unfortunately, we are not seeing a real recovery.
HOW DO SCIENTISTS MEASURE TEMPERATURE?
Bastardi claimed, "By 2030, the Earth will be back down to where it was in the '70s when we started measuring with satellites….How were you measuring temperatures back in the 1920s and '30s? You weren't using satellites…."
Satellites are a relatively new way to measure the Earth's temperature. However, thermometer readings and "proxy" data derived from ice cores, tree rings, coral reef growth rings and other sources also allow scientists to determine Earth's temperature in the recent and distant past. It is not scientifically valid to dismiss non-satellite sources of temperature information.
Furthermore, satellites have provided valuable evidence that human activity is indeed driving global warming. Satellite evidence shows that the lower-level atmosphere—which contains excess carbon dioxide from burning fossil fuels and forests—is expanding. The boundary between the lower atmosphere and the higher atmosphere has shifted upward in recent decades. This boundary likely has changed because heat-trapping gases accumulate in the lower atmosphere and that layer expands as it heats up, much like warming the air in a balloon.
Bastardi went on to suggest that we should wait at least 15 years to find out if global warming is human-induced based on evidence collected from satellite observations. Unfortunately, waiting for further evidence from satellites would increase the risk of locking in the worst consequences of climate change.
Human activities have pumped excess amounts of carbon into the atmosphere and emissions continue to grow. Further, natural processes that absorb carbon from the atmosphere are failing to keep up with the growth in emissions. For instance, as the ocean absorbs carbon dioxide, it becomes more acidic. Combined with increasing ocean temperatures, the increased acidification diminishes the ocean's ability to continue absorbing carbon. The ocean is now absorbing less carbon from the air than it was just half a century ago. Thus, more carbon dioxide from burning fossil fuels and forests is staying in the atmosphere.
Researchers at the Massachusetts Institute of Technology have contrasted the higher risk associated with failing to quickly reduce emissions with the lower risk associated with taking preventative action. Their visualization details the higher risks associated with delaying policies that would quickly and dramatically lower emissions.
The Union of Concerned Scientists puts rigorous, independent science to work to solve our planet's most pressing problems. Joining with citizens across the country, we combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future.
