Questions and answers on climate change

READERS: Ask us your questions about climate science at Trib Nation. We'll try to answer some of them in print.

March 02, 2010|By Michael Hawthorne | Tribune staff reporter

Is there scientific consensus?

The 2007 report from the IPCC, a group of scientists from 113 countries who studied the peer-reviewed research, concluded they are 90 percent confident that global warming is caused by humans. Scientific research does not claim anything with absolute certainty, but this is about as close as it gets.

The conclusion that humans are causing global warming also is shared by the National Academy of Sciences, the nation's leading scientific advisory body, and similar academies in 18 other countries.

The level of confidence has increased over the years as research improved. A 1975 report from the National Academy concluded "we do not have a good quantitative understanding of our climate machine and what determines its course. Without the fundamental understanding, it does not seem possible to predict climate."

By 2001, with more information in hand, the Academy was more certain: "Greenhouse gases are accumulating in Earth's atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise."

Scientists say the changes can't be explained by natural climate influences such as sunspot cycles, volcanic eruptions, water vapor, natural absorption of carbon dioxide, or shifts in ocean and atmospheric conditions. Computer models only reproduce warming measured during the past 50 years when the observed increase in greenhouse gases is included.

"This is not a small change in the history of climate," said Ray Pierrehumbert, a University of Chicago geophysicist who helped write an earlier IPCC report.

But the IPCC report said most of the Himalayan glaciers would be gone by 2035. Isn't that false?

Yes, two sentences in a section of the report erroneously stated that 80 percent of the Himalayan glaciers would soon be gone due to climate change. The conclusion is attributed to an environmental group's report, but isn't backed up by the peer-reviewed science.

The IPCC acknowledged that the statement, buried in the group's 3,000-page report, slipped through procedures intended to ensure that only valid research is cited. Peer review helps provide that check by requiring scientific papers to be vetted by other scientists before publication.

Still, the IPCC says the broader conclusion hasn't changed: Many glaciers already have melted significantly, which could affect the water supply for more than one-sixth of the world's population. Though some glaciers have grown, the rate of melting has accelerated worldwide since the 1970s, according to multiple independent studies.

Did the National Oceanic and Atmospheric Administration misplace weather stations and exaggerate warming?

Anthony Watts, a weather forecaster whose Web sites, Watts Up With That and, have become focal points for climate skeptics, enlisted volunteers across the country to photograph weather stations. Citing NOAA's own criteria, Watts concluded last year that hundreds of the stations were in poorly located sites, next to parking lots or heating vents or other areas that could inflate temperatures.

"The U.S. temperature record is unreliable," Watts concluded. "And since the U.S. record is thought to be the best in the world, it follows that the global database is likely similarly compromised and unreliable."

A new peer-reviewed study by scientists at the National Climatic Data Center, the federal office that tracks climate trends, agrees that problems with the locations of many weather stations are real.

But the temperature records from the poorly located stations cited by Watts actually have a slightly cool bias, not a warm one, according to the review, scheduled to be published in the Journal of Geophysical Research-Atmospheres.

"Fortunately, the sites with good exposure, though small in number, are reasonably well distributed across the country," the researchers concluded, adding that the "good" or better stations cited by Watts show warming over time similar to NOAA's overall data.

There also are multiple other surface and satellite measurements of global temperatures, all of which show a warming trend.

Watts says he is writing his own paper, which has yet to be accepted for publication by a scientific journal.

What about the "Climategate" e-mails?

More than 1,000 e-mails were stolen from the computer server of a research center at the University of East Anglia in southeast England. The messages show some scientists discussed how to block skeptics from obtaining data, wrote derisively about their critics and competitors, and discussed ways to hide data.

The e-mails, some of which date more than a decade, show one group of scientists privately were less certain about some of their conclusions even as they said publicly they were certain about the larger issue of climate change. But several independent reviews, including ones by The Associated Press and Penn State University, have found there is no evidence that any of their science was faked.