The Chicago Tribune Online has a helpful Q&A that summarizes where climate science stands today. It also addresses the IPCC, emails, and temperature stations issues.
Its “just the facts” approach is superior to more than 90% of what has been written by the media these days (see Boykoff on “Exaggerating Denialism: Media Representations of Outlier Views on Climate Change” and here):
The only small flaw in the piece is it only randomly links to original sources, so I have added the relevant links below.
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 surfacestations.org, 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….
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.
One e-mail that skeptics have seized upon refers to scientific efforts to reconstruct past temperatures. Phil Jones, then the director of the East Anglia center, wrote: “I’ve just completed Mike’s trick of adding in the real temps to each series for the past 20 years (from 1981 onward) and from 1961 for Keith’s to hide the decline.”
At issue was some high-latitude tree-ring data that stopped matching observed temperatures in the 1960s. The “trick” refers to a technique that Penn State scientist Michael Mann published in the journal Nature in 1998. Mann plotted more recent temperature data along with earlier tree-ring data. The decline discussed in the e-mail didn’t involve “hiding” actual temperatures but rather what Mann and others considered the declining reliability of some tree-ring data, Mann has said.
Scientists are still trying to figure out why some high-latitude tree-ring data matches decades of earlier temperature records, but the two sets of data stopped correlating in the 1960s. One theory, outlined in a 1995 paper from East Anglia climate scientist Keith Briffa, is that tree growth is becoming more sensitive to changes in temperature.
Mark Frankel, director of scientific freedom, responsibility and law at the American Association for the Advancement of Science, reviewed the e-mails frequently cited by skeptics for the AP and said he found “no evidence of falsification or fabrication of data, although concerns could be raised about some instances of very ‘generous interpretations.’”
See Must read AP analysis of stolen emails: An “exhaustive review” shows “the exchanges don’t undercut the vast body of evidence showing the world is warming because of man-made greenhouse gas emissions.”
Penn State conducted its own academic inquiry of Mann, concluding: “The so-called ‘trick’ was nothing more than a statistical method used to bring two or more different kinds of data sets together in a legitimate fashion by a technique that has been reviewed by a broad array of peers in the field.” The university inquiry also found no evidence that Mann falsified or suppressed data, tried to destroy data or e-mails, or misused information.
Another panel will probe whether Mann violated academic rules governing exchanges between scientists.
Then there is a December editorial from Nature, a respected British scientific journal: “Nothing in the e-mails undermines the scientific case that global warming is real “” or that human activities are almost certainly the cause. That case is supported by multiple, robust lines of evidence, including several that are completely independent of the climate reconstructions debated in the e-mails.”
See Nature editorial here.
It snowed a lot on the East Coast last month. What does that mean?
Scientists say they don’t have the ability to look at a single year or single weather event and determine whether it could be attributed to climate change. Temperatures fluctuate from year to year, but the long-term average has been increasing.
Citing peer-reviewed research, the IPCC concluded that severe weather “” blizzards, droughts, hurricanes, floods and the like “” could become more common as the climate changes. But several scientists said they still don’t have the ability to determine if that’s happening now. And studies have shown that snowstorms tend to happen during warmer-than-usual winters, in part due to added moisture in the air.
“We don’t know for sure if these tipping points are out there, or if they are, how soon we could cross them,” said Michael Schlesinger, an atmospheric scientist at the University of Illinois.
Didn’t scientists predict in the 1970s that we were experiencing global cooling and heading toward another Ice Age?
Those who make that argument frequently cite mid-1970s cover stories in Time and Newsweek. But a 2008 scientific review of published studies between 1965 and 1979 show the vast majority predicted global warming. “The myth’s basis lies in a selective misreading of the texts both by some members of the media at the time and by some observers today,” the review concluded.
What is happening with ice in Antarctica?
The U.S. Geological Survey reported last week that “every ice front in the southern part of the Antarctic Peninsula has been retreating overall from 1947 to 2009, with the most dramatic changes occurring since 1990.” Ice lost from the Wilkins Ice Sheet alone “totals more than 4,000 square kilometers, an area larger than the state of Rhode Island.”
Meanwhile, sea ice in the Antarctic has increased since satellite measurements began in 1979, even though the oceans have been getting warmer. Scientists attribute that to a variety of factors, including strong winds that create more open water conducive to forming sea ice.
Why is such straight reporting so rare these days?