Frank Warner, The Morning Call

Penn State global warming scientist Michael E. Mann regrets he did not instantly object when a fellow climatologist asked him in 2008 to delete e-mails subject to Freedom of Information requests.

“I wish in retrospect I had told him, ‘Hey, you shouldn’t even be thinking about this,’” Mann told The Morning Call in his first interview since the university last month launched an investigation into his conduct. “I didn’t think it was an appropriate request.”

Despite the request by his British colleague Phil Jones, Mann did not delete e-mails, a Penn State University panel of inquiry found on Feb. 3. But the panel ordered further investigation, still in progress, over a general allegation of scientific misconduct by Mann.

Penn State officials said Friday they could not yet provide further information on the probe. The investigation is a response to the uproar, commonly referred to as Climategate, over revelations of questionable comments made by climate scientists in e-mails made public in November. The furor has shaken the scientific community and fueled doubts about climate change. Mann, recognized internationally for his studies documenting global warming and the threat it poses, denies any wrongdoing and says he is cooperating fully with the Penn State investigation.

And in a wide-ranging interview, Mann says that not all global warming science is settled. It’s not yet certain, for example, that the heat is reducing the world population of polar bears or that it increases the number of hurricanes, he said. But he said there is almost no doubt the last half of the 20th century was the hottest 50-year period of the last millennium. That conclusion is reflected in Mann’s famous 1,000-year “hockey stick” chart of temperatures.

“There have been warming trends and cooling trends in the past,” Mann said. “Over the past 50 years, there has only been a warming trend. Contrarians cannot point to a sustained period—a 20- or 30-year period—of cooling over the past 50 years. If they could, you can be sure we would have heard about it.”

Mann has been controversial since 1998, when he and two colleagues published the “hockey stick” chart of the Northern Hemisphere’s temperatures from 1400 to 1998. The chart later was expanded to 1000 to 1999. It shows temperatures shooting up quickly in the 20th century—represented by the upward curving hockey stick “blade”—and reaching record highs late in the century.

Global warming skeptics have called Mann an alarmist, saying his studies have downplayed the heat of the Medieval Warm Period, around the year 1000, and overemphasized the heat of the last few decades. But in the interview with The Morning Call, Mann says at least a dozen studies have replicated his work and confirmed his conclusions. The more relevant question scientifically is whether our findings have been independently verified by independent teams using alternative methods and alternative data sources,” he said. “And the answer is definitively yes.”

Global warming might be happening just as Mann describes it, but he hasn’t made the case, said Stephen McIntyre, a Mann critic. McIntyre said Thursday that Mann’s 1,000 years of temperatures have yet to be proved accurate or valid. A mathematician in Toronto, McIntyre said Mann’s calculations rely too heavily on unreliable studies of the tree rings of ancient strip-bark trees. Mann said his studies combine several types of data, including data from tree rings, corals, ice cores and sediment. He also argued that some who challenge global warming are not real skeptics “because their skepticism is one-sided.”

“I would call them contrarians or, frankly in some cases, climate change deniers,” he said. “I’m a skeptic. When I see a scientific claim being made, I want to see it subject to scrutiny and validation.” Not every doomsday scenario is accurate either, he said, but scientists have reached a consensus that civilization faces serious problems if CO2 emissions are not reduced.

Read more of Mann here.

When first implemented in 1990 as Version 1, USHCN included an adjustment for urbanization (NCDC’s Tom Karl (1988)) well supported in the peer review literature. In 1999, NASA’s James Hansen published this graph of USHCN v.1 annual mean temperature (below, enlarged here):

As for the Medieval Warm Period, the 11 other studies Dr. Mann mentioned were all done by members of the same team using the same or similarly contaminated data and improper analyses. One, Keith Briffa, used “Mike’s trick” to “hide the decline” which meant to append UHI contaminated station data after 1960 on tree ring data that was used to rid the climate history of the MWP and Little Ice Ages because the tree ring data showed an inconvenient cooling after 1960. They were indeed able to replicate his same error but it does not prove he was right. Instead you should turn to the CO2 Science MWP project where to date they have collated peer review studies by 813 individual scientists from 485 separate research institutions in 43 different countries ... and counting that confirmed the Medieval Warm Period and the fact it was real and global in nature. Ironically one of the papers was a dissertation by a student of one of the authors of the original Mann etal paper that started it all.