Since 1998, when Dr. Michael Mann published his famous hockey stick graph of global temperatures, the scientist has been at the center of the world's climate-change wars - a fierce debate between those who believe in human-caused climate change and those who either deny its existence or downplay its significance.
In several papers, Mann and his colleagues produced research that charted temperatures for the past millennium or so, which showed an almost level but slightly cooling trend line (the shaft of the hockey stick) that suddenly spiraled upward sharply and at an accelerating rate around 1900 (the upturned blade).
In addition, Mann, a Distinguished Professor of Atmospheric Science and director of the Earth System Science Center at Penn State University, has also written several books, "The Hockey Stick and the Climate Wars" and "Dire Predictions: Understanding Climate Change."
Some on the other side of the debate have challenged Mann's research, while he and others have defended it - indeed, the National Academy of Sciences affirmed Mann's findings in June 2006 - but beyond Mann's own research, skeptics have challenged the central contentions of those who believe in human-driven climate change, and they further point to what they call a pause in global warming since 1998.
In a recent exclusive interview with The Times, Mann addressed some of the arguments of the critics and stood by his and other research showing a substantial warming of the globe.
Satellite versus surface warming
One of the major claims made by skeptics is that anthropogenic (human-driven) climate-change advocates use surface measurements of global temperatures as evidence of significant warming, but satellite data contradict those findings.
Indeed, many say the data point to an absence of significant warming since the late 1970s, which flies in the face of human-caused warming, given the ongoing rise of carbon-dioxide emissions during the past four decades. In one analysis, John Christy and Roy Spencer of the University of Alabama in Huntsville adjusted and analyzed satellite data, and their results showed a warming trend significantly below the surface temperature trend.
However, Mann says independent analysis of Christy's and Spencer's study revealed serious flaws in their work.
"A lot has indeed been made of (the difference between the surface and satellite measurements)," Mann told The Times. "Originally the satellite records that were put forth by one specific set of scientists, John Christy and Roy Spencer, seemed to contradict the surface evidence of warming."
For one thing, Mann said, the satellites are not quite measuring surface warming but the lower part of the atmosphere, so he said there's a disconnect in terms of what's being measured.
"But nonetheless there did appear to be a discrepancy with the observations that were showing consistent warming, and the satellites seemed to show no trend," Mann said. "Now what was discovered eventually when other scientists got ahold of their data and were able to analyze it independently, they figured out that there actually been two pretty serious errors in their algorithm that basically were counteracting or undoing the warming that was actually taking place in the data."
When those other scientists analyzed and corrected those calculations, Mann said, it turns out that they actually agreed with the surface observations.
But that wasn't the end of things as they relate to satellite versus surface discrepancies.
"Then another group came into the mix some years later, and so there are now different products, the Christy-Spencer product and this group called RSS," Mann said. "Christy and Spencer are climate-change contrarians. They've been prominent denialists of climate change."
But that wasn't true with RSS, Mann said.
"On the other hand, the folks at RSS are not contrarians in any way," he said. "They are very mainstream scientists, and their product in recent years seemed to be showing less warming than the surface observations, and so that was actually taken more seriously because there was a feeling that they really had credibility, that they were honest brokers and just describing what was evident in the data. And so a lot of the critics were saying, 'Well forget Christy and Spencer, forget their record, and look at the RSS record that's showing less warming.'"
But then, about a month ago, Mann said, RSS published an article identifying some errors in its own calculations. So what to make of all this?
Mann said the long history of the satellite data - the conflicting data and the "whiplash" effect of conflicting studies - and the complicated adjustments that have to be made to the satellite data make them less useful and reliable than surface data. For example, there's the solar heating of the satellite itself: It heats up in the day and cools down at night. Then, too, scientists have to account for the orbit of the satellite, which slowly decays and moves through the atmosphere vertically. All those things have to be adjusted and accounted for.
"There's so many corrections and the history of errors, my view is, let's look at the ground truth, literally," Mann said. "There are so many complementary surface observations, and in the end the surface is where we live. We don't live up in the atmosphere."
All that said, other scientists, such as Judith Curry, the former chairwoman of the School of Earth and Atmospheric Sciences at Georgia Tech, say the real story is not whether there continues to be some incremental warming but the overall flattening of the rise in global temperatures since 1998. That is to say, even if the earth is still warming somewhat, it is not warming nearly as fast as climate-change models predicted and that would have been expected if increasing concentrations of green-house gasses were driving the warming.
Mann, however, says Curry is another contrarian.
"There was a time when I would have said that she was part of the mainstream scientific community, but she's gone off in a direction where she's very critical of climate science in general," he said. "She's often called upon by those looking to criticize and discredit climate science, so she's got a point of view here. I would say that there is a small grain of truth to what she is saying, but it really isn't much more than a grain of truth."
Interestingly enough, Mann said he had found himself in the middle of that particular debate.
"It has to do with the fact that we published some work a few years ago showing that there had been a slow down in the rate of warming," he said. "Not a pause. Not a hiatus. It isn't that the warming stopped but that natural internal cycles that are related to the El Nino phenomenon were acting in a way to sort of temporarily offset the warming of the surface, and now, if anything, that oscillation appears to have slipped in the other direction, and that's why we are seeing this really surprising record warmth."
If you live by the natural fluctuations, you die by natural fluctuations, Mann said, and it's a zero-sum game in the end: "It is easy to make too much of a decade of data," he said. "When you talk about time scale, that's short, and it's subject to the vagaries of this internal variability."
As for the controversy, Mann said there was an article published by Tom Karl, the head of the NOAA National Climatic Data Center, and his colleagues that asserted there had been no slow down in warming at all. That provoked Rep. Lamar Smith of Texas, who didn't like the study, to subpoena NOAA to see all their correspondence.
"A brouhaha ensued, and ironically one of the things he cited was a recent article that I am a co-author on, where we reiterated that there had been a temporary slow down and we think we understand the factors that were behind it, and it's probably ended now, but there was something real there," Mann said. "And Lamar Smith seized on that and he said, 'Look, there's another group of prestigious scientists that said there was a slow down,' and he used that as sort of a wedge to step up his attack on Tom Karl and his colleagues."
Mann said he is disappointed in the way the science has become a political football.
"It's very frustrating to me to see the science being politicized," he said. "Even given the extreme level of politicization we've seen before, it's now come to a higher level where we see groups of scientists pitted against each other in ways that neither are comfortable with."
And so he said he and his co-authors spoke out and made the point that the two papers simply represented an honest difference of interpretation of what the data show.
"It's healthy in the scientific community that scientists weigh in," Mann said. "You can imagine how dangerous it would be if we start to criminalize certain interpretations."
The Paris Agreement
The so-called Paris Agreement is a United Nations Climate Change Convention agreement among participating nations to reduce greenhouse gas emissions worldwide by having individual nations agree to certain targeted emission reductions over time.
Mann praises the accord and its framework, and he says he thinks it can be successful.
"I actually think the Paris Accords were remarkably successful because they took a different approach," Mann said. "For the first time they asked participating nations of the world to come up with voluntary reductions they would be willing to make. So there is this starting point where each of the countries came in having already made a voluntary commitment to lower their carbon emissions by a certain amount."
Mann said the voluntary nature of the accord is critical because it's very difficult to have the force of law in an international agreement to hold individual nations accountable.
"That's very difficult and so the IPCC (Intergovernmental Panel on Climate Change) has decided instead to employ a sort of name-and-shame approach where the principle is, if you're not living up to your responsibility, if your commitments pale in comparison to your peer countries, then there is a certain stigma attached to that and there is an incentive not to do that," he said. "There is an incentive to try and be at least as good as your neighbors. I call it the front-lawn phenomenon. If your neighbor has a really nicely cut, freshly cut, well-maintained lawn, you feel a little more pressured to keep yours up, and that's the principle at work here."
Mann said the commitments made in Paris would be enough to cut global emissions by about 50 percent over the next 50 years.
"It's enough of a reduction in carbon emissions arguably to get us halfway to where we're headed in the absence of any reductions," he said. "We're headed toward a 4-to-5 degree Celsius warmer planet by the end of this century, 7-9 degree Fahrenheit warmer planet by the end of the century, and if you total up the estimated impact of the reductions that were on the table in Paris, it's enough to get us halfway from that 4-5 degree Celsius warming to the 2 degree Celsius warming that many feel defines the threshold for truly dangerous and potentially irreversible changes in climate."
The long and short of it, Mann said, it gets us about halfway to where we need to be, and he thinks that's a remarkable accomplishment.
"It doesn't solve the problem," he said. "Those agreements alone aren't going to get us on the track to keeping warming below 2 degrees Celsius, but it's a great framework to have in place and to try and improve upon in the years ahead. So I was among those who were pretty optimistic about what came out of Paris."
Even so, Mann said there's a range of opinion and some insist Paris was a failure because it didn't achieve the reductions necessary to keep warming below 2 degrees.
"In my view, that's just too great of an ask," Mann said. "All you can ask at any one summit is that it helps get us on the path that we need to be on. And I think it did that."
Fairness and equity
Mann also addressed several arguments made by critics of the agreement, namely that the United States will probably be the only nation to keep its commitments, while nations such as China and India are allowed even within the framework to continue to increase their emissions for a certain number of years, while the U.S. and other industrial nations must start reducing emissions.
"It would be a compelling argument if it were true," Mann said. "Again, there's a grain of truth to it, but it's the framing which I think is wrong. This idea that it's only the U.S. acting and the rest of the world is lagging, the opposite of that is now true. Which is to say, China, for example, is now investing far more in renewable energy than we are here in the U.S."
Mann said it is true that a bilateral agreement a year ago between the U.S. and China set different targets for the industrial county - the U.S. - and the developing-and-soon-to-be-industrial country - China - but he said there is a reason for that.
"The discussion boils down to a matter of ethical considerations or responsibility where if you have an industrial country where we have been burning fossil fuels for two centuries without any cost, with no price on carbon, arguably we have enjoyed the economic benefits of having free access to a relatively cheap form of energy without having had to pay for the damages that it may be causing," Mann said.
On the other hand, he said, China has just been ramping up its economy over the last decade or so, and so it is earlier in that industrial transition.
"Their argument would be, 'Look, you guys had two centuries of burning this stuff and we deserve our turn, don't we?' and some would argue that there is an element of truth to that principle and that's why negotiations get a little complicated and often end up being a bit asymmetric," Mann said. "And it is true China is simply being asked to bring their emissions to a peak by 2030 or something like that, whereas the U.S. is being asked to bring their emissions down by a certain percentage by 2025 or 2030. So that is true, but there's a reason for it, and there's an argument to be made that the requirements for the industrial countries shouldn't be the same as the requirements for the developing nations."
Mann said it might be possible for developed nations to help out the developing nations so they can reduce their emissions faster.
"We can tell them we don't want them to burn carbon, and they may argue that's hindering their ability to grow their economy, but we could provide incentives, that the industrial world will provide a certain amount of funding to help them overcome that," Mann said. "These arguments get complicated, and they boil down to issues of fairness and equity."
In the end, though, when people ask why the U.S. should do anything when the rest of the world isn't, that's not an accurate picture of what is going on, Mann said.
"China has made a commitment to peak their emissions by 2025, and, when they made that agreement, I think they were being quite savvy," he said. "They knew that they could not only achieve that but that they could exceed it, and China is ahead of what they promised. They've actually seen a pretty rapid decrease in the number of coal-fired power plants that are commissioned, and so they are moving away from coal rapidly."
Mann said a decade ago or so China was adding five coal-fired power plants a week, and now they're actually reducing their coal-fired power plants.
"They're ramping up their renewable energy," he said. "Some would say we are falling behind China in moving toward the 21st century renewable-energy economy. I think there's an argument that that's true, and we risk falling behind in our competitiveness."
Editor's note: An interview with H. Sterling Burnett, managing editor of Environment & Climate News and a research fellow on environmental policy at the Heartland Institute, will be published in a future edition of the River News.
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