Candid Comments From Climate Scientists

By Dr. Roger Pielke Sr.

There is a news release by Paul Voosen on Greenwire titled

Provoked scientists try to explain lag in global warming (Tuesday, October 25, 2011)

There are some interesting quotes from climate scientists in this article that highlight a large degree of uncertainty with respect to the climate system, and the human role in it, even among scientists closely involved with the IPCC reports. The long article focuses on the question

‘Why, despite steadily accumulating greenhouse gases, did the rise of the planet’s temperature stall for the past decade?”

Interesting quotes and text {rearranged to order the persons’ quoted; I highly recommend reading the entire article include [highlight added]:

From John Barnes [Barnes’s specialty is measuring stratospheric aerosols].

“If you look at the last decade of global temperature, it’s not increasing,” Barnes said. “There’s a lot of scatter to it. But the [climate] models go up. And that has to be explained. Why didn’t we warm up?” Barnes has kept a lonely watch for 20 years [at the Mauna Loa Observatory in Hawaii]. Driving the winding, pothole-strewn road to this government-run lab, he has spent evening after evening waiting for the big one. His specialty is measuring stratospheric aerosols, reflective particles caused by volcanoes that are known to temporarily cool the planet. Only the most violent volcanic eruptions are able to loft emissions above the clouds, scientists thought, and so Barnes, after building the laser, waited for his time. To this day, there hasn’t been a major volcanic eruption since 1991, when Mount Pinatubo scorched the Philippines, causing the Earth to cool by about a half degree for several years. But Barnes diligently monitored this radio silence, identifying the background level of particles in the stratosphere. And then, sitting in his prefab lab four years ago, not far from where Charles Keeling first made his historic measure of rising atmospheric carbon dioxide levels, Barnes saw something odd in his aerosol records. Barnes laments the boggling complexity of separating all the small forcings on the climate. It makes Charles Keeling’s careful work identifying rising CO2 levels seem downright simple. “It’s really subtle,” he said. “It’s hard to track how much is going into the oceans, because the oceans are soaking up some of the heat. And in a lot of places the measurements just aren’t accurate enough. We do have satellites that can measure the energy budget, but there’s still assumptions there. There’s assumptions about the oceans, because we don’t have a whole lot of measurements in the ocean.”

From Jean-Paul Vernier

Five years ago, a balloon released over Saharan sands changed Jean-Paul Vernier’s life. Climbing above the baked sand of Niger, the balloon, rigged to catch aerosols, the melange of natural and man-made particles suspended in the atmosphere, soared above the clouds and into the stratosphere. There, Vernier expected to find clear skies; after all, there had been no eruption like Pinatubo for more than a decade. But he was wrong. Twelve miles up, the balloon discovered a lode of aerosols. Vernier had found one slice of the trend identified by Barnes at Mauna Loa in Hawaii. It was astonishing. Where could these heat-reflecting aerosols be originating? Vernier was unsure, but Barnes and his team hazarded a guess when announcing their finding. It was, they suggested, a rapidly increasing activity in China that has drawn plenty of alarm. A French scientist who moved to NASA’s Langley Research Center in Virginia to study aerosols, Vernier, like Barnes, turned toward a laser to understand these rogue sulfates. But rather than using a laser lashed to the ground, he used a laser in space. The same year as the Niger balloon campaign, NASA had launched a laser-equipped satellite aimed at observing aerosols among the clouds. Vernier and his peers suspected, with enough algorithmic ingenuity, that they could get the laser, CALIPSO, to speak clearly about the stratosphere. The avalanche of data streaming out of the satellite was chaotic — too noisy for Barnes’ taste, when he took a look — but several years on, Vernier had gotten a hold of it. He had found an answer. Mostly, the aerosols didn’t seem to be China’s fault.

From Kevin Trenberth

The hiatus [in warming] was not unexpected. Variability in the climate can suppress rising temperatures temporarily, though before this decade scientists were uncertain how long such pauses could last. In any case, one decade is not long enough to say anything about human effects on climate; as one forthcoming paper lays out, 17 years is required. For some scientists, chalking the hiatus up to the planet’s natural variability was enough. Temperatures would soon rise again, driven up inexorably by the ever-thickening blanket thrown on the atmosphere by greenhouse gases. People would forget about it. But for others, this simple answer was a failure. If scientists were going to attribute the stall to natural variability, they faced a burden to explain, in a precise way, how this variation worked. Without evidence, their statements were no better than the unsubstantiated theories circulated by climate skeptics on the Internet. “It has always bothered me,” said Kevin Trenberth, head of the climate analysis section at the National Center for Atmospheric Research. “Natural variability is not a cause. One has to say what aspect of natural variability.” Until 2003, scientists had a reasonable understanding where the sun’s trapped heat was going; it was reflected in rising sea levels and temperatures. Since then, however, heat in the upper ocean has barely increased and the rate of sea level rise slowed, while data from a satellite monitoring incoming and outgoing heat — the Earth’s energy budget — found that an ever increasing amount of energy should be trapped on the planet. (Some scientists question relying on this satellite data too heavily, since the observed energy must be drastically revised downward, guided by climate models.) Given this budget ostensibly included the solar cycle and aerosols, something was missing. Where was the heat going? Trenberth repeated the question time and again. Recently, working with Gerald Meehl and others, Trenberth proposed one answer. In a paper published last month, they put forward a climate model showing that decade-long pauses in temperature rise, and its attendant missing energy, could arise by the heat sinking into the deep, frigid ocean waters, more than 2,000 feet down. The team used a new model, one prepared for the next U.N. climate assessment; unlike past models, it handles the Pacific’s variability well, which ”seems to be important,” Trenberth said. “In La Niña, the colder sea surface temperatures in the Pacific mean there is less convective action there — fewer tropical storms, etc., and less clouds, but thus more sun,” he said. “The heat goes into the ocean but gets moved around by the ocean currents. So ironically colder conditions lead to more heat being sequestered.” It is a compelling illustration of how natural variability, at least in this model, could overcome the influence of increasing greenhouse gases for a decade or more, several scientists said. However, according to one prominent researcher — NASA’s Hansen — it’s a search for an answer that doesn’t need to be solved. That is because, according to Hansen, there is no missing energy. Trenberth questions whether the Argo measurements are mature enough to tell as definite a story as Hansen lays out. He has seen many discrepancies among analyses of the data, and there are still “issues of missing and erroneous data and calibration,” he said. The Argo floats are valuable, he added, but “they’re not there yet.”

From Susan Solomon

“What’s really been exciting to me about this last 10-year period is that it has made people think about decadal variability much more carefully than they probably have before,” said Susan Solomon, an atmospheric chemist and former lead author of the United Nations’ climate change report, during a recent visit to MIT. “And that’s all good. There is no silver bullet. In this case, it’s four pieces or five pieces of silver buckshot.” Already Solomon had shown that between 2000 and 2009, the amount of water vapor in the stratosphere declined by about 10 percent. This decline, caused either by natural variability — perhaps related to El Niño — or as a feedback to climate change, likely countered 25 percent of the warming that would have been caused by rising greenhouse gases. (Some scientists have found that estimate to be high.) Now, another dynamic seemed to be playing out above the clouds. In a paper published this summer, Solomon, Vernier and others brought these discrete facts to their conclusion, estimating that these aerosols caused a cooling trend of 0.07 degrees Celsius over the past decade. Like the water vapor, it was not a single answer, but it was a small player. These are the type of low-grade influences that future climate models will have to incorporate, Livermore’s Santer said. Solomon was surprised to see Vernier’s work. She remembered the Soufrière eruption, thinking “that one’s never going to make it into the stratosphere.” The received wisdom then quickly changed. ”You can actually see that all these little eruptions, which we thought didn’t matter, were mattering,” she said.

From Jim Hansen

These revelations are prompting the science’s biggest names to change their views. Indeed, the most important outcome from the energy hunt may be that researchers are chronically underestimating air pollution’s reflective effect, said NASA’s James Hansen, head of the Goddard Institute for Space Studies. Recent data has forced him to revise his views on how much of the sun’s energy is stored in the oceans, committing the planet to warming. Instead, he says, air pollution from fossil fuel burning, directly and indirectly, has been masking greenhouse warming more than anyone knew. It was in no “way affected by the nonsensical statements of contrarians,” Hansen said. “These are fundamental matters that the science has always been focused on. The problem has been the absence of [scientific] observations.” NASA’s Hansen disputes that worry about skeptics drove climate scientists to ignore the sun’s climate influence. His team, he said, has “always included solar forcing based on observations and Judith’s estimates for the period prior to accurate observations.” “That makes the sun a bit more important, because the solar variability modulates the net planetary energy imbalance,” Hansen said. “But the solar forcing is too small to make the net imbalance negative, i.e., solar variations are not going to cause global cooling.” “Unfortunately, when we focus on volcanic aerosol forcing, solar forcing and stratospheric water vapor changes, it is a case of looking for our lost keys under the streetlight,” Hansen said. “What we need to look at is the tropospheric aerosol forcing, but it is not under the street light.” “I suspect that there has been increased aerosols with the surge in coal use over the past half decade or so,” he said. “There is semi-quantitative evidence of that in the regions where it is expected. Unfortunately, the problem is that we are not measuring aerosols well enough to determine their forcing and how it is changing.” More fundamentally, the Argo probe data has prompted Hansen to revise his understanding of how the climate works in a fundamental way, a change he lays out in a sure-to-be-controversial paper to be published later this year. For decades, scientists have known that most of the heat trapped by greenhouse gases was going into the ocean, not the atmosphere; as a result, even if emissions stopped tomorrow, they said, the atmosphere would continue to warm as it sought balance with the overheated oceans. In a term Hansen coined, this extra warming would be “in the pipeline,” its effects lingering for years and years. But exactly how much warming would be in the pipeline depended on how efficiently heat mixed down into the oceans. Hansen now believes he has an answer: All the climate models, compared to the Argo data and a tracer study soon to be released by several NASA peers, exaggerate how efficiently the ocean mixes heat into its recesses. Their unanimity in this efficient mixing could be due to some shared ancestry in their code. Whatever the case, it means that climate models have been overestimating the amount of energy in the climate, seeking to match the surface warming that would occur with efficient oceans. They were solving a problem, Hansen says, that didn’t exist. At first glance, this could easily sound like good news, if true. But it’s not. “Less efficient mixing, other things being equal, would mean that there is less warming ‘in the pipeline,’” Hansen said. “But it also implies that the negative aerosol forcing is probably larger than most models assumed. So the Faustian aerosol bargain is probably more of a problem than had been assumed.”

From John Daniel [a researcher at the Earth System Research Lab of the National Oceanic and Atmospheric Administration]

When the record came in 1998, though, scientists faltered. It’s a pattern often seen with high temperatures. They cut out too much nuance, said John Daniel, a researcher at the Earth System Research Lab of the National Oceanic and Atmospheric Administration. “We make a mistake, anytime the temperature goes up, you imply this is due to global warming,” he said. “If you make a big deal about every time it goes up, it seems like you should make a big deal about every time it goes down.”

From Ben Santer

For a decade, that’s exactly what happened. Skeptics made exaggerated claims about “global cooling,” pointing to 1998. (For one representative example, two years ago columnist George Will referred to 1998 as warming’s “apogee.”) Scientists had to play defense, said Ben Santer, a climate modeler at Lawrence Livermore National Laboratory. “This no-warming-since-1998 discussion has prompted people to think about the why and try to understand the why,” Santer said. “But it’s also prompted people to correct these incorrect claims.” “Susan’s stuff is particularly important,” Santer said. “Even if you have the hypothetical perfect model, if you leave out the wrong forcings, you will get the wrong answer.”

From Judith Lean

The answer to the hiatus, according to Judith Lean, is all in the stars. Or rather, one star. Only recently have climate modelers followed how that 0.1 percent can influence the world’s climate over decade-long spans. (According to best estimates, it gooses temperatures by 0.1 degrees Celsius.) Before then, the sun, to quote the late comedian Rodney Dangerfield, got no respect, according to Lean, a voluble solar scientist working out of the the space science division of the Naval Research Laboratory, a radar-bedecked facility tucked away down in the southwest tail of Washington, D.C. Climate models failed to reflect the sun’s cyclical influence on the climate and “that has led to a sense that the sun isn’t a player,” Lean said. “And that they have to absolutely prove that it’s not a player.” According to Lean, the combination of multiple La Niñas and the solar minimum, bottoming out for an unusually extended time in 2008 from its peak in 2001, are all that’s needed to cancel out the increased warming from rising greenhouse gases. Now that the sun has begun to gain in activity again, Lean suspects that temperatures will rise in parallel as the sun peaks around 2014. This consistent trend has prompted Lean to take a rare step for a climate scientist: She’s made a short-term prediction. By 2014, she projects global surface temperatures to increase by 0.14 degrees Celsius, she says, driven by human warming and the sun.

From Graeme Stephens

Over the past decade, for the first time, scientists have had access to reliable measures of the ocean’s deep heat, down to 5,000 feet below sea level, through the Argo network, a collection of several thousand robotic probes that, every few days, float up and down through the water column. This led Hansen to conclude that net energy imbalance was, to be briefly technical, 0.6 watts per square meter, rather than more than 1 watt per square meter, as some had argued. (Recently, the satellite group measuring the energy imbalance has revised its figure, which now sits at 0.6 watts, matching Hansen’s estimate, according to Graeme Stephens, the head of NASA’s Cloudsat mission. It suggests there isn’t a missing energy. Trenberth disagrees with this analysis, and it’s likely to be a question of ongoing debate.)

From Robert Kaufmann

This past summer, Robert Kaufmann, the BU geographer, made waves when he released a modeling study suggesting that the hiatus in warming could be due entirely to El Niño and increased sulfates from China’s coal burning. While the figures Kaufmann used for the study were based on the country’s coal combustion, and not actual emissions — a big point of uncertainty — many scientists saw some truth in his assertions.

From Martin Wild

During the 1980s and ’90s, the rapid decline of air pollution in the United States and Europe dominated the world’s aerosol trends. While those emissions have continued to decline in the West, returns, from a brightening standpoint, have diminished, just as coal combustion ramped up in Asia. It’s not that the world is getting dimmer again; it’s that it’s no longer getting brighter. “It’s not an obvious overall trend anymore,” said Martin Wild, a lead author of the United Nations’ next climate assessment at the Swiss Federal Institute of Technology, Zurich. But, he added, “it fits quite well with [coal power] generation. For me, it’s quite striking that it seems to fit quite nicely. But it could still be by chance.”

From Daniel Jacobs

Kaufmann’s findings may only be relevant for so long. Since 2006, China has begun to mandate scrubbers for its coal-fired power plants, though it is uncertain how often the scrubbers, even when installed, are operated. But change is coming, said Daniel Jacob, an atmospheric chemist at Harvard University. “The sulfate sources have been leveling off, because they’ve been starting to put serious emission controls on their power plants,” Jacob said. “It’s interesting. When you look at the future emission scenarios from the [next U.N. climate report], you see SO2 emissions dropping like a rock, even in the coming decades. Because basically China is going to have to do something about its public health problem.”

The end of the article highlights the developing debate among even these scientists.

“….many of the scientists sorting out the warming hiatus disagree with one another – in a chummy, scholarly way. Judith Lean, the solar scientist, finds Kaufmann’s work unpersuasive and unnecessarily critical of China. Kaufmann finds Solomon’s stratosphere studies lacking in evidence. Hansen and Trenberth can’t agree on a budget. It seems staggering, then, that in a few years’ time a new consensus will form for the next U.N. climate change report. But it will, and lurking beneath it will remain, as always, the churning theories and rivalries, the questions, the grist of scientific life. So, in the end, can anyone say explicitly what caused the warming hiatus? “All of these things contribute to the relative muted warming,” Livermore’s Santer said. “The difficultly is figuring out the relative contribution of these things. You can’t do that without systematic modeling and experimentation. I would hope someone will do that.” Barnes, for his part, would love to separate whether any background aerosols he found tucked away in the stratosphere came from Chinese coal burning. It is difficult to figure out, but he has some hope it could happen. “Maybe when coal burning triples,” he said, “then we might sort it out.”

These extracts from the Greenwire article illustrate why the climate system is not yet well understood. The science is NOT solved.

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