He began his talk by saying that in 1957, measurements of CO2 began to be made at Mauna Loa (by Charles David Keeling), which established that CO2 is increasing in our atmosphere, largely because of human activity--from fossil fuel emissions. It's approaching 390 parts per million (ppm). Last weekend, the "A" on A Mountain near the university was painted green by a bunch of people wearing shirts that say "350" on them, because they want atmospheric CO2 to be stabilized at 350 ppm, which was the level in 1990, which is the benchmark year for the Kyoto Protocol.
But this isn't remotely feasible, he said, citing the Intergovernmental Panel on Climate Change (IPCC). Even the most optimistic scenario in the IPCC Report has atmospheric carbon continuing to rise until 2100, hitting about 600 ppm. If we reduced emissions to 0, the best case would end up with stabilization at around 450 ppm. Our lifetime will see increasing CO2 levels, no matter what we do. (In other words, the Kyoto benchmark sets a standard for emissions levels to return to, not for a level of atmospheric carbon to return to.)
If you look at the earth's history on a longer scale, atmospheric carbon has been much higher in the past--it was at about 2500 ppm during the dinosaurs. During the last 600,000 years, however, it has been much lower, and fell below 200 ppm in the last glacial period. This, Balling said, shows what he would identify as a dangerous level of CO2--falling below 160 ppm, which causes plants to die.
There are other greenhouse gases besides CO2 that have an effect, such as methane and NO2, that humans are producing, he said.
At this point, he said the greenhouse effect is real--CO2 doubling causes warming--and this has been known for 120 years and "nobody is denying that."
There are climate models, which he said he has great respect for--it's basic physics plus fantastic computing and applied math. Climate modelers, he said, are their own worst critics. Problems for climate models include clouds, water vapor, rain, and the ocean, but lots of things are modeled correctly and the results are generally pretty good. Clouds, he said, are the biggest area of debate. The IPCC models say that clouds amplify warming, but satellite-based measurements suggest that clouds dampen (but don't eliminate) warming. Thus, he concluded, IPCC may be predicting more warming than will actually occur.
He next discussed empirical support for warming, and pointed out that the official plot of global temperatures has no error bars, and the numbers reported come from sensors that don't cover the entire world. How you come up with a global average can be done in different ways, and the different methods produce different results. You can take grid cells, average by latitudinal bands, get two hemispheric averages, and average them together. You can just average all of the data we have. He said that Roger Pielke Sr. questions the use of average temperatures and suggests looking at afternoon high temperatures. Looking at the older end of the chart, he asked, "where were the sensors in 1900? Why no error bars?"
He asked, "Is the earth warming," and said "right now the earth is not warming. I expect it to keep going up, but over the last decade there's been essentially none." He pointed to a recent article in Science magazine, "What happened to global warming?" Many are writing about this, he said, and there could be "1001 different things including sun and oceanic processes." (I don't believe this is correct unless you measure from 1998, which was an El Nino year. Most of the top 10 warmest years in history are post-1998.)
"Scientists are questioning the data," he said, showing photos from Anthony Watts' blog of poorly situated weather stations. "The albedo of the shelter in my backyard has changed as it has decayed," and caused it to report warmer temperatures. He said that people are having a field day taking photos of poor official sites. (What Balling didn't say is that what's important in the data is not absolute temperature but the temperature trends, and the good sites and bad sites both show the same trends.)
He pointed out that there are corrections to the temperature based on time of measurement, urban heat islands, instruments used, etc. If you look at the raw data for the U.S. from 1979-2000, you see 0.25 degrees Celsius of warming. Sonde data shows 0.24 degrees, MSU's measurements show 0.28, IPCC shows 0.28, and FILNET shows 0.33. He suggested that these corrections on the official data may be inflating the temperature (again, see my previous comment on trends vs. absolute temperature). Sky Harbor Airport produces the official temperature results for Phoenix, maximizing urban heat island effect. Many of the city records are from the worst sites, and he suggests looking at rural temperatures might give a different result.
Another factor is stratospheric turbidity from volcanic eruptions, and he showed a plot of orbital temperatures from satellites vs. stratospheric turbidity. He said that volcanism accounts for about 30% of the trend variability.
The big player in the game, he said, is the sun. Solar irradiance measures showed a significant decline in solar output in 1980, but earth temperature continued upward--he said he mentioned this because he thought it would be used as an objection. In response, he said that "the sun doesn't increase or decrease output over the entire spectrum and there are interactions with stratospheric clouds." He said that there are astrophysicists who argue that this is the major cause of global warming. In the Q&A, he said that there's one group that thinks cosmic ray flux is the major factor in global temperature because it stimulates cloud formation, while another group says that cosmic ray flux is little more than a trivial effect. He also said that this debate takes place in journals that "I find very difficult to read."
There are other confounding variables like El Nino and La Nina, but he said there has "definitely been warming over the last three decades with a discernable human contribution."
He put up a graph of the Vostok Reconstruction of temperature based on ice core data, on a chart labeled from -10 to +4 degree temperature changes in Celsius, which were mostly in the negative direction, and said we've seen periodic rapid changes up and down without any human contribution.
He talked about the IPCC "hockey stick" graph from 2001, which led to a huge debate about the possibility of bad statistical methods that guaranteed the hockey stick shape. He observed that 1000 years ago it was as warm or warmer than today, the Medieval Warming Period, which was missing from the "hockeystick" graph. There was also a "Little Ice Age," also missing from the graph. He said the IPCC has backed away from the hockey stick and its most recent report includes clear Medieval Warming Period and Little Ice Age periods in its graphs.
He showed a photo of a microwave sounding unit for temperature measurement, and the polar satellite record from 1978 to present, which showed a big peak in 1998 from El Nino. He said he wrote his book saying that there was no warming in 1992, when it was true. After 1998, the temperature came back down quickly, and, he said, the satellite record, like the Science article, hasn't seen warming. He then corrected himself to say, "well, some warming, but not consistent with the IPCC models."
He said there has been high latitude warming, and the difference between winter and summer warming has supported the numeric models. "But a problem has evolved, which is the most powerful argument of the skeptics." The models predict that there should be warming at the surface, which increases at higher altitude as you go up into the atmosphere. "There should be very strong warming in the middle of the atmosphere, but it's not in the data." This is the main anti-global warming argument of Joanne Nova's "The Skeptics Handbook" that has been distributed to churches throughout the U.S. by the Heartland Institute (an organization supported by the oil industry that has sometimes gotten into trouble due to its carelessness).
At this point, Balling started asking various questions and answering them by quoting from the IPCC reports:
More hurricanes? The IPCC doesn't say this. He cited the 1990, 1996, 2001 (executive summary, p. 5), and 2007 (p. 6) reports, all of which say that there's no indication or no clear trend of increase or decrease of frequency or intensity of hurricanes or tropical cyclones as a result of warming.
The southwestern United States may become drier? Here, he answered affirmatively, pointing out that an ASU professor has an article that just came out in Science on this topic. Atmospheric circulation is decreasing, and soil moisture measures show the southwest is becoming drier. On this, he said, there's "evidence everywhere," and the Colorado River basin in particular is being hit hard. And this is consistent with IPCC predictions. He cited Roy Spencer to say that "extraordinary prediction require extraordinary evidence." (This actually comes from Carl Sagan, who said "extraordinary claims require extraordinary evidence" in Cosmos.)
Frequency of tornadoes? It's down, not up, and IPCC 2007 p. 308 says there is no evidence to draw general conclusions.
Ice caps are melting? Balling said Arctic yes, Antarctic, no. He cited the IPCC 2007 p. 6 regarding Antarctic sea ice extent indicating a lack of warming, and p. 13 that it's too cold for widespread surface melting. He contrasted this with a slide of a homeless penguin used to argue for action on global warming. The Arctic ice cap "has its problems," he said, and its extent has declined though has "rebounded a bit" recently. (In the Q&A, he said that half of the loss in the last six years has been recovered.) He said that experts in sea ice extent identify relative temperature, ocean currents, and wind as more important than temperature--"it's not a thermometer of the planet." In the past, northern sea ice has dropped as southern sea ice has increased, with the overall global extent of sea ice relatively unchanged. In the Q&A, he made it clear that he wasn't saying that temperature wasn't a factor, but that global temperature is definitely not a factor and temperature is less important than the other factors he identified.
Sea levels changing? He said there's no doubt about this, but the important question is whether the rise is accelerating. He cited Church et al. J. Climate 2004, p. 2624 for a claim of "no detectible secular increase" in rate of sea level rise, but noted that another article this week says that there is. IPCC 2007, p. 5 says that it is unclear if increasing is a longer-term trend. The average has been 1.8 mm/year, but with variable rates of change. IPCC 2007, p. 9 says that 125,000 years ago sea levels were likely 4-6m higher than in the 20th century, due to retreat of polar ice.
He said that ice melting on Kilimanjaro has been a "poster child" for global warming, but that this sharp decline "started its retreat over 100 years ago," at the end of the Little Ice Age (1600-1850), and is related to deforestation and ocean patterns in the Indian Ocean rather than global warming. It's not in an area where significant warming is expected by climate models, and local temperatures don't show it.
He then talked about a few factors that cause temperature forcing in a negative direction (i.e., cooling)--SO2, which makes clouds last longer, increased dust, and ozone thinning. He said that his entry into the IPCC was his work at the U.S./Mexico border where he found that overgrazed land on the Mexican side caused warming, and it was much cooler on the U.S. side of the border. The dust, however, had a global cooling effect.
The 2001 IPCC report lists global radiative forcings in the negative direction: stratospheric ozone, sulfate, biomass burning, and mineral aerosols. In the positive direction include CO2 and solar irradiance. The 2007 report adds many more, including contrails from aircraft. A chart from the report lists the level of scientific understanding for each factor, and he observed that it's "low" for solar irradiance.
He cited a quote from James Hansen (Proc. Nat. Acad. Sci. p. 12,753, 1998) saying that we can't predict the long term, and said he agrees.
He observed that the Pew Foundation poll for Sep. 30-Oct. 4 asked Americans if they think there is evidence of global warming being caused by humans and only 36% said yes--he said he's one of those 36%.
He concluded by observing that if you look at the difference between doing nothing at all, or stabilizing at 1990 levels in 1990, that only produces changes of a few hundredths of a degree of temperature in 2050--so no matter what we do, "we won't live long enough to see any difference."
In the Q&A session, Prof. Billie Turner said that "our academy is about to issue a statement that we are 97% sure that we will not be at a 1-degree Celsius increase but a 2-degree Celsius increase by 2050" (or about double what Balling's final slide showed). He objected that Balling's talk began with the "lunatic green fringe" and contrasted it with the IPCC, which he said would be like him beginning a talk with Dick Cheney's views before giving his own. He said this may be an effective format, but it "gives a slant on the problem that isn't real in the expert community." Turner also pointed out that on the subject of mitigation, if you are going to make a calculation in economic terms you have to use a discount rate. The Stern Review used a high discount rate, and concluded that it is worth spending a lot of money now on mitigation; William Nordhaus and Partha Dasgupta, on the other hand, used a low discount rate and concluded that it's not worth spending money on now.
Balling said that he gets email from "lefties" that ask him to "please keep criticizing" because "this [global warming] is just an excuse to keep the developing world from catching up." In conversation with a small group afterward, Balling made it clear that he thinks people shouldn't be listening to Limbaugh and Hannity on climate change, and in answer to my question about what sources the educated layman should read and rely upon, he answered unequivocally "the IPCC," at least the scientific portions authored by scientists. He had some criticisms for the way that the technical summaries are negotiated by politicians, however, and said that S. Fred Singer has made hay out of comparing the summaries to the actual science sections and pointing out contradictions. He also said that Richard Lindzen at MIT, who he said may be the best climate scientist around, thinks the whole IPCC process is flawed, and that John Christy, lead author of the 2001 IPCC report, thinks the IPCC process should allow an "alternative views" statement by qualified scientists who disagree.
In a very brief discussion afterward with the climate modeling grad student in my climate change class, he said that the biggest weakness of the talk was that Balling didn't talk about ocean temperatures, being measured by the Argo project of NASA's Jet Propulsion Laboratory. These measures had shown some recent cooling (but a long-term warming trend), but after discovering an error, Joshua Willis found that warming has continued.
Balling supports the science, but he still leans to minimizing the negative effects, and uses some apparently bad arguments to do so. His position clearly advocates a "wait and see" approach, and argues that we needn't be in a hurry to mitigate since nothing we do will have any effect in our lifetimes--but it could have an enormous effect on what is required for mitigation and adaptation for future generations.