John R. Christy, a professor of atmospheric science at the University of Alabama, Huntsville, and Alabama's state climatologist, is an expert on Earth's recent temperature history, as derived from microwave sensors on polar-orbiting satellites. Though he has contributed since the early 1990s to reports of the Intergovernmental Panel on Climate Change—the large collaboration of scientists that regularly assesses global warming for the United Nations—Christy considers the expert consensus overstated and unduly alarmist.
IEEE Spectrum: Tell us please about your work on the world's temperature and its significance.
John Christy: Since 1978, we've been able to monitor the bulk atmospheric temperature, which tells you whether heat has been accumulating or not. What we've found is an upward trend over 31 years of about 13/100 of a degree Celsius per decade. But you also see typical ups and downs: During the first two decades, temperatures were fairly flat, and increases were below the three-decade average. But with the big 1997 El Niño, there was a shift upward, and after that, temperatures were flat again but above average.
Spectrum: How does this record from microwave satellite observations differ from the temperature record compiled from other sources?
JC: Readings taken at the surface show 0.16 or 0.17 degrees of warming per decade—a bit more than the microwave readings. That may not seem such a great difference, but climate models indicate that if greenhouse gases are causing this warming, the upper atmosphere ought to be warming by about 1.2 times that of the surface, not less.
Spectrum: Is this discrepancy at the heart of your issues with what's often described as the "consensus temperature record"? Professors at the University of East Anglia, in the UK, have played a big role in establishing that record, and I see that in their hacked e-mail, you are one of the individuals who was mentioned most frequently in a negative way.
JC: They rely on readings from surface thermometers, but those have often been affected by developments like urbanization and deforestation, so they are not a precise proxy for what's going on in the atmosphere, where greenhouse gases are supposed to have their largest effect.
Spectrum: What has been the relationship between the East Anglia researchers and Britain's Hadley Centre for Climate Prediction and Research? (Former Prime Minister Margaret Thatcher set up Hadley two decades ago, locating it with Britain's prestigious Meteorological Office, to be a world authority on all matters having to do with climate change.)
JC: I was a visiting scientist at Hadley for two summers and got to see firsthand how they work together with East Anglia. At the end of the month, East Anglia's Phil Jones would send the land data to Hadley, which would take a critical look and combine that with their sea-surface data, and then the two teams would release what would be known as the HadCRU (for East Anglia's Climatic Research Unit) temperature data set.
Spectrum: So what's described as the "consensus temperature history" is, in effect, the Hadley-East Anglia history?
JC: Right.
Spectrum: I'm sure you don't want to speak for whoever hacked into East Anglia's e-mail, but is it a fair guess that East Anglia was picked precisely because of its key role in establishing the consensus temperature record?
JC: Actually, the mail may not have been hacked. Evidently, it was compiled to comply with a Freedom of Information request, and that folder may have been released as an inside job or inadvertently.
Spectrum: Had Freedom of Information requests been lodged because of concerns that inconvenient data were being concealed or dissenting views suppressed?
JC: What's disturbing in the mail is the resistance to share fundamental data with the outside community. That raised a lot of suspicions and red flags, and now we see that those suspicions were well justified.
Spectrum: The e-mail scandal obviously raises basic questions about the culture and ethics of science as it was being practiced at East Anglia, but tell me this: In what you've seen, is there any evidence that the temperature record was seriously distorted, or is there evidence of outright fraud?
JC: When it comes to the record of surface temperatures that Phil Jones led, I don't think it's going to change very much. More serious is the paleoclimate reconstruction from tree rings and so on. Here there was an attempt to give an impression of a time series that the underlying data did not support.
Spectrum: So the temperature record for the past few decades is fairly intact, but the record going back, say, a thousand years may now be open to dispute?
JC: That's right.
Spectrum: From ice cores, we have a pretty accurate temperature record going back about a million years. So why are the recent decades and the past thousand years so singularly controversial?
JC: Well, the key here is that we want to know just how warm it was during the medieval warm period. If it was warmer then than now, natural variability would seem to be a legitimate reason for current warming.
Spectrum: Do you agree with MIT's Richard Lindzen that we are now just bouncing back from the "little ice age" that lasted from the 15th century to the 19th century?
JC: For the most part, yes.
Spectrum: Dr. Christy, you and I seem to be almost exact contemporaries, having graduated from college at the end of the sixties. But I see you only got your Ph.D. in atmospheric sciences in 1987. May I ask what you were doing in the intervening years?
JC: I was very much involved in missionary work, and I taught physics and chemistry for two years in Africa. That experience informed a lot of what I do and think today. I saw firsthand what it means to have energy and what it means to not have it. Without energy, life is brutal and short.
Spectrum: We often hear the religious-minded speak about our responsibility to be stewards of the earth. What do you think about that?
JC: It sounds like you're on the side of the angels when you say you want to save the planet. But if you're talking about preventing energy from expanding in the Third World, you're condemning people to perpetual poverty. What's more, it's economic development that creates the cleanest environments we have. You don't find clean rivers or clean air in the poorest countries.