We here at Science Buzz have discussed global warming a time or two. And long-time readers know that I am The Science Museum’s resident global warming skeptic. Not a denier – I recognize that the Earth’s temperatures have been generally increasing over the last 25 to 30 years, and I’ll admit that human-produced carbon dioxide could well be a contributing factor. However, I am skeptical about claims that human activity is the sole or even primary cause of this warming; that there is a simple, direct correlation between our actions and global climate; or that the planet is headed toward some sort of ecological disaster in the next 10 years if we don’t do something drastic now.
Toward that end, I keep an eye on the various global warming threads, and try to temper the more intemperate comments made by those who hold different views. (And they do the same for me, of course.) So, in the course of a debate, if someone says “the Earth is warming,” I correct them by pointing out that the Earth has warmed: global temperatures rose in the 1980s and ‘90s, peaked in the US in 1998, and have held steady or dropped slightly since.
I have recently learned that this was wrong. As painful as it is for me to admit, I must set the record straight: temperatures in the US did not peak in 1998. They actually peaked in…
In 1934, the world’s population was a fraction of what it is today. (One-sixth, more or less.) Manufacturing and industry were smaller. The number of cars and the miles traveled in them were far fewer. Commercial air travel – a huge producer of greenhouse gases – was in its infancy.
(1934 was also the year my mother was born and, in a coincidence science has thus far been unable to explain, the year Yoko Ono was born.)
And yet despite the lower levels of greenhouse gas, 1934 was warmer than any other year, before or since. And while global temperatures had been generally increasing since about 1890, they leveled off around 1940 and even took a slight dip in the 1970s. All of which indicates that record-high temperatures may not be the harbinger of doom so many assume them to be.
So, how could I have made such a drastic mistake? Well, I’m not the only one. Y’see, I was relying on a temperature chart produced by NASA scientists Reto Reudy and James Hansen. Their graph showed temperatures spiking in the late ‘90s, and staying near that peak.
Of course, other people were studying that chart, too. One of them, Steve McIntyre, thought it looked a little fishy. So he asked Hansen for the formula he used to produce his chart. Hansen, operating in the spirit of openness and transparency that is the hallmark of science and a requirement of the federal government…refused. (Other scientists have also accused some federal agencies of not sharing their data so it can be reviewed.) So McIntyre reverse-engineered the formula from the published data. And he found something interesting.
Temperature data from many reporting stations around the country suddenly jumped around the year 2000. After some digging, McIntyre found an error in the formula used to process the data. As a result, Reudy and Hansen reported many years as being warmer than they really were.
(Is this the same James Hansen who has accused the Bush administration of playing politics with science, trying to suppress views that contradict their positions and cherry-picking data that advances its agenda? Why, yes it is!)
NASA has recomputed the figures and issued a new set of corrected data. It now shows that five of the ten warmest years on record occurred before World War II, when global temps leveled off and later fell. Four of the years in our current decade which were supposed to have been near record highs were actually colder than 1900.
Minnesotans can be proud that their state played a role in uncovering this mistake. It was data at the Detroit Lakes station that first led McIntyre to believe something was amiss.
So, what lesson do we learn from all this? That I need to be more skeptical. I have to stop believing everything I read in the New York Times. I need to recognize that even rocket scientists can sometimes make mistakes.
So my promise to you, dear readers, is I will check my sources and do my best never to fall for this sort of mistake again.