Thanks for the question, Timmy. As you know, Beijing’s weather over the past few days has sparked off a great deal of discussion, not to mention hacking coughs, upper respiratory infections, and airport closings. At the heart of the controversy are seemingly contradictory claims by observers.
On one side, many are reporting on the severe hazards of the air, such as this article in Xinhua:
Experts are worried that particulate matter in the air, which is in higher concentrations in North China because of the heavy fog since the weekend, may lead to various respiratory diseases including lung infections and cancer.
Shi Yuankai, vice-president of the Chinese Academy of Medical Sciences Cancer Hospital, said longtime exposure to particulate matter especially the particulate matter smaller than 2.5 micrometers (PM2.5) which can go directly to the alveoli of the lungs, is a major health hazard.
On the other side include Beijing municipal officials who insist that the recent weather is normal for this time of year:
Zhang Mingying, a meteorological engineer at the Beijing Meteorological Bureau, told the Global Times on Monday that the recent fog is normal in terms of frequency during this time of year according to their monitoring.
“Heavy fog has occurred 6 times a year on average over the past 30 years and December’s fog was the seventh occurrence this year. Therefore, it is a normal climate condition in Beijing,” said Zhang. (CDT)
As usual, the media focus on the argument, the “He said/she said” tenor of the discussion, is all wrong. As usual, it’s up to science to give us the answers.
After a bit of research this afternoon, I was able to uncover an old meteorological study conducted by the Horse & Buggy Foundation, based on a grant from the Automobile Lobby Research Council, on the connection between air pollution and carbon dioxide emissions. The study dates back to 1984, but apparently the director, an H&B Foundation fellow named Dr. Bob Loblaw, has been doing some consulting with the Beijing government. His 1980s U.S. findings are therefore quite relevant.
Dr. Loblaw’s basic discovery was something he referred to as the “air pollution sensor variable Doppler effect,” or NAMBLA effect for short. In order to understand the NAMBLA effect, one has to not only understand the relativistic Doppler Effect with respect to light, but also something about human nature.
Let’s take a look at the Doppler Effect first. You may have studied this in school with respect to sound waves. First, imagine a light source and an observer. Just for fun, let’s call the former a star and the latter Edwin Hubble. Imagine light as a series of waves.
Now imagine that the star is traveling towards Edwin Hubble very quickly. What happens to those light waves that he sees? Well, they are squeezed together. If the star is moving away very quickly, then the waves are stretched out. From the perspective of Edwin Hubble, when objects are moving away from him, he sees those stretched out light waves at a lower frequency, shifted to the red end of the spectrum. This is called a “red shift.”
Loblaw’s genius was to take the research of Hubble and others and apply it to meteorological phenomenon. This was radical thinking at the time, and he was lucky to have the generous support of General Motors, the Ford Motor Company and other philanthropic enterprises.
Loblaw’s breakthrough was as follows. Imagine the above scenario, but we’ll change the facts around slightly. Let’s assume that the light source is now a fog bank, and the observer is a meteorologist sent out to obtain data on air pollution.
Understanding human nature (he minored in psychology at Oral Roberts University), Loblaw understood that most researchers, when faced with very spooky fog, would have a tendency to be afraid. You can imagine a lone scientist stepping out onto the roof of a building surrounded by a thick fog bank. Very creepy.
Loblaw theorized that the normal tendency of the meteorologist in that situation would be to run away very rapidly. Furthermore, these scientists would not want to go out there again, but would rely on the incomplete data obtained during their panicked flight.
You can probably see where this is going. Loblaw calculated that depending on the speed of the scientist and the distance to the fog bank, the data would include a significant red shift error. Loblaw assumed that the average scientist would, when confronted by a creepy fog bank, run away at a speed of .8c, or 239,833,966 m/s. Some of his peers suggested that the average meteorologist might not be in that kind of shape, but this issue was never fully resolved.
Loblaw also assumed that the most important data with respect to air pollution included simple photographic evidence, such as the color of cloud formations. Over the course of his career, Loblaw has been highly critical of so-called particulate matter data, which he believes are irrelevant to the study of air pollution. When confronted on this issue at an academic conference in 1993, Loblaw reportedly stated “Who are you going to believe, your own eyes or some invisible widgets that some government bureaucrat says can destroy your lungs? I mean, really!” Good enough for me.
So what happens when a grayish color is shifted to the red end of the spectrum? A relative shift of that kind would . . . wait for it . . . tend to make the object appear darker, or what Loblaw described as “dirtier.” This was Loblaw’s basic conclusion, that relative observer motion in these tests introduced an error that caused fog to appear grayer than it really was, in other words to make the sky appear more polluted. (In future papers, Loblaw extended his theory to explain observer error for fixed-position objects, like stationary eyeballs and monitoring equipment.)
I don’t know about you, but I’m glad I took the time to educate myself about this controversy. It turns out that we can rely on municipal data after all (based on suggestions made by Loblaw, they only hire brave scientists who do not run away when confronted by creepy fog). Based on this knowledge, I went out for a long run earlier today. Apparently I was in worse shape than I thought. Not only is my speed much less than that of the average scientist, but I also couldn’t seem to catch my breath — not that that’s relevant to this discussion.
So be careful who you believe, and try to stay apolitical when it comes to weather reports. Note on the spectrum image included above that red shifts lean to the right.