Carbon dioxide is essential for life on earth—without it there would be no photosynthesis, which provides nearly all the metabolic energy of the biosphere. Natural sources generate hundreds of billions of tonnes of CO2 every year, without which the planet would be close to freezing everywhere. So how can 12 US states be bringing a case to the supreme court arguing that CO2 is a pollutant and must be regulated?
The simple answer is that human-made CO2, as the principal greenhouse gas, is apparently responsible for most of the global warming of the past century. The more we pump into the atmosphere, the hotter we get. That's why Massachusetts, California and ten other states are suing the US Environmental Protection Agency (EPA), saying that it must start regulating CO2 emissions just like other pollutants.
The lawsuit, due to be heard over the winter, was brought after the EPA ruled in 2003 that CO2 is not a pollutant—itself a response to a contrary legal opinion from the Clinton administration. The argument was based on a technicality: although the Clean Air Act, the keystone of airborne pollutant control in the US, gives the EPA the authority to regulate pollutant emissions, it says nothing about climate change. By saying that CO2 and other greenhouse gases are not pollutants, the EPA is merely stating that they are not covered by the act. The lawsuit is thus about establishing how far the EPA's responsibility extends.
The motor industry mocks the idea of CO2 as a pollutant. Quite aside from its role in photosynthesis, CO2 is non-toxic; indeed, we breathe it out constantly, says the Alliance of Automobile Manufacturers. But the argument shows how futile it is to try to divide up chemicals into good and bad—as environmentalists often do. Take cobalt: mildly toxic and a suspected carcinogen, but also the essential component of vitamin B12, without which we may suffer pernicious anaemia. The poison, as Paracelsus said, is in the dose.
The case of Massachusetts et al v the EPA is more likely to depend on legal than on scientific considerations, however. If it hinges on the wording of the Clean Air Act, things will get sticky, for the act was badly drafted in the crucial section: the definition of an air pollutant, it says, is "any air pollution agent… which is emitted into… the air" —a tautology that could leave both sides grasping at straws. If the EPA loses, it could be forced to regulate CO2 emissions from cars—but only if its scientists find that the gas is a danger to public health. That could take years.
The Royal Society and censorship
Opinion has been similarly split over another recent climate change spat. When Bob Ward of the Royal Society wrote in September to Esso (the British branch of oil giant ExxonMobil) admonishing the company for funding US groups sceptical of the human role in climate change, he invited accusations of censorship. What gives the Royal Society the right, critics asked, to impose a scientific consensus by stifling contrary opinion? Yet Ward's letter was simply a request to be told when ExxonMobil planned to carry out an alleged pledge it had made to stop funding these bodies. He complains that both the Esso corporate report and the websites of the groups they sponsor mislead the public about current scientific understanding of global warming by suggesting that there are still too many uncertainties to assert a human influence. The complaint is valid; the issue is whether it is any business of the Royal Society's to interfere with "free speech."
But that's a fatuous argument. Scientists and scientific institutions have always spoken out against misinformation of this kind. In the US, that is the only defence against the advance of creationism. Suppressing controversial research is one thing; denouncing those who bend or ignore facts is another. Sadly, the Royal Society may now have contributed to climate-sceptic conspiracy theories—while doing no more than its public duty.
The dark side to proteins
Amyotrophic lateral sclerosis is a motor-neuron disease better known by the name of the baseball player Lou Gehrig, whom it forced into retirement in 1939 (Dmitri Shostakovich was another famous sufferer). This neurodegenerative disease is akin to Alzheimer's and a host of other dementias in that it is caused by deposits of abnormal protein in neurons. An international team has now identified the protein responsible for Lou Gehrig's disease: a little-known molecule called TDP-43. In affected neurons this protein has been chemically tagged for destruction by the cellular clean-up apparatus because it is "misfolded": the chain-like molecule has collapsed into the wrong shape, like neat balls of wool unravelled and entangled. That is basically the problem in Alzheimer's too, where misfolded proteins form recalcitrant "amyloid plaque"—lumps of useless yet somehow damaging material. Other work just published by Princeton researchers shows that the formation of amyloid plaque is generic to a whole class of proteins—unlike the enzyme action of properly folded proteins, it doesn't depend strongly on precise chemical structure. This supports the disturbing hypothesis that protein misfolding in neurodegenerative diseases is a general problem indicative of a "dark side" to proteins: an evolutionary design flaw that potentially erupts in old age.
