Healthy carbon?

During February's annual meeting of the American Association for the Advancement of Science, researchers described how global warming could threaten humans. In one scenario, warming oceans increase algal blooms and result in a buildup of toxins in shellfish, which poison or kill those who eat them. In a second scenario, dust from warming-induced desertification settles in the oceans and encourages the proliferation of Vibrio bacteria, which would spread disease via seafood.

Elsewhere, scientists have pointed at dengue fever, which returned to the United States in 2009, and West Nile virus, introduced in 1999. Both are carried by mosquitoes, which thrive in warm weather. Even the CIA is worried: The agency established a department two years ago to study the impact of climate change on national security. The spread of disease is among the threats the office expects to encounter.

However, researchers who are paid to uncover global warming threats aren't necessarily paid to find anything else: Dr. Craig Idso, chairman of the Center for the Study of Carbon Dioxide and Global Change, told me by email that governmental organizations "either completely ignore or downplay the positive benefits of rising CO2 (and temperature for that matter) to a fault."

Idso's new book, The Many Benefits of Atmospheric CO2 Enrichment, cowritten with his father Sherwood Idso, describes 55 ways that increased CO2 would benefit plants, the environment, and human health.

Plants, for example, typically increase photosynthesis and growth in response to an increase in atmospheric CO2. Roots spread wider and seed production increases. Many foods become more nutritious: Oranges produce more vitamin C, soybeans more of their beneficial isoflavone compound. As plant growth increases, it sustains animal populations and stabilizes erosion. The overall picture is that the planet becomes more productive as CO2 increases.

Even if toxic seafood is a legitimate issue, Idso's organization points to numerous studies showing that cold spells, not heat waves, are far more likely to kill humans. A study of Spanish data last year found the death rate from cardiovascular, respiratory, and digestive system diseases was 15 percent higher in winter than in summer.

Scientists disagree about whether warming will increase infectious diseases or merely shift their geographic range. Many believe international travel and trade do more to spread diseases like dengue fever and West Nile virus than climate change ever will: University of Oxford ecologist Sarah Randolph wrote in 2009, "There is no single infectious disease whose increased incidence over recent decades can be reliably attributed to climate change."

Killer smile

Paleontologists working in Brazil found a skull from an extinct animal unusual for the fossil record: It had molar-like teeth that closed together comfortably-ideal for chewing plants-along with two crayon-sized saber teeth, which would be expected in a carnivore. The researchers chalked the animal up as a vegetarian, but puzzled over the sabers. They speculated the pig-sized Tiarajudens eccentricus used them to scare predators, impress mates, or fight rivals. Musk deer have similar canines, proving beasts need not be predators to sport a mean smile.