So which of these opposing world views is the more correct? A simple experiment was conducted a few years back that pretty much answers the question in favor of the climate skeptics.

Working within and around Baltimore, Maryland (USA), Ziska et al. (2004) characterized the gradual changes that occurred in a number of environmental variables as they traveled from a rural location (approximately fifty kilometers from the city center) to a suburban location (about ten kilometers from the city center) to an urban location (only half a kilometer from the city center). And at each of these locations, they excavated four 2-meter by 2-meter plots to a depth of approximately 1.1 meter, after which they filled them with identical soils, the top layers of which contained the seeds of plants that occurred naturally throughout the surrounding area.

The plants produced by the seeds that sprouted in the spring were allowed to grow to maturity in the fall, after which they were cut at ground level, removed, measured for height, dried in ovens and weighed. And what did the researchers learn from this simple experiment? They report that along the entire transect, the only consistent environmental trends they detected were a rural-to-urban increase of 21% in the average daytime atmospheric CO2 concentration and increases of 1.6°C in maximum daytime temperature and 3.3°C in minimum nighttime temperature, which changes, in their words, "were consistent with most short-term (about 50-year) global change scenarios regarding CO2 concentration and air temperature."

So what did the increases in the air's CO2 content and temperature do for the plants that sprouted and grew in the suburban and urban plots? The three researchers discovered that "productivity, determined as final above-ground biomass, and maximum plant height were positively affected by daytime and soil temperatures as well as enhanced CO2, increasing 60 and 115% for the suburban and urban sites, respectively, relative to the rural site." And what do these amazing findings imply?

Dr. Ziska and his colleagues say their results suggest that "urban environments may act as a reasonable surrogate for investigating future climatic change in vegetative communities." And we note that their results clearly indicate that the "twin evils" of the radical environmentalist movement (increasing environmental temperatures and rising atmospheric CO2 concentrations) will likely lead to dramatic increases in the productivity of earth's natural ecosystems. In fact, literally thousands of experiments, conducted all around the world (see our Plant Growth Data Base), have demonstrated that nearly all plants grow bigger and better in CO2-enriched air, while numerous other studies have additionally demonstrated that when the air's CO2 content rises, the temperatures at which earth's plants function best tend to rise right along with them (see section II.B of our Major Report The Specter of Species Extinction: Will Global Warming Decimate Earth's Biosphere?).

Therefore, do not fear a CO2-enriched and possibly warmer future ... yearn for it ... and for the many benefits it will bestow upon the planet's plants.

Sherwood, Keith and Craig Idso

Reference
Ziska, L.H., Bunce, J.A. and Goins, E.W. 2004. Characterization of an urban-rural CO2/temperature gradient and associated changes in initial plant productivity during secondary succession. Oecologia 139: 454-458.