The wind-turbine article was well-written and relatively balanced; however, it continues the notion that "renewables" are environmentally benign ("Will wind turbines ruin your view," Page One, July 9). Although they are clearly superior to fossil fuels, the processes of manufacturing, transporting, installing and maintaining renewables entail considerable carbon emissions.

Further, since they are very small units, the carbon cost of the electricity they produce over their life cycle is significant. National Geographic's April 2006 issue presented comparative life-cycle carbon emissions per kilowatt-hour of output for various generating sources. While coal and oil were over 200 grams, solar emits nearly half of natural gas's carbon output level, and hydro, biomass and wind all greatly exceed nuclear, which has virtually none, largely due to the massive amounts of electricity generated relative to the carbon involved in construction and operation.

This merely illustrates that the issues are rarely as straightforward as proponents of any particular solution purport. However, if global warming is the most crucial issue confronting our world, then we ignore the carbon footprint of renewables at our peril.