Sun, gravity and rocks – what do they have in common? They are the ultimate source of virtually all energy on earth. All fossil fuels, such as coal and oil; wood; and biofuels are organic compounds resulting from the capture of solar energy by plant photosynthesis. Solar energy also powers the air currents that we call "wind" and plays a major role in the hydrologic cycle. The natural decay of radioactive elements in rocks, primarily uranium, thorium and probably potassium, is the major source of heat at the earth's core (geothermal energy) and the nuclear fission or fusion of highly refined (concentrated) radioactive elements provides energy for power plants and our "atomic" weapons. The force of Earth's can be converted into hydropower by harnessing running water, while the gravitational pull of the moon provides a largely unexploited source of tidal energy.
Thus we have three sources of energy, but with the exception of passive heating, none of these sources is directly useful – they all require capture, storage, conversion and distribution in order to provide the "work" desired by mankind. For example, electricity is converted and distributed energy from the sun (coal, oil, wind, bio-fuel, or "solar"), rocks (nuclear) or gravity (hydro-electric). Whether we burn gasoline or ethanol in our internal combustion engines, both are solar energy captured by plant photosynthesis, either refined or distilled, and then distributed to our engines. The only real difference is that one has been stored in the ground for about 320 to 360 million years while the other has not. [See "Too Valuable to Burn" for another perspective on this ancient carbon.] We use the heat energy of a nuclear reaction to make steam, which drives a generator and makes electricity to be distributed to users. Electricity is again a distribution medium, not the ultimate source of the energy.
The sun remains our largest source of energy, either through fossil energy stored as coal or oil, or such fuels as wood and biofuels. As we attempt to reduce the emission of greenhouse gases from the combustion of coal and oil, we are primarily turning toward other forms of solar energy such as solar-driven air currents (wind) or "direct solar" (photovoltaics, steam/electric), and increased reliance upon hydro. It is ironic that these so-called "clean", "green", or "renewable" energy sources are all extremely sensitive to climate change: and, in fact, are already being negatively impacted by climate change. The western, and southeastern regions of the United States are in the midst of a prolonged, severe and increasing drought, which has already curtained the production of hydro-power, and as also occurred in other regions throughout the world. "Direct solar" energy conversion requires copious amounts of water for cooling and steam generation. In the U.S. the Southwest receives the most dependable supply of solar energy, but this water-short arid region is also impacted by multi-year drought.
The wind industry is rapidly expanding, with many countries placing increasing reliance upon wind to help meet emission reduction targets. But, a research study just reported in the esteemed "Journal of Geophysical Research"(1) suggests a significant reduction of about 10% in wind (speed and duration) in the mid-west and eastern regions of the United States. Similar results have been reported from Europe and Australia. It has been suggested that the reduction is caused by global climate change with the warming conditions at the poles reducing air pressure gradients.
Throughout the world agriculture has been impacted by climate change. Growing season temperatures, water supply, pests and disease are climate sensitive and directly influence agricultural production. While plant breeding has resulted in exceptionally hardy varieties, the monoculture resulting from reliance on these "improved" varieties has resulted in an agricultural system that may prove to be especially vulnerable to effects of a rapidly changing climate, thus reducing the supply of materials for bio-fuels in addition to food.
The fact remains, that our current emphasis on wind, bio-fuels and "solar energy" is not introducing new energy sources, but rather new methods of capturing, or converting energy from the sun. And the quandary is that while we are banking upon these alternate, "green" sources of solar energy to reduce slow global warming and subsequent climate change, the changing climate may already be reducing the effectiveness of their implementation. In this regard, the longer we delay an effective global program to reduce warming of our planet, the less likely its success.
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1.) Pryor, S. C., R. J. Barthelmie, D. T. Young, E. S. Takle, R. W. Arritt, D. Flory, W. J. Gutowski Jr., A. Nunes, and J. Roads (2009), Wind speed trends over the contiguous United States, J. Geophys. Res., 114, D14105, doi:10.1029/2008JD011416.
