We need to drastically change our energy mix, relying far more on renewable energy. If we can make this shift, we might avoid the most disastrous effects of global climate change. Over the last 600,000 years, the carbon-dioxide content of the atmosphere varied between 200 and 290 parts per million. It started to climb out of this range just 120 years ago, now it is at 390 parts per million, and the recent report of the Intergovernmental Panel on Climate Change (IPCC) pointed out that only drastic measures will limit it to values below 500 parts per million.
We are thus embarking on an unprecedented experiment with our Earth, the result of which is difficult to predict. It is likely that the change of atmospheric composition through human emissions might end the Holocene, the last 12,000 years of relative climate stability, leading not just to a gradual global warming but to global climate instability with storms of hitherto unknown strengths.
What can we do to avoid this frightening scenario? Increasing energy efficiency and avoiding waste is, without doubt, where we must begin. In addition, we urgently need to increase as fast as possible the proportion of renewable energies in our energy mix. Among those, direct solar energy harvested as solar thermal energy and through photovoltaic energy conversion are the most promising. Further research to improve technologies in this important area is badly needed and continuing worldwide, but technologies allow us to embark today on an aggressive growth program to harvest this virtually unlimited source of energy: The sun provides the Earth each hour with the amount of energy we humans use in a whole year!
About 90 percent of all photovoltaic energy is based on crystalline silicon solar cells that yield efficiencies in the 15 to 20 percent range, a very respectable number if compared with nature, where photosynthesis works with less than 1 percent efficiency. The cost of photovoltaic energy follows a learning curve: Over the last 20 years, we have seen production costs decrease by 20 percent to 30 percent for each doubling of the total installed capacity of photovoltaic units. Thus, the most effective way to ultimately establish direct solar energy as the most cost-effective energy production technology is to substantially increase its production.
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We need to drastically change our energy mix, relying far more on renewable energy. If we can make this shift, we might avoid the most disastrous effects of global climate change. Over the last 600,000 years, the carbon-dioxide content of the atmosphere varied between 200 and 290 parts per million. It started to climb out of this range just 120 years ago, now it is at 390 parts per million, and the recent report of the Intergovernmental Panel on Climate Change (IPCC) pointed out that only drastic measures will limit it to values below 500 parts per million.
