Like any other human activity, producing and using energy cause impacts on environment and human health. This topic is broached upon for every individual energy source, but the table below gives a non exhaustive summary:

1. All these risks are real, but none is more adverse to human health than energy scarcity.

2. Most of those risks have local, sometimes regional impacts. Some impacts occur only during accidents, other happen during everyday use. The prominent risk is, by far, the deterioration of the greenhouse effect, because it has a global planetary impact and because it happens during normal routine operation.

 

Even though our planet Earth has its own central heating system (Geothermal energy, caused by the radioactive decay of some Earth elements), its surface temperature is determined mostly by the balance between the amount of energy Earth receives from the Sun as visible light and the amount it radiates back to Space as infrared radiation. In this balance, our atmosphere plays the part of the window panes in a greenhouse: it allows free passage to most of the visible radiation but it absorbs most of the infrared radiation, which is then radiated partly to space and partly back to Earth, causing its surface to heat up. The Greenhouse effect is vital to us: in its absence, the average Earth surface temperature would measure – 18°C instead of + 14°C. At – 18°C, no liquid water, no sap, no blood, no life as we know it.

The most potent Greenhouse effect gas (GHG) is the ordinary water vapour going into the atmosphere from oceans evaporation. Human action on water vapour is negligible but some GHG of human origin, prominent among which is carbon dioxide CO2, followed by methane CH4, increase the absorption of infrared radiation by the atmosphere and, therefore, the greenhouse effect.

Climate specialists from all over the world have sent, in December 2007, the following recommendations to Governments before the Bali Conference:

"The 2007 IPCC report, compiled by several hundred climate scientists, has unequivocally concluded that our climate is warming rapidly, and that we are now at least 90% certain that this is mostly due to human activities. The amount of carbon dioxide in our atmosphere now far exceeds the natural range of the past 650,000 years, and it is rising very quickly due to human activity. If this trend is not halted soon, many millions of people will be at risk from extreme events such as heat waves, drought, floods and storms, our coasts and cities will be threatened by rising sea levels, and many ecosystems, plants and animal species will be in serious danger of extinction.
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The prime goal (of the international negotiation) must be to limit global warming to no more than 2 ºC above the pre-industrial temperature, a limit that has already been formally adopted by the European Union and a number of other countries. Based on current scientific understanding, this requires that global greenhouse gas emissions need to be reduced by at least 50% below their 1990 levels by the year 2050. In the long run, greenhouse gas concentrations need to be stabilised at a level well below 450 ppm (parts per million; measured in CO2-equivalent concentration). In order to stay below 2 ºC, global emissions must peak and decline in the next 10 to 15 years, so there is no time to lose".

The increase in CO2 concentration is mostly due to the combustion of oil, coal and gas and to deforestation while the methane increase comes from agriculture (rice paddies, cattle). Given the prominent role of CO2, energy is deeply involved in the phenomenon and remedialmeasures must address energy issues.

Energy plays a crucial part in the Development/Environment nexus. Before 2050, we should have:

- Doubled the world energy production,
- Divided by 2 the world CO2 emissions.

While 80% of our energy is presently produced by CO2 emitting sources (oil, coal and gas).

Faced with such a challenge, we must implement as soon as possible the whole range of available measures:

1. Save Energy and improve the efficiency of its uses (it’s a matter of technology but also a matter of individual behaviour !),
2. Decrease the share of fossil fuels in our energy mix, and therefore increase the share of nuclear power and renewable sources,
3. Implement wherever reasonably feasible CO2 capture and storage, notably at the outlet of coal-fired power plants.

 

Among OECD countries, France and Sweden emit relatively little CO2 because they generate electricity mostly from nuclear and hydro power.

 

As we have seen, with large well distributed reserves, coal is back and here to stay. But coal is the energy source with the worst impact on the climate (it emits about twice as much GHG as natural gas does, for the same final use). Faced with this return of King Coal, we shall prevent a climate catastrophe only if we capture on a grand scale CO2 at the outlet of those facilities which emit a lot of this GHG (coal-fired power plants, cement factories, steelworks, refineries), followed by the storage of this captured CO2 to prevent its leakage to the atmosphere. A few pilot facilities are already demonstrating the technical feasibility of the processes involved in CCS, but on a (relatively) small scale, and CCS will not come cheap.