• The world’s most powerful nations are gathering in St Petersburg this weekend for the G8 summit. On the agenda are global energy security, trade and Iran. So why are the greens going blue in the face asking that they come clean on global warming? Wasn’t that the topic of last year at Gleneagles?

Well, the two are so intimately connected that meaningful talk of energy security must take into account the impact on climate change by different sources of energy.

• What’s the connection?

The Earth is warming by the greenhouse effect. When the sun’s rays hit the Earth’s surface, they warm it up and then bounce back as infrared waves. The Earth’s atmosphere, however, traps some of this heat, so it is not completely lost and the Earth plunged to sub-zero temperatures. This trapping is aided by the so-called greenhouse gases, primary ones among them being water vapour and carbon dioxide. Given the more or less stable composition of the atmosphere for all these millennia, the Earth’s surface had maintained an average temperature of 14 degrees Celsius. Trouble is, if the concentration of greenhouses gases in the atmosphere increases, the Earth will trap far more heat than it has been doing so far. This will substantially raise its temperature. There is conclusive evidence that this is actually happening. The New Scientist reports that the 20th Century recorded an average global warming of 0.6 degrees Celsius. Burning fossil fuels is the leading source of increased CO2 in the atmosphere.

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