Artificial human activity is resulting in an extra 7 billion tons of CO2 being pumped into the air every year. This will continue to swirl around in the atmosphere for more than 100 years, and in doing so will trap more and more of the Sun’s infrared energy, resulting in an increase in the Earth’s average surface temperature: the greenhouse effect.

In the pre-industrial age, the natural level of CO2 in the atmosphere was around 280ppm (parts per million). In 2004, that level had increased by over 35 per cent to 379ppm. Most current models that predict serious climate change are based on computational models presupposing a level of over 550ppm. If the current trend continues, this level will be reached in the second half of the century and surpassed soon after.

Most of the CO2 being released into the atmosphere arises not from homes and businesses, but from industry. Industrial production processes are hugely energy-intensive and account for most of the world’s energy consumption. But that doesn’t mean non-industrial business and home users can shrug their shoulders and wait for a technological fix to the problem.

The Department of Trade and Industry estimates that for every kilowatt-hour (kWh) of electricity consumed in this country, around 430g of CO2 is released into the atmosphere as a direct result. How? From the fossil-fuel power stations – both coal- and gas-fired – that provide power to the national grid (the 430g figure is calculated based on the average mix of electricity generation from fossil-fuel plants, nuclear generation and renewable sources).

It might sound strange, but every time you plug a mains appliance into the wall you’re directly responsible for increased environmental CO2 emissions. If you switch it off, that emission rate is cut to zero. And if you pay attention to your usage habits and conserve energy where possible, you can drastically reduce the amount of atmospheric CO2 you’re responsible for generating.

The kilowatt-hour is a measure of the total energy consumed by an appliance: it’s simply the number of kW it uses, multiplied by the time it is in use for.

• A computer that consumes only 0.1kW (or 100W) but is left on for ten hours a day uses 0.1kW x 10hrs = 1kWh.
  
  
• Based on an average unit electricity price of 10p per kWh, that means our hypothetical computer costs 10p per day, and remember that for each kilowatt-hour consumed, around 430g of CO2 gets dumped into the atmosphere.
  
  
• This essentially means that our hypothetical computer costs around £36.50 to operate and accounts for almost a quarter of a tonne of CO2 dumped into the atmosphere per year.