If rising food and fuel prices aren't convincing enough, there's a world of good reasons to be a little more conscious of the cost of running your Mac.

We know global temperatures have climbed 0.8 degrees Celsius since the start of the industrial revolution. We know the polar ice caps are shrinking and cataclysmic climatic events -- such as Hurricane Katrina, Burma's Cyclone Nargis, and the recent flooding in China that forced a million people from their homes -- are increasing in frequency.

But what's this got to do with you and your Mac? Well, ball-park estimates suggest there are one billion computers in use worldwide, sucking an estimated 2.4 billion kilowatt-hours of energy each day. The average nuclear power station generates about 12.4 billion kilowatt-hours per year. Gartner last year estimated the IT industry accounts for approximately 2 percent of CO2 emissions, making the industry as bad as air travel.

Most power is generated using fossil fuels, which also create CO2 emissions, cause climate change, damage ecosystems and endanger the livelihood of millions.

Former US vice president and Apple board member, Al Gore, said in his film An Inconvenient Truth: "We're facing a global crisis and action is required." What can you, just one Mac user, do? You can think global, but act local.

1. How can I save power?

Keep it simple: switch things off. And take the plug out. Many household appliances continue to consume energy when they're turned off: TVs, Macs, and mobile phone, iPod and camera chargers cost the average household an extra £50 (US$87) per year in electricity by being plugged in, but not used. And such waste pushes around 18 million tons of CO2 into the atmosphere.

One solution is a multi-socket power strip with its own power cut-out technology, such as those sold by OneClick Technologies (www.oneclickpower.com) under the Intellipanel range.

Your Mac has an off button, too. Use it. Also, beware the Apple TV -- this constantly scans and syncs content with your Mac, and may be worth unplugging when not in use.

Change your electricity supplier. There's a growing number of energy firms claiming to offer 100 percent green electricity. Find out who can help you at www.green.energyhelpline.com. You'll save money and reduce your environmental impact, too.

Going shopping? Look for products with energy-saving labels, such as the widely used Energy Star label. Be sure to check Epeat assessments on products you're eyeing up (www.epeat.net).

All new Macs ship with OS X's Energy Save feature turned on. Apple estimates Macs use 77 percent less energy in low-power mode. You can save more energy by navigating to the Energy Saver preference panel and adjusting the settings there. You'll see two options, one for the monitor, the other for the computer. Bear in mind that background processes (exporting video into different formats, for example) will cease when your Mac is shut down, so you may want to set your display to go dark long before you ask the computer to stop. A screen saver isn't an energy saver -- your Mac's display consumes as much energy displaying the screen saver as it does when in normal use.

2. How can I reduce my carbon footprint?

Your carbon footprint reflects the damage your actions and lifestyle create in terms of carbon dioxide emissions. Climate change is the result of a build up of greenhouse gases, chiefly carbon dioxide (CO2), in the atmosphere. The UN Intergovernmental Panel on Climate Change in 2001 said: "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities."

Travel contributes to your carbon footprint. Air travel is the most damaging. Do you need to make that trip? Use iChat, conference calls and video feeds to help reduce business trips.

Businesses should consider teleworking. Defined targets boost personal responsibility, ease congestion, reduce the carbon footprint and increase productivity. Executives face increasing pressure from customers, employees and business partners