Australia's best bet for reducing greenhouse gases over the next 10 years is to ramp down coal, ramp up natural gas and invest in renewables. The strategy also makes the best sense over the long-term.

Australia is about to enter a huge electricity-generation replacement cycle during which old, clapped-out, coal-fired electricity generation capacity must be replaced. Why not make a virtue of necessity?

Solar energy is falling rapidly in price, but needs a few more years. Wind is price competitive, but sporadic. Geothermal energy presents medium-term logistical difficulties. Wave and tidal energy require more research. Proper carbon capture and storage and 'next generation' nuclear solutions still remain decades away.

What to do?

Gas is the best medium-term "off the shelf" solution. It's plentiful, proven and reliable. Best of all, natural gas can play a  positive future role in a global electricity system dominated by renewables. Investing in expanding gas fired power today is like putting a downpayment on a clean energy future.

Australian gas production and distribution giant Santos estimates that if Australia's aging, coal-fired power plants were retrofitted with gas turbines and their coal operations progressively shut down, Australia could reduce carbon emissions significantly at a highly competitive, proven cost.

And if such a natural gas electricity-generation capacity ramp up were undertaken, it would provide breathing room for renewables like solar thermal, geothermal and other renewable energy supplies to fall in price sufficiently for significant renewable capacity to come online after 2015.

As that occurred, the gas capacity could be shifted to providing 'peaking power' and load balancing since renewables can be intermittent and gas-fired capacity is an ideal, rapid-response energy source for meeting electricity demand spikes.

DESERTEC-Australia lays out this vision in more detail in "2050: Australia-Clean Energy Superpower," and its subchapter "Low Emission Rollout." Between 2010-2020, DESERTEC believes natural gas could satisfy up to 40% of Australia's electricity as Australia's coal-fired power capacity is reduced and renewable energy supplies are ramped up.

Over the long-term, natural gas could settle down to providing about 25% of Australia's electricity, with its surplus capacity operating primarily as a backstop power source and load balancer.

Similar plans tare under consideration in Europe. The Czech presidency of the European Union has proposed progressively cutting operating hours of EU coal-fired power plants in coming years with an eye toward encouraging other, cleaner energy sources to take their place.

This kind of strategy makes sense given price forecasts of renewable energy, primarily solar. Forecasters increasing in agree solar technologies are like to reach 'grid parity' (ie competitiveness with coal) by 2010-2015.

The message is: ramp down coal; ramp up gas; invest in renewables. And keep an eye on nuclear and clean coal -- even though neither is expected much before 2025.

Stewart Taggart is a director of Acquasol Infrastructure Ltd, which is developing a municipal-scale, solar-powered desalination plant in South Australia. Mr. Taggart is also founder/administrator of DESERTEC-Australia, DESERTEC-USA and DESERTEC-China.