By John Ware Presenter, Are We There Yet?

With vast aviation expansion already under way and air travel forecast to soar, is the government sending out mixed messages to frequent flyers?

The government lacks a "clear strategy" on transport - which includes dealing with greenhouse gases from transport, says the Transport Select Committee. Transport is the only sector of the economy in which greenhouse gas emissions have been rising consistently since 1990, and which are projected to carry on rising.

ARE WE THERE YET? Tuesday 27 March 2007 1930 GMT on BBC Two

Growth in transport that the environment can tolerate is central to a fully integrated transport system, which transport ministers say they are striving to create.

But the maths on aviation emissions look as if they may not add up.

Ryanair boss, Michael O'Leary, says his low-cost airline is "Europe's greenest".

Yet Ryanair now runs 500 routes and is growing by 25% a year.

It is budget airlines like Ryanair that are driving the huge increase in air travel.

Commitment to Kyoto

According to the Department of the Environment, Food and Rural Affairs, total UK carbon emissions are now 161.5 million metric tons [mmt], which breaks down as follows:

But the UK's commitment to Kyoto means that our carbon emissions must dramatically fall from today's level to 65 mmt by 2050 - a reduction of 60%.

'Recklessly' unambitious

Aviation emissions are among the fastest growing greenhouse gases

This is the UK's reduction contribution that is required to stabilise future atmospheric concentration of CO2 at 550 parts per million [ppm].

There is no guarantee this level will prevent climate change disasters, because it still represents 28% more carbon than is in the atmosphere right now.

The Germans regard it as "recklessly" unambitious.

Nevertheless, the Department for Transport is forecasting a near tripling of air travel by 2050 based on 2003 levels, and is giving the green light to a huge expansion of airports and new air corridors.

Other forecasters believe air travel could grow by nearly seven times the 2003 level.

Either way because our total emissions will have reduced, aviation will become a much bigger proportion: anything between 27% and 67%, according to Oxford University's Environmental Change Institute.

To compensate for the exceptional growth in aviation emissions, we will have to cut down even more on all those other emissions - business, industry, agriculture and public sector, residential cars, buses and trains by 71% to 87% - says the Oxford Institute.

'Severe pain'

Each country must take action domestically Gordon Brown

So homes, cars and businesses would have to meet unrealistically ambitious targets, just so aviation can be allowed to grow (the bulk of that growth on budget airline short breaks).

The Transport Select Committee says that if the government "continues its policy of allowing just this one industry to grow, it will either cause severe pain to all other sectors, or provoke so much opposition as to fatally undermine its 2050 target."

Ministers are sending out conflicting messages.

Junior environment minister Ian Pearson has attacked Mr O' Leary as the "irresponsible face of capitalism" for not believing that climate change is the aviation industry's problem.

The prime minister's message, however, is that we should all carry on flying, because that is what he is going to do.

For him, not flying away on holiday or on business is "just not practical".

Then again, the chancellor has doubled airport passenger duty to reduce the growth in flying, saying that "each country must take action domestically" to reduce aviation emissions.

And Environment Secretary David Miliband says aviation emissions are a "very serious problem" and stresses: "We've all got to do more."

Meanwhile the EU, while championing the fight against global warming, has just clinched an "open skies" deal the US which could lead to millions more passengers flying the Atlantic over the next five years.

But all forecasts quoted above already assume that improvements in technology, operations and air traffic management.

Radical design

Encouraging holidaying at home would help reduce emissions

The scope for further significant fuel efficiencies is limited by the basic design of the aircraft which has not changed whether it is Ryanair's new fuel efficient jets, or an old biplane. Both have a fuselage with two wings sticking from them.

This airframe will always create more wind resistance and a higher fuel burn than if the fuselage and wings were blended smoothly into one.

Such a radical design, the SAX-40, is currently on British and American drawing boards. But the American military would need to invest billions before it can be adapted as a commercial prospect which could take 25 years.

So what other options are there for reducing aviation emissions?

Holidaying at home

Duplicating France's high speed rail network in Britain could cost up to five times as much as it did in France because of higher engineering costs, due to much more congested terrain and stricter planning rules.

A reduction in emissions would also be limited because much of the increase in low cost flying is to destinations that would take longer than three to four hours by high speed train, the point beyond which it ceases to compete with airplanes.

The simplest option is to do more holidaying at home.

"Are We There Yet?" on aviation emissions? Answer: "No, and unlikely to" unless solar panelled wings can generate enough power to lift several hundred tons of airliner off the ground... which seems unlikely.