In what purported to be a good-news story, the Scottish Government says the country's greenhouse gas emissions have fallen by around 15% in 15 years. The drop in carbon dioxide, at around double the UK average, is even more impressive. Yet behind the headline figures lurk some awkward and unwelcome truths. The closure of the huge Ravenscraig steel works, the winding down of the "dash for gas" in the North Sea and the decline in manufacturing explain these figures.

At the same time, emissions from travel have increased by 11% as we go further, more often, in more powerful vehicles. Nor do the figures reflect the massive rise in air travel as international flights are excluded. Research by the Tyndall Centre on climate change suggests that the expansion in international aviation and shipping since 1990 cancels out the developed world's cuts in carbon emissions.

Scotland has an ambitious target of an 80% cut in emissions by 2050 in the Climate Change Bill but,to have a realistic hope of hitting it, we should be cutting emissions by 3% a year by now. By that measure, 15% over 15 years will not do. All parties enjoy flaunting green credentials but last week's Green Standard report from leading environmental groups gave only the Liberal Democrats a pass mark. Despite eye-catching proposals on taxing gas-guzzlers and domestic flights, the Conservatives have yet to commit to the concept of green growth.

The SNP Government cannot hit its admirable targets with a few wind and wave power projects, while ignoring the poor energy efficiency of our existing housing stock and rapidly rising transport emissions. The latter must involve policies that encourage a switch from cars to public transport. Removing tolls from the Forth and Tay bridges will have the opposite effect. A report from the Link umbrella group yesterday pointed out that the £87m this is likely to cost over the next four years could pay for alternative sustainable transport opportunities.

Alex Salmond, the First Minister, talks about justice for east coast commuters, following the abolition of tolls on the Skye and Erskine bridges. What about justice for African farmers, Pacific islanders and the people of countries such as Bangladesh, in the front line in the battle against global warming, according to the Intergovernmental Panel on Climate Change? All countries face a bleak future if global warming is not kept below a two-degree rise.

The moral case for the developed world doing most to reduce emissions is unanswerable. We have the capacity to make a difference. We may be travelling in the right direction on climate change but we need to travel faster.