Even if ministers adopt all the measures they have currently proposed to cut carbon emissions, Scotland will still fall eight million tonnes short of the target cut mandated by the Scottish Parliament for 2027 in the Climate Change Act.
The revelation, which comes as Scotland seeks to promote its "world-leading" climate targets on the global stage, has been described as potentially disastrous by environmentalists. They are demanding a "step change" in policy.
Next weekend the Scottish Environment Minister, Paul Wheelhouse MSP, is flying to Doha in Qatar for crucial international talks on combating climate change. Before he goes he is due to give a speech in Edinburgh about Scotland's efforts to boost global "climate justice".
Yesterday, Wheelhouse pointed out that in the past Scotland had cut carbon emissions more than most other countries in the European Union. Between 1990 and 2010, Scottish emissions fell by 22.8%, compared to an average of 14.3% for 27 member states.
But an official presentation posted online last week from the Scottish Government's director of energy and climate change, David Wilson, exposes a large gap between Scotland's planned and legally required carbon reductions in the future.
A graph shows a gap opening up between polluting "business as usual" and the statutory reduction target of about 18 million tonnes by 2027. If the Scottish Government sticks to policies it has already agreed, the gap decreases to about 13m tonnes.
If ministers adopt all the other pollution-reduction policies so far officially proposed, the gap comes down to eight million tonnes. But even in this scenario, the graph suggests every annual target from 2014 onwards will be missed.
"Some of the scenarios we have been developing just show quite how difficult it is," said Wilson. "The longer you go out, the more and more challenging it gets."
Dr Richard Dixon, director of WWF Scotland, called on ministers to deliver a new package of measures to cut carbon pollution. "The news that the plans so far won't hit most of the targets in the next decade, and miss by a mile in the 2020s, is potentially disastrous," he said.
"Scotland needs to be that beacon of hope that shows that world-leading targets are achievable."
The Scottish Government has delayed publishing a long-awaited report on the policies and proposals for cutting climate pollution until the new year. "The final plan must be a clear and credible package that acts on the advice of the Government's own official advisers to deliver a step-change in policy effort," said Dixon.
Some of the worst pollution comes from cars. "There is no prospect of the Government meeting its climate targets unless it takes action to cut transport emissions," said Colin Howden, director of transport campaign group Transform Scotland.
"Unfortunately, Alex Salmond's Government appears entirely wedded to making things worse. The roads budget has risen by 40% in the past five years while the funds available for investment in sustainable transport has remained flat."
Labour's environment spokeswoman, Claire Baker MSP, was astonished by the Scottish Government's prediction. "This admission shows that their rhetoric is far from reality," she said.
"This highlights the increasing incompetence of the Scottish Government when it comes to environmental matters. I will be raising the issue at the earliest opportunity in Parliament."
The Scottish Government has already admitted missing the first annual climate target in 2010, though it is hoping to meet the targets for 2011 and 2012. "Scotland has world-leading climate change legislation, and we are halfway to meeting our target of a 42% cut in emissions by 2020," Wheelhouse told the Sunday Herald.
"But we are not complacent and are very clear about the scale of the challenge ahead and we are taking action to deliver the emissions reductions within our powers."
He said a new report on the proposals and policies that would help cut climate pollution, previously promised before Christmas, would not now be published until "early in the new year".
Wheelhouse promised to press for tougher action to cut emissions at the Doha climate summit next week. "I hope that other countries will be encouraged to match Scotland's level of ambition," he said.
Three major reports last week flagged up the worldwide dangers of global warming in the run-up to the summit. The World Meteorological Organisation said greenhouse gases had reached a record high, the United Nations Environment Programme called for urgent action to avoid disruptive temperature rises, and the European Environment Agency warned southern Europe was getting drier and northern Europe wetter.