Industrialised nations have added greenhouse gas emissions equivalent to the annual totals of France or Australia to a 1990 baseline against which cuts required by UN climate treaties are measured.

Emissions reported by 34 nations for the 1990 base year that underpins UN efforts to rein in global warming have risen 3.5 per cent overall to 17.6 billion tonnes in the most recent annual data, from 17 billion in the first UN compilation in 1996, a Reuters survey showed.

That difference - adding about 600,000 tonnes of gases emitted mainly by burning fossil fuels to the problem - is more than the current annual emissions of countries such as Italy, Australia or France.

The biggest rises have been by the United States and Russia.

Governments refine their emissions counts year by year, in some cases adding new gas sources. In many cases revisions to the 1990 baseline also add to emissions in subsequent years, swelling totals that are contributing to warm the planet.

'One possible reason for a small upward trend could be the permanent improvement in the completeness of national greenhouse gas inventories,' said Sergey Kononov, head of the unit at the UN Climate Change Secretariat that compiles emissions data.

Eighteen nations that submitted data in 1996 have since revised up their 1990 totals, while 16 have revised down, according to the Reuters survey.

Kononov saw no sign that countries were tampering with the data - a higher 1990 baseline might make it easier to make 'cuts' and would undermine UN treaties and faith in carbon markets.

Obama cuts

'To our knowledge, there has been no reason for such a worry,' he told Reuters. 'In general, the degree of variation seems to be in line with the usual level of uncertainties in greenhouse gas inventories.'

US President Barack Obama wants to cut US emissions back to 1990 levels by 2020. US officials say revisions to 1990 have also swollen numbers for subsequent years, making cuts no easier to achieve.

'Any additions or changes are always made going back to 1990 wherever possible,' said Perry Lindstrom of the US Energy Information Agency.

He said one tiny addition, for instance, was emissions from plastics burnt to generate energy from municipal waste that were not estimated for the original data in the mid-1990s.

The United States, the top emitter behind China according to many experts, has revised up its 1990 emissions by 290,000 tonnes to 6.1 billion since the mid-1990s. US emissions were up 14.4 per cent since 1990 in 2006.

About 190 nations have agreed to work out a new UN climate treaty in December in Copenhagen to step up a fight against warming that the UN Climate Panel says will bring more heatwaves, droughts, floods and rising seas.

Under the UN's existing Kyoto Protocol, almost all developed nations have promised to curb emissions by an average of at least 5 per cent below 1990 levels by 2008-12.

Still depressed by the 1991 collapse of the Soviet Union, emissions by all industrialised nations were 4.7 per cent below the 1990 benchmark in 2006, the last year for which data is available.

After the United States, Russia has made an upwards revision of about 250,000 tonnes for 1990, the last year of smokestack industry under communist rule.

Other big upwards revisions include France and Japan. Among big downwards revisions are Australia, Ireland and Italy.-Reuters