The United Nations climate change report expected to guide policy-makers with the most up-to-date assessment of the problem is being heavily influenced by governments, Canada's top scientist involved with the document said Tuesday.

But John Stone said that because they have had a hand in writing the synthesis report, politicians will now have even less excuse to ignore its "conservative" conclusions.

"The rationale for having the governments here is so they own the summary for policy-makers and it's in language which is useful and accessible to them," he said from Valencia, Spain, where the International Panel on Climate Change is expected to release the document.

The synthesis report is the fourth and final part of the Nobel Prize-winning panel's latest assessment.

Previous documents have focused on the physical processes underlying climate change, the impacts on various ecosystems and possible solutions. Friday's report will summarize those three and add a brief summary to be used by political leaders to develop policy.

Stone, an adjunct research professor at Carleton University in Ottawa and a former Environment Canada climate science director, said that while "every figure, every table, every sentence is negotiated," all statements in the summary document must be backed up by science. 

" (Governments) can't actually manipulate the science," he said.

But some environmentalists fear the changes will be enough to remove the edge of urgency from the report. Keith Stewart of the World Wildlife Fund said that sections dealing with the basic science of climate change and its impacts are being toned down.

"We have no quibble with the process but we do think that it is unfortunate if not disgraceful that governments are attempting to undermine the case for action," he said.

"There have been documented cases of governments weakening the strength of some of the statements," said Matthew Bramley of the environmental think-tank Pembina Institute.

Stone said some countries -- which he referred to as "the usual suspects" -- are being more intransigent than others.

But Steven Guilbeault of the Quebec-based group Equiterre said the science of climate change is now so convincing that little can be done to mute its conclusions.

"They may succeed in one or two things, but the scientific consensus is so strong that they're wasting their breath," he said.

Stone said the Canadian delegation has only intervened once so far in the process. And Bramley agreed that the Conservative government has accepted the panel's findings.

However, he said the Tories have sent mixed messages on the issue by cutting funding for climate science.

As well, he said the Harper government's targets for greenhouse gas reduction aren't even close to what the panel suggests.

The panel says that greenhouse gas emissions must be cut until they are between 20 and 45 per cent lower than 1990 levels by 2020. That would keep the average temperature increase to two degrees, the limit of what scientists feel is relatively safe.

However, federal targets are to reduce emissions 20 per cent below 2006 levels by 2020. That actually works out to two per cent above 1990 levels, Bramley said.

And researchers have suggested that current policies won't even accomplish those modest goals.

"There are serious questions over the credibility of Canada's position," Bramley said.

Stone said it's time for governments to tackle climate change.

"What we need is the governments to use their will to put in place the mechanisms that will get the individuals, companies, (and) governments themselves to actually begin to reduce emissions, to bend that curve downwards," he said.

"I'm frankly getting worried. And I am not an alarmist," said Stone. "I'm going by what science I read, because there's an urgency, and I don't see Canada or lots of other countries tackling this issue with the urgency I believe we need to apply to the issue."