Two hundred scientists from around the world are meeting for a UK conference on climate change.
Environmentalists believe Mr Blair could do more
Participants at Avoiding Dangerous Climate Change, at the Met Office in Exeter, will try to agree on the definitions of danger levels.
This, they hope, will lead to a better understanding of methods the world can employ to avoid catastrophic warming.
The environment secretary said the UK had shown that the economy could grow as greenhouse gas emissions were cut.
Margaret Beckett told the BBC: "What we're hoping they'll do is look at what they think the consequences of different levels of climate change would be - particularly in terms of what it means in different regions and sectors... and particularly what they think our options are in terms of how we tackle it."
Mrs Beckett defended Britain's record on climate change, saying that although it had not met its own "very stringent" target on emissions it had met - and exceeded - its Kyoto Protocol target three years early.
She stressed that the economy had grown during the same period, which she said was particularly important for the world's poorest countries.
"If they thought they had to leave their people in really dire poverty or tackle climate change then it would be very hard to persuade them that they should take action," she added.
The conference, sponsored by the Department for Environment, Food and Rural Affairs (Defra), will try to answer three questions:
- For different levels of climate change what are the key impacts, for different regions and sectors, and for the world as a whole?
- What would such levels imply in terms of greenhouse gas stabilisation concentrations and emission pathways required to achieve such levels?
- What technological options are there for achieving stabilisation of greenhouse gases at different concentrations in the atmosphere, taking into account costs and uncertainties?
The secretary of the steering committee which has organised the conference is Dr Geoff Jenkins, a veteran of 30 years' work at the Met Office.
Tony Blair's support
He told the BBC News website: "The UN climate convention calls on countries to act to prevent 'dangerous anthropogenic (human-caused) interference with the climate system' from the build-up of greenhouse gases.
"So the conference will be aiming to identify what's dangerous and what that implies for greenhouse emissions, though without specifying any actual numbers."
Prime Minister Tony Blair announced his support for the meeting last year.
He will be able to put the definitions the conference comes up with before ministers of the G8 group of countries later this year.
But campaign group Friends of the Earth says Mr Blair will have to do more to cut emissions if he wants to show leadership on the problem.
Director Tony Juniper said Tony Blair had understood the scale of the problem but that the group had been disappointed at the government's response in terms of specific policies.