The Climate Institute will issue these predictions today as the Federal Government and Opposition inch closer to a deal, according to Coalition sources.

They predict the Government will give enough ground to secure Opposition support for the scheme, centrepiece of the plan to tackle climate change.

But Climate Institute chief executive John Connor warns the Opposition's proposals ''carry tens of billions of dollars of extra fiscal and political risk''.

''Giving even more handouts or exemptions to the big polluters risks future budgets, may undermine global action to tackle climate change and may have perverse short-term impacts on jobs growth,'' Mr Connor said.

The institute assesses the impacts based on modelling conducted by the Centre for Policy Studies at Monash University and McLennan Magasanik Associates.

The Government and Opposition have used this model in recent assessments of the economic impact of climate change policy.

The institute examines the impact of the Carbon Pollution Reduction Scheme without and with amendments put forward by the Opposition.

The major parties have agreed to permanently exclude agriculture, which will see ''an additional emissions reduction bill for government and business in the order of $7billion in 2020''.

Under both scenarios, Australia's trillion-dollar economy grows to $1.2 trillion by 2020 and about 800,000 new jobs will be created across the economy over the same period.

But the Opposition's amend-ments will have an impact on employment in the short term, with the institute forecasting between 10,000 and 30,000 fewer jobs will be created annually between now and 2015.There is little difference by 2020.

Domestic emissions peak and begin to decline from 2011 under both scenarios.

But the Opposition's proposals will result in a far smaller change in domestic emissions, requiring 44per cent of the target to be met with international permits worth an extra $7.1 billion to 2020.

It is only 12 per cent under the Government's scheme.

''The Opposition's proposal, to provide much larger handouts to major emitting industries and exclude agriculture from the scheme, result in a deficit of over $36 billion to 2020,'' the institute said.

''The Government scenario generates a small surplus by 2020, although this assumes emission reduction policies for agriculture.''