Celebrities, scientists, doctors and businesspeople and hundreds of others have today come together to launch a fresh nationwide push for action on climate change.

The new movement, Our Climate Declaration, calls on the Government to phase out the extraction and burning of fossil fuels by 2050 - including stopping all new coal mines and coal-burning plants and ending deep sea oil exploration and fracking for oil and gas - and adopting bolder policy.

This included a new Climate Commission to set a binding carbon budget, replacing the Emissions Trading Scheme (ETS) with a carbon tax, strengthening the country's Paris Agreement obligations, making the energy, transport and farming sectors more sustainable, and boosting carbon sinks with 1.3 million ha of marginal land restored to native forest.

It also calls on all Kiwis to do their part through grassroots community climate action plans, where organisations investigate their own climate impact and make plans to reduce it.

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Backing the declaration - launched at live broadcast events at Auckland, Wellington, Christchurch and Dunedin this afternoon - are well-known Kiwis including actress Robyn Malcolm, businessman Phillip Mills, journalist Rod Oram, musician Peter Scholes, botanist Emeritus Professor Sir Alan Mark and climate scientist Professor James Renwick.

"If you sign up to this, you are saying you will do something yourself, and especially, you will call on the Government to do more," said Renwick, of Victoria University's School of Geography, Environment and Earth Sciences.

"If we are going to stop warming at 1.5C [of future temperature rise], we've got about five years left at present emission levels - and to stop the warming at 2C, we've got maybe 20 years left, or possibly a bit left.

"We are already over 1C, to get to 1.5C, or 2C, it's not going to take that long ... and after that we start melting big chunks of ice sheets."

Dr Joanna Santa Barbara, national chairwoman of the push, said it was known what had to be done.

"And it has to be done by people at all levels - citizens, businesses, local councils and government.

"We are not waiting - the problem is too serious and too urgent - and we are setting out to do it ourselves."

The declaration further called for a decrease in emissions from the aviation industry, a halt to the expansion of "industrialised, intensive farming", renewable energy, better protection for biodiversity, insulation for all homes and plans for "fair resettlement" of climate refugees with guidance from tangata whenua.

The launch comes in the same month Hamilton student Sarah Thomson is taking Climate Change Minister Paula Bennett to the High Court over what Thomson argues is a lack of action over the issue.

The 26-year-old's lawsuit challenges a claimed failure to review climate targets after the UN's Inter-governmental Panel on Climate Change released its Fifth Assessment Report in 2013.

The suit further challenged the Government's target to slashing domestic greenhouse gas emissions by 11 per cent below 1990 levels and 30 per cent below 2005 levels by 2030, which Thomson argued was "unreasonable and irrational" against the seriousness of the issue.

Bennett has told the Herald the Government was "very comfortable" that its Paris target was fair and ambitious.

She has also pointed to a range of work the Government was doing in the space, including an improvement of the ETS, phasing down the use of hydrofluorocarbons by 80 per cent, spending $2 billion on public transport, increasing renewable electricity to 90 per cent by 2025, eliminating fossil fuel subsidies, investing $20 million a year in agricultural greenhouse gas research, and the planting of more than 5.5 million trees this winter.

The Government has also set up three new expert groups to look at adaptation, agriculture and forestry to address climate change and begun toward doubling the number of electric vehicles registered every year to reach 64,000 by 2021.

New Zealand and climate change

• Under present projections, the sea level around New Zealand is expected to rise between 30cm and 100cm this century, while temperatures could also increase by several degrees by 2100.

• Climate change would bring more floods (about two-thirds of Kiwis live in areas prone to flooding); make our freshwater problems worse and put more pressure on rivers and lakes; acidify our oceans; put even more species at risk and bring problems from the rest of the world.

• Climate change is also expected to result in more large storms compounding the effects of sea level rise.

• New Zealand has pledged to slash its greenhouse gas emissions by 30 per cent from 2005 levels and 11 per cent from 1990 levels by 2030.

• While the Ministry for the Environment's latest Greenhouse Gas Inventory showed gross New Zealand emissions were 0.1 per cent lower in 2014 than 2015, emissions had increased 24.1 per cent from 1990.