The United Nations urged the world today to kick an all-consuming addiction to carbon dioxide.

Secretary-General Ban Ki-Moon said on a statement to mark the UN's World Environment Day - hosted by Wellington today - that global warming is becoming the defining issue of the era and will hurt rich and poor alike.

"Our world is in the grip of a dangerous carbon habit," he said. "Addiction is a terrible thing. It consumes and controls us, makes us deny important truths and blinds us to the consequences of our actions," he said.

His point man in Wellington, UN Environment Programme (UNEP) executive director Achim Steiner, today said New Zealand was chosen to host World Environment Day because it was one of the first nations to commit to carbon neutrality and has provided climate change leadership.

World Environment Day, conceived in 1972, is the United Nations' principal day to mark global green issues and aims to give a human face to environmental problems and solutions.

Global carbon emissions from burning fossil fuels are rising quickly and scientists have warned global warming is bringing rising seas, melting glaciers and more intense storms, droughts and floods.

Prime Minister Helen Clark - a key advocate of the aspiration for carbon neutrality - said: "We take pride in our clean, green identity as a nation and we are determined to take action to protect it. We appreciate that protecting the climate means behaviour change by each and every one of us."

Her words were echoed by Mr Ban: "Whether you are an individual, an organisation, a business or a government, there are many steps you can take to reduce your carbon footprint.

"It is a message we all must take to heart," he said.

The Government mounted a huge series of official "events" to mark the day, many of them featuring VIP guests, including Mr Steiner, Kiribati president Anote Tong, and the chairman of the UN's Intergovernmental Panel on Climte Change, Dr Rajendra Pachauri.

These events included UN art competitions and displays, a "science breakfast", a panel discussion at Victoria University, and press conferences and "photo opportunities".

At community level, many towns staged presentations or projects to reduce the number of cars on the road, rehabilitate landfills, promote gardening and renewable energy, plant trees and re-cycle objects.

New Zealand Post asked staff to bring a magazine or book to work and swap it to reduce their carbon footprint.

Mr Pachauri said the IPCC's fourth climate change assessment report had noted "we have only seven years" to take action if rising temperatures are to be limited to no more than a global average of 2.4degC.

Even a 2degC temperature rise is expected to subject up to 2 billion people to water shortages by 2050 and threaten extinction for 20 per cent to 30 per cent of the world's species, according to the 2007 report by the UN network of 2000 scientists.

"After 2015 and there on we have to bring about a reduction in emissions of greenhouse gases world wide and ... we don't have more than seven years. The earlier we can start the better," Mr Pachauri said in Wellington.

A summit of G8 nations in Hokkaido, Japan, next month, is due to set a formal goal - agreed a year ago -- that global carbon emissions should be reduced by 2050 to 50 per cent below 1990 levels.

But some nations think the cuts should be deeper, leading to a reduction of 80 per cent of carbon emissions by 2050 to try to stabilise carbon dioxide concentrations in the air to limit global warming.

So far, New Zealand is having difficulty in meeting its 2012 target for the current first commitment period - just bringing emissions down to the 1990 level.

It is now producing 20 per cent more greenhouse gas than that benchmark.

Environment Minister Trevor Mallard told the main UNEP press conference, held at Te Papa, that NZ was a "logical choice" to host the event this year.

He said the Government is introducing an emissions trading scheme, an energy strategy focused on renewable sources, and tackling climate change at many levels.

He did not mention that petrol and diesel will not now come into the scheme until 2011, and that farmers won't be accountable at all for methane from their livestock - a third of the nation's emissions -- until after 2012.

- NZPA