The United Nations urged the world on Thursday to kick an all-consuming addiction to carbon dioxide and said everyone must take steps to fight climate change.

U.N. Secretary-General Ban Ki-Moon said global warming was 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," Ban said in a statement to mark World Environment Day, which is being marked by events around the globe and hosted by the New Zealand city of Wellington.

"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 in the speech to reinforce this year's World Environment Day theme of "CO2 Kick the Habit".

"Whether you are an individual, an organization, 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.

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.

New Zealand, which boasts snow-capped mountains, pristine fjords and isolated beaches used as the backdrop for the "Lord of the Rings" film trilogy, has pledged to become carbon-neutral.

"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," said New Zealand Prime Minister Helen Clark.

New Zealand, like many countries, staged art and street festivals to spread the message on how people can reduce carbon usage. New Zealand Post has asked staff to bring a magazine or book to work and swap it to reduce their carbon footprint.

In Australia, Adelaide Zoo staged a wild breakfast for corporate leaders to focus on how carbon emissions threaten animal habitats.

GLOBAL EVENTS

In Bangladesh's capital Dhaka, people plan to clean up Gulshan Baridhara Lake that has become badly polluted, and in Kathmandu the Bagmati River Festival will focus on cleaning up the river there.

Many Asian cities, such as Bangalore and Mumbai, plan tree-planting campaigns, while the Indian town of Pune will open a "Temple of Environment" to help spread green awareness.

Global carbon emissions from burning fossil fuels are rising quickly and scientists say the world faces rising seas, melting glaciers and more intense storms, droughts and floods as the planet warms.

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

But some nations think the cuts should be deeper, leading to a reduction of 80 percent of carbon emissions by 2050 to try to stabilise CO2 concentrations in the air to limit global warming.

The U.N. Environment Programme (UNEP) said the cost of greening of the world's economy would cost as little as a few tenths of global GDP annually over 30 years and would be a driving force for innovation, new businesses and employment.

The UNEP urged greater energy efficiency in buildings and appliances and a switch towards cleaner and renewable forms of electricity generation and transport systems.

It said more than 20 percent of new investment in renewable energy was in developing countries, with China, India and Brazil taking the lion's share. Renewables now provide over 5 percent of global power generation and 18 percent of new investment in power.

But the U.N. body said an estimated 20 percent of carbon emissions came from deforestation and urged developing nations to save their forests as carbon sinks.