The Kyoto Protocol has finally come into force. After years of debate among all the nations of the world, some of them at least have committed to joint action.

The protocol puts binding targets for reducing greenhouse gases on developed countries, including New Zealand. Yet all acknowledge the protocol will not stop global warming.

It is simply a first but important step. It shows that most nations agree we have a big problem and that something should be done about it.

Although there are uncertainties, the science of climate change can no longer be denied.

The recently-released Impacts of a Warming Arctic: Arctic Climate Impact Assessment predicts the likely extinction of the polar bear and loss of the ancient culture and lifestyle of thousands of Inuit peoples.

The Inuit culture relies on the summer harvest at the edge of the ice, as does the polar bear.

This major study, conducted by scientists in Canada, the United States, Russia and Nordic Europe, says, because of global warming caused by human activities elsewhere, this sentinel ecosystem is on the verge of irreversible change that may have these tragic results.

The study findings are that global warming is happening in the Arctic at twice the rate of the world average and that, given likely scenarios of future global emissions and resulting warming, the loss of summer sea ice could be total as soon as 2070.

Over the next 100 years, Arctic temperatures are likely to increase between 4 and 7 degrees. This will force more warming across the planet's atmosphere as the white, reflective ice is replaced by heat-absorbing darker land and ocean surfaces.

This study puts a human face on the risks of the unprecedented experiment that mankind is conducting with planet Earth. Emissions of greenhouses gases, mostly from fossil fuels from human activities, are resulting in the accumulation of heat-trapping gases in Earth's atmosphere at levels not seen for hundreds of thousands of years.

The rate of increase of these gases, from industrialised countries and the developing world, is unprecedented.

Other studies show we are perilously close to possibly triggering an irreversible melting of the Greenland ice sheet that would commit the globe to a sea-level rise of about 7m over time. Still more research into the rate of melting of the Antarctic demonstrates that there are clear signs of the huge ice shelf melting more rapidly than previously anticipated.

More immediate are the possibilities of crop failures and food poverty for many millions in the Indian subcontinent, or the progressive die-off of the Amazon rainforest, or the oceans turning acid or the Gulf Stream stopping.

These are not just the stuff of disaster movies: they are real possibilities with real consequences even in our part of the world.

At the Environmental Defence Society's Climate Change and Business Conference held in Auckland last November, we heard from a West Australian farmer who told us cropping in that part of the region was close to collapse because of droughts. He called for urgent action on climate change from his Government.

Recently I met representatives of the South Australian wine industry who are deeply concerned about the impact of climate change on the Barossa Valley. In New Zealand, we are already experiencing more extreme weather events.

It's not too late, but if there is no huge increase in global efforts to reduce emissions over the next 20 years, the odds are that we will have missed our chance. More emissions mean more atmospheric warming and more warming speeds up climate change and makes it more difficult to reverse or slow down.

Yet every day, global emissions of greenhouse gases are rising. We are already at 370 parts per million of CO2 in the atmosphere and many respected scientists are saying we should not let it get above 400.

The bad news is that the Americans, who produce 25 per cent of global emissions, and the Australians, have decided not to ratify and so are outside the Kyoto framework.

The Australians have said they will meet their Kyoto targets anyway.

It would actually be cheaper for them to do so inside Kyoto because they would then be able to access the Kyoto flexibility mechanisms by which they can get credit for lower-cost action in developing countries. They also have a new climate change minister who seems to be thinking hard. I'd watch that space.

There seems little chance of the Americans changing their position. Their Administration is almost alone in denying climate science in spite of there being much more proof of climate change than things they were quick to believe in like weapons of mass destruction in Iraq.

What they need to understand, as a Pentagon report pointed out, is that climate change is a bigger threat to world stability than global terrorism because of its potential to create millions of displaced people.

The optimist might hope that President George W. Bush reinvents himself as a multilateralist in his second term and takes heed of the urgings from his friend, British Prime Minister Tony Blair.

Blair is a world leader on climate change and has been hugely influential in building a European consensus around the need for action. Later this year, Britain will lead the G8 and the European Union - a real opportunity to put pressure on a United States seemingly keen to build bridges with Europe.

New Zealand is on the right track but could do more.

Having ratified the protocol, our Government now needs to implement the proposed carbon charge to give stronger price signals to investors and consumers to encourage renewables and energy efficiency, and make proposals for new fossil-based plant carbon honest.

This charge should be fiscally neutral, as the Government has promised.

It could be offset by income and company tax cuts or reductions in GST to ensure that it is a true shift in taxation, not an increase.

If the world can combine good science, government policies and forward-thinking business efforts, we can make a difference.

The protocol is merely a first step in what needs to become concerted and vigorous global action to control and reduce the proliferation of greenhouse gases.

Climate change is the biggest threat facing mankind. If we are to have any chance of dealing with it, businesses need to play a part and do what they do best - adapt, innovate and lead.

* Gary Taylor is chairman of the Environmental Defence Society which, with others, hosted the inaugural Australia New Zealand Climate Change and Business Conference last year.