Today the Kyoto Protocol on climate change comes into force.

It is significant because for the first time the international community has got together and agreed on action to tackle global warming.

But while Kyoto is a step forward, it would be a dangerous mistake to believe that it provides a solution to the scale of the problem our world now faces.

The United States has refused to sign up and major developing countries that are rapidly expanding their industrial capacity - such as China and India - are not required by Kyoto to make any cuts in their greenhouse-gas emissions.

Even for those countries that are required to make cuts, the levels are inadequate to meet the rapidly worsening situation that we now face.

The urgency of the issue is now becoming clear. Climate change is no longer an abstract concept.
Today we can see that polar ice caps are melting. Sea levels are rising. The Earth's temperature is undoubtedly on the increase. The five hottest years on record have occurred in the past seven years.

People know from their own personal experience that something strange is happening to the weather. When I first came to Tyneside in 1977, winters meant ice and snow. I well remember the danger of February mornings in Wallsend with pavements like a skating rink.

Compare that with the situation today. The odd flurry of snow is the exception. Bulbs are popping up a good month earlier than before.

We are paying an increasingly heavy price as a result of extreme weather. The heatwave that hit Europe in the summer of 2003 resulted in 26,000 premature deaths.

Floods and gales are affecting the quality of life we enjoy.

It is at times like this that people look for political leadership. So Tony Blair was right when he said last year that in the long term, climate change is the single most important global issue that the world faces. No country, however rich and powerful, will be immune to the effects of global warming.

Tony Blair has put climate change on the world's agenda by making it a priority for his leadership this year of the G8 group of major industrialised countries and for the UK presidency of the European Union starting in July.

Such action is not without political risk. There are two main dangers. The first is that potentially unpopular political decisions need to be taken now with the benefits not being seen for 10 or 20 years.
To put it bluntly, there is a mismatch in timing between the electoral disadvantage and environmental advantage.

Secondly, no nation acting alone can resolve climate change. There has to be concerted international action, with all countries playing their part. In particular, this means that a way has to be found to engage the United States, which is responsible for a quarter of the world's carbon emissions.

These are the political challenges facing Tony Blair. If he is to make a success of the G8 and the European Union presidency, then his Government is going to have to lead by example.

The United Kingdom is on track to go significantly beyond the cuts in greenhouse-gas emissions required under our Kyoto obligations. However, we have also set our own national target relating specifically to carbon dioxide emissions - to reduce them by 20pc below 1990 levels by 2010.

As things stand at present, much more will need to be done if this goal is to be achieved. For the sake of our international credibility we must remain committed to this target and use the present review of our climate-change programme to come forward with a package of integrated policies that will put us back on track to meet this ambitious carbon emissions reduction.

The European emissions trading scheme, which has just started, has huge potential to change the way thousands of businesses think about their energy use. The UK, as one of the strongest advocates of the scheme, must now give its full support, even if that means standing up to those vested interests who will want to put their own short-term gain ahead of the long-term interests of us all.

By our own actions at home, we will be in a strong position to lead on the international stage. The G8 has the potential to be the vehicle by which the United States can engage in discussions on climate change. It is vital that a way is found to bring the US on board.

Today we should give a single cheer for Kyoto but recognise that there needs to be a fresh injection of political will if we are to achieve a new global consensus that will provide the world with the means to meet the challenge of climate change.