The Kyoto Protocol, which aims to slow global warming, has come into effect seven years after being agreed.
Some 141 countries - who account for about 55% of greenhouse gas emissions - have ratified the treaty, with Russia being the last to join in November 2004.
However, the world's biggest polluter, the US, has been criticised by environmentalists for not joining after claiming it would harm their economy.
Another non-signatory is Australia, who has dismissed the treaty for being too costly.
Do you think the agreement will make a difference? Do you think it can work? Did you feel the need to protest?
This debate is now closed. Read a selection of your comments below.
The following comments reflect the balance of opinion we have received so far:
Kyoto is a pipe dream pure and simple - an attempt by the left to over regulate commerce and industry (in the western world). Put it mildly I believe science has forgotten the very notion of scientific enquiry. Sound economic and environmental policy should not be predicated on voodoo science!
Fernando F, Montreal, Canada
I'm sick of hippies driving around in semi-broken down vans pumping out copious amounts of pollution, covered in sticker with witty slogans about saving the earth (yet strangely enough nothing about the factories in which they were printed) and telling me off for buying non-recycled toilet paper.
Leah, Melbourne, Australia
Until human catastrophe hits home, people will continue to frantically consume earth's resources. We have to wait for more floods, large-scale water/food contamination, droughts, massive earthquakes, torn up cities; then we'll react accordingly. Human thought generally sees preparedness as a waste of time and money.
Gene Odyssey, Germany
It is easy for Europeans to flaunt Kyoto as the a monumental achievement, but it is fatally flawed. India, and China more importantly, are called "developing economies" and therefore are subject to lax restriction under Kyoto. Many in the USA see this as a ridiculous provision, that the same country, China, stealing million of American jobs and technologies is being given another break.
Kyle Sweet, Ledyard, Connecticut, USA
Ratifying this treaty will have unknown effects on society. It is for this reason that people are so scared to give it a chance. With the idea of economic loss comes widespread human fear; are we that concerned with losing a dollar? What people don't seem to realize is that jobs and or money lost will be made up in other, environmentally cleaner, areas such as eco tourism and environmental planning.
Katherine Card, Newmarket, Canada
I would like to ask a question of USA and Australia: Where will you use your strong economies when Earth will become almost impossible to sustain life? It's time to think beyond local interests and act on a mutual goal.
Khalid Khateeb, Melbourne, Australia
Even though Kyoto will not change much (especially without the US) it's better than doing nothing. Surely the economic damage caused by Kyoto will not be as much as the damage caused by constant flooding, heat waves and hurricanes caused by global warming. Besides, our oil might run out in 50 years and then it might be better to be prepared.
Guttormur, Reykjavík, Iceland
I think that climate change is like the Y2K "bug". Do nothing, and it might all crash around your ears, do something and you might never know if it was going to crash around your ears.
Mick, Crawley, UK
US factories should already be somewhat compliant with the Kyoto treaty and automobile emissions have been decreased also. I think more people buying hybrid automobiles would make the most difference.
I heard a report the other day that if you put the predicted changes that the Kyoto treaty will bring into a climate model then after 100 years global warming will only be put back 6. That is shocking - why are we doing it?! The American government is the only one taking an objective view and not succumbing to the green lobby. All respect for them!
Peter T, Larne, NI
The Kyoto protocol won't work unless all nations agree on the agenda. The US should make use of the latest technology to reduce emission of