Foremost among these is ratification of the Kyoto Protocol on limiting greenhouse gas emissions - a contentious document that some say is too weak but which the United States has rejected outright and over which Russia is dithering.
\"Ratification or rejection by Russia of Kyoto would be a defining moment for humanity this year,\" Tony Juniper, head of the British branch of international pressure group Friends of the Earth told Reuters.
\"Kyoto is the key. If we don\'t sort that out, a lot of other environmental programmes will be fatally undermined,\" he added in an interview.
Rejection by Russia would cripple the 1997 Kyoto Protocol which aims to cut carbon dioxide emissions by eight percent below 1990 levels by 2012.
\"It will be a bad blow if Kyoto runs into the sand. The Protocol is a small step but a crucial one. It is a start. The longer we wait, the worse it gets and the harder it will be to put it right,\" Juniper said.
\"We should already be getting down to discussing the second phase targets for the treaty by now, but it has not even been ratified yet,\" Juniper said.
He said sceptics believed that Russian President Vladimir Putin, rather than being deeply concerned about the effects on the environment or industry of Kyoto, was simply waiting to see whether the United States would offer more for him to reject it than the European Union would for him to ratify.
There is no fixed deadline for Russia to ratify but it is widely assumed that if it does not do so this year, it never will.
Either way, Putin is not expected to make any move before his expected re-election next month.
But while Kyoto and the whole issue of climate change will be crucial in 2004, many others are vying for attention, from world trade and the environment to bio-diversity and genetically modified organisms (GMOs).
\"There has been quite an important shift in global political alliances which was highlighted by the failure of the World Trade Organisation talks at Cancun last September,\" Juniper said.
\"For the first time there the larger developing nations like Brazil, India and South Africa stood together against the big industrialised nations. It was a turning point,\" he added.
The United States was trying to use its superpower status to pick off smaller nations one at a time in bilateral trade talks, but had to remember that there was a limit to its arm-twisting ability.
\"We will have to see where that goes. But it is important to realise that U.S. world power depends on a functioning world economy. It can\'t have it all its own way,\" Juniper said.
There was also likely to be some movement on GMOs, with the Europeans showing signs of bowing to U.S. pressure to permit imports of modified maize and Washington perhaps taking legal action against any attempt to insist that foods containing GMOs be clearly labelled as such in the shops.
\"That will be worth watching,\" Juniper said. \"But with the U.S. election campaign just starting, I think they will be more concerned with domestic issues.\"