MONTREAL, Dec 1 (Reuters) - Activists at the U.N. climate change conference in Montreal shot straight for the Canadian heart on Thursday by warning of the unthinkable -- the end of ice hockey due to global warming.

Players in the "Climate Change Classic" faced off in a game set in the year 2020. Having become too warm for ice, Canada's national obsession became a frustrating exercise of trying to pass the puck while sloshing in ankle-deep water.

The action-slowing practice of firing the puck to the opposite end of the rink was no longer known as icing, but "slushing."

Finally, players dropped their sticks and gloves and gave up, declaring that global warming had succeeded in doing what even the 2004-5 National Hockey League lockout failed to do -- kill hockey.

A tearful memorial service followed.

Representatives from 189 countries are meeting in Montreal this week and next to start what could be years of negotiations on reducing emissions of heat-trapping greenhouse gases after the current phase of the Kyoto Protocol ends in 2012.

Activists from 10 environmental and youth groups staged the vision of too much warmth to show what might happen if delegates fail to make major commitments to cut down on gases like carbon dioxide, which are blamed for global warming.

"We really wanted something to reach out to new individuals, people who aren't typically interested in climate change but really need to be," Mike Hudema of the group Global Exchange said as he donned socks to cover his chilled, wet feet following the game and funeral.

"We thought of something that is a fairly fundamental Canadian value and showed how it's going to be impacted as another way we can get more people speaking out and really pressuring our government to do something."