OTTAWA - Federal Liberal Leader Stephane Dion says Canada must act aggressively now to avert the destructive consequences of climate change.

He's reacting to today's report from the Intergovernmental Panel on Climate Change that warns global warming poses major threats to the planet and humankind.

Dion is calling on Prime Minister Stephen Harper to endorse the revised version of the Clean Air Act including its plan to have a carbon budget for Canada that will help the country honour its Kyoto commitments.

He says in a statement the report makes it clear that human activity is changing our planet in a fundamental way, and that human beings can't continue to use the atmosphere as an unlimited and free dump.

Greenpeace Canada says attacking climate change is no longer a political issue for Harper, but a moral one and it's calling on Ottawa to pass climate change legislation.

The panel says up to 30 per cent of the Earth's species face an increased risk of vanishing if global temperatures rise just 3.6 degrees above the average in the 1980s and 90s. It says dry areas could become more arid while other places face greater threats of flooding, severe storms and the erosion of coastlines.