Tim Flannery, author of The Weather Makers: How Man Is Changing the Climate and What It Means for Life on Earth
 was quoted in an AP article

“What the report establishes is that the amount of greenhouse gas in the atmosphere is already above the threshold that can potentially cause dangerous climate change,” Flannery told the Australian Broadcasting Corp. late Monday. “We are already at great risk of dangerous climate change, that’s what these figures say. It’s not next year or next decade, it’s now.”

At this point, even zero emissions from this point forward may not be enough to reverse damage to the planet.