LONDON -- The impact of human activity on the Earth is running out of control, and the amount of time in which action can be taken to prevent potentially catastrophic climate change is rapidly dwindling, a leading scientist from the Australian National University told a global scientific climate conference in London yesterday.

Not only is the impact on the Earth's environment and climate already being seen at all levels, but the damage is accelerating, professor Will Steffen told the opening day of the four-day Planet Under Pressure conference, which has gathered together some 2,800 scientists from around the globe.

"The last 50 years have without doubt seen one of the most rapid transformations of the human relationship with the natural world," he said. "Many human activities reached takeoff points sometime in the 20th century and sharply accelerated towards the end of the century. We saw a 'great acceleration.'"

He added, "It is the scale and speed of the great acceleration that is truly remarkable. This has largely happened within one human lifetime."

The conference has already declared that the Holocene Epoch is now over and that the Anthropocene -- in other words, the epoch when the impact of human activity will be clearly seen in the future in the geological record -- has already begun.

Steffen said the impact of human activity was already being felt on a planetary level on the carbon, water and nitrogen cycles, citing as an example that people now generate more reactive nitrogen artificially than the planet does naturally.

"Where on Earth are we going?" he asked, pointing to melting ice sheets and vanishing Arctic permafrost, which has the potential to release far more carbon dioxide over coming centuries than is currently produced from burning fossil fuels.

Moving beyond 'critical thresholds'
"The key point is, either we turn around a lot of these trends -- the carbon dioxide trend, deforestation and so on -- or we allow them to continue and push beyond critical thresholds," Steffen said.

Speakers at the conference pointed to the growth of so-called dead zones in coastal areas due to high carbon dioxide emissions as well as phosphorus extraction and fertilizer production, also noting higher air and oceanic temperatures, ocean acidification, biodiversity loss, growing populations and rising water stress.

Professor Diana Liverman of the University of Arizona said there were some hopeful signs -- the rate of population growth is slowing, carbon and energy intensity is starting to decline, and in some areas, forests are growing -- but they are offset by many overwhelming factors.

"Average resource consumption per person, already high in some regions, is growing steeply in emerging economies even as many poor people cannot meet basic human needs," she said. "In some countries, people are consuming far too much, including carbon, water and other resources embodied in trade. We have a long way to go to turn things around."

But sociologist Kari Marie Norgaard of the University of Oregon, who has written a book on the subject of climate change and public attitudes called "Living in Denial," said that while science may be clear -- albeit under challenge from the climate skeptics -- the general public is far from convinced.

"Climate change poses a massive threat to our present social, economic and political order. From a sociological perspective, resistance to change is to be expected," she said. "People are individually and collectively habituated to the ways we act and think. This habituation must be recognized and simultaneously addressed at the individual, cultural and societal level."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500