Climate Tipping Points

Reader Contribution by Richard Hilderman and Ph.D.

The continuing increase in atmospheric carbon dioxide levels could trigger a large, abrupt shift in the climate which is termed a tipping point. Climate change becomes uncontrollable and the planet enters a chaotic era lasting thousands of years before natural processes can bring the climate under control once a tipping point has been reached.

Climate history demonstrates that the transition from ice ages to warm, interglacial periods (such as we are in now) is not smooth. The transitions are dramatic with sharp changes setting off accelerated warming that triggers the disappearance of summer ice in the Arctic, melting of the Greenland ice sheet, melting of the West Antarctic ice sheet and large scale destruction of rainforests.

The Paleocene epoch which occurred 55 million years ago is an example of the Earth undergoing a large and abrupt climate shift. At this time the planet was undergoing a gradual global warming similar to the warming trend the planet is experiencing today. A sudden release of an enormous amount of carbon flooded the atmosphere following this gradual warming period. It is hypothesized that the source of this carbon was methane escaping from the ocean floor and the permafrost. Global surface temperature rose 9-16o F and the ocean became acidic. Fossil records demonstrate that mid-latitude flora migrated toward the North Pole. On the ocean floor 30 to 35% of the fauna became extinct.

The Paleocene epoch lasted about 120,000 years. It took another 40,000 years for the planet to return to cooler conditions through the removal of carbon from the atmosphere by rock weathering. In other words, it took the planet 40,000 years to transfer the excess carbon from the short-term carbon reservoir to the long-term reservoir (my posting entitled “Carbon Cycle”).

Geological evidence clearly demonstrates that the climate has changed dramatically in the past in response to natural forces. Why should we be concerned about the current global warming trend?  The answer to this question is simple. The release of carbon dioxide into the atmosphere from the burning of fossil fuel is not part of the natural cycle. This unnatural release of carbon dioxide triggers a carbon overload in the atmosphere. Global warming is a result of this carbon overload. The current global warming trend is accelerating faster than past warming trends.

Will the release of carbon dioxide into the atmosphere by the continued burning of fossil fuel induce a climate tipping point? The amount of carbon that entered the climate system during the Paleocene epoch is about the same amount of carbon that is projected to enter the system this century if fossil fuel use continues to grow at the current pace. The Earth’s atmosphere can safely handle around 700 billion tons of carbon but the atmosphere now contains about 800 billion tons. As the world population continues to increase so will atmospheric levels of carbon. Methane plumes have recently been detected rising from the floor of the Arctic Ocean.  Between 2003 and 2008 the Greenland ice sheet lost an area 10 times the size of Manhattan and this past 2010 summer a 100 square mile island of ice (four times the size of Manhattan) broke off the Greenland ice sheet. In 2008 the Northwest Passage was ice free for the first time in history (see my posting entitled The Arctic Feedback Factor and Climate Change).

The planet did not have to deal with over 6 billion human inhabitants during previous climate shifts. Humans can’t regulate the climate. Humans through the burning of fossil fuel make it more difficult for Mother Nature to keep the climate under control. The good news is the technology that exists today will allow us to solve the carbon problem! Solving the carbon problem will be discussed in future blog posts.