Before 2100: Tipping Points in Global Warming?

Before 2100, are we on the brink of tipping some areas of the world into irreversible change? A new study, bringing together research from scientists around the world, suggests that indeed we are. The study, “Tipping Elements in the Earth’s Climate System,” will soon appear in the Proceedings of the National Academy of Science. The lead author, Professor Tim Lenton of the University of East Anglia and his colleagues have listed nine critical areas with an additional five that need more study or did not presently meet the criteria stated below.

Human activities may have the potential to push components of the Earth system past critical states into qualitatively different modes of operation, implying large scale impacts on human and ecological systems.

A “tipping element” is a sub continental area that can be “switched to a different state by small perturbations.”

In some cases, less than one degree of warming is necessary.

In some cases, once the tipping point is reached, transition to the new state will be abrupt and quick, even in terms of human life. Other tipping points may take centuries to complete; nonetheless, the effect on even our children and grandchildren will be considerable. For example, if Greenland passes its tipping point, even though it may take 300 plus years to complete the transition to a new state, our children, and grandchildren and we will experience the effects of that transition.

Tipping points had to meet the following criteria:

1. The parameters controlling the system had to be “transparently” combined into a single control parameter, e.g., given specified temperature rise. A slight, adverse change in the tipping element had to be enough to trigger the transition to a new state.
2. Human activities are interfering with the system such that decisions taken within a ‘‘political time horizon’’ can determine whether the tipping point is reached.
3. The time to observe the change and the time to trigger it lie within a time horizon with which we can deal. In other words, the tipping point cannot be so far in the future as to make present decisions seemingly irrelevant.
4. People care about the tipping element, e.g., Amazonian die-off, Greenland melting….

Below are the nine identifiable areas whose tipping points may occur before 2100. We may be closer to any or all of them than we would like to think.

1. Disappearance of Arctic Summer Sea Ice—approximately 10 yrs to complete—is the most critically sensitive. Indeed, it may already have passed the tipping point. Because of the albedo effect, disappearance will accelerate global warming.
2. Melting of the Greenland Ice Sheet—approximately 300+ years to complete—is the most understandable for most. If the GIS becomes unstable, reaches its tipping point, then a sea rise of 2-7 meters is in the offing.
3. Collapse of the West Antarctic Ice Sheet—more than 300 years to complete—has already seen sizable chunks of ice calf into the sea. Like the Greenland Ice Sheet, it will contribute substantially to sea rise: plus 5 meters.
4. Disruption of the Atlantic Thermohaline Circulation—approximately 100 years to complete. The ATC is the oceanic circulatory system, transporting heat, for example, northward, where dense, heavy, saltier water dives to bottom; then moves southward (The Gulf Stream is part of this system.) This circulation can be interrupted if enough fresh water from ice melt and rivers freshens/lightens northern waters so much that they are no longer heavy enough plunge to the bottom. For a good overview of how the current works worldwide, see Wiki.
   The ATC affects weather patterns around the world. One certain effect of its interruption is a cooling in Britain and elsewhere, to say nothing of affecting weather patterns worldwide. The study notes that the IPCC did not take into account fresh water run-on from the Greenland Ice Sheet. Consequently, the IPCC’s prediction of little effect on the ATC this century may not be correct.
5. Increase in El Nino—Southern Oscillation—approximately 100 years to complete (gradual). With more global warming, we may begin to experience a more “persistent” El Nino state, leading to more sustained droughts in Asia, northeast Australia, and elsewhere. Additionally, one of the world’s great fishing grounds of the western coast of South America may disappear. In short, both fishing and agricultural will certainly be affected.
6. Collapse of Indian Summer Monsoon—possibly less than a year to complete. The IPCC report did not show an “obvious” threshold this century, but the IPCC models did not adequately take into account “brown haze” and land use changes. That brown haze, which can be seen from space, is a direct result the rapid industrialization in Southeast Asia. Ironically, the rise in CO2 acts stabilizes the CISM, but the brown haze with its sulfate aerosols are destabilizing. If the Summer Monsoon ceases—or is significantly weaken—expect sustained droughts in India.
7. Greening of Sahara/Sahel because of changes in the West African Monsoon (WAM)—approximately ten years to complete. Ironically, this may be good news: a greening of the Sahara.
8. Dying of the Amazon Rain Forests—approximately 50 years to complete. A large fraction of precipitation in the Amazon is recycled. Even without increased global warming, if we continued deforestation, we may pass the tipping point. Once the tipping point is reach, the forest will no longer be able “to grow back.” Instead, it will simply wither away. The lungs of the world will be gasping with ever-drier air.
9. Dying of the Boreal Forests—approximately 50 years to complete. The huge Boreal forest encircle the polar regions, spanning large areas of Canada and Russia. Gone will the trees that can live only in this region of the world. With them, all the biodiversity with which they are associated.

Five other tipping points were included in the report, but they did not receive real scrutiny because they did not, at this time, meet the criteria above.

The five were:

1. Disappearance of the Tundra, resulting in amplified warming.
2. Ocean anoxia, leading to marine mass extinction.
3. Melting of the permafrost, increasing CO2 and methane in the atmosphere.
4. Melting of frozen methane hydrates, amplified global warming, to say the least!
5. Formation of Antarctic Bottom Water, i.e., decreasing oceanic circulation, affecting the oceans ability to store carbon.

Some may claim that we can handle these changes; in fact, they will put a positive gloss on some of them, Arctic Sea Ice Melt, for example. Suddenly we have a real Northwest Passage. Think of the benefits to a shorten trade route. But changes do not happen in a vacuum. Everything is connected. How will Arctic sea ice melt accelerate global warming, thus bring other tipping points closer?

I suspect we are entering a period of great uncertainty, one that will affect all of us, one that will touch every discipline and every life.

We are on the edge of a triple threat. The first is the economic mess with which we are now entangled. The second is the depletion of resources, especially oil. The third is global warming.

We do not have a stellar history of dealing with problems of such large magnitude. The subprime debacle is a good case in point. We reacted only when we could no longer avoid the issue. Rarely do we anticipate problems. Certainly, we should have anticipated the subprime mess. But our leaders are rather myopic folk. We chose them. They told us what we wanted to hear. We react to problems; we do not like to anticipate them. Our leaders do exactly as we want and expect them to do. They are us.

We also have difficulty seeing the conflict between rationality at the individual level and rationality at the collective level.

An individual makes rational decisions that improve only his lot. We applaud such decisions as long as we are not directly and immediately affected. We have enthroned such behavior as the touchstone as to how the market place should work: Each man’s greed will ultimately lead to the betterment of all.

Rational decisions at the individual level, however, may not be rational decisions at the collective level.

For example, suppose a company resists installing scrubbers or decides to dump its toxic wastes into a river or unprotected landfill. In terms of profitability, the company is making a rational decision. But if all companies did it, collectively it would be irrational.

The threat of global warming is going to challenge us collectively as nothing ever has.

Note: The link to the study will not work until after the study actually appears. I think it is scheduled for the February 12 edition. Other sites, such as Science Daily, have in part, covered the story. I have included parts of the study that have not been covered: Methodology, etc.

Final Note: The study is now publically available, together with supporting material at the PNAS Website. The text of the study can be found here.