The bad news is it could be too late.

Scariest Thing about Climate Change: Climate Flips

By Patricia Beaulieu in the Spring 1997 Alternatives Journal 23:2

Much of the climate change debate so far has rested on the comfortable assumption that with increased concentrations of greenhouse gases, global average temperatures will rise slowly over decades, perhaps even over a century.

The expected eventual effects are nasty - more frequent and severe storms, sea-level rise, additional precipitation in some regions and drought in others, species and habitat loss, increase in forest fires, disease and insect infestation and so on. Along the way there will also be more extreme weather events with very damaging effects. But at least the warming will be gradual.

Or maybe not.

There is another, more troublesome possibility. Scientists examining the historical record in Greenland ice cores say some past climate shifs seem to have happened quickly. If so, we may be facing a rapid flip from the current climate regime to a much different warmer regime.

The underlying theory is that regional and global climate systems are like other complex systems - they can adjust only so far to accommodate new factors such as increased atmospheric carbon dioxide and the associated greenhouse effect. When such a system approaches the threshold at the outside edge of its adjustment capabilities, it may fluctate wildly. Then it fragments and reorganizes into a new stable regime.

While the flip re-establishes a state of decreased fluctations, the new regime may be very different from its predecessor.

The fear in climate change circles is that the increasingly frequent extreme weather events we are seeing now may be a sign that our climate system is already nearing its threshold and a rapid climate flip may be just ahead.

Historical evidence supporting such a possibility comes from ice core research. Like tree rings, ice cores provide yearly evidence of some environmnetal conditions. Snow and therefore ice accumulation is lower in cold periods in Greenland.

Ice core data from Greenland suggest that the climate of the North Atlantic during the last warm, interglacial period fluctuated more than that of the present (perhaps because of an enhanced hydrological cycle associated with the warmer mean climate) and there were rapid transitions between warm and cold periods occuring over just a few decades. (1)

The warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate, of whichthe best known is the Younger Dryas event, which endedapproximately 10,000 years ago.

Apparently it ended very quickly. Results from the Greenland ice core GISP2 indicate that the transition from the cold Younger Dryas period to the subsequent Preboral period occured in one to three years during which snow accumulation doubled. (2)

Alley and his colleagues calculate that the two-fold accumulation increase indicates a warming of approximately seven degrees Celsius in the North American climate system. (3)

If they are right, in only a few years Greenland's climate flipped into a new state that was on average about seven degrees warmer and twice as snowy.

It does not follow that the same quick, regional warming and similarly severe other changes happened globally at the same time. Perhaps the effects of more gradual global changes led to an unusually rapid shift in the North Atlantic regional climate.

The concept of system flips is increasingly accepted in ecology. When natural and human-caused stresses drive an ecosystembeyond the bounds of its normal state, the system may flip into another phase with significantly different characteristics. (4)

This has happened, for example, in parts of the Great Lakes - St. Lawrence River Basin where nutrient loadings from untreated sewage and agricultural runoff, combined with other stresses, triggered euthophication with alge blooms and murky water. This favoured pelagic fish that live and feed near the surface.

When remediation reduced these stresses, the pelagic fish system survived for a while. But when the waters cleared enough to allow light to reach further down, the system "flipped" or re-organized itself into a state favoring benthic (bottom-feeding) fish.

The resulting aquatic ecosystem is again stable, but very different from the two that preceded it, i.e., the pristine oligotrophic and the modifies eutrophic states.

In the case of the global climatic system the danger is that stresses from greenhouse gas effects are pushing the present syastem over the threshold where it must flip into a new warmer system that will be stable, but different from the climate on which our agriculture, economy, settlements and lives depend.

Patrica Beaulieu is a student in Environmnetal and Resource Studies at the University of Waterloo, Ontario.

NOTES
(1) A.J. Weaver and T>M>C> Hughes, "Rapid Interglacial Climate Fluctuations Driven by North Atlantic Ocean Circulation," Nature, 367 (1997), p. 447.

(2) R.B. Alley et all, "Abrupt Increase in Greenland Snow Accumulation at the End of the Younger Dryas Event," Nature, 362 (1993), pp. 527-529.

(3) Ibid.

(4) H.A. Regier and J.J. Kay, "An Heuristic Model of Transformations of the Aquatic Ecosystems of the Great Lakes-St. Lawrence River Basin," Journal of Aquatic Ecosystem Health (in press).

For William Calin's material on related topics.