The Breakdown of Climate: Human Choices or Global Disaster

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Review: During the period 900-1250, known as the Medieval Optimum, temperatures were about 1C warmer than today, grapes were grown in England and the great cathedrals were built. There was a sudden switch in climate in the late Middle Ages, the decade 1310-1320 was disastrous and many starved. By the beginning of the 15th century the seas around Greenland had frozen and the old Viking population had died out. The River Thames regularly froze over. Storms were severe and in 1413 the Scottish town of Forvie was covered by what is now a 30m high sand dune. Although scientists are divided there seems to be a correlation between sunspot activity and climate change. During the Medieval Optimum solar activity may have been double today's and it was during the mini ice age that followed that solar activity dropped to a low level.

Sunspot activity, on an 11-year cycle, peaked in 1969 and 1979 and was preceded by troughs in 1964 and 1976. Over a period of 90,000-100,000 years the earth shifts its course around the sun from one that is circular to one that is more elliptical. There is another cycle every 25,000 years when the Northern Hemisphere enjoys its summer when closest to the sun. Then there is the Milankovich Wobble, which may be the impetus that switches one climate regime to another. Interglacial periods last about 10,000 years with glacial periods, when ice sheets 1km thick have stretched from NY State to the Rockies, of about 90,000 years. We are due for an ice age but perhaps this is being offset by global warming.

The equator receives 2.5 times as much energy as the poles and if that energy was not distributed by the winds, oceans and forests the equator would be 14C warmer and the poles 25C colder than today. Although the winds have a lower thermal capacity than water, in a week the atmospheric jet streams can distribute the ash from volcanic eruptions throughout the world. The Gulf Stream, equivalent to 100 river Amazons carries to the north water 8C warmer than the returning, deep, cold water. Tropical forests transfer prodigious quantities of energy in the form of water vapor by taking up latent heat which is carried away in massive rain clouds, with the heat being distributed by air currents in higher latitudes. This energy transfer is the equivalent of six million atomic bombs daily over the Amazon Basin.

Climate has clanged dramatically and rapidly over the last 1000 years and it appears that we are now living through one of those periods. Since the industrial revolution man has increasingly affected nature's processes. Since the war we have added to the atmosphere three times the CO2 released by mankind over the rest of time put together. Models indicate that temperatures will rise by 0.4C per decade due to CO2 build up - an increase which is unprecedented in human history. Rain forests act as regulators of atmospheric and ocean systems but their wholesale destruction over the last 40 years has seriously jeopardized the efficiency with which energy is transferred from the equator to higher latitudes resulting in a greater area of ocean warming up. Hurricanes occur when the ocean temperature is over 26C to a considerable depth. 1995 was a record year with 16 hurricanes. In one day a full-blown hurricane may unleash the energy equivalent of half a million Hiroshima-sized bombs. The El Nino has changed in the last 30 years from once or perhaps twice per decade to several years running; two in the past 15 years may have been stronger than any in the last five centuries. The latest El Nino, with temperature rises of 6C involved massive releases of energy from the Pacific Ocean, with violent downpours in desert regions and droughts elsewhere. Farmers had their crops wiped out. The Goddard Space Center reports a surface loss of Greenland's ice sheet of about 30cms per year. Mean annual temperatures 1m below the surface in Canada have increased 1C since 1989. An increase of only 0.25% in the fresh water flowing into the North Atlantic will bring the warm northward flowing Gulf Stream to a shuddering halt. Global warming is more intense over the poles.

Man is managing 40% of the land surface for production but a reliable food base requires that climate remains within reasonable limits. Insurers tell us that the cost of natural disasters has risen 85 times since the 1960s indicating that serious changes are taking place. With more frequent El Ninos rainfall becomes unpredictable. With warmer oceans, hurricanes become more frequent. With melting ice caps the flow of the Gulf Stream might be affected and temperatures in Northern Europe would plunge. The unpredictability and rapidity of climate change has very serious consequences for agriculture and feeding people. For the first time in modern history US grain production fell below consumption in the 1988 drought. Normally the US provides half the world's grain exports. Demand for grain is rising as more people in developing countries eat meat. One-third of grain feeds animals. The rise in sea level, likely to be greater than currently predicted, would threaten one-third of the world's cropland.

There is still disagreement whether it is best to carry on with business-as-usual and pick up the bill later or to act now to reduce future costs. Peter Bunyard points out that we are woefully ignorant of our impact on the planet. We face the danger than many, interconnected, though separate positive feed backs could all be triggered at the same time, all acting synergistically to exaggerate the impacts of the others. We will never be truly effective while the earth's resources are handed over to corporate, profit-seeking interests. We need to learn how to manage ourselves and our relationship to the environment. Then we might have hope of bringing an end to the destruction that is threatening our very existence.
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