Chilling news: the world's oceans store heat, fresh water, salt, and carbon dioxide, and circulate them around the globe. They transport about as much heat as the atmosphere does, and that makes them a powerful influence on the world's climate.

El Nino is a prime example of how oceans affect climate: this mass of warm water that builds in the western Pacific Ocean contains 20 to 30 times more water than all the Great Lakes put together. It also has vast amounts of energy: according to one calculation it contains more energy than a million large power plants, at 1,000 megawatts each, running full tilt for a year.

While scientists don't know exactly what triggers the phenomenon, we're all well aware of its effect. Every three to seven years, an El Nino event occurs. It may last for many months, disrupting the flow of the trade winds in the tropical Pacific and wreaking havoc on the climate worldwide. During the last 40 years, ten of these major events have been recorded, the worst of which occurred in 1997-1998. This one caused drought in Southern Africa, Southern India, Sri Lanka, the Philippines, Indonesia, Australia, Southern Peru, Western Bolivia, Mexico, and Central America. At the same time, it brought heavy rain and flooding to Bolivia, Ecuador, Northern Peru, Cuba, and the U.S. Gulf States, as well as typhoons in Tahiti, and Hawaii.

And, it appears that El Nino is brewing up again. In August 2004, U.S. scientists reported that water over vast stretches of the tropical part of the Pacific Ocean was warming to levels that in the past have preceded El Nino events.

One of the largest potential threats to all marine and coastal resources is global warming. Global climate change will warm average ocean temperatures, alter marine circulation patterns, and affect marine biological productivity.

Scientists recently concluded that global warming over the last four decades has altered the salt balance of the Atlantic Ocean: that matters because it's the salt level that allows the ocean to move warm water around the planet. Too little salt and winter in Eastern North America and Northern Europe could become more frigid. Temperatures might drop by five to 10 degrees Celsius in the next 10 to 50 years. That could mean earlier freeze-ups in shipping lanes, rivers, and harbours, crop failures, shorter growing seasons, and sky-high energy bills.

The study, published in Nature in December 2003, says potential changes in circulation of the ocean could affect evaporation, precipitation, fresh-water cycles, and climate. The study documents changes in the salt content of tropical and sub-tropical parts of the Atlantic Ocean. These are becoming saltier, partly because higher global temperatures have resulted in more evaporation of ocean water than in the past. The freshwater vapor from evaporation moves north and south to the poles, cools, and replenishes colder oceans through precipitation.

In the end, higher levels of evaporation ultimately increase levels of precipitation in these areas, thus reducing the salinity in the far north and south. The salt water is further diluted by melting glaciers and ice sheets, which exposes more of the ocean surface, allowing still more moisture to evaporate into the atmosphere. Normally, the saltier water sinks--mostly in the North Atlantic--from the surface of the ocean to the bottom where it's pulled back to the Equator. As the deep, cold water shifts from north to south, warm water from the southern Gulf Stream heads north closer to the surface, warming both the water and the air.

A drop in the salt level reduces the ability of the surface water to sink, slowing down the whole water exchange process, often called the Great Ocean Conveyor. Without this exchange, scientists think Berlin, Germany might have the same climate as Edmonton, which is at the same latitude; Stockholm, Sweden might be as chilly as Iqaluit. As it is now, these ocean currents deliver enormous heat, equal to the power generation of a million nuclear power plants. It's this heat-transferring process that creates the temperate climate of the British Isles as well. Climate change will contribute to rising sea levels too. The Intergovernmental Panel on Climate Change (IPCC) predicts about a one-metre rise in sea levels during the next 80 years.

Higher sea levels increase the impact of storm surges, accelerate habitat destruction, alter tidal ranges, change sediment and nutrient circulation patterns, and make flooding worse. Rising sea levels will displace approximately one billion people who live within a few metres of sea level. Many of these people will be living in the poorest and most heavily populated countries of the world.

The sea level has been rising worldwide for the last 10,000 years. Scientists know that rates of sea level rise have gradually fallen from more than 100 centimetres per century way back then to about 20 centimetres per century today. But, global warming is pushing it back up again. The IPCC figure includes the effect of rising ocean temperatures which is expected to add about 30 centimetres to sea level this century, and glacial runoff, which could add another 40 centimetres. That adds up to a 90-centimetre boost in sea level by 2100, a rate of increase that global coastlines haven't experienced in about 8,000 years.

Even small sea rises could have enormous effects, causing erosion, mudslides, and severe damage. The Environment Agency, a public body that aims to protect and improve the environment in England and Wales, recently warned that: "Most of the U.S. eastern seaboard is at risk from rising tides in the coming decades. Communities in which millions of people live face inundation. And, the Dutch may, by some estimates, need to spend two trillion pounds (about $5 trillion) in the next century to maintain their dykes against the sea."

The Agency goes on to explain that some estimates suggest there will be tens of millions of environmental refugees from rising sea levels within a few decades. "They may come in the greatest numbers from the doomed coastal islands of Bangladesh, where millions of the country's poorest live, and the Nile delta, where millions have nowhere to go and nobody to build them sea walls."

Other climatologists outline similar devastation with many small island nations in danger of being wiped off the globe entirely if sea levels continue to rise as predicted. Even if parts of low-lying islands (such as Tuvalu, Kiribati, or the Maldives) remain above sea level, many will have their supplies of drinking water cut because sea water will combine with their freshwater aquifers. This could happen with a rise of only 50 centimetres.

SUGGESTED ACTIVITIES:

1. A growing body of evidence from joint archaeological and paleoclimatological studies shows linkages among ocean-related climate shifts, "megadroughts," and rapid collapses of civilizations, including the Akkadian empire in Mesopotamia 4,200 years ago, the Mayan empire in central America 1,500 years ago, and the Anasazi in the American southwest in the late 13th century. Choose a fallen empire and investigate this theory.

2. Warmer temperatures have led to sightings of robins and salmon in Canada's Far North, Virginia opossums in Southern Ontario, and hungry polar bears on Manitoba's Hudson Bay coastline because sea ice is melting earlier, giving them less time to fatten up on seals, their main prey. Investigate how a warmer climate is affecting life throughout your province or territory. (Check out the Canadian Council of Ministers of the Environment at: http://www.ccme.ca/)

3. In 2002, scientists were puzzled by the finding that Antarctica, the world's coldest continent, had cooled dramatically over the previous 35 years, which is against the general warming trend nearly everywhere else on Earth. Research this phenomenon to find out if anyone has come up with the reasons why it's getting colder and the implications for the rest of the world.

HURRICANES AND TORNADOES

The hurricane season of 2004 was devastating and the predictions are for repeats in years to come as ocean temperatures rise. The Woods Hole Oceanography Institution (WHOI) reported that in both the eastern and western hemispheres, tropical storm activity has been well above normal for several years. March 2004 saw the first South Atlantic hurricane ever recorded. WHOI says that "while no single factor can be ascribed as being most important in the genesis of hurricanes, it is ocean heat that drives a cyclone's thermal engine. Climate models and observations both support the notion that as the global thermometer continues to rise, the tropical and subtropical oceans are becoming increasingly warm. Most climate simulations agree that greenhouse warming will enhance the frequency and intensity of hurricanes and typhoons in the coming century."

The National Oceanic and Atmospheric Administration reported a record number of tornadoes in the United States during 2004 as well, surpassing the previous record by almost 300 (1,717 compared with 1,424 in 1998, and 1,368 in 2003). The findings are based on a preliminary review of reports filed by NOAA National Weather Service forecast offices and compared to historical records dating back to 1950.

Every year, an average of 1,200 tornadoes kill about 55 Americans, injure 1,500 people, and cause more than $400 million in damage, to 2004, record tornado reports were largely the result of an active hurricane season. Tornadoes frequently occur in the northeast quadrant of northward advancing tropical systems or their remnants.

Tropical Storm Bonnie and five land-falling hurricanes--Charley, Frances, Gaston, Ivan, and Jeanne--affected the mid-Atlantic and Southeast states during August and September 2004.

Four of the six hurricanes affected Florida, making it the only state since 1886 to sustain the impact of four hurricanes in one season (Texas also had four hurricanes in 1886). Hurricane Charley in August was the strongest hurricane (category 4 at landfall) to strike the U.S. since Andrew in 1992; it caused an estimated $14 billion in damage. Hurricanes Frances, Ivan, and Jeanne quickly followed Charley in September.

Hurricane Gaston also impacted the U.S. in August making landfall in South Carolina. In total, the hurricane season cost the U.S. an estimated $42 billion, the most costly season on record. That record has been calculated back to 1900. While there was extensive wind damage in Florida and other coastal locations, flooding was the major impact farther inland. Frances hit the Southeast and southern Appalachians after a wetter-than-average summer, causing millions of dollars in flood damage to the region. Shortly thereafter Ivan travelled a similar path through the mountains and led to widespread flooding, loss of power, and landslides.

LONG-RANGE FORECAST

Earth's climate during the past 500,000 years has been characterized by cold periods (glacials) lasting about 100,000 years, followed by warmer stretches (inter qlacials) lasting about 10,000 years, according to a 2004 British Antarctic Survey.

The study says about 430,000 years ago, the glacial periods started to lengthen and interglacials started to shorten. The longest interglacial period in history, which began about that time, lasted about 28,000 years and strongly resembles the current stage. Given that the current interglacial cycle has lasted about 12,000 years, scientists think another glacial period will start in about 15,000 years.

FACT FILE

Even though oceans hold 1,000 times more heat than the atmosphere does, the atmosphere moves heat around much more quickly which evens out their effectiveness:

Websites

Nova Online--http://www. pbx.org/wgbh/nova/elnino

World View of Global Warming--http://www. worldviewofglobalwarming. org/pages/rising-seas.html

Program in Atmospheres, Oceans, and Climate--http:// paoc.mit.edu/paoc/