Unmasking the heat

The weather machine seems to have gone into overdrive. Scientists assert that the rise in temperature is unprecedented, at least since the 15th century. And, in the 20th century, an increase in the level of greenhouse gases is cited as the main reason for the new phenomenon. Is it a result of global warming?

Published: Wednesday 15 July 1998

Unmasking the heat

-- W eather report 1997-98 : Fires engulf the bone-dry forests of Indonesia, tornadoes shred parts of the us , droughts sap the Australian outback, deadly storms lash China's coastal provinces, floods swamp the otherwise parched Ethopia, central Pacific islands receive a bumper harvest of seven cyclones, fires sweep across the fragile rainforests of South America and thousands of living beings the world over fall prey to the violent mood swings of the El Nio or the infant Jesus.

The devastation has added a new urgency to a long-running scientific mission: the quest to be able to forecast weather precisely and understand the cause and effects of the unnatural climate swings. It is now presumed that El Nio has existed for at least two million years. But, according to us scientists, its frequency and intensity is on the increase.

In the 19th century, El Nio appeared on an average every seven-and-a-half years, now it comes every five years. Are other factors to blame or is it because of the "greenhouse effect", resulting from human activity, in particular the release of carbon dioxide into the atmosphere?

A report in a recent issue of Nature (No 6678, 23 April, 1998) argues that the 20th century has been exceptionally warm. Climatologists assert that the Earth's surface has warmed ever since the beginning of the Industrial Revolution and three of the hottest years in this century were banded together in the nineties -- 1990, 1995 and 1997.

Scientists of the University of Massachusetts, usa, have an artful solution! They have taken a clutch of long-term historical records and matched them with what is termed "proxy" records of past temperatures. Annual variations are preserved in a variety of natural settings, such as laminated deposits in polar ice, growth-rings of trees, chemical evidence of climatic change contained in tiny marine fossils, seasonal growth patterns of corals along with fossilised pollen in lake sediments. The researchers calibrated these natural variations against historical records so they could use these natural records to extract meaningful information about temperatures which was then combined with the available thermometric records.

Their verdict: the twentieth century has been the warmest in 600 years and the three warmest years of the nineties were hotter than any other period since the Middle Ages (see graph: On the boil ).

Until the 20th century, they found that a variety of mostly natural factors combined to influence the climate. These included changes in solar radiation and volcanic haze, reflecting sunlight and heat-trapping greenhouse gases, mainly carbon dioxide, in the atmosphere. But in the 20th century, greenhouse gases -- from burning of fossil fuels like coal, oil and natural gas -- have been the most dominant factor. Atmospheric concentration of carbon dioxide has risen phenomenally.

As is generally known, a certain level of greenhouse gases in the atmosphere is needed to keep the planet warm to sustain life. But the beneficial natural levels of these gases in the atmosphere are being continuously boosted by human activities, especially the burning of fossil fuels. If these emissions are not curbed, the amount of the greenhouse gases in the atmosphere will have doubled by the end of the next century compared with pre-Industrial Revolution levels.

"Our conclusion was that the warming of the past few decades appears to be closely tied to emission to greenhouse gases by humans," said Michael E Mann, chief author of the report on the new study. Other kinds of analyses have essentially come to the same conclusion.

El Nio at work The heat and dry weather conditions were not only experienced in India. Climatic swings -- droughts or deluges -- prevailed in almost every part of the globe. The first five months of 1998 were the planet's hottest on record, say scientists of the us -based National Oceanographic and Atmospheric Administration. They further stated that the average global temperature from January through May was about 17.2 c, marginally hotter than the previous record set in 1997. The El Nio phenomenon is the main reason behind the mercury ascent.

" Even if it sounds unbelievable, it has actually caused most of the problems," says Mojib Latif, a climatologist at the Max Planck Institute for Meteorology at Hamburg, of the El Nino which has left a trail of destruc-tion in every continent. After 1982, this is the second tough El Nio in one generation, causing damages of over us $10 billion.

North America
The El Nio caused an extremely violent tornado season in the us in 1998 . In Florida and Alabama, hundreds of people lost their homes. The whirlwind left behind a 16-km-long trail of destruction in Georgia. In California, the storms caused floods and landslides. In the first quarter of the year, damages amounted to approximately us $1 billion.

The winter in the North American east coast was unusually mild but the west coast was extremely humid. The insect population benefited the most from the humidity. Los Angeles suffered an invasion of rats while the flowering deserts of California were swamped by killer bees. America was also inflicted by a wave of allergies, the worst in 40 years. Since El Nio is now on the decline, and its colder sister La Nia is due to set in, meteorologists predict an extremely dry season ahead in south and west usa , bringing with it the hazard of uncontrollable forest fires.

Central America
Mexico recorded only one-tenth of the normal rainfall this year. Raging fires are gobbling the country's last virgin cloudforest, the Chimalapas. The fires ravaging the mystical forests are so huge and remote that authorities could not even count the number of blazes. With 22 ecosystems and 62 species of reptiles comprising the cloudforest, firefighters have been unable to employ most effective methods of dousing the blaze. An estimated 16,800 acres have been destroyed since the fires started last year.

In Panama, 1997 was the driest year of the century recording 35 per cent less than normal rains . The drought has also disrupted sea traffic which passes through the Panama Canal. Even normal monsoons may not be able to fill Panama's rivers and lakes. And, as the country gets about 70 per cent of its energy from hydroelectric plants, Panama is suffering a severe energy crisis.

South America
In Peru and Ecuador, heavy rainfall caused disastrous landslides and floods, destroying roads, bridges and often whole villages. At least 500 people died and 250,000 were left homeless. The floods transformed the Sechura desert in north Peru into a 1,000 sq km lake. The repairs of the roads will cost the two nations us $1.5 billion. Though the Peruvian fishing fleet is equipped for an El Nio attack, the fishing industry, which exports of us $1 billion annually, suffered huge losses. The warm temperatures in the Pacific forced the large sardine schools to moved southwards. This caused about 85 per cent of Peruvian seabirds to starve.

Uninterrupted rains have submerged almost 60,000 sq km of land in Argentina and Paraguay. More than 120,00 people have lost their homes.

Brazil in contrast is suffering from an unprecedented drought. While droughts in Brazil's northeast are periodic, the one this year was made worse by El Nio. Low rainfall is painting the landscape beige and fires have destroyed almost 60,000 sq km of rainforests. According to estimates, almost 10 million people are suffering from the effects of drought. Experts fear forest fires may lead to long-term climate changes, mostly dry spells in South America.

Violent rains and catastrophic floods were El Nio's Christmas gift to the eastern African region. Floods in Somalia left 1,600 people dead. Kenya measured 10 times more than normal rainfall in October. Bad harvests and high transport costs caused the prices for some vegetables to rise by almost 400 per cent.

In Uganda, where 65 per cent of the foreign exchange earnings come from coffee, exports were almost halved. Tanzania has estimated its El Nio damages at us $117 million and has requested the World Bank for us $47 million in aid. Incessant rains brought the danger of an epidemic. In east Africa, at least 17,000 people have contracted cholera, typhoid or malaria since the rains started.

Australia was prepared for the El Nio onslaught. Forest fires had destroyed thousands of houses and taken countless lives in the last El Nio season of 1982. Though this drought caused more fires than last time, preventive measures reduced damages. The Australian firefighters were better equipped and had already prepared corridors for the fires in advance. Despite this, the bush fires in southeastern Australia destroyed at least 200,000 hectares of meadowland. Bush fires are normally caused by lightning. However, because of the extreme dryness, they spread very rapidly. Two firefighters lost their lives while dousing the blaze.

Southeast Asia
Indonesia and Malaysia experienced the worst drought in 50 years. Forest fires destroyed two million hectares of forests in just three months of 1997 causing damages of about us $2.5 billion. A haze cloud, the size of western Europe, shrouded Southeast Asia. The main cause of the fires may have been the plantation owners' ritual of clearing forests, by burning them, but the conditions propelled by El Nio aggravated the blaze, making firefighting impossible. At least 70 million people have been affected by the smog, and it is still unclear what long term effects this will have on their health.

La Nia on the prowl
The increase in El Nio's frequency is perhaps only one of the manifestations of global warming. Others can be just as threatening -- like La Nia, which follows every El Nio with the cooling of the Pacific. This climatic pattern generally produces sharp reversals of weather patterns around the globe. Some scientists say that 1998 may witness an unusually strong La Nia, when the cold sister of the temperamental El Nio gets to work. Asia braces itself for the onslaught. In Indonesia, meteorologists believe a downpour could produce flash floods, landslides, severe soil erosion and depletion of fish reserves. Philippines has already taken measures to repair drainage and flood-control systems nationwide . Officials believe that the devastation La Nia might cause may be more than what its moody sister had wreaked.

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