Effects of global warming on India

Lakshadweep, comprising tiny low-lying islands, are at risk of being inundated by sea level rises associated with global warming.

The effects of global warming on the Indian subcontinent vary from the submergence of low-lying islands and coastal lands to the melting of glaciers in the Indian Himalayas, threatening the volumetric flow rate of many of the most important rivers of India and South Asia. In India, such effects are projected to impact millions of lives. As a result of ongoing climate change, the climate of India has become increasingly volatile over the past several decades; this trend is expected to continue.

Greenhouse gases in India

Elevated carbon dioxide emissions contributed to the greenhouse effect, causing warmer weather that lasted long after the atmospheric shroud of dust and aerosols had cleared. Further climatic changes 20 million years ago, long after India had crashed into the Laurasian landmass, were severe enough to cause the extinction of many endemic Indian forms. The formation of the Himalayas resulted in blockage of frigid Central Asian air, preventing it from reaching India; this made its climate significantly warmer and more tropical in character than it would otherwise have been.

Effects of global warming on India and Bangladesh

Several effects of global warming, including steady sea level rise, increased cyclonic activity, and changes in ambient temperature and precipitation patterns, have affected or are projected to affect India. Ongoing sea level rises have submerged several low-lying islands in the Sundarbans, displacing thousands of people. Temperature rises on the Tibetan Plateau, which are causing Himalayan glaciers to retreat.

Environmental

Increased landslides and flooding are projected to have an impact upon states such as Assam. Ecological disasters, such as a 1998 coral bleaching event that killed off more than 70% of corals in the reef ecosystems off Lakshadweep and the Andamans, and was brought on by elevated ocean temperatures tied to global warming, are also projected to become increasingly common.

The first among the countries to be affected by severe climate change is Bangladesh. Its sea level, temperature and evaporation are increasing, and the changes in precipitation and cross boundary river flows are already beginning to cause drainage congestion. There is a reduction in fresh water availability, disturbance of morphologic processes and a higher intensity of flooding and other such disasters. In comparison to the United States, Bangladesh only contributes 0.1% of the world’s emissions yet it has 2.4% of the world’s population. In contrast the the United States makes up about 5 percent of the world's population, yet they produce approximately 25 percent of the pollution that causes global warming.

Economic

The Indira Gandhi Institute of Development Research has reported that, if the predictions relating to global warming made by the Intergovernmental Panel on Climate Change come to fruition, climate-related factors could cause India's GDP to decline by up to 9%; contributing to this would be shifting growing seasons for major crops such as rice, production of which could fall by 40%. Around seven million people are projected to be displaced due to, among other factors, submersion of parts of Mumbai and Chennai, if global temperatures were to rise by a mere 2 °C (3.6 °F).

Villagers in India's North Easter state of Meghalaya are also concerned that rising sea levels will submerge neighbouring low-lying Bangladesh, resulting in an influx of refugees into Meghalaya—which has few resources to handle such a situation.

If severe climate changes occur, Bangladesh will lose land along the coast line. This will be highly damaging to Bangalies especially because nearly two-thirds of Bangladeshis are employed in the agriculture sector, with rice as the single-most-important product. The economy has grown 5-6% over the past few years despite inefficient state-owned enterprises, delays in exploiting natural gas resources insufficient power supplies, and slow implementation of economic reforms. However, Bangladesh remains a poor, overpopulated, and inefficiently-governed nation. If no further steps are taken to improve the current conditions global warming will effect the economy severely worsening the present issues further.

Past climate change
Thick haze and smoke along the Ganges River in northern India.

However, such shifts are not new: for example, earlier in the current Holocene epoch (4,800–6,300 years ago), parts of what is now the Thar Desert were wet enough to support perennial lakes; researchers have proposed that this was due to much higher winter precipitation, which coincided with stronger monsoons. Similarly, Kashmir, which once had a warm subtropical climate, shifted to a substantially colder temperate climate 2.6–3.7 mya; it was then repeatedly subjected to extended cold spells starting 600,000 years ago.

Pollution

Thick haze and smoke, originating from burning biomass in northwestern India and air pollution from large industrial cities in northern India, often concentrate inside the Ganges Basin. Prevailing westerlies carry aerosols along the southern margins of the steep-faced Tibetan Plateau to eastern India and the Bay of Bengal. Dust and black carbon, which are blown towards higher altitudes by winds at the southern faces of the Himalayas, can absorb shortwave radiation and heat the air over the Tibetan Plateau. The net atmospheric heating due to aerosol absorption causes the air to warm and convect upwards, increasing the concentration of moisture in the mid-troposphere and providing positive feedback that stimulates further heating of aerosols.

Awareness

Tribal people in India's remote northeast plan to honour former U.S. Vice President Al Gore with an award for promoting awareness on climate change that they say will have a devastating impact on their homeland.

Meghalaya -- meaning 'Abode of the Clouds' in Hindi -- is home to the towns of Cherrapunji and Mawsynram, which are credited with being the wettest places in the world due to their high rainfall.

But scientists state that global climate change is causing these areas to experience an increasingly sparse and erratic rainfall pattern and a lengthened dry season, affecting the livelihoods of thousands of villagers who cultivate paddy and maize. Some areas are also facing water shortages.

El Niño and La Niña

El Niño is a weather event involving the eastward migration of a mass of warm water normally found in the western equatorial Pacific Ocean.

Periodically (usually every three to seven years), the easterly trade winds in the Pacific weaken and allow the pool of warm water to drift from Australia to the western coast of South America, often triggering heavy rains there.


This vast pool of warm water is thought to set off a chain reaction that can affect jet stream and weather patterns around the world, especially in the winter months in the northern hemisphere. El Niño is sometimes referred to as ENSO for El Niño–Southern Oscillation. The Southern Oscillation is a seesaw of air pressures on the eastern and western halves of the Pacific.

La Niña is essentially the opposite of El Niño. La Nina is a migrating pool of cooler-than-usual ocean water. The cool water can suppress rain-producing clouds, which leads to dry conditions.

Peruvian fishermen first noticed the effects of a new El Niño at Christmas ime, when storminess off the coast reduced the supply of fish. "El Niño" is Spanish for "the boy child," and is used to refer to the Baby Jesus. The name La Niña ("the girl child") was coined to deliberately represent the opposite of El Niño.

Because even the most dedicated scientists do not thoroughly understand El Niño and La Niña (we do not know, for instance, why the trade winds suddenly die down and allow the warm water pool to move eastward), we can only describe certain tendencies in the weather.

In the past, El Niño has often brought heavy rains to southern California and to a portion of the South from Atlanta to Cape Hatteras; it can bring relatively mild winter temperatures to the northern third of the country. However, these effects are not consistent in every El Niño event on record.

The stronger the La Niña, the more severe the droughts. Tha La Niña in 2009 is creating severe drought in much of the world, causing an agricultural crisis.


El Niño

The data from TOPEX/Poseidon, and in the future Jason-1, helps us study and understand the complex interactions between the oceans and the atmosphere which affect global weather and climate events. One well-known example of this interaction is an El Niño event.

El Niño was named by people who fish off the western coast of central America to refer to the warm current that invades their coastal waters around Christmastime. El Niño events disrupt fisheries and bring severe weather events worldwide.

In a normal year, the trade winds blow westward and push warm surface water near Australia and New Guinea. When warm water builds up in the western Pacific Ocean, nutrient-rich cold water comes up off the west coast of South America and fosters the growth of the fish population.


During an El Niño event, the trade winds weaken and warm, nutrient-poor water occupies the entire tropical Pacific Ocean. Heavy rains that are tied to the warm water move into the central Pacific Ocean and cause drought in Indonesia and Australia. This also alters the path of the atmospheric jet stream over North and South America.

The effects of El Niño disrupt normal winter conditions throughout the Pacific Ocean, and can persist into May or June. Reliable predictions of an El Niño occurrence will lead to better preparation for its widespread impact.

La Niña

Warm El Niños and cold La Niñas follow each other against the backdrop of the ocean seasons. During a La Niña, the trade winds are stronger and cold, nutrient-rich water occupies much of the tropical Pacific Ocean. Most of the precipication occurs in the western tropical Pacific Ocean, so rain is abundant over Indonesia.

Excess Rain in Monsoon

Most scientists agree that global warming presents the greatest threat to the environment.

There is little doubt that the Earth is heating up. In the last century the average temperature has climbed about 0.6 degrees Celsius (about 1 degree Fahrenheit) around the world.

From the melting of the ice cap on Mount Kilimanjaro, Africa's tallest peak, to the loss of coral reefs as oceans become warmer, the effects of global warming are often clear.

However, the biggest danger, many experts warn, is that global warming will cause sea levels to rise dramatically. Thermal expansion has already raised the oceans 4 to 8 inches (10 to 20 centimeters). But that's nothing compared to what would happen if, for example, Greenland's massive ice sheet were to melt.

"The consequences would be catastrophic," said Jonathan Overpeck, director of the Institute for the Study of Planet Earth at the University of Arizona in Tucson. "Even with a small sea level rise, we're going to destroy whole nations and their cultures that have existed for thousands of years."

Overpeck and his colleagues have used computer models to create a series of maps that show how susceptible coastal cities and island countries are to the sea rising at different levels. The maps show that a 1-meter (3-foot) rise would swamp cities all along the U.S. eastern seaboard. A 6-meter (20-foot) sea level rise would submerge a large part of Florida.

Uncertainties

Just as the evidence is irrefutable that temperatures have risen in the last century, it's also well established that carbon dioxide in the Earth's atmosphere has increased about 30 percent, enhancing the atmosphere's ability to trap heat.
The exact link, if any, between the increase in carbon dioxide emissions and the higher temperatures is still under debate.

Most scientists believe that humans, by burning fossil fuels such as coal and petroleum, are largely to blame for the increase in carbon dioxide. But some scientists also point to natural causes, such as volcanic activity.
"Many uncertainties surround global warming," said Ronald Stouffer at the U.S. National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey. "How much of it would still occur if humans were not modifying the climate in any way?"

The current rate of warning is unprecedented, however. It is apparently the fastest warming rate in millions of years, suggesting it probably is not a natural occurrence. And most scientists believe the rise in temperatures will in fact accelerate. The United Nations-sponsored Intergovernmental Panel on Climate Change reported in 2001 that the average temperature is likely to increase by between 1.4 and 5.8 degrees Celsius (2.5 and 10.4 degrees Fahrenheit) by the year 2100.

Ozone Layer

The thickness of the ozone layer—that is, the total amount of ozone in a column overhead—varies by a large factor worldwide, being in general smaller near the equator and larger as one moves towards the poles. It also varies with season, being in general thicker during the spring and thinner during the autumn in the northern hemisphere. The reasons for this latitude and seasonal dependence are complicated, involving atmospheric circulation patterns as well as solar intensity.

Since stratospheric ozone is produced by solar UV radiation, one might expect to find the highest ozone levels over the tropics and the lowest over polar regions. The same argument would lead one to expect the highest ozone levels in the summer and the lowest in the winter. The observed behavior is very different: most of the ozone is found in the mid-to-high latitudes of the northern and southern hemispheres, and the highest levels are found in the spring, not summer, and the lowest in the autumn, not winter in the northern hemisphere. During winter, the ozone layer actually increases in depth. This puzzle is explained by the prevailing stratospheric wind patterns, known as the Brewer-Dobson circulation. While most of the ozone is indeed created over the tropics, the stratospheric circulation then transports it poleward and downward to the lower stratosphere of the high latitudes. However in the southern hemisphere, owing to the ozone hole phenomenon, the lowest amounts of column ozone found anywhere in the world are over the Antarctic in the southern spring period of September and October.
Brewer-Dobson circulation in the ozone layer.

The ozone layer is higher in altitude in the tropics, and lower in altitude in the extratropics, especially in the polar regions. This altitude variation of ozone results from the slow circulation that lifts the ozone-poor air out of the troposphere into the stratosphere. As this air slowly rises in the tropics, ozone is produced by the overhead sun which photolyzes oxygen molecules. As this slow circulation bends towards the mid-latitudes, it carries the ozone-rich air from the tropical middle stratosphere to the mid-and-high latitudes lower stratosphere. The high ozone concentrations at high latitudes are due to the accumulation of ozone at lower altitudes.

The Brewer-Dobson circulation moves very slowly. The time needed to lift an air parcel from the tropical tropopause near 16 km (50,000 ft) to 20 km is about 4-5 months (about 30 feet (9.1 m) per day). Even though ozone in the lower tropical stratosphere is produced at a very slow rate, the lifting circulation is so slow that ozone can build up to relatively high levels by the time it reaches 26 km.

Ozone amounts over the continental United States (25°N to 49°N) are highest in the northern spring (April and May). These ozone amounts fall over the course of the summer to their lowest amounts in October, and then rise again over the course of the winter. Again, wind transport of ozone is principally responsible for the seasonal evolution of these higher latitude ozone patterns.

The total column amount of ozone generally increases as we move from the tropics to higher latitudes in both hemispheres. However, the overall column amounts are greater in the northern hemisphere high latitudes than in the southern hemisphere high latitudes. In addition, while the highest amounts of column ozone over the Arctic occur in the northern spring (March-April), the opposite is true over the Antarctic, where the lowest amounts of column ozone occur in the southern spring (September-October). Indeed, the highest amounts of column ozone anywhere in the world are found over the Arctic region during the northern spring period of March and April. The amounts then decrease over the course of the northern summer. Meanwhile, the lowest amounts of column ozone anywhere in the world are found over the Antarctic in the southern spring period of September and October, owing to the ozone hole phenomenon.