Category Science

WHAT IS AN INTERGLACIAL PERIOD?

          It is thought that Ice Ages occur roughly every 100,000 years. The last one ended around 10,000 years ago, so we may experience another in 90,000 years time. Scientists call the time between Ice Ages an interglacial period.

         An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene interglacial began at the end of the Pleistocene, about 11,700 years ago.

          During the 2.5 million years of the Pleistocene, numerous glacials, or significant advances of continental ice sheets, in North America and Europe, occurred at intervals of approximately 40,000 to 100,000 years. The long glacial periods were separated by more temperate and shorter interglacials.

          During interglacials, such as the present one, the climate warms and the tundra recedes polewards following the ice sheets. Forests return to areas that once supported tundra vegetation. Interglacials are identified on land or in shallow epicontinental seas by their paleontology. Floral and faunal remains of species pointing to temperate climate and indicating a specific age are used to identify particular interglacials. Commonly used are mammalian and molluscan species, pollen and plant macro-remains (seeds and fruits). However, many other fossil remains may be helpful: insects, ostracods, foraminifera, diatoms, etc. Recently, ice cores and ocean sediment cores provide more quantitative and accurately-dated evidence for temperatures and total ice volumes.

          Interglacials and glacials coincide with cyclic changes in the Earth’s orbit. Three orbital variations contribute to interglacials. The first is a change in the Earth’s orbit around the sun, or eccentricity. The second is a shift in the tilt of the Earth’s axis, or obliquity. The third is the wobbling motion of Earth’s axis, or precession.

          Warm summers in the Southern Hemisphere occur when it is tilted toward the sun and the Earth is nearest the sun in its elliptical orbit. Cool summers occur when the Earth is farthest from the sun during the summer. Such effects are more pronounced when the eccentricity of the orbit is large. When the obliquity is large, seasonal changes are more extreme.

          Interglacials are a useful tool for geological mapping and for anthropologists, as they can be used as a dating method for hominid fossils.

          Brief periods of milder climate that occurred during the last glacial are called interstadials. Most but not all interstadials are shorter than interglacials. Interstadial climate may have been relatively warm but not necessarily. Because the colder periods (stadials) have often been very dry, wetter (not necessarily warmer) periods have been registered in the sedimentary record as interstadials as well.

          The oxygen isotope ratio obtained from seabed sediment core samples, a proxy for the average global temperature, is an important source of information about changes in the climate of the earth.

          An interglacial optimum, or climatic optimum of an interglacial, is the period within an interglacial that experienced the most ‘favourable’ climate and often occurs during the middle of that interglacial. The climatic optimum of an interglacial both follows and is followed by phases within the same interglacial that experienced a less favourable climate (but still a ‘better’ climate than the one during the preceding/succeeding glacials). During an interglacial optimum, sea levels rise to their highest values but not necessarily exactly at the same time as the climatic optimum.

Picture Credit : Google

 

DO CLIMATES CHANGE?

            The world’s climates have been through many changes since the planet was formed over 4000 million years ago. The Earth has been both hotter and colder than it is now. In the age of the dinosaurs, there were no polar ice caps, and tropical and desert climates were predominant. Since that time, there have been several Ice Ages, when the polar ice sheets expanded to cover up to one-third of the planet. The planet will continue to experience such dramatic changes, as well as minor fluctuations in the weather. Many people are concerned that the activities of mankind will have a catastrophic effect on our planet’s weather patterns.

            The Earth’s climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era — and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives.

            The current warming trend is of particular significance because most of it is extremely likely (greater than 95 percent probability) to be the result of human activity since the mid-20th century and proceeding at a rate that is unprecedented over decades to millennia.

            Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale. This body of data, collected over many years, reveals the signals of a changing climate.

            The heat-trapping nature of carbon dioxide and other gases was demonstrated in the mid-19th century. Their ability to affect the transfer of infrared energy through the atmosphere is the scientific basis of many instruments flown by NASA. There is no question that increased levels of greenhouse gases must cause the Earth to warm in response.

            Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly ten times faster than the average rate of ice-age-recovery warming.

Picture Credit : Google

 
 
 

What is the Arecibo message?

It is an interstellar message that was beamed into space in 1974 with the hope of making contact with extra-terrestrial life. It was transmitted on November 16, 1974 from the Arecibo radio telescope in Puerto Rico to the globular start cluster M13 about 25,000 light years away. The event marked the remodeling of what was then the world’s largest single-aperture telescope. The cluster M13 was chosen because it was at the right place at the right time.

The Arecibo message was the most powerful broadcast ever beamed deer space at the time. It contained 1679 binary digits, arranged in 73 lines of 23 characters per line. It was transmitted at a frequency of 2,380 MHz. the ‘phone call’ to the universe was less than three minutes long.

The message was created by Frank Drake, (an American astronomer and astrophysicist) with the help of Carl Sagan, (American astronomer-author) and the observatory staff. The message had seven components:

  1. The numbers one to ten
  2. The atomic numbers of the elements which make up our DNA – hydrogen, carbon, nitrogen, oxygen and phosphorous
  3. The formulas for the sugars and bases in the nucleotides of DNA
  4. The number of nucleotides in DNA and a graphic of the double helix structure of DNA
  5. The human figure along with its average height and the population of Earth
  6. The solar system
  7. The Arecibo Observatory and the diameter of the transmitting antenna dish.

It will take nearly 25,000 years for the message to reach its intended destination and an additional 25,000 years for any reply. The message was more a display of the achievement of human technology than an expectation of contact with aliens.

To mark the event’s 45th anniversary in November 2019, the Arecibo Observatory has asked young people around the world to devise an updated version of the message.

 

Picture Credit : Google

What are the impacts of deforestation?

  • During photosynthesis, trees absorb CO2 from the atmosphere, and store it as carbon for long time periods. At present, forest store as much as 45% of all land carbon. Deforestation affects this carbon cycle.
  • Deforestation is considered to be one of the contributing factors to global warming and climate change. Trees absorb not only the carbon dioxide that we exhale, but also the heat-trapping greenhouse gases that human activities emit. With increase in deforestation, larger amount of these gases will enter the atmosphere and global warming will increase further. About 300 billion tonnes of carbon, 40 times the annual greenhouse gas emissions from fossil fuels, is stored in trees, according to Greenpeace.
  • While fossil fuel combustion is the largest source of carbon dioxide emission, deforestation is the second largest. When trees die (or are cut or burnt), they release the stored carbon dioxide into the air.
  • Forests release large quantities of water into the atmosphere via perspiration. This replenishes the clouds and triggers rain, which in turn, maintains the forests. When forests are destroyed, it affects rainfall and thereby causes drought.
  • As much as 70% of the world’s plants and animals live in forests. They are losing their habitats due to deforestation. Loss of habitat can lead to species extinction. For instance, in Malaysia and Indonesia, Bornean rainforests are cut down to make way for producing palm oil. The effect of deforestation is so much that it is driving the extinction of orangutans, the world’s largest tree-dwelling great apes, native to the rainforests of Borneo and Sumatra. Removing trees deprives the forest of its canopy, which blocks the sun’s rays during the day and retains heat at night. That disruption leads to more extreme temperature swings that can, in turn, affect plants and animals.
  • Trees roots stabilize the soil around the tree and hold them in place. When they are cut, the soil is free to wash or blow away, which can lead to soil erosion.
  • Deforestation can also cause flooding. Coastal vegetation lessens the impact of waves and winds associated with a storm surge. Without this vegetation, coastal villages are susceptible to damaging floods.

 

Picture Credit : Google

What is deforestation and what are the causes of deforestation?

Deforestation is the destruction of forests in order to make the land available for other uses. The Earth loses 18.7 million acres of forests per year, which is equal to 27 football fields every minute, according to the World Wildlife Fund (WWF).

Common methods of deforestation are clear cutting and burning of trees. These methods leave the land completely barren. Clear cutting is when large swaths of land are cut down all at once. This sudden change causes severe damage to the ecosystem.

Cause of deforestation

  • A major contributor to deforestation is the practice of slash-and-burn technique of farming. Farmers clear forest by cutting down trees, burn them and then grow crops in the soils fertilized by the ashes. Typically, the land produces for only a few years. The farmers abandon the area and move on to a new patch of land and begin the process again.
  • Grazing of livestock, mining and drilling are the other major causes.
  • Trees are also cut to be used as fuel.
  • Forests are also cleared for housing and urbanisation; for industries, dams and other infrastructural projects.
  • Wood is used in the making of paper, furniture and the construction of buildings. Some of the loggers act illegally. They also build roads to access more and more remote forests, and this leads to further deforestation.
  • Not all deforestation is intentional. Some are caused by a combination of human and natural factors such as wildfires, which may prevent the growth of young trees.

 

Picture Credit : Google

How deforestation increases the pace of climate change?

  • In the concrete jungle that Mumbai is, Aarey Milk Colony is a treasured green patch. It has over 5, 00,000 trees. On October 4, 2019, when the Bombay High Court allowed the State government to go ahead with the felling of 2,600 trees to make space for a proposed Metro Rail car shed, the residents protested. But it was too late, as the Brihanmumbai Municipal Corporation (BMC) acted soon after the order and had already cut 1,500 trees (under the cover of darkness). The issue became bigger and uglier – clashes broke out between the police and environmental activists, leading to the arrest of at least 29 persons. Thea matter was taken to the Supreme Court and it, in a special hearing on October 7, 2019, ordered the BMC to halt the felling of trees in the Aarey forest. But it did not order the halt or shifting of the metro shed project from Mumbai’s Aarey in its subsequent hearing.
  • In September, reports emerged that the Jharkhand’s Water Resources Department has approved the cutting of around 3.44 lakh trees in Jharkhand’s Palamau Tiger Reserve to make way for the North Koel reservoir, also known as Mandal dam. As per latest estimation, the reserve has nil tigers. However, the felling of so many trees will damage the ecosystem, warn wildlife experts. The reserve has already suffered significant damage because of the expansion of road and railway network.

Development projects such as these are among the top reasons for the deforestation. According to the central government statistics, between 2015 and 2018, about 20,000 hectares of forest land was cleared for development activities such as mining, thermal power plants, dams, roads, railways and irrigation projects. Under the Forest (Conservation) Act, 1980, forest areas can be diverted by the environment ministry for non-forestry purposes such as mining. To compensate, authorities should carry out afforestation at a different place. However, they are in no way a substitute the diverse and natural forests that have been lost permanently due to deforestation, say experts.

It is an irony that the world, while seeking to slow the pace of climate change on the one side, continues to cut down trees in large numbers on the other hand. Trees are part of the solution in our fight against climate change.

 

Picture Credit : Google