Arctic ice melting faster than predicted: WWF

Posted on April 28, 2008 by Rashid Faridi

Arctic sea ice is melting “significantly faster” than predicted and is approaching a point of no return, conservation group the World Wildlife Fund (WWF) warned in a new study released on Wednesday.

The volumes of the Greenland Ice Sheet and ice in the Arctic Ocean were estimated at 2.9 million and 4.4 million cubic metres respectively in September 2007, the lowest ever levels recorded, the organisation said.

The sea ice shrank to 39 per cent below its 1979-2000 mean volume, it said. “Recently observed changes are happening at rates significantly faster than predicted” by the 2005 Arctic Climate Impact Assessment (ACIA) and last year’s report by the Intergovernmental Panel on Climate Change (IPCC), WWF said.

The melting of arctic sea ice and the Greenland Ice Sheet was happening so fast that experts were now questioning whether the situation is close to “tipping point,” where sudden and possibly irreversible change takes place.

“When you look in detail at the science behind the recent Arctic changes it becomes painfully clear how our understanding of climate impacts lags behind the changes that we are already seeing in the Arctic,” said Martin Sommerkorn, one of the authors of the report.

The WWF will present its report, comprised of the latest research in the region, to the meeting on Thursday of the Arctic Council, which groups Canada, Denmark, Finland, Iceland, Norway, Russia, Sweden, and the United States.

The conservation group’s researchers also warned of the devastating effect the rapid melting of the arctic ice could have on polar bears in Canada, where two thirds of the world’s population of the animals live.

“Previous models had predicted that melting sea ice would mean some polar bear populations could become extinct by 2050. The new evidence points to even earlier regional extinctions,” said Peter Ewins, director of species conservation at WWF-Canada.

The Committee on the Status of Endangered Wildlife in Canada will present the government with its estimates of the status of polar bears there on Friday.

source:http://timesofindia.indiatimes.com

Posted in Global Warming, News | Leave a comment

Arctic Getting Wetter Due to Global Warming

Posted on April 27, 2008 by Rashid Faridi

In addition to heating up faster than almost anywhere else on the planet, the Arctic has gotten wetter and snowier because of global warming, according to a new study. The extra precipitation could freshen ocean water in the Arctic and North Atlantic, researchers say, which might disrupt the so-called ocean conveyor belt, a current that runs through the Atlantic and carries warm water northward from the Equator.

The new study is the first to show that changes in precipitation in the Arctic are in part human-induced, said study leader Francis Zwiers of the government agency Environment Canada.

The study also shows that previous computer models underestimated how much precipitation would change because of global warming.

Contrary to the simulations, Arctic rain and snowfall increased by 7 percent over the past 50 years, the study found. In just the Canadian Arctic, precipitation jumped 11 percent.

“That might not seem very big, but a 10 percent change is quite a lot” when it comes to precipitation, Zwiers said.

The discrepancy means that models predicting future change “may underestimate what’s coming down the pipeline,” he said.

“If people are using these models for planning, they should keep in mind that what the models show may be weaker than what will happen.”

Source: http://news.nationalgeographic.com/news/2008/04/080425-wet-arctic.html

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The universe

Posted on April 27, 2008 by Rashid Faridi

The universe

Introduction

The universe can be defined as the whole of existing things from the scale of sub-micron to outer space. It consists of approximately 100 000 000 000 (one hundred thousand million) galaxies, each containing approximately 100 000 000 000 stars. The most distant objects that we know of are quasars, some 16 000 000 000 light years away. The age of the universe is approximately 15 000 million years (Ma) or 15 billion years (Ga), though there is some debate on this. liftoff.msfc.nasa.gov/academy/universe/age.html


Origin of the universe

Recent astronomical observations have shown that the universe is expanding away from a local group of galaxies. This appears to have begun by a huge explosion some 15 billion years ago. This ‘Big Bang’ is the most accepted theory which best explains our present observations on the structure of the universe.

In the ‘Big Bang’ theory, the universe began with a primeval fireball which contained all matter and energy within the universe concentrated within a single body. During the first few minutes, the expansion was dominated by radiation at temperatures of 1011 K (The Kelvin scale is used to measure very high and very low temperatures, 0° C = 273° K). Matter consisted of only protons, neutrons and electrons. Within three to four minutes, the effects of radiation diminished and more complex forms of matter (such as the deuterium nucleus : neutron+proton) evolved. Later, most of the matter became hydrogen (a proton+electron) at a temperature of 109 K.

Hundreds of millions of years after the initial ‘Big Bang’, immense condensations of matter occurred, eventually forming galaxies. Our own solar system is only some 4600 million years old.

Composition of the universe

The universe is composed mainly of hydrogen with approximately 20% helium. All other chemical elements comprise less than 1%. All elements originated as hydrogen. Within the first two minutes of the ‘Big Bang’, hydrogen atoms fused together and helium and lithium were produced. Element production ceased at this point in the ‘Big Bang’ and all other elements heavier than lithium (Li) were produced during later fusion reactions within the interiors of stars.

During supernova events when massive stars exhaust their nuclear fuel in only a few days to months, collapse occurs and the enormous amount of energy caused by intense neutron flux produces the heavier elements such as uranium and gold. The violent explosion also distributes these elements back into space. As the formation of elements proceeds through innumerable star cycles, forming and exploding, the gas and dust produced is slowly enriched in the heavier elements.


Galaxies

The largest objects in the universe are galaxies which can be divided into several types depending upon their shape:

  • Spiral galaxies are the most common and distinctive type (e.g. the Milky Way).
  • Barred spiral galaxies are not as compact as spiral galaxies and have an inner bar which comprises the centre of the galaxy from which arms reach out.
  • Elliptical galaxies are small and difficult to observe because of their low luminosity.
  • Irregular galaxies comprise only a small percentage of all types and lack any distinctive symmetry.
A spiral galaxy in Antlia
A spiral galaxy in Antlia, NGC 2997. Photo: © David Malin/Anglo-Australian Observatory.
A barred spiral galaxy
A barred spiral galaxy, NGC 1365, in Fornax. Photo: © David Malin/Anglo-Australian Observatory.


An elliptical galaxy
An elliptical galaxy, NGC 5078 and its distorted companion IC 879, in Hydra. Photo: © David Malin/Anglo-Australian Observatory.
Large Magellanic Cloud
Large Magellanic Cloud. Photograph from UK Schmidt plates. Photo: © David Malin/Anglo-Australian Observatory/Royal Obs. Edinburgh


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Stars

Stars are the most familiar objects in the universe as we can see them almost every night with the naked eye. They vary in size from small white dwarfs to super giants. There are approximately 1022 stars in the universe. They are being formed in galaxies all the time (e.g. nearby stars in the Orion Nebula were born less than one million years ago). Stars shine as they burn-up their nuclear fuel and eventually die. Our sun is an example of a common though smaller than average sized star. It formed approximately 4.6 billion years ago and will most likely last for another 4.6 billion years before it dies out and engulfs all of our solar system’s inner planets, including the Earth.

Groupings of stars as seen from the Earth are known as constellations. They are accidental groupings (that is, they are not in any way related to each other).

The luminosity of a star is a measure of its total energy output. The luminosity scale is measured relative to our own sun (a luminosity of 1). The luminosity of stars varies widely from 10-6 to 5 x 105. The temperature of a star is always given as its surface temperature. These range from 3500° K to 80 000° K (The Kelvin scale is used to measure very high and very low temperatures, 0° C = 273° K). The colour of a star is closely related to its surface temperature. The hottest stars are blue, followed by white, and the coolest stars are yellow, to orange and finally red in colour with decreasing temperature.

  • Supergiants and giant stars are those of enormous size and great luminosity despite having low surface temperatures.
  • White dwarfs are relatively hot small stars with a great density.
  • Neutron stars contain matter which is 1014 times denser than water yet have diameters of only 20 km.
  • Pulsars are small rapidly rotating objects (up to 30 times per second) which emit radiation at regular intervals.
  • Quasars are extremely bright distant objects that extend to the limit of the universe as we know it.
  • Black holes are stars that have collapsed under their own gravitational forces. They are of such high density that their gravitational force is strong enough to even prevent any light or matter escaping.
South celestial pole over water
South celestial pole over water. Photo: © David Miller/DMI.
The super giant Antares and surrounding nebula
The super giant Antares and surrounding nebula. Photograph from UK Schmidt plates. Photo: © David Malin/Anglo-Australian Observatory.


Importance of the sun

The Earth obtains most of its heat and light energy from the sun. This solar energy causes water evaporated on the surface of the Earth to rise into the atmosphere before precipitating elsewhere on the Earth’s surface. Wind is a result of air circulation caused by solar heating. The temperature of the surface of the sun is 6000° K (The Kelvin scale is used to measure very high and very low temperatures, 0° C = 273° K).

The temperature at the centre of the sun is 15 000 000° K.

The sun consists of:

  • an interior which contains most of the mass of the sun and where the sun’s energy is produced
  • the photosphere is the layer from which the sun’s energy escapes and from where light comes from (thickness of 1000 km)
  • the chromosphere has a very low density and is red in colour due to clouds of hydrogen gas (thickness of 500 km)
  • the corona can only be seen during a total eclipse, has a low density and has a temperature of 1 500 000° K

Sunspots are dark markings on the photosphere of the sun between 5° – 35° north and south of the sun’s equator. The sun’s energy is produced through nuclear fusion reactions in which hydrogen atoms are fused together to form helium.

Deformed sun at sunrise
Deformed sun at sunrise. Photo: © David Miller/DMI.
Solar eclipse
Solar eclipse 11 July, 1991, La Paz, Mexico. Diamond ring effect. Photo: © Akira Fujii/DMI.


Measuring astronomical objects

Electromagnetic radiation is the key to our understanding of the universe. It includes all forms of energy that travel through space in the form of waves, visible light, X-rays, ultraviolet, infrared and radiowaves. The electromagnetic spectrum is made up of radiation of varying wavelengths travelling at the speed of light. It is measured and detected using a number of different instruments.

When any element is heated, its gas emits a characteristic spectrum. The chemical composition of many objects can then be determined by examining the spectra of its heated vapours. Conversely, a cool gas absorbs the wavelengths characteristic of the atoms in it.

The fundamental measure of distance in space is the light year which is the distance that light travels through space in one year (9.46 x 1012 km). The speed of light is 300 000 km per second.

The Astronomical Unit (AU) is the mean distance between the Earth and our sun (measured in kilometres).

source:http://www.austmus.gov.au

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Fog: A ground Level Cloud

Posted on April 27, 2008 by Rashid Faridi

Fog is a cloud in contact with the ground. Fog differs from other clouds only in that fog touches the surface of the Earth. The same cloud that is not fog on lower ground may be fog where it contacts higher ground such as hilltops or mountain ridges. Fog is distinct from mist only in its density. Fog is defined as cloud which reduces visibility to less than 1 km, whereas mist is that which reduces visibility to less than 2 km.

The foggiest place in the world is the Grand Banks off the island of Newfoundland, Canada. Fog is frequent there as the Grand Banks is the meeting place of the cold Labrador Current from the north and the much warmer Gulf Stream from the south. The foggiest land areas in the world are Point Reyes, California, and Argentia, Newfoundland and Labrador, both with over 200 foggy days a year.

Fog forms when the difference (Δ) between temperature and dewpoint is (5 °F) 3 °C, or less.

Fog begins to form when water vapor (a colorless gas) condenses into tiny liquid water droplets in the air. Conversely, water vapor is formed by the evaporation of liquid water or by the sublimation of ice. Since water vapor is colorless, it is actually the small liquid water droplets that are condensed from it that make water suspended in the atmosphere visible in the form of fog or any other type of cloud. Fog normally occurs at a relative humidity around 100%. This can be achieved by either adding moisture to the air or dropping the ambient air temperature. Fog can form at lower humidities, and fog can sometimes not form with relative humidity at 100%. A reading of 100% relative humidity means that the air can hold no additional moisture and the air will then become supersaturated if additional moisture is added. Fog formation does require all of the elements that normal cloud formation requires with the most important being condensation nuclei. When the air is saturated, additional moisture tends to condense rather than staying in the air as vapor. Condensation nuclei must be present in the form of dust, aeresols, pollutants, etc. for the water to condense upon. When there are exceptional amounts of condensation nuclei present, especially hydroscopic (water seeking such as salt, see below) then the water vapor may condense below 100% relative humidity.

Fog can form suddenly, and can dissipate just as rapidly, depending what side of the dewpoint the temperature is on. This phenomenon is known as flash fog.

Another type of formation also common is sea fog (also knows as salt fog or salty Fog). This is due to the peculiar effect of salt. Clouds of all types require minute hygroscopic particles upon which water vapor can condense. Over the ocean surface, the most common particles are salt from salt spray produced by breaking waves. Except in areas of storminess, the most common areas of breaking waves are located near coastlines, hence the greatest densities of airborne salt particles are there. Condensation on salt particles has been observed to occur at humidities as low as 70%, thus fog can occur even in relatively dry air in suitable locations such as the California coast. Typically, such lower humidity fog is preceded by a transparent mistiness along the coastline as condensation competes with evaporation, a phenomenon that is typically noticeable by beachgoers in the afternoon.
Fog occasionally produces precipitation in the form of drizzle. Drizzle occurs when the humidity of fog attains 100% and the minute cloud droplets begin to coalesce into larger droplets. This can occur when the fog layer is lifted and cooled sufficiently, or when it is forcibly compressed from above. Drizzle becomes freezing drizzle when the temperature at the surface drops below the freezing point.

The thickness of fog is largely determined by the altitude of the inversion boundary, which in coastal or oceanic locales is also the top of the marine layer, above which the airmass is warmer and drier. The inversion boundary varies its altitude primarily in response to the weight of the air above it which is measured in terms of atmospheric pressure. The marine layer and any fogbank it may contain will be “squashed” when the pressure is high, and conversely, may expand upwards when the pressure above it is lowering.

Fog as a visibility hazard

Light fog reducing visibility in suburban street. Cyclist is very hazy at about 200m (219 yards). Zero visibility occurs before the end of this street, which is at about 400m (437 yards).

Fog reduces visibility. Although most sea vessels can penetrate fog using radar, road vehicles have to travel slowly and use low-beam headlights. Localised fog is especially dangerous, as drivers can be caught by surprise.

At airports, some attempts have been made to develop methods (such as using heating or spraying salt particles) to aid fog dispersal. These methods enjoy some success at temperatures below freezing.

Accidents

Fog contributes to accidents, particularly with modes of transportation. Ships, trains, cars and planes cannot see each other and collide. Notable examples of accidents due to fog include the July 28, 1945 crash of a B-25 Mitchell into the Empire State Building, and the July 25, 1956 collision of the ocean liners the SS Andrea Doria and MS Stockholm.

The worst accident in aviation history occurred in the fog when 2 Boeing 747s collided in 1977 in Tenerife. One 747 had clearance to taxi down a foggy runway and the other could not see any distance down the runway when the captain decided to take off without proper clearance.

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Posted in Environment, Urban Studies | 7 Comments