Wednesday, December 26, 2012
Does the concept vary from season to season in the mind of the mass?
Dr. Nitish Priyadarshi
Total northern hemisphere is reeling under cold wave. Most part of the area is under thick cover of ice and snow. People are being killed due to severe cold waves. Lakes are freeze; leaves are drooping down due to the loads of the snow. Every where its white cover. Where there is no snow cold waves are showing impact on the population. Agriculture fields are under threat of frost bite. In India scores of people have been killed due to chilling wind and dropping of temperature. People like me are not able to understand whether we are moving towards global cooling or we are passing through major global warming period.
When ever I talk about global warming concept today people are confused. They ask questions, why you are talking about global warming when it’s too cold. They are not easily accepting the concept of warming in chilling cold. It’s totally opposite in peak warm season. People put question mark on global cooling. They easily accept the concept of global warming. Does the concept vary from season to season in the mind of the mass? Every body can’t have scientific concept. Their thinking on the global warming or global cooling vary from hot to cold and cold to hot season. Even the media avoid doing the story on global warming in winter season.
Now a day’s media is also playing a big role in floating the concept, causes and effect of global warming. When I was in school I never heard of any such words like global warming or global cooling. We use to enjoy every season without any thought or any fear of climate change.
Every time a year is fixed to show that till that date or year there will be major changes on Earth ecosystem due to increasing green houses gases or global warming. When the date passes without any major impact again other date is fixed.
It is not the question that how much we can believe on such predictions, but the question is can we predict the effects of global warming/cooling or climate change with accuracy? The way the increasing trend of global warming is shown or predicted, it seems that in coming 30 to 40 years earth will be totally devoid of any life and earth will die. I don’t think so.
Is really global warming is there or we are just exaggerating it? It is said that main cause of the global warming is due to increase in carbon dioxide level in the atmosphere.
Between 1940 and 1970, global temperatures went down slightly, even though carbon dioxide levels went up. This has been attributed to the cooling effect of sulphate aerosols.
Studies of ice cores show that carbon dioxide levels rise and fall with or after (as much as 1000 years) temperature variations. This argument assumes that current climate change can be expected to be similar to past climate change.Most computer models suggest that the globe will warm up 1.5 degree centigrade to 4.5 degree centigrade if carbon dioxide reaches the predicted level of 600 ppm by the 2050. Although this may be largely true, there are other possible mechanisms that could act in the opposite direction. For instance the sulphate aerosols-the tiny bit of dust that are also added to the atmosphere when fossil fuels are burned by human activity, may cool the climate. The aerosols reflect away the sun’s radiation. Thus, they partially counter the warming that may be caused by the greenhouse gases. However, the degree to which these emissions might reduce the impact of greenhouse gases is not yet fully understood.
Other theory says that, in the past million years, the Earth experienced a major ice age about every 100,000 years. Scientists have several theories to explain this glacial cycle, but new research suggests the primary driving force is all in how the planet leans.
The Earth's rotation axis is not perpendicular to the plane in which it orbits the Sun. It's offset by 23.5 degrees. This tilt, or obliquity, explains why we have seasons and why places above the Arctic Circle have 24-hour darkness in winter and constant sunlight in the summer. Tilt varies between 21.5 and 24.5 degrees over a cycle of roughly 41,000 years. The greater the tilt, the more the seasonal imbalance in heat delivery from the Sun and the less the chance of ice remaining through the summer in temperate climates. At present we are near a neutral point between the extremes of this oscillation of tilt, thus neither favouring nor promoting an ice age.
Scientists who assess the planet’s health see indisputable evidence that earth has been getting warmer, in some cases rapidly. Most believe that human activity, in particular the burning of fossil fuels and the resulting buildup of green house gases in the atmosphere, have influenced this warming trend. In the past decades scientists have documented record-high average annual surface temperatures and have been observing other signs of change all over the planet: in the distribution of ice, and in the salinity, levels, and temperatures of the oceans.
Everywhere on earth ice is changing. The famed snows of Kilimanjaro have melted more than 80 percent since 1912. Glaciers in the Garhwal Himalayas in India are retreating so fast that researchers believe that most central and eastern Himalayan could virtually disappear by 2035. Artic sea ice has thinned significantly over the fast half century, and its extent has declined by about 10 percent in the past 30 years.
This is one of the aspect of the global warming which most of scientists believe is man made. There is small minority of atmospheric and other scientists who disagree with this general scientific consensus. According to these scientists we still know too little about natural climate variables that could change the assessment (up or down). In addition, computer models used to predict climate change are improving but still are not reliable.
They also point out that some signs of global warming may not necessarily be caused by human activities. For example, while many glaciers are shrinking, others are growing. Also, glaciers shrink and grow naturally over long periods of time for reasons that are largely unknown.
Finally, they contend that global warming may be a lot less damaging than many people think and can be beneficial for some regions. For example, some countries may be able to increase crop productivity because of more rainfall and longer growing seasons.
They also claim that more carbon dioxide in the atmosphere could increase the rate of photosynthesis in areas with adequate amounts of water and other soil nutrients. This would remove more carbon dioxide from the atmosphere and help slow atmospheric warming.
The history of earth’s climate is characterized by change. Times of glaciations on the earth have been followed by warm intervals and the duration in years of both cold and warm intervals has varied by several orders of magnitude.
What ever may be the truth we have no options but we have to opt wait and watch theory.
Nature of the earth today is not fully understood. I am sure no one can say with accuracy what’s happening in the nature and also what’s going to happen in the future. It’s all the speculations and hypothesis.
Monday, December 17, 2012
By 2050, groundwater pumping will cause a global sea level rise of about 0.8 millimeters per year.
Dr. Nitish Priyadarshi
Slowly but surely, the sea level continues to rise. Recent research suggests this increase is also driven by the exploitation of underground water by humans that eventually flowed into the sea.Climate change, with its associated melting ice caps and shrinking glaciers, is the usual suspect when it comes to explaining rising sea levels. But a recent study now shows that human water use has a major impact on sea-level change that has been overlooked.
Science community was shocked by the claim that 42% of the sea-level rise of the past decades is due to groundwater pumping for irrigation purposes. What could this mean for the future – and is it true?
Global warming is melting glaciers and causing sea levels to rise. The volume of water is also expanding because of heat. This ‘thermal expansion’ contributes significantly to the surge in the sea levels. But there is yet another important reason for the rising sea levels, as a team of hydrologists led by Yadu Pokhrel from Rutgers University (USA) has discovered for the first time.
Experts had already identified a flaw in existing models. If one takes ice melting and the expansion of water because of higher temperatures into account the oceans should have risen by 1.1 mm per year in the second half of the 20th century. However in reality, they rose by 1.8 mm.
Groundwater makes up about twenty percent of the world's fresh water supply, which is about 0.61% of the entire world's water, including oceans and permanent ice. Global groundwater storage is roughly equal to the total amount of freshwater stored in the snow and ice pack, including the north and south poles. This makes it an important resource which can act as a natural storage that can buffer against shortages of surface water, as in during times of drought.
Most of the Earth’s liquid freshwater is found, not in lakes and rivers, but is stored underground in aquifers. Indeed, these aquifers provide a valuable base flow supplying water to rivers during periods of no rainfall. The contribution from groundwater is vital; perhaps as many as two billion people depend directly upon aquifers for drinking water, and 40 per cent of the world’s food is produced by irrigated agriculture that relies largely on groundwater.
During the last 30 to 40 years there has been an enormous rise in food production in many countries through the increased use of irrigation. Much of this irrigation water has been drawn from groundwater as people realise the advantages to increased productivity of timely irrigation and security of application.
Due to human usage, groundwater reaches the ocean through the sewage system and rivers as well as the hydrological cycle in the atmosphere- and contributes about 42 per cent of the rise in the sea levels.
Because of population growth and increased irrigation, ground and drinking water consumption has doubled over the last few decades.
A recent study from Yoshihide Wada and other researchers from Utrecht University attempted to assess the status of global groundwater depletion—that is, the amount of water that is being drawn out from underground reservoirs that is not being replaced by precipitation—and came up with some startling conclusions. Chief among them that depletion of groundwater may be contributing to as much as 25 percent of observed sea-level rise in recent years.
As people pump groundwater for irrigation, drinking water, and industrial uses, the water doesn’t just seep back into the ground — it also evaporates into the atmosphere, or runs off into rivers and canals, eventually emptying into the world’s oceans. This water adds up, and a new study calculates that by 2050, groundwater pumping will cause a global sea level rise of about 0.8 millimeters per year. Other than ice on land, the excessive groundwater extractions are fast becoming the most important terrestrial water contribution to sea level rise.Taking into account the seepage of groundwater back into the aquifers, as well as evaporation and runoff, the researchers estimated that groundwater pumping resulted in sea level rise of about 0.57 mm in 2000 — much greater than the 1900 annual sea level rise of 0.035 mm.
The amount of groundwater pumped out by Delhiites and others across northern India is highest in the world and is contributing as much as 5% to the total rise in sea levels.
A new study using satellite data has found that the region - a swathe of over 2,000km from west Pakistan to Bangladesh along north India - extracts a mind boggling 54 trillion litres from the ground every year, a figure that's likely to cause serious concern over the future of water availability.
Thursday, December 6, 2012
There is a general relationship between leaf shape and the climate.
Dr. Nitish Priyadarshi.
Fig.1 Leaf of tropical areas having drip tip for water run off.
How could the shape of plant leaves indicate temperature, you ask? Surprisingly, they do so very well. There is a general relationship between leaf shape and the climate. In 1978 Jack Wolfe, of the United States Geological Survey, put the relationship on a quantitative footing. Using data for present –day forests in eastern Asia, he showed that there is a remarkable correlation between the mean annual temperature and the shapes of the leaves. The particular features of leaves that seem to be most distinctive in this regard is the nature of the leaf margin. In tropical areas, where temperatures and precipitation are high, leaves tend to be large and have smooth edges, without serrations, and they often have a narrow, elongated tip-sometimes referred to as a drip tip (Fig.1.)- that facilitates water runoff. In contrast, leaves in cooler regions are typically smaller, narrower, and usually have jagged edges. In today’s forests these characteristics are specific to climatic conditions through out the globe.
Warmer leaf temperatures promote both photosynthesis and transpiration; thus, plants in drier climates tend to have smaller leaves to reduce evaporative cooling, while in more humid climates larger leaves are common because the attendant water cost is less critical (Givnish, 1984).
Since plants are stationary they must respond developmentally and ultimately evolutionarily, to their environment. As a result, it's not surprising that leaf morphology (shape) has been shown to be related to climate. For example, some the following correlations have been reported (a) leaf length is directly related to the mean annual temperature (MAT), (b) leaf area is directly correlated to both MAT and mean annual precipitation (MAP); and (c)leaf width is directly correlated with MAP. Thus, leaves are longer and larger in climates with warmer temperatures and higher rainfall.
Another interesting observation that was first reported more than 100 year ago is that woody deciduous plants having leaves with toothed margins (termed serrate) predominate in temperate climates while species with smooth (termed entire) leaf margins predominate in frigid (arctic) and tropical climates.
Givnish TJ. 1984. Leaf and canopy adaptations in tropical forests. In: Medina E, Mooney HA, Vasquez-Yanes C, eds. Physiological ecology of plants of the wet tropics. The Hague, the Netherlands: Dr. W. Junk Publishers, 51–84.
Macdougall,J.D. 1996. A short history of planet earth, mountains, mammals, fire, and ice. John Wiley & Sons, Inc. Canada.