Some scientists disagree with Global Warming Theory.

They say it is natural.

by

Dr. Nitish Priyadarshi

Rising temperature are already the clearest sign of climate change. So far, according to the IPCC, global average temperatures have risen 0.6⁰ C above the pre-industrial average. Nine of the hottest years on record have occurred since 1988; six of the first eight months of 1998 were the warmest since records began in 1866; and July 1998 was the hottest month ever.

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.

However recent studies cast doubt on such a generalization for two reasons. First, this effect would slow as the plants reach maturity and take up less carbon dioxide. Second, it is a temporary effect. When the plants die and are decomposed or burned, the carbon they stored is returned to the atmosphere as carbon dioxide.

Are we heading towards major disaster or it is a simply a natural shifting of climate as it happened in the geological past. During the last 2 billion years the Earth's climate has alternated between a "Ice House", like today's world, and a steaming "Hot House", like the world of the dinosaurs. Jurassic climate stayed warm and became more humid. The polar areas were ice-free during this Period.

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 if we don’t stop carbon emission recklessly. But it is also true that the climate of the earth is changing from the time of its birth from hot to cold and cold to hot. Earlier too the earth has passed through global warming due to natural causes, but this time we the humans are culprits for the changes. When man-made factors are added to the natural ones, the ecosystem may be damaged beyond repair.

Satellites Unlock Secret to Northern India's Vanishing Water.

Reviewed and Submitted by
Dr. Nitish Priyadarshi

As animated here, groundwater storage varied in northwestern India between 2002 and 2008, relative to the mean for the period. These deviations from the mean are expressed as the height of an equivalent layer of water, ranging from -12 cm (deep red) to 12 cm (dark blue). Credit: NASA/Trent Schindler and Matt Rodell.

The map, showing groundwater withdrawals as a percentage of groundwater recharge, is based on state-level estimates of annual withdrawals and recharge reported by India's Ministry of Water Resources. The three states included in this study are labeled. Credit: NASA/Matt Rodell

The map shows groundwater changes in India during 2002-08, with losses in red and gains in blue, based on GRACE satellite observations. The estimated rate of depletion of groundwater in northwestern India is 4.0 centimeters of water per year, equivalent to a water table decline of 33 centimeters per year. Increases in groundwater in southern India are due to recent above-average rainfall, whereas rain in northwestern India was close to normal during the study period. Credit: I. Velicogna/UC Irvine

WASHINGTON -- Using NASA satellite data, scientists have found that groundwater levels in northern India have been declining by as much as one foot per year over the past decade. Researchers concluded the loss is almost entirely due to human activity. More than 26 cubic miles of groundwater disappeared from aquifers in areas of Haryana, Punjab, Rajasthan and the nation's capitol territory of Delhi, between 2002 and 2008. This is enough water to fill Lake Mead, the largest manmade reservoir in the United States, three times. A team of hydrologists led by Matt Rodell of NASA's Goddard Space Flight Center in Greenbelt, Md., found that northern India's underground water supply is being pumped and consumed by human activities, such as irrigating cropland, and is draining aquifers faster than natural processes can replenish them. The results of this research were published today in Nature. The finding is based on data from NASA's Gravity Recovery and Climate Experiment (GRACE), a pair of satellites that sense changes in Earth's gravity field and associated mass distribution, including water masses stored above or below Earth's surface. As the twin satellites orbit 300 miles above Earth's surface, their positions change relative to each other in response to variations in the pull of gravity. Changes in underground water masses affect gravity enough to provide a signal that can be measured by the GRACE spacecraft. After accounting for other mass variations, such changes in gravity are translated into an equivalent change in water. "Using GRACE satellite observations, we can observe and monitor water storage changes in critical areas of the world, from one month to the next, without leaving our desks," said study co-author Isabella Velicogna of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the University of California, Irvine. Groundwater comes from the natural percolation of precipitation and other surface waters down through Earth’s soil and rock, accumulating in cavities and layers of porous rock, gravel, sand or clay. Groundwater levels respond slowly to changes in weather and can take months or years to replenish once pumped for irrigation or other uses. Data provided by India's Ministry of Water Resources to the NASA-funded researchers suggested groundwater use across India was exceeding natural replenishment, but the regional rate of depletion was unknown. Rodell and colleagues analyzed six years of monthly GRACE data for northern India to produce a time series of water storage changes beneath the land surface. "We don't know the absolute volume of water in the northern Indian aquifers, but GRACE provides strong evidence that current rates of water extraction are not sustainable," said Rodell. "The region has become dependent on irrigation to maximize agricultural productivity. If measures are not taken to ensure sustainable groundwater usage, the consequences for the 114 million residents of the region may include a collapse of agricultural output and severe shortages of potable water." Researchers examined data and models of soil moisture, lake and reservoir storage, vegetation and glaciers in the nearby Himalayas in order to confirm that the apparent groundwater trend was real. The loss is particularly alarming because it occurred when there were no unusual trends in rainfall. In fact, rainfall was slightly above normal for the period. The only influence they couldn't rule out was human. "For the first time, we can observe water use on land with no additional ground-based data collection," said co-author James Famiglietti of the University of California, Irvine. "This is critical because in many developing countries, where hydrological data are both sparse and hard to access, space-based methods provide perhaps the only opportunity to assess changes in fresh water availability across large regions." GRACE is a partnership between NASA and the German Aerospace Center, DLR. The University of Texas Center for Space Research in Austin has overall GRACE mission responsibility. GRACE was launched in 2002.

Article source:

http://www.nasa.gov/topics/earth/features/india_water.html