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Leftovers from Ice Age Glaciers can be found anywhere, in every continent. Even in Africa. But like you have seen in the previous page, they need some specific climatic conditions to exist—high rainfall in winter and cool temperatures in summer. So they are mainly concentrated in regions above the snow line. In mountainous areas or the polar regions. However, snow line occurs at different altitudes: in Washington State the snow line is around 1600 metres, while in Africa it is over 5100 metres, and in Antarctica it is at sea level. Glaciers, say scientists, are remnants from the last Ice Age, when ice covered nearly 32 percent of the land, and 30 percent of the oceans. What is an Ice Age? It occurs when the planet experiences ‘ice-cool’ temperature for long stretches of time. These periods last long enough to make polar ice reach down to lower latitudes. For example, during the last Ice Age, giant glacial ice sheets extended from the poles to cover most of Canada, all of New England, much of the upper Midwest, large areas of Alaska, most of Greenland, Iceland, Svalbard and other Arctic islands, Scandinavia, much of Great Britain and Ireland, and the northwestern part of the former Soviet Union.Within the past 750,000 years, scientists know that there have been eight Ice Age cycles. They are punctuated by warmer bouts—called interglacial periods. Currently, the Earth is nearing the end of an interglacial, meaning that another Ice Age is due in a few thousand years. This is part of the normal climate variation cycle. Frozen links…to past and futureBecause glaciers are so sensitive to changes in temperature, they are used as barometers by scientists. To study ‘paleocli-matic data’, that is, climatic conditions of the past ages. And to find vital clues to what may happen in the future.
To see a long-term climate record an ice core is drilled and extracted from the glacier. Ice cores are long cylinders that are carved out of ice sheets. Since each layer (consisting of dust, air, sediment particles) in the ice core corresponds to one year, the frozen archives tell us that there have been several Ice Ages. In this way, past eras can be reconstructed, showing how and why climate changed, and how it might change in the future. Ice cores have been taken from around the world, including Peru, Canada, Greenland, Antarctica, Europe, and Asia. Scientists have analysed various components of cores, particularly the trapped air bubbles. Just think about it. Glaciers actually preserve bits of atmosphere from thousands of years ago in these tiny air bubbles! Reaching the melting pointAbsolutely fascinating, right? The bad news is, if glaciers are the ‘crystal balls’ to read the future of global climate, they paint a horribly alarming picture for Planet Earth. Since the early 20 the century, with few exceptions, glaciers around the world have been shrinking at unprecedented rates. In fact, some ice caps, glaciers and even an ice shelf have disappeared altogether in this century. Many more are retreating so rapidly that they may vanish within a matter of decades.  What is Global Warming?What triggers this ‘Melt’? Build up of greenhouse gases (GHGs)—the major ones being carbon dioxide, methane and water vapour in atmos-phere, say scientists. They heat up the Earth like a garden green-house. The Earth’s surface temperature increases, glaciers melt as a result of the rising heat, and cause oceans to slowly creep up and swallow low-lying islands.Nature had, of course, provided an in-built solution to this problem. The Earth’s ecological sinks — its oceans and vege-tation— have the capacity to absorb the harmful gases. When GHG emissions exceed the cleansing capacity of these ‘carbon sinks’, global warming crosses its limit.And we have crossed this limit. Many times over. Cores drilled through a glacier in the high Tibetan Plateau reveal that the last 50 years were the warmest in 1,000 years."In the last 100 years alone, the global mean temperature has increased by about 0.5 to 1° C ... and the rapid receding of glaciers, to a major extent, is a consequence of global warming," says Jagdish Bahadur, a leading glaciologist and former joint advisor at the Department of Science and Technology, New Delhi.The cores say more. In the late 18 th Century, there were at least eight major droughts caused by a failure of the South Asian monsoon in this region (now a part of India). Then the dry spell lasted for seven years, and more than six hundred thousand people died here. In a similar situation, now, with a population of over six billion people, the scale of disaster would be far far higher.Scientists predict worse if concentrations of GHGs continue to build up in Earth’s atmosphere. In fact, the damages are evident already. "Glaciers in the Himalaya are receding faster than anywhere else, and if the present rate continues, the like-lihood of them disappearing by the year 2035 is very high," says the International Commission for Snow and Ice ( ICSI ) in its recent study on Asian glaciers. "But if the Earth keeps getting warmer at the current rate, it might happen much sooner," says Syed Iqbal Hasnain of the School of Environmental Sciences, Jawaharlal Nehru University, New Delhi. And the doomsday prophecies are coming true. Over the last 25 years, the Gangotri glacier has shrunk more than 850 metres, with a recession of 76 metres from 1996 to 1999 alone! Now let us consider how this melt down is going to affect the global climate: The most critical link between glaciers and climate is maintaining the earth’s water balance. In fact, glacier melt has contributed as much as 30 per cent of sea level change in the 20 th century. Alaska’s melting glaciers, sea ice, and a type of frozen soil called permafrost are adding an extra 0.3 millimetre an year to the depth of oceans. Between the 1950s and 1990s, Alaskan glaciers contributed only half that much water. If drastic steps are not taken, the world can expect sea levels to rise by 19-86 cm by 2100. This will spell doom for small island states and low-lying deltas like Bangladesh and Egypt. There will be dramatic changes in weather patterns. Storms and hurricanes will become more frequent. Threats of natural hazards, ranging from cloudbursts, avalanches, landslides, to glacial lake outburst floods (GLOFs), mudflows and earthquakes will intensify.
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