The Earth's climate has changed throughout history. Because glaciers are so sensitive to temperature fluctuations and provide clues about the effects of global warming. 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.
Evidence for rapid climate change
According to NASA followings points shows the evidence for rapid climate change:
Global temperature rise: The earth's average surface temperature has risen about 1.1 degrees Celsius since the late 19th century.
Warming oceans: Ocean showing warming of 0.302 degrees Fahrenheit since 1969
Shrinking ice glaciers: Greenland and Antarctic ice sheets have decreased in mass.
Rise in sea level : Global sea level rose about 8 inches in the last century.
Extreme events: The number of record high temperature events like heavy rainfall, floods etc
Ice cores from glaciers are like fossils of ancient Earth's weather patterns. A glacier is a large mass of ice formed by compaction and re-crystallisation of snow, moving slowly by creep down slope, due to the stress of its own weight, and surviving from year to year. The flow movement, irrespective of whether it is a few centimetres a day or, as in the case of surging glaciers, tens of metres a day, differentiates a glacier from a dead ice body.
How Glaciers formed
Glaciers are massive and incredibly powerful, but they begin with small snowflakes. A glacier is basically an accumulation of snow that lasts for more than a year. In the first year, this pile of snow is called a névé. Once the snow stays around for more than one winter, it's called a firn. Every year new layers of snow bury and compress the previous layers. This compression turns the snow to ice. The compression of the glacier continues for several years which compressed most of air out of it and they looks blue in colour. For most glaciers, this process takes more than a hundred years.
An assessment of about 200,000 glaciers in the world, some of which have been monitored since the mid 19th century, has found that about two thirds of the current rate of glacial melting is due to human influences on the climate. The planet's average surface temperature has risen about 2.0 degrees Fahrenheit (1.1 degrees Celsius) since the late 19th century. Global warming is the rise in average global temperature that has happened over the past century. The 'industrial revolution' is the main cause of this rise in average temperature.
Effect of climate change in Indian glaciers
The youngest and highest Himalayan mountains sustain enormous fresh water reservoirs in the form of snow, glaciers, natural lakes, permafrost and wetlands, and support a population of ~1.3 billion. In fact, the Hindu Kush-Himalaya (HKH) harbors ~50% (by area) of all the glaciers. Himalaya and Karakoram (H-K), mostly based on historic data, vary between 43,178 km2 and 49,650 km2. The climate in H-K is strongly influenced by the varying dominance of the Asian monsoon and winds from the west. Monsoon-affected glaciers are more sensitive to temperature change than winter-accumulation–type glaciers because the temperature increase directly reduces solid precipitation (i.e., snow accumulation) and extends the melting period. Loss rates have probably accelerated in recent decades, but the observed tendencies are not regionally uniform.
According to study published in the international general Annals of Glaciology has been done by Anil V Kulkarni of the Indian Institute of Sciences, Bangalore. Kulkarni was previously with India Space Research Organisation (ISRO) and headed its glacier monitoring unit. Behaviour of glaciers in the wake of climate change as the overall spread of the glaciers may not fall but water content may go down.
The Chandra basin lost 11.1 gega-tonnes of water from 1984-2012, which is about one-fifth of the estimated volume. However, the loss in smaller and low altitude glaciers was about 67% during the period, the study found.
Kulkarni, in another study, had said that Himalayan glaciers have retreated by about 13% in last four decades with the water loss increasing from 9 gega-tonnes per year in 1975-1985 to 20 GT/year in 2010-2015 period.
According to study published by G B Pant Institute of Himalayan Environment and Development Ministry of Environment and Forests (MoEF) that from mid 1970s to 2011 have revealed the following interesting findings related to the glaciers in the Indian Himalayas:
1. Glacier melt contributes to about 25 per cent to 30 per cent of the total discharge of glacier ice. Maximum discharge takes place from mid-July to mid-August.
2. About 30 tonnes of ice melt per day per square km² during the melt season.
3. Smaller glaciers in the Himalayas - less than 5km long - exhibit an ice thickness of the order of 250 m in the cirque region, and an ice thickness of the order of 40-60m along the middle regions.
4. Sonapani glacier has retreated by about 500m during the last one hundred years. On the other hand, Kangriz glacier has practically not retreated even an inch in the same period.
5. Glacier movements are primarily due to climate and snowfall, snout movements appear to be peculiar to each particular glacier
Over long periods, glacial response to climate change becomes obvious as glaciers retreat and, in some cases, disappear.
Source: indiawaterportal.org, How stuff Works, Bolch et al 2012. VOL 336 SCIENCE www.sciencemag.org, hindustantimes.com, independent.co.uk, helpsavenature.com, NASA