Climate change means less water, less food

Climate
Climate change means less water, less food
By Joydeep Gupta, Apr 12, 2008 - 9:59:30 AM

New Delhi, April 12 - Rainfall in India and other tropical and sub-tropical countries has gone down from the 1970s due to global warming, says the Intergovernmental Panel on Climate Change -, predicting that food supplies will also go down in these regions.

Climate change means more evaporation of fresh water, changing rainfall patterns, reduced snow cover and widespread melting of ice and changes in soil moisture and runoff, all becoming highly probable, says the latest report by the UN body.

This would have 'wide-ranging consequences on human societies and ecosystems', says the IPCC, the organisation that shared the Nobel Peace Prize last year for its seminal fourth assessment report that has focussed world attention on the menace of climate change.

'Over the 20th century precipitation has mostly increased over land in high northern latitudes, while decreases have dominated from 10degreeS to 30degreeN since the 1970s.' Most of India falls in this range.

'Changes in water quantity and quality due to climate change are expected to affect food availability, stability, access and utilisation.

'This is expected to lead to decreasing food security and increased vulnerability of poor rural farmers, especially in the arid and semi-arid tropics and Asian and African mega-deltas,' says the report. The mega-deltas include those of the Ganges and the Indus.

'Globally, the area of land classified as very dry has more than doubled since the 1970s,' says the report released during a meeting of the IPCC in Hungary capital Budapest this week.

'There have been significant decreases in water storage in mountain glaciers and Northern Hemisphere snow cover,' the IPCC points out. The panel chaired by Rajendra K. Pachauri has over 2,500 scientists from all around the world, and over 7,000 reviewers of their work.

'Climate model simulations for the 21st century are consistent in projecting precipitation increases in high latitudes - and parts of the tropics, and decreases in some subtropical and lower mid-latitude regions -, the IPCC scientists warn.

'By the middle of the 21st century, annual average river runoff and water availability are projected to increase as a result of climate change at high latitudes and in some wet tropical areas, and decrease over some dry regions at mid-latitudes and in the dry tropics.'

The report says it is likely that the proportion of land surface in extreme drought at any one time will increase, in addition to a tendency for drying in continental interiors during summer, especially in the subtropics, low and mid-latitudes.

'Water supplies stored in glaciers and snow cover are projected to decline in the course of the century, thus reducing water availability - through a seasonal shift in stream flow, an increase in the ratio of winter to annual flows, and reductions in low flows - in regions supplied by melt water from major mountain ranges, where more than one-sixth of the world population currently lives,' the report predicts with a high level of confidence.

'Higher water temperatures and changes in extremes, including floods and droughts, are projected to affect water quality and exacerbate many forms of water pollution - from sediments, nutrients, dissolved organic carbon, pathogens, pesticides and salt - as well as thermal pollution, with possible negative impacts on ecosystems, human health, and water system reliability and operating costs.'

The scientists say 'sea-level rise is projected to extend areas of salinisation of groundwater and estuaries, resulting in a decrease of freshwater availability for humans and ecosystems in coastal areas.'

Even in areas that will see an increase in water supply due to climate change, 'this benefit is likely to be counterbalanced by the negative effects of increased precipitation variability and seasonal runoff shifts on water supply, water quality and flood risks,' says the report.

Climate change affects the function and operation of existing water infrastructure - including hydropower, structural flood defences, drainage, and irrigation systems - as well as water management practices.

Adverse effects of climate change on freshwater systems aggravate the impacts of other stresses, such as population growth, changing economic activity, land use change and urbanisation, the report points out.

'Current water management practices may not be robust enough to cope with the impacts of climate change on water supply reliability, flood risk, health, agriculture, energy and aquatic ecosystems.'

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