Nicole - Global warming’s effect on the world’s water supply

Global warming’s effect on the world’s water supply

Following the viewing of Al Gores presentation – An Inconvenient Truth my eyes have been well and truly opened and from the points he mentioned I became particularly concerned with possibly one of the most serious consequences of global warming – the change in the world’s water supply.  

If scientists’ models of global warming and climate change is correct, we can expect to see melting of the polar ice caps. Whether they are totally decimated or minimally reduced, the sea levels will definitely change.  Over the past century they have risen six to ten inches and are still rising. So far, this increase hasn’t affected any country’s water supply in any significant way but just a few more inches could possibly make a difference between an adequate water supply, water rationing or even a severe shortage of drinkable water.

As the sea levels rise, the fresh water sources such as rivers and streams that run into it will be absorbed by the salt water. Upstream, where the water is fresh, supplies will have been cut short by the encroaching ocean and as the earth’s surface temperature rises, reservoirs will evaporate more quickly and reserves will begin to be inadequate.

The increase of wildfires over the past five decades will also begin to have a devastating effect on the water supply. Hillsides and valleys absorb rain allowing the water to travel in to the natural freshwater supplies. As fires leave the lands bare and desolate, rain will rush down the hillsides towards the flat lands, causing flooding, ruining crops and affecting the habitat. Much of the fresh water will end up in the ocean, rendering it useless for consumption.

Research by scientists Tim Barnett, Jennifer Adam and Dennis Lettenmaier of the University of Washington, shows that human-produced greenhouse gases, and the resulting warmer climates they produce, will have a significant influence on ice and snow-dependent regions that will result in costly disruptions to water supply and resource management systems.  They argue that their predictions and observations "portend important issues for the water resources of a substantial fraction of the world's population."   According to the scientists, the forces driving these changes described as "greenhouse physics", show that in a warming climate more water will fall in the form of rain rather than snow, filling reservoirs to capacity earlier than normal. Additionally, a warming climate will result in snow melting earlier in the year than in previous decades, disrupting the traditional timing of water available from snow runoff streams. Together, they say, these changes mean less snow accumulation in the winter and earlier snow-derived water runoff in the spring, challenging the capacities of existing water reservoirs. According to Barnett, water shortages will occur in areas where reservoir capacity cannot hold the annual cycle of rain/snow.

Barnett and other scientists with the Accelerated Climate Prediction Initiative

extended their study to regions that heavily depend on glacier-derived water for their main dry season water supply and warn that in glacier dependent regions "once the glaciers have melted in a warmer world, there will be no replacement for the water they now provide."   For example Glacier-covered areas in Peru have experienced a 25 percent reduction in the past three decades, and the authors suggest that "at current rates some of the glaciers may disappear in a few decades, if not sooner."

A study by scientists from the University of British Columbia in Vancouver, Canada, published in the journal Nature: Geoscience, concludes that, globally, mountain glaciers and ice caps are projected to lose 15-27% of their volume by 2100, although the extent of the damage varies widely. The analysis suggests glaciers in the Alps and New Zealand will shrink by more than 70% but shrinkage is predicted to reach about 10% in Greenland and high-mountain Asia.  The researchers argue this will result in "substantial impacts" on regional water availability, as well as a rise in sea levels of 8.7-16.1cm by 2100.  This broadly confirms the range projected by the UN's climate change body, the Intergovernmental Panel for Climate Change (IPCC).

However total sea level rise could be considerably higher due to the effects of melting Greenland and Antarctic ice sheets – which make up more than 99% of the water on Earth bound up in glacier ice – and thermal expansion in the ocean.

The information I have read has certainly made me think.  It seems hard to disbelieve the evidence when it has been collected and analysed by so many professionals.  My thinking is that something is definitely affecting global warming and if this evidence is the most sound to date then we should perhaps act on it until somebody proves otherwise.  The reduction of CO2 emissions cannot do any harm to our world.  However, we do need to make far more people across all ages aware of the situation to ensure that we do our best to preserve our world.