Water, Climate and Disasters

Most of the impacts from climate change are water based: More drought and more flooding; less ice and snow; rising sea levels; more cases of violent and sporadic rainfall. Recent climate research shows that the effects on the hydrological cycle are likely to be more serious than thought before. Over the next half century, current IPCC projections of rising temperatures and sea levels and increased intensity of droughts and storms will mean huge numbers of people, particularly in coastal zones, will be displaced. Impacts are already being felt and the poor are hit hardest.

A recent report projects that by 2030, worldwide deaths will reach almost 500,000 per year, people affected by climate change annually could rise to over 600 million and the total annual economic losses from climate change impacts could be USD 300 billion (Global Humanitarian Forum 2009 ).

According to report findings, climate change adaptation efforts need to be scaled up by a factor of 100 in developing countries, which account for 99 percent of casualties due to climate change. The populations most gravely at risk are over half a billion people in some of the poorest areas that are also highly prone to climate change – in particular, the semi-arid dry land belt countries from the Sahara to the Middle East and Central Asia, sub-Saharan Africa, South and South East Asia, and small island developing states (ibid).

Floods and droughts

Almost two billion people were affected by natural disasters in the last decade of the 20th century, 86 percent of them by floods and droughts (WHO, 2004). Flooding increases the threat from contamination of drinking-water systems from inadequate sanitation, with industrial waste and by refuse dumps (WHO 2004). In the Zambezi river, which supports 32 million people in Angola, Zambia, Botswana, Namibia, Zimbabwe and Mozambique, climate change is blamed for an increase in rainfall and flooding. Already in 2009, the Nambian government declared flooding a national disaster. 100 have died, 55,000 displaced and 350,000 lost their livelihoods (UNDP 2009). Flooding in Angola left 222,000 families homeless (UN-OCHA 2009). 

The Ganges-Brahmaputra-Meghna (GBM) Basin, with 540 million people – many among the world’s poorest - shared by Bangladesh, Bhutan, China, India, and Nepal, faces risks from both melting mountains and increasingly intense monsoons: 70 million people in India and Bangladesh were seriously affected by the 2007 monsoon, 4,500 were killed, and 75,000 km2 of cropland were destroyed; there are probably many climate migrants leaving the basin today to mitigate risks (World Bank, 2008).

A global average temperature increase of 3-4°C, could cause floods resulting in 330 million climate refugees (UNDP Human Development Report 2007/2008). Changed run-off patterns that could result from that warming would likely push an additional 1.8 billion people to live in water scarce areas by 2080 (ibid).

Melting snow and ice

As the climate warms, snow and ice melt faster with profound impacts on rivers downstream. Initially, increased melting rates increases river discharge, which can cause flooding. With time glaciers shrink, discharge hits a new equilibrium water supplies for communities downstream decreases, particularly during the dry season. Snow and ice in the Greater Himalayan region are the direct water towers for 150 million people, and drain into ten of the largest rivers in Asia, whose basins support 1.3 billion people (ICIMOD 2008). In the Hindu Kush range, changes in the river ecosystem resulting from decline in the glaciers and perennial snow can already be seen. Historically, high level discharge in rivers lasted throughout the cropping season, from April – September. Now it has shifted into shorter, more intense run off in April and May, leaving most of the cropping season relatively dry. It is likely that dry seasons will continue to become drier and wet seasons wetter, which in turn could mean larger and more frequent rain storms, flash floods and landslides (ibid).

Rising sea levels

Water bodies expand when they are heated. Global warming is causing the oceans to expand and therefore rise. The global ocean surface temperature for June 2009 was the warmest on record 0.59 degree C above the 20th century average of 16.4 C (NOAA 2009). Global average sea level rose at an average rate of 1.8 mm per year over 1961 to 2003, but the rate was faster over 1993 to 2003 at about 3.1 mm per year (IPCC 2007). Melting glaciers and mountain ice caps also add to sea-level rise. The IPCC estimated in 2007 that sea levels may rise 20-60 cm by 2100, but noted that this included little input from the melting of ice sheets in Greenland and Antarctica. The ice sheets of Greenland and Antarctica represent the most dramatic threat to sea level rise, if melted completely sea levels could rise 7 metres and 62 metres respectively (IPCC 3rd Assessment, Synthesis Report, Summary for Policy Makers). Rising oceans contaminate surface and underground freshwater with salt water and flood low-lying and coastal areas. It is estimated that a one-metre sea-level rise could flood 17 percent of Bangladesh  and leave tens of millions without homes. More than 70 percent of the world's population lives on coastal plains, and 11 of the world's 15 largest cities are on the coast or estuaries (Greenpeace 2009) making vulnerability to dramatic sea level rise widespread.