RISING GHG EMISSIONS
Global warming is caused by emissions of CO2 and other greenhouse gases. In 2009 the atmospheric concentrations of CO2 reached 385 ppm (1). This is higher than the natural range over the last 650,000 years (2).
If no measures are taken, the global greenhouse gas emissions are expected to nearly double by 2050. This will lead to dangerous global
warming (3,4).
Achievement of necessary cuts in anthropogenic greenhouse gas emissions represents an unprecedented global challenge.
The fourth assessment report from the IPCC states that long-term unmitigated global warming is "likely to exceed the capacity of natural, managed and human systems to adapt"(2). A global warming of the climate system is described as "unequivocal". Most of the increase in temperature is classified as "very likely due to the observed increase in anthropogenic GHG-concentrations". Emissions of the most important GHG, CO2, grew by approximately 80 percent between 1970 and 2004.
The consequences of global warming will be many, and they will be intricate. Despite regional differences, it is stated with confidence that the negative impacts of climate change on freshwater systems outweigh the benefits (2). Higher water temperatures and changes in weather extremes, including floods and droughts, are projected to affect water quality and exacerbate many forms of water pollution (5).
Rising sea-levels are projected to extend areas of salinization of groundwater and estuaries. The result will be a decrease of freshwater availability in coastal areas. By 2050, it is predicted that the areas experiencing negative effects on water supplies will be twice as large as the areas positively affected (2).
References:
1) Earth Systems Research Laboratory (ESRL) / National Oceanic and Atmospheric Administration (NOAA): co2now.org
2) Intergovernmental Panel on Climate Change (2007): Climate Change 2007. Synthesis report.
3) International Energy Agency (2006): Energy Technology Perspectives 2006. International Energy Agency report.
4) Intergovernmental Panel on Climate Change (2000): IPPC Special Report – Emission Scenarios.
5) Intergovernmental Panel on Climate Change (2008): Climate Change and Water. Technical Paper of the Intergovernmental Panel on Climate Change. B. C. Bates, Z.W. Kundzewicz, S. Wu and J.P. Palutikof.