How Important is the Global Water Cycle for Climate?

Home / How Important is the Global Water Cycle for Climate?

Although we hear about it almost daily, how many of us really understand the nature of climate and how it functions?

Because it effects us all and the choices that we make effect it, then we all need to have a far greater understanding of what regulates climate and how it relates to our day-to-day lives. This would be much more productive than trying to adapt to the increasingly extreme weather conditions or waiting for governments to eventually make decisions that consider the long-term good of the many. An important point that is often missed out of climate change discussions is the fact that the water cycle and climate cycle are not two separate systems.
“Water is at the heart of both the causes and the effects of climate change (NRC, 1998)”    Download: USGCRP. A plan for a new science initiative on the global water cycle, chapter 1, 2001.pdf   

This may seem simple but unless climate and the water cycle are put in their right context side by side, efforts to address either water or climate problems will be seriously undermined.

The global water cycle and climate change need to be addressed together, recognising that anything that impacts upon the water cycle, also impacts upon climate and vice versa. For example – mass deforestation sets off a chain of reactions that destabilise the water cycle, which then have knock on effects upon climate systems. These effects can range from cyclones and hurricanes, to flooding and drought. Generally these alarming repercussions are looked at in isolation but it is only really by looking at the entire water cycle and climate system collectively that cohesive solutions can be applied.
“While attention thus far has focused on the impact of climate changes on the water cycle, the altered paradigm recommends concentrating attention on the impact of changes in the water cycle on climate changes.”   Download: M. Kravcík et al. Water for the Recovery of the Climate – A New Water Paradigm, 2007.pdf   
Up until recently the concept of climate included the global water cycle in its three phases of liquid, solid and gas. It was clearly understood that it was changes in this cycle, which were altering climate and the US Global Change Research Program, involving NASA was initiated in the 1990’s to gain greater understanding of the processes involved. In September 1999, as an essential element of this multi billion-dollar program, a water cycle study was initiated. This was with the aim of determining whether human induced changes were affecting the intensification of the water cycle and how this affected climate. One of their conclusions was that changes in land cover and land use can have significant, even drastic, impacts on the water cycle at local and regional scales. Seeing that massive deforestation programs have been happening globally, these impacts are also at international scales.
“To determine the net effect of water on climate, then the full cycle of evaporation, water vapour transport, cloud formation, precipitation, and run off must be considered as an integral system.”   Download: USGCRP. A plan for a new science initiative on the global water cycle, chapter 2, 2001.pdf   
Increased quantities of greenhouse gases in the upper atmosphere are widely recognised to be a major cause of the amplification of climate change. However water vapour is not often mentioned. This seems to be a great oversight because water vapour is the most abundant greenhouse gas in the atmosphere. According to studies it accounts for approximately 60% of the greenhouse effect. Whereas Carbon Dioxide accounts for approximately 26%. Therefore as the global water cycle becomes destabilised and there are larger quantities of water vapour in the atmosphere, it has a direct feedback effect on climate.

More attention needs to be given to the significant effects that water vapour greenhouse gas has in the atmosphere.

“For many, the term ‘climate’ refers to long-term weather statistics. However, more broadly and more accurately, the definition of climate is a system consisting of the atmosphere, hydrosphere, lithosphere, and biosphere. Physical, chemical and biological processes are involved in interactions among the components of the climate system. Vegetation, soil moisture, and glaciers, for example, are as much a part of the climate system as are temperature and precipitation.”   Download: Pielke. R. Sr, A broader view of the role of humans in the climate system, 2008.pdf   
Because of the complex interconnectivity between the water cycle, climate, ecosystems and other Earth systems, we cannot look at something like climate change in isolation from the various environmental elements, which regulate climate. There is a sound, scientific basis for the need to preserve essential life supporting ecosystems.
“The climate system is a complex, interactive system consisting of the atmosphere, land surface, snow and ice, oceans and other bodies of water, and living things.”   Download: IPPC. Historical Overview of Climate Change Science, 2001.pdf   

Trophic cascades give a clear and simple example of the connectivity that exists between biodiversity, ecosystems and Earth systems.

For too long now the essential connectivity between the global hydrological cycle, climate and human induced climate change has been sidelined in international climate talks and water conferences. Instead the idea put forwards at the International Conference on Water and the Environment held in Dublin in 1992, where it was stated that: “Water has an economic value in all its competing uses and should be recognized as an economic good.”, became the favoured approach.

However reducing the status of water to that of an economic good does not serve the fundamental needs of the majority of humanity nor the other living species on Earth.

Although water is the foundations and bedrock upon which all economies rest, viewing water in this way has allowed it to fall into the category of ‘valuable, limited commodity. This is bringing about the mass privatization of freshwater. It is now being treated as a marketable good that can be sold at any price, water companies wish to place upon it. In the meantime safeguarding the global water cycle and implementing effective solutions, which include preserving the ecosystems, which maintain it and dealing with rebalancing the quantities of atmospheric water vapour greenhouse gas, are being ignored.
“The Global Water Cycle is an integral part of the Earth/ Climate system; water vapor constitutes the Earth’s most abundant and important greenhouse gas”    Download: USGCRP, Draft White Paper, chapter 2, Strategic Plan for the Climate Change Science Program, 2002.pdf   
Because freshwater, as we know it, only exists as part of a three phase recycling process known as the hydrological cycle, then any group claiming ownership of it, should also be obliged to bear the responsibility of all it’s three phases. They would therefore be accountable for all damages brought about by its instability. This includes extreme weather events related to the intensification of the water cycle and the severe reduction in quantity of freshwater worldwide, linked with aquifer depletion and glacial melt.

Water privatisation is not a viable option when considering all the implications. It only distracts attention and resources away from re-stabilising the global water cycle.

“water resources management decisions have the potential to alter the climate system in ways that can affect predictability of water cycle components at all three time scales.”   Download: USGCRP, The Water Cycle Science Plan, Part 2, 2001.pdf   
If we truly wish to leave our children, grandchildren and future generations a world in which they can live in some kind of peace and harmony, which accords in any way whatsoever with the ideas of sustainability and human rights, then addressing human induced climate change needs to include the rebalancing of the hydrological cycle.
“The hydrological cycle influences climate in a variety of ways. The exchanges of moisture and heat between the atmosphere and the Earth’s surface fundamentally affect the dynamics and thermodynamics of the climate system. In the forms of vapour, clouds, liquid, snow and ice, as well as during phase transitions, water plays opposing roles in heating and cooling the environment.”    Download: Moustafa T Chahine, The Hydrological cycle and its influence on climate, 1992.pdf   
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