A. Operational Definition
The term flood refers to an excess accumulation of water across a land surface, which results when water rises or flows over land not normally submerged.
(Tyndall Centre for Climate Change Research, 2004).This phenomenon occurs most commonly when natural watercourses do not have the capacity to convey excess water from heavy rainfall as is the case in monsoon areas. They can also result from other phenomenon such as intense thunderstorms, tsunamis, earthquakes, volcanic eruptions as well as dam breakage and snowmelt.
Flood events materialize from the accumulation of rainwater in poorly-drained environments, as slow-onset riverine floods, rapid-onset flash floods, and as coastal floods caused by tidal and wave extremes. Inland and coastal flooding may also be associated with windstorm events. Floods also vary greatly in magnitude and impact, velocity of flow and speed of onset, spatial extent, duration and seasonality. The risk of flooding depends on the intensity and duration of rainfall, the capacity of the watercourses to convey runoff, and the saturation of soil.
A flood event that has severe consequences (variously defined) may be termed a flood disaster, and the human impact of flood disasters is concentrated disproportionately in developing countries. Floods are natural phenomena which can induce both positive and negative effects. On the positive side, floods irrigate ecosystems suffering from prolonged drought and help in fertilizing nutrient deficient soil. Conversely, as a natural disaster floods endanger mankind and cause damage worth millions of dollars every year to buildings, infrastructure and businesses, destroys agricultural land and crops, and affects the health of communities.
Several measures are being advocated and implemented to protect land and communities from floods including the recreation of the natural course of rivers, the building of dams and hazard conscious usage of flood-prone land.
Location map, year 2007
Major Floods reported by news services and satellite data observation Updated January 5, 2008 Base image from NASA/JPL
B. Intensity and Frequency and Relationship to Climate Change
Over the years, warning systems, dams and levees have been immensely improved to enhance protection against floods. However, some protective measure can only be achieved at great cost and often at the expense of agricultural productivity thereby limiting the productive use of flood-prone land, which poses a problem especially in poorer, developing countries. Though protective measures have evolved, the number of floods, their devastating strength as well as the loss of life continue to steadily increase.
While it remains unclear whether frequency is related to climate change, there is however more evidence emerging on the risks of inland and coastal flooding. (Tyndall Centre for Climate Change Research, 2004) Information on trends in recent flood events is inconclusive, but global trends in sea level and temperature now provide strong evidence connecting floods to climate change. The weight of international scientific opinion has swung decisively towards the perspective that a process of anthropogenically-forced global climate change is now under way, over and above normal climatic variability. Over the next 100 years, the annual average of global near-surface temperatures are predicted to rise between 1.4°C and 5.8°C causing an increase in flood hazards in some areas due to sea level rises, changes in seasonal precipitation and the pattern of wind storms. The Intergovernmental Panel on Climate Change (IPCC) thus predicts that climate change is likely to cause an increase in flood hazards in many areas of the world especially in low-lying coastal sites or in zones that currently experience heavy rainfall.
One of the problems for attributing a causal link between flood trends and climate change is that flood dynamics may have multiple social, technical and environmental drivers. For instance, alterations in land cover and urbanization influence the water absorption capacities of land surfaces, thereby exacerbating potential flooding from heavy rainfall. Moreover, the loss of wetlands, population growth and settlement pattern combine to form cumulative trends in land use change that might be associated with flood trends at a regional and global scale. (Tyndall Centre for Climate Change Research, 2004)
(Tyndall Centre for Climate Change Research, 2004).This phenomenon occurs most commonly when natural watercourses do not have the capacity to convey excess water from heavy rainfall as is the case in monsoon areas. They can also result from other phenomenon such as intense thunderstorms, tsunamis, earthquakes, volcanic eruptions as well as dam breakage and snowmelt.
Flood events materialize from the accumulation of rainwater in poorly-drained environments, as slow-onset riverine floods, rapid-onset flash floods, and as coastal floods caused by tidal and wave extremes. Inland and coastal flooding may also be associated with windstorm events. Floods also vary greatly in magnitude and impact, velocity of flow and speed of onset, spatial extent, duration and seasonality. The risk of flooding depends on the intensity and duration of rainfall, the capacity of the watercourses to convey runoff, and the saturation of soil.
A flood event that has severe consequences (variously defined) may be termed a flood disaster, and the human impact of flood disasters is concentrated disproportionately in developing countries. Floods are natural phenomena which can induce both positive and negative effects. On the positive side, floods irrigate ecosystems suffering from prolonged drought and help in fertilizing nutrient deficient soil. Conversely, as a natural disaster floods endanger mankind and cause damage worth millions of dollars every year to buildings, infrastructure and businesses, destroys agricultural land and crops, and affects the health of communities.
Several measures are being advocated and implemented to protect land and communities from floods including the recreation of the natural course of rivers, the building of dams and hazard conscious usage of flood-prone land.
Location map, year 2007Major Floods reported by news services and satellite data observation Updated January 5, 2008 Base image from NASA/JPL
B. Intensity and Frequency and Relationship to Climate Change
Over the years, warning systems, dams and levees have been immensely improved to enhance protection against floods. However, some protective measure can only be achieved at great cost and often at the expense of agricultural productivity thereby limiting the productive use of flood-prone land, which poses a problem especially in poorer, developing countries. Though protective measures have evolved, the number of floods, their devastating strength as well as the loss of life continue to steadily increase.
While it remains unclear whether frequency is related to climate change, there is however more evidence emerging on the risks of inland and coastal flooding. (Tyndall Centre for Climate Change Research, 2004) Information on trends in recent flood events is inconclusive, but global trends in sea level and temperature now provide strong evidence connecting floods to climate change. The weight of international scientific opinion has swung decisively towards the perspective that a process of anthropogenically-forced global climate change is now under way, over and above normal climatic variability. Over the next 100 years, the annual average of global near-surface temperatures are predicted to rise between 1.4°C and 5.8°C causing an increase in flood hazards in some areas due to sea level rises, changes in seasonal precipitation and the pattern of wind storms. The Intergovernmental Panel on Climate Change (IPCC) thus predicts that climate change is likely to cause an increase in flood hazards in many areas of the world especially in low-lying coastal sites or in zones that currently experience heavy rainfall.
One of the problems for attributing a causal link between flood trends and climate change is that flood dynamics may have multiple social, technical and environmental drivers. For instance, alterations in land cover and urbanization influence the water absorption capacities of land surfaces, thereby exacerbating potential flooding from heavy rainfall. Moreover, the loss of wetlands, population growth and settlement pattern combine to form cumulative trends in land use change that might be associated with flood trends at a regional and global scale. (Tyndall Centre for Climate Change Research, 2004)
References
1. Floods, health and climate change: a strategic review“, Tyndall Centre for Climate Change Research, working paper 63, 2004Olbernhau: The Flood 2002 in Germany
1 comentarios:
"but global trends in sea level and temperature now provide strong evidence connecting floods to climate change." You should quote that evidence, because global temperature is currently static or falling, sea level is not accelerating.
Climate models cannot predict, they only offer projections. Those projections are based on the inputs used, which are subject to personal interpretation, for example clouds cannot be modelled properly. The sign of feedbacks is not known with great accuracy so that they can be either negative or positive.
The lack of knowledge was highlighted by this paper from the Hadley Centre:
Stabilising climate to avoid dangerous climate change — a summary of relevant research at the Hadley Centre January 2005
What constitutes ‘dangerous’ climate change, in the context of the UN Framework Convention on Climate Change, remains open to debate.
Once we decide what degree of (for example) temperature rise the world can tolerate, (how would they know?) we then have to estimate what greenhouse gas concentrations in the atmosphere should be limited to, and how quickly they should be allowed to change.
These are very uncertain because we do not know exactly how the climate system responds to greenhouse gases. (What an admission!)
The next stage is to calculate what emissions of greenhouse gases would be allowable, in order to keep below the limit of greenhouse gas concentrations.
This is even more uncertain, thanks to our imperfect understanding of the carbon cycle (and chemical cycles) and how this feeds back into the climate system.
(an even greater admission!!)
You should state whether by "climate change" you mean a naturally changing climate, or a proxy for Anthropogenic Global Warming, in which cold events can be attributed to global warming. This was suggested by the Tyndall Centre in 2004:
"The Social Simulation of the Public Perception of Weather Events and their Effect upon the Development of Belief in Anthropogenic Climate Change" September 2004.
To endorse policy change people must ‘believe’ that global warming will become a reality some time in the future.
Only the experience of positive temperature anomalies will be registered as indication of change if the issue is framed as global warming.
Both positive and negative temperature anomalies will be registered in experience as indication of change if the issue is framed as climate change.
We propose that in those countries where climate change has become the predominant popular term for the phenomenon, unseasonably cold temperatures, for example, are also interpreted to reflect climate change/global warming.
Social engineering at work which has been highly effective in selling an agenda.
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