are a number of online resources about climate forces that relate
to centennial time scale as well as climate events that have occurred
during the past 100 years.
Pacific Decadal Oscillation
Pacific Decadal Oscillation (PDO) Overview of PDO from the University
Pacific Decadal Oscillation (PDO) from NASA/JPL
Pacific Decadal Climate Variability Since AD 1661 from
NOAA Paleoclimatology Program- Biondi, et. al.
on PDO by Mantua for more.
North Atlantic Oscillation
Earth Observatory NAO website provides an overview of research
being conducted on NAO.
Floods in the United States During the 20th Century from USGS.
Global Warming &
Global Climate Change Researcher_Explorer offers a variety
of tools and tutorials on data analysis.
Global Warming Website contains a wealth of information
on the human dimension to climate change and anthropogenic forcing.
Often Does a 100 Year Flood Occur?
of 1938 flood on South Boulder Creek from Denver Public Library.
talk about a "100 year flood" or a "500 year event,"
they don't actually mean that the event-- whether it is a flood
or a severe storm-- will happen once every 100 years or 500 years.
Rather, it is a statistical way of expressing the probability
of something happening in any given year.
year" storm event has a one in one hundred or 1% chance of
happening in any given year. A "500 year" event has
a one in five hundred or .2% chance of happening in any year.
In the United States, the Federal Emergency Management Agency,
FEMA has established
the Federal Flood Insurance Program to protect homeowners and
businesses against the risk of floods that cause billions of dollar
of damage every year. Flood maps have been developed for communities
throughout the nation indicating where the "100 year"
and "500 year" floodplains are located, and citizens
who live in the 100 year zone must pay flood insurance.
Paleoclimatic records may allow us to provide better calculations
of the probability of 100 year and 500 year events in the future.
But exactly how the flood zones are calculated can be a matter
of controversy since weather records of severe storms are limited
primarily to the past century, which may not be representative
of long-term climate patterns. Also, there are many variables
involved with surveying and mapping out where floods are likely
to occur and modeling the hydrology of a particular drainage.
Make your own Online Hazards Map, including flood maps from the