IS THE FREQUENCY OF EXTREME WEATHER INCREASING?

1. Are floods becoming more frequent?

2. Are hurricanes becoming more frequent and more powerful?

3. What sources might you use to find the best data to answer these questions? What measurements could be used to obtain the answers?

 

1. FLOODS

Global warming will change rainfall patterns and increase the number of severe storms. In the past 30 years, tropical cyclones have increased in their intensity and their duration (Emanuel, 2005). The frequency of severe storms has been increasing and many areas of the U.S., such as the eastern states, has received an increased amount of rainfall (Blatt, 2005). An increase in the number and severity of floods are expected. Many areas of the Northeast United States have experienced record flooding in recent years.

About 60% of the country of Bangladesh is less than 20 feet above sea level and is vulnerable to seasonal floods. On average, about 21% of Bangladesh is flooded per year with as much as 70% in severe floods. As a result of global warming, Africa will experience higher levels of desertification and additional droughts and floods. Asia will experience an increase in the number of tropical cyclones which will displace tens of millions of people (IPCC, 2001).

--after Gore, 2006

By the end of the 21st century, the rise in sea level is expected to impact the lives of millions of people. In the 21st century, the global temperature is predicted to increase between 1.4 and 5.8 degrees Celsius which would increase sea level somewhere between 9 and 88 centimeters (IPCC, 2001). An increase of 25 cm would have serious consequences on the delta regions of the Nile, Ganges, and Yangtze Rivers and would require the evacuation of many small island nations of the Indian Ocean and the Pacific. A one meter rise in sea level increase would flood many coastal areas, such as the beaches of the eastern United States. Florida, Louisiana, and North Carolina would be most affected; the Louisiana coast could lie 30 miles inland of its present location. A number of cities such as Venice, Bangkok, and Taipei would be threatened. Eighty percent of the Marshall Islands would be underwater. A one meter increase would flood up to 15% of the arable land in Egypt, 11% of the land of Bangladesh (where the floods of 1987-8 displaced millions of people), and require the raising of most of Miami's bridges and reconstruction costs to 1/3 of Miami's area. More than 100 million people would be displaced. Some coastal areas depend on underground freshwater aquifers (such Miami) which would be threatened by saltwater intrusion (IPCC, 1990; Mizra, 2002). More than one sixth of the global population receives a significant amount of their water supply from seasonal glacier and snow melt. Without this frozen water supply, many areas will pass more water on to oceans and have less for human use (Barnett, 2005).

2) HURRICANES

Warmer temperatures lead to increases in the number and severity of hurricanes. When the surface temperature of ocean water increases 1oF, the risk of hurricanes doubles. Forty five million Americans live in coastal areas vulnerable to hurricanes (Blatt, 2005). Recent years have seen an increase in the number of hurricanes and tropical storms. In 2003, three simultaneous hurricanes existed in different regions of the Caribbean and Atlantic; this was the first time such an event was observed. In 2004, a record number of hurricanes (four) hit Florida. In 2005, the hurricane season began earlier than ever before, ended later than ever before, and witnessed the greatest number of hurricanes and tropical storms (26 named storms including 3 which reached Category 5 strength). In 2005, hurricane Katrina (which was a Category 5 storm just before landfall) flooded New Orleans, costing more than 1,300 lives and $125 billion in damage.

3) OTHER EFFECTS

Changing weather patterns could increase the numbers of droughts, floods, and fires. At first, a little bit of global warming might not seem alarming. After all, many people would actually prefer to have a slightly warmer climate than what they currently experience. However, changes in global temperature would affect a number of aspects of the climate. Rainfall patterns could shift and this would affect the crops which could be grown in agricultural regions. This change will increase the ratio of rain to snow and significantly decrease the amount of runoff in the Northeast U.S (Huntington, 2003). California depends on melted snowfall for much of its water and warmer weather could increase the frequency of drought (as observed in the warm years 1990-1 when the snow pack had lost 15% volume and California experienced severe drought). In order to feed the ever growing world population, world rice production must increase at a rate of about 1% per year. Unfortunately, global warming (and, more specifically, increases in the minimum temperatures during the dry season) decrease the productivity of rice crops. It is estimated that for each increase in dry season minimum temperature of 1 degree Celsius, grain yield can decline by as much as 10% (Pen, 2004). In warmer seasons, destructive fires more common in the West and the Florida everglades. Areas of the southeastern United States have recently undergone the worst drought on record. In coastal areas, decreased rainfall has led to an increased salinity of coastal estuaries and other wetlands (Thomson, 2002).

 

--after Gore, 2006

An enormous area of Africa has been plagued by severe drought in recent decades.

GRAPH

--after Hulme, 1993

1. In reference to efforts to curb carbon dioxide emissions, those are those who feel that the cost is too great. What costs are associated with an increased number of hurricanes? An increased number of floods? Wildfires? Droughts?

2. At what point does the threat of severe weather outweigh concerns about the costs of greater efficiency? Who determines which costs determine policy?

 

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