The National Research Council has identified five climate changes of particular importance to infrastructure and factors that should be taken into consideration when designing future structures. These factors include increases in very hot days and heat waves, increases in Arctic temperatures, rising sea levels, increases in intense precipitation events, and increases in hurricane intensity. Heat waves affect communities that live in traditionally cooler areas because many of the homes are not equipped with air conditioning units. Rising sea levels can be devastating for poor countries situated near the ocean and in delta regions, which experience increasingly overwhelming storm damage. In parts of eastern Caribbean nations, almost 60 percent of the homes were constructed without any building regulations. Many of these endangered populations are also affected by an increase in flooding in locations that lack adequate drainage. In 1998, close to 200 million people were affected by flooding in China’s Yangtze River Valley; and in 2010, flooding in Pakistan affected 20 million people. These issues are made worse for people living in lower income areas and force them to relocate at a higher rate than other economic groups.