Written by Jalia Carlton-Carew

In politics, the legitimacy of climate change is frequently debated among politicians though scientific research proves the phenomenon to be very real. Dr. Leila Carvalho, a professor in the Department of Geography at UCSB, researches climate variability in monsoon regions. Large seasonal winds produced by changes in atmospheric pressure and precipitation patterns are called monsoons. Monsoons often bring to mind intense rain storms, but equally intense dry spells can also result from a monsoon. Dry and cool air from the winter season forms a dry monsoonal wind. Monsoonal winds occur when the ocean’s temperature greatly differs from the temperature on land. Due to water’s high heat capacity, the temperature variations are far more notable on land than in the ocean. During the summer season, the intensity from the sun’s rays causes land temperatures to increase. The warm air, created by the warm surface, rises and generates low air pressure. Furthermore, the cool air, above the ocean’s cool surface, falls but remains at high pressure. The moisture formed from the ocean and land’s circulating air pressure eventually leads to precipitation. Monsoons are found in numerous regions such as Asia, India, Australia, Africa and the Americas.

Carvalho, a native to South America, studies variations and extremes in the region’s climate. One important factor that influences climate change is the natural resource needs of their growing population. Tropical South America has experienced rapid increase in temperature in recent years. The increase in anthropogenic greenhouse gases and land-use and change are among the most important factors responsible for this rapid warming. The replacement of forest by pastures have major impacts on the release of greenhouse gases into the atmosphere which contribute towards climate change. São Paulo, a heavily populated city in Brazil, is vulnerable to these environmental changes. High temperatures and variability in rainfall cause São Paulo to experience intense dry weather. “In the years of 2013 through 2015, there was an extreme drought in São Paulo,” Carvalho says. As a response to the drought, residents in São Paulo would experience water cutoffs repeatedly. The shortage in available water forced the government to use the city’s emergency reserves. Access to water was only available at odd times of the morning and remained blocked throughout the day. Overtime, these inconveniences created tensions among neighbors and led to fights over water access. Additionally, the inadequate storage of water by the population increased dramatically mosquito-borne diseases such as dengue in the city.

If the precipitation patterns in South America are not taken into consideration, then more water shortages will occur in the future. Among the most consistent projections of climate change in South America by the end of the 21st century is the intensification of dry conditions over Eastern Brazil, whereas wet conditions would prevail over subtropical areas. Dr. Carvalho along with her students have shown additional evidence that these changes are already occurring and influencing the frequency and intensity of extreme events (drought and floods) in populated areas of South America. Carvalho predicts that, “In the future, a large percentage of the South American population will experience dry conditions because of the movement of precipitation.” Carvalho believes that “decision-makers need to understand this better.” Studying the patterns of precipitation will help politicians implement preferable water management practices for the people. “Precipitation is the most difficult variable to measure because it is not constant in time,” Carvalho concludes. To protect South Americans from experiencing such unfavorable circumstances again politicians will need to invest in improved data coverage and better environmental policy to support sustainable agriculture and land-use.

A few of Carvalho’s students study weather variability in the subtropical region of South America and in the Andes mountains. Most recently, Carvalho has started a project that studies fire weather regimes in Santa Barbara. One of Carvalho’s students will join the project with their research on the gusty winds in the Santa Barbara area.