This study confirmed that temperatures have increased in the past few decades and that climate change will lead to more heat waves, a longer hot season, and stressful working temperatures in the future for Da Nang. The number of very hot days in which the heat index exceeds 34�C, the threshold currently set by Vietnam?s Ministry of Health at which indoor workers engaged in light, desk-based work, has been increasing in the past few decades, though the number of nights in which the heat index exceeded 28�C decreased. According to projections from multiple GCMs, each running a low (RCP 4.5) and high (RCP 8.5) emission scenario, climate change is highly likely to increase day and night ambient and heat index temperatures. In the future, average heat index temperatures during the day are likely to be ~35�C or higher in all seasons ? this will have a profound impact on human health and the labor productivity of Da Nang?s workers. The length of the hot season is likely to increase by two to three months a year by 2050.

A previous study by COHED revealed that awareness of precautions for dealing with heat stress remains low. Certain populations, such as women-headed households or the self-employed, are at particular risk of suffering from heat stress and lost labor under today?s climate conditions because they have fewer resources for taking time off in the middle of the day to rest or to invest in different cooling strategies like air conditioning (Dao et al. 2013). Construction workers, agricultural laborers, street vendors and fishermen (all outdoor workers), and indoor workers engaged in manufacturing or sewing, or those in poorly ventilated and constructed buildings will be particularly hard hit. Many workers currently have little bargaining power within the workplace to ask for cooling measures, breaks or protective clothing; without these things in the future, they will consistently be unable to meet the productivity demands of their employers.

As both day and night temperatures continue to climb due to climate change, as well as an increase in the area influenced by the city?s urban heat island effect due to development and land use change, passive cooling measures like opening windows or hanging wet sheets for evaporative cooling will become less effective. People will need air conditioning, at least at night, in order to recover from the impacts of heat stress they suffered while working during the day. Poorer populations that currently rely on such measures will be hit particularly hard by the projected increases in ambient and heat index temperatures. These populations, particularly if they are migrants, often rent cheap housing without adequate ventilation, active cooling measures like air conditioners, and little insulation. These buildings retain heat at night and, under future warmer nighttime temperatures, will not allow low-income laborers to recover from heat stress they experienced during the day. As health impacts mount due to climate change, and people find that their labor productivity decreases, particularly poor populations may find themselves locked into a poverty spiral.

At the same time, while air conditioning will become increasingly necessary to improve working conditions for indoor workers and for people at night, outdoor workers do not have this luxury. New strategies (beyond the scope of ISET?s research component) will need to be explored for helping to protect outdoor workers. Additional research also needs to be done to understand the potential impacts of increasing usage of air conditioners on Da Nang?s urban heat island. If more buildings are equipped with air conditioners, which generate a lot of heat, this will raise urban heat temperatures and increase the daytime and nighttime heat index in a manner that was beyond the scope of this study to investigate. Because of the urban heat island effect, augmented by increased air conditioning and automobile use, some pockets of Da Nang might locally be up to 10�C warmer than the city-averaged heat index. Outdoor workers in these pockets will be at significant risk of heat stroke and, possibly, death in the hot season if their localized heat index approaches 45 to 55�C and their employers do not allow them to rest and take protective measures. Accounting for localized urban heat island effects in the heat index warnings issued by the responsible agency, and holding employers accountable for protecting workers? health, will become increasingly important.

COHED is working with a number of partners, including the Da Nang Preventative Medicine Centre and the Institute for Labour, Science and Social Affairs (MOLISA), to improve the capacity of low-income laborers in dealing with increasing temperatures under climate change. Measures to increase awareness among employers and laborers, as well as a range of adaptive measures, are needed to improve the capacities of Da Nang?s residents in dealing with increasing heat threats. COHED and other project partners will be using the heat index information generated from this study activity to inform their efforts on improving heat capacity in Da Nang. Keywords: Climate Modeling and Scenario Planning; Extreme Heat; Health; Social Vulnerability