Sunny skies and mild temperatures are a trademark of San Diego, which help make its tourism industry the third largest in the country — amounting to nearly $9.9 billion annually, which translates to a regional impact of over $16 billion generated for the economy, according to the San Diego Tourism Authority.But San Diego is about to experience too much of a good thing as climate change drives up regional temperatures.Over the next 40 years, global temperatures could increase twice as fast as they have in the last 40, and southern California temperature increases likely will follow this trend, according to UC San Diego. Rising temperatures pose significant challenges for the region’s residents, businesses and communities that are accustomed to a mild Mediterranean climate. Hotter temperatures will negatively affect San Diego’s heat-exposed industries — including construction, agriculture and transportation — threatening $32 billion and 220,000 workers in the local economy, according to two new reports on health (PDF) and water (PDF) by The San Diego Foundation, in partnership with Climate Education Partners