El Nino is far more than a transient weather event; it is a silent killer that shortens lives and drains economies, potentially causing cumulative economic losses of US$250 billion (HK$1.95 trillion) to US$300 billion in Hong Kong over the 21st century, according to a study jointly led by professor Benjamin Horton, dean of the School of Energy and Environment at City University, and researchers from Nanyang Technological University in Singapore.