Global warming is brewing a dangerous combo: record-breaking high temperatures and high humidity levels. There has been a 16x surge in global population exposure to extreme, hazardous humid heat - wet bulb globe temperature (WBGT) above 33°C - between the 1950s and 2020s. India has registered a 19x increase, making it a global hotspot. Humid heat stress is about climate change, poor urban planning and the inability to value natural capital. This is a recipe that endangers economic growth and development gains.

Unchecked greenhouse gas emissions aren't the only factor accentuating humid heat stress in India. Particularly poor urban planning and congestion, and the transformation of natural tree canopies and urban water bodies into unplanned and runaway constructions of concretised real estate have converted cities and towns into serious heat traps. Studies on urban heat trends have found that poor planning and unplanned development can increase warming in cities by up to 60%, creating dangerous microclimates.

Humid heat stress is a health hazard. The cocktail of high temperatures and increased moisture in the air wreaks havoc on the human body's ability to cool itself. Entrapped heat puts proper functioning of vital organs at risk. Health impacts such as cardiovascular strains, impaired kidney functioning and heat strokes are disproportionately higher among young children and the elderly. Healthy working-age populations - and not just those working outdoors - are not spared, with their productivity impaired. A new Indian Institute of Tropical Meteorology and Gauhati University study shows that in the 1950s humid heat stress led to loss of 12 8-hour workdays in a year. That number has gone up to 65 workdays in the 2020s. For outdoor and informal sector workers, humid heat stress shaves off 9-10% of wages. It is a drag on the economy, estimated to put about 4.5% of GDP at risk by 2030. Tackling humid heat stress must move up the policy - and political - priority ladder, embedding measures that protect human health and productivity.