Opinion | 4 black rain days in a week show Hong Kong’s climate fight urgency

The past week has seen four incidences of black rain. On Tuesday, two separate warnings were issued before 9am, so parents were all working from home as kindergarten and holiday activities were cancelled, leaving the city much quieter than usual.

This quiet prompted me to ask three questions. Is this the usual bad weather or driven by climate change? If it is long-term change, what are the impacts and costs? And what are we doing about it?

According to the Hong Kong Observatory, annual rainfall is increasing slowly but occurring in much more intense periods. Black rainstorms are more frequent and intense, meaning more intense run-off. The most recent black rain warning was the second-longest on record, with the longest coming in 2023. Meanwhile, typhoons have increased noticeably in strength.

Why is this? There is a general agreement that the Earth’s climate is changing because of a combination of natural and human factors, including variation in sunlight, Earth’s orbital changes and volcanic activity. However, natural effects have been overshadowed by the increasing atmospheric concentration of greenhouse gases from human activity since the Industrial Revolution.

The Intergovernmental Panel on Climate Change (IPCC) has produced six assessment reports since 1990. As the science becomes clearer, each report is more certain, urgent and strident than the last. Human-induced climate change has become a major challenge of our time, and now it is on the streets of Hong Kong.