On Boxing Day – 26 December 2004, a 9.1-magnitude earthquake struck off the coast of Indonesia, unleashing a massive tsunami that swept across the Indian Ocean.

Waves as high as 51 meters (167 feet) inundated communities in Aceh, Indonesia, with flooding extending up to five kilometres (three miles) inland.

The devastation spread across Thailand, Sri Lanka, Maldives and India, with tsunami waves travelling at speeds of 800 kilometres per hour (500 miles per hour). The impacts extended to Somalia and Tanzania, and waves reached as far afield as Mexico, Chile and even the Arctic.

In addition to the lives lost, more than 1.7 million people were displaced, and the economic toll reached an estimated $10 billion. Children bore a particularly heavy toll, with thousands killed or orphaned.

A wake-up call for humanity

Philémon Yang, President of the UN General Assembly, described the tsunami as “the first global disaster of the 21st century and one of the most devastating in recent history.”

He urged nations to reaffirm their resolve to protect future generations and integrate disaster preparedness and resilience into sustainable development strategies.

Kamal Kishore, UN Special Representative for Disaster Risk Reduction, called the tsunami a “wake-up call for humanity”.

“It really showed us how such low-frequency, high-impact hazards, can have impacts that will ripple across the entire global system and across multiple geographies,” he said.

Progress through global collaboration

The tragedy also catalysed unprecedented global collaboration.

“Following the Indian Ocean tsunami in 2004, it was evident that transboundary problems require solutions that reach across borders,” emphasised Armida Salsiah Alisjahbana, the Executive Secretary of the UN Economic and Social Commission for Asia and the Pacific (ESCAP).

In the two decades since the tragedy, working together the international community has made significant strides in disaster preparedness.

In 2005, nations convened under the Intergovernmental Oceanographic Commission of UNESCO (IOC-UNESCO) to establish the Indian Ocean Tsunami Warning and Mitigation System (IOTWMS). Today, 27 national tsunami warning centers can issue alerts within minutes of seismic events.

Compared to just 25 per cent in 2004, over 75 per cent of coastal communities in high-risk areas now have access to tsunami early warning information, according to the UN Economic and Social Commission for Asia and the Pacific (ESCAP).

Furthermore, UN initiatives like the Tsunami Ready Programme and the Tsunami Project continue to empower local leaders and communities with life-saving knowledge and resources. Similarly, the Multi-Donor Trust Fund for Tsunami, Disaster and Climate Preparedness is developing vital early warning systems for all.

Climate change amplifying risks

However, challenges have also grown more complex.

Climate change is amplifying the frequency and severity of water-related disasters, often cascading with and compounding geophysical events like earthquakes and volcanoes.

ESCAP estimates that 68 million people in 43 Asian and Pacific countries, along with $2.3 trillion in infrastructure along coasts, remain at significant risk. In the Indian Ocean basin alone, over 2,600 educational facilities, 1,200 ports, and 140 power plants are vulnerable.

We must do more

Mr. Kishore underscored the need for sustained awareness and preparation.

“We have to continue to keep the awareness of Tsunami risk high,” he said.

“It is crucial that we do not forget the 2004 Indian Ocean tsunami, and continue to do everything we can to protect ourselves, our children and our future generations from the impact of future tsunamis.”

Indian Ocean tsunami: Survivors recall the fateful day