Record Sea Level Rise Threatens African Coastlines, Amplified by El Niño

Africa’s coastal regions are experiencing an accelerating rate of sea level rise, with a particularly dramatic surge linked to the 2023-2024 El Niño event. This poses a significant threat to coastal communities, infrastructure, and economies across the continent.

The Impact of the 2023-2024 El Niño

The 2023–2024 El Niño was the fifth-most powerful El Niño–Southern Oscillation event in recorded history [1]. Recent analysis of satellite altimetry data reveals that this El Niño produced the largest detrended sea level anomaly on record – 27 millimeters – exceeding even the 1997-1998 event [2]. This surge contributed to a global sea level rise of 2.3 centimeters (0.9 inches) between 2023 and 2024, representing 19% of the total increase observed since 1993 [3].

The most significant impacts have been observed in the western Indian Ocean and eastern central Atlantic Ocean. Over 70% of the sea level increase during this period was attributed to thermal expansion – the warming of ocean water – which was nearly four times greater than usual during the El Niño event [2].

Accelerating Trends in Sea Level Rise

While sea levels have been rising for decades due to global warming, the rate of increase is accelerating. The rate of rise has more than doubled from 0.06 inches per year during much of the 20th century to 0.14 inches per year from 2006 to 2015 [2]. A marked shift occurred around 2009, with the rate increasing from 2.7 millimeters (0.11 inches) per year to 4.7 mm (0.18 inches) per year [2]. The 2023-24 El Niño specifically caused a 27 mm (1.06 in) rise, a 41% increase compared to the 19.2 mm (0.76 in) rise during the 1997-98 El Niño [2].

Vulnerability of African Coastal Communities

Africa’s extensive coastline, stretching approximately 18,950 miles (30,500 km), is particularly vulnerable. The oceans surrounding the continent are warming and rising faster than the global average, putting over 200 million coastal residents and critical infrastructure at risk [3]. Major cities like Lagos, Nigeria, and Dar es Salaam, Tanzania, are especially threatened.

The continent’s 38 coastal countries heavily rely on the ocean for food and economic security, making them particularly susceptible to the impacts of rising sea levels. Low-lying deltas and minor island states are at the highest risk, facing compounding threats from flooding, land subsidence, and declining marine productivity [2].

Addressing the Challenge

Mitigation planning, including the construction of sea walls and other protective barriers, is crucial. But, managed retreat from vulnerable coastal areas may also be necessary. Even with the elimination of pollution today, at least 8 to 20 inches of sea level rise is projected by 2100 due to the heat already trapped in the atmosphere [2].