Global sea levels surged beyond expectations in 2024, a year officially recorded as Earth’s hottest since modern recordkeeping began in 1850. According to a newly released analysis by NASA, the rise measured 0.23 inches (0.59 cm), significantly higher than the previously predicted 0.17 inches (0.43 cm).
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This acceleration in sea level rise is a direct consequence of climate change, driven by greenhouse gas emissions that trap heat in the atmosphere and warm the planet. “Every year is a little bit different, but what’s clear is that the ocean continues to rise, and the rate of rise is getting faster and faster,” said Josh Willis, a researcher at NASA’s Jet Propulsion Laboratory.
Role of Thermal Expansion
Typically, rising sea levels result from two primary factors: the melting of glaciers and polar ice caps, which add freshwater to the ocean, and thermal expansion, where seawater expands as it warms. In recent years, melting ice has been the dominant contributor to rising water levels. However, in 2024, this pattern reversed, with two-thirds of the increase coming from thermal expansion.
NASA explained that this unusual shift was largely due to an excessive amount of ocean warming. The expansion of seawater was significantly influenced by extreme weather patterns, including El Niño, which redistributes large masses of warm water in the Pacific Ocean. Strong ocean currents and intense winds also played a role by mixing warm surface waters with deeper, cooler layers.
A Rising Ocean, A Growing Threat
NASA’s long-term satellite monitoring has documented a steady increase in sea levels over the past 30 years. Since 1993, global sea levels have risen by approximately four inches (10 cm). Alarmingly, the annual rate of rise has more than doubled in that time, reflecting the worsening impact of climate change.
Higher sea levels pose a serious threat to coastal communities and island nations, increasing the risk of flooding, coastal erosion, and saltwater intrusion into freshwater sources. As the world continues to burn fossil fuels and release greenhouse gases, scientists warn that sea levels will keep rising, further endangering millions of people living in low-lying regions.
Tracking the Ocean’s Future
NASA’s ability to track these changes relies on an uninterrupted series of ocean-observing satellites. Since 1992, missions such as TOPEX/Poseidon and Sentinel-6 Michael Freilich have provided precise measurements of sea surface height. The upcoming launch of the Sentinel-6B satellite will ensure this critical dataset continues into its fourth decade.
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With 2024 serving as a stark reminder of the rapid pace of climate change, scientists stress the urgency of reducing greenhouse gas emissions. As NASA’s Nadya Vinogradova Shiffer put it, “With 2024 as the warmest year on record, Earth’s expanding oceans are following suit, reaching their highest levels in three decades.” The findings reinforce the need for immediate global action to curb emissions and mitigate climate change’s devastating effects before sea level rise reaches even more catastrophic levels.
