Sea level increased 0.3 inches in 2022-2023: Are coasts for rising waters?

NASA leads the analysis based on more than 30 years of satellite observations, launching the initial satellite in 1992 and the latest one in 2020. Sea levels have risen by around four inches since 1993, overall. The rate of increase has also accelerated, more than doubling from 0.07 inches per year in 1993 to the current rate of 0.17 inches per year.

The NASA-led analysis is based on sea level data, including over 30 years of satellite observations. The US-French TOPEX or Poseidon mission, launched in 1992, marked the beginning. The Sentinel-Six Michael Freilich mission, which also launched in 1992, is the latest satellite in a series that has helped uncover this sea level record as of November 2020.

The data reveals an overall rise in global average sea level by about four inches since 1993. It also uncovers an acceleration in this rise's rate, from 0.07 inches per year in 1993 to the current rate of 0.17 inches per year – more than a double increase.

The report indicates that the current acceleration rate suggests global average sea levels will rise another 20 centimeters by 2050, doubling the amount of change over the next three decades compared to the last 100 years and leading to more frequent floods. The effect will continue to grow.

Seasonal Effects

The transition between La Nina and El Nino events primarily caused a large rise in global sea levels from 2022 to 2023. A mild La Nina between 2021 and 2022 caused a lower-than-expected sea level rise that year. A powerful El Niño developed in 2023, which helped fuel an average rise in sea surface height.

Cooler than normal ocean temperatures in the equatorial Pacific Ocean characterize La Niña. El Nino involves temperatures that are warmer than average in the equatorial Pacific Ocean. Periodically, climate events occur and influence rainfall and snowfall patterns, as well as sea levels worldwide.

“During La Niña, rain that normally falls in the ocean falls on the land instead, temporarily taking water out of the ocean and lowering sea levels,” said Josh Willis, a sea level researcher at NASA’s Jet Propulsion Laboratory in Southern California. “In El Niño years, a lot of the rain that normally falls on land ends up in the ocean, which raises sea levels temporarily.”

A Human Footprint

The report states that seasonal or periodic climate events can influence the global average sea level annually. However, an interconnected trend has directly caused sea level rise in response to global warming over more than three decades, due to the excess heat that greenhouse gases trap in the Earth's atmosphere.

“Long-term datasets like this 30-year satellite record allow us to differentiate between short-term effects on sea level, like El Niño, and trends that let us know where sea level is heading,” said Ben Hamlington, lead for NASA’s sea level change team at JPL.

The report notes that international collaboration and scientific and technological innovations from NASA and other space agencies make these multi-decade observations possible. In particular, radar altimeters enhance the accuracy of sea level measurements worldwide.

These instruments calculate sea height by bouncing microwave signals off the ocean surface. They record the time it takes for the signal to travel from the satellite to Earth and back, as well as the strength of the return signal.

The report stated that researchers periodically cross-check sea level measurements against data from other sources. These sources include tide gauges and satellite measurements of factors such as atmospheric water vapour and Earth's gravity field that could affect the precision of those sea level measurements.

The researchers then used this information to update the 30-year-old dataset, which produced updated information on sea levels over the years. It showed a sea level rise of 0.08 inches by 2021-2022.

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