Findings Reveal Rapid Warming of the World’s Oceans

Ocean temperatures have reached a new record this month. Scientists observe that sea surface temperatures are rising more rapidly than ever, and they don’t fully understand why this is happening.

Findings from a new critical study show that the Earth’s systems continue accumulating heat in the last 49 years, between 1971 to 2020. A majority of this heat, 89%, is stored by the ocean, and the rest goes to land (6%), the atmosphere (1%), and 4% into melting the cryosphere (Von Schuckmann, Minière et al., 2023)

However, in the last 14 years, from 2006 to 2008, the Earth’s warming rate has been higher than in the previous 50 years.

The study presents the Earth’s heat inventory, a measure of the Earth’s energy imbalance (EEI). The EEI quantifies how much heat has accumulated in the Earth’s system and where the heat is stored.

The Earth’s energy imbalance is the most fundamental global climate indicator that the scientific community and the public can use to measure how well the world controls anthropogenic climate change.

The Earth’s accumulated heat can, directly and indirectly, trigger changes in the climate system, bringing adverse consequences to the environment and human systems.

Surplus heat absorbed by the ocean leads to ocean warming, which makes it less efficient in absorbing greenhouse gases. Ocean warming can kill marine life, create stronger weather events, and raise sea levels due to melting sea ice and glaciers and thermal expansion. 

On land, heat accumulation increases soil respiration and may lead to decreased soil water. Melting of the permafrost due to warming could result in many disruptive consequences in ground morphology and the release of planet-warming gases like methane and carbon dioxide.

Regarding inland water, increasing heat storage can lead to the lake’s warming, resulting in algal blooms, lake stratification, and reduced lake ice cover.

Scientists are still determining the causes of the rapid ocean warming.

The study notes that the drivers of heat accumulation are still unclear. However, studies have discussed some of the contributing factors for this, including a decreased reflection of energy back into space by clouds and sea ice and increases in well-mixed greenhouse gases (GHG) and water vapour.

Another study refers to a combination of rising concentrations of well-mixed GHG and recent reductions in aerosol emissions to account for the increase.

Regarding the decline in aerosol emissions, the BBC notes that in 2020, the International Maritime Organisation put in place a regulation to reduce the sulphur content of fuel burned by ships. This has led to decreased aerosol emissions from the floating vessels. Surprisingly aerosols that dirty the air also helps reflect heat into space – removing them may have caused more heat to enter the waters.

Another thing that worries scientists is the settling in of El Niño, a weather event that heats the ocean, which is expected to come in in the following months. Some scientists think El Niño will further increase ocean and atmosphere warming and the Earth’s temperature – reaching new temperature records by the end of 2025.

For the past three years, this naturally occurring event has been in a cooler phase called La Niña and has helped keep global temperatures in check. But researchers now believe that a strong El Niño is forming, which will have significant implications for the world.

“If a new El Niño comes on top of it, we will probably have additional global warming of 0.2-0.25C,” said Dr Josef Ludescher from the Potsdam Institute for Climate Research (McGrath & Poynting, 2023).

Find the link to the full study in the “Source” section below.