The Pace of Global Warming, Previously Slowed by Unintentional Geoengineering, Is Accelerating

The rate of global warming is expected to accelerate, according to a new study published by a team led by renowned climatologist and climate activist Dr. James Hansen, due to the otherwise well-meaning reduction of atmospheric pollutants. It has been discovered that these pollutants resulted in an unintended geoengineering effect that reflected a portion of the Sun’s rays back into space before they could warm the surface waters of the oceans, temporarily masking the advance of climate change.

While studying changes in the Earth’s albedo through data gathered by NASA’s Clouds and Earth’s Radiant Energy System (CERES), Hansen’s team found that the overall reflectiveness of the planet over the world’s oceans has decreased substantially over the past decade, resulting in the water absorbing more solar radiation—and storing the resulting heat—than in decades past, increasing the planetary energy imbalance more than had been anticipated by earlier research.

“That imbalance has now doubled,” Hansen stated during a November 2 press conference. “That’s why global warming will accelerate. That’s why global melting will accelerate.” He also affirmed that this is why 2023, forecast to be the hottest year on record, has seen consecutive record-breaking temperatures over the past five months, temperatures that have far exceeded expectations; for instance, September 2023 was the warmest September on record, recorded at 1.44°C (2.59°F) over the 20th-century average, nearly 47 percent higher than the previous record-holder of 2020.

Hansen’s study found that the sudden increase in planetary temperatures was caused by an unexpected culprit: a decrease in cloud cover over the oceans that was generated by the collective exhaust emitted by global marine traffic. Beginning in 2010, the International Maritime Organization (IMO) placed restrictions on the sulfur content of marine fuels used by ocean-going ships, limited to one percent for ships operating near the coasts of North America and in the North Sea, Baltic Sea and English Channel; over the course of a series of progressive limit increases, that limit was reduced to just 0.5 percent and expanded to include all ships operating around the world by 2020, resulting in a global reduction in ship tracks—the clouds produced by ship exhaust—by more than 50 percent.

Although these measures resulted in the intended effect of reducing the amount of sulfur-based pollution being emitted into the atmosphere, it had the unintended effect of warming the world’s oceans: water molecules tend to condense on the particles that make up the sulfur aerosols that are a component of engine exhaust, resulting in a larger-scale phenomenon known as “ship tracks”, cloud formations that reflect sunlight back into space. However, along with the reduction in these man-made clouds came a corresponding increase in the amount of sunlight reaching the Earth’s surface, causing an increase in the temperature of the oceans that the tracks would normally have formed over.

This result of this inadvertent geoengineering wasn’t subtle: the study found that although the initial sulfur restrictions made in 2010 made little impact, further restrictions made in 2015 did, with the average amount of solar energy reaching Earth since 2020 increasing by slightly more than 30 percent over the average recorded in the half-decade between 20215 and 2020, the years that the two most recent restriction increases were implemented.

Since water is a potent absorber of thermal energy, this means that the oceans have been storing the heat that would otherwise have been more immediately apparent if it had occurred over land. Unfortunately, that energy isn’t trapped indefinitely, and is being emitted at an increasing rate as the oceans absorb more and more solar radiation, meaning we’re likely to blow past the 1.5°C (2.7°F) limit called for by the Paris Climate Accords, according to the study.

“The 1.5-degree limit is deader than a doornail,” said Hansen, “And the two-degree limit can be rescued, only with the help of purposeful actions,” such as CO2 emission reductions and large-scale carbon capture efforts.

The reason this effect wasn’t predicted by previous climate studies is because they relied on models that hadn’t anticipated the more recent IMO sulfur restrictions being put into practice, leaving the effects of reduced ship tracks out of the equation.

“We’ve never done the experiment of reducing emissions over the oceans by 80 per cent before,” explained study co-author and climate researcher Leon Simons. “So now we are starting to have the evidence. We now have about three and a half years of evidence of what happens… to the oceans if you reduce sulfur emissions from shipping by 80 percent.”

Although this prognosis appears dire, the paper’s authors point out that there are measures that can be taken to reduce the effect of global warming back to a “Holocene-level global temperature”:

• “A global increasing price on GHG emissions accompanied by development of abundant, affordable, dispatchable clean energy
• “East-West cooperation in a way that accommodates developing world needs
• “Intervention with Earth’s radiation imbalance to phase down today’s massive human-made ‘geo-transformation’ of Earth’s climate.”

“Current political crises present an opportunity for reset, especially if young people can grasp their situation,” the paper stated.

Although not involved in the study, Michael Diamond, an assistant professor at Florida State University’s department of earth, ocean and atmospheric science, agrees that these sulfur aerosols have so far “masked” roughly one-third of the warming effect of global warming.

“However, it’s important to emphasize that we are not doomed to experience all of that ‘masked’ warming as we clean up air pollution, if we also reduce concentrations of shorter-lived greenhouse gases like methane at the same time,” Diamond advised.