Scientists warn global warming is happening faster than expected due to reduced shipping pollution

In the past five months, global temperature records have been broken, surprising scientists. Many people are asking why.

a New research published in Oxford Open Climate ChangeA research team led by prominent US climate scientist James Hansen suggests that one of the main drivers is an unintended global geoengineering experiment: the reduction of ship wakes.

When merchant ships travel at sea, they emit exhaust gases containing sulfur. This can contribute to the formation of ocean clouds through aerosols (also known as ship wakes) that radiate heat into space.

However, in 2020, as part of efforts to curb harmful aerosol pollution emitted by these ships, the International Maritime Organization (IMO) imposed strict regulations on ships, increasing the sulfur content in their fuel from 3.5 percent to 0.5 percent. reduced to %.

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With fewer ocean clouds, more heat is absorbed into the ocean, accelerating the energy imbalance, with more heat being trapped than released.

Hansen said in a call with reporters Thursday that the planet’s energy imbalance is much higher than it was a decade ago.

“That imbalance has now doubled. That’s why global warming is accelerating. That’s why global melting is accelerating,” he said.

Asked if this was evidence of the extreme warming we’ve seen over the past five months, Hansen said: “Yes, absolutely.”

1.5°C limit ‘more dangerous than a door nail’

Hansen said IMO regulations aimed at reducing aerosol pollution could have a long-term warming effect on the climate, raising global temperatures by 1.5 degrees or even 2 degrees above pre-industrial levels. He said there is. Stay within that range even faster under the Paris Agreement.

“The 1.5 degree limit is more dangerous than a door nail,” Hansen said. 1988 Congressional testimony on climate change helped sound the alarm on global warming. “And only with the help of deliberate action can we salvage the two-degree limit.”

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Before shipping sulfur was cut, the only way to calculate its impact was through modeling, climate scientist Leon Simmons, co-author of a recent study, told CBC News. That’s likely why scientists failed to recognize the rapid warming, he said. Arrival.

But since the reduction of sulfur in shipping, we are seeing the effects manifest in real time.

“We’ve never done an experiment that reduces ocean emissions by 80 percent,” Simmons said. “So now we’re starting to have evidence. We have about three and a half years of evidence about what happens to the oceans if we reduce sulfur emissions from shipping by 80 percent.”

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But not everyone agrees.

American climatologist Michael Mann blogged about the paper’s findingssaid.[Hansen] His co-authors have published a new paper in the journal Oxford Open Climate Change that goes far outside the mainstream. It’s not a problem. Healthy skepticism is valuable in science. But when it comes to challenging common scientific understanding, the bar is high, and I don’t think they’ll ever meet it. ”

Simmons pointed out that Mann “hasn’t studied this at all.”

“He doesn’t mention the most important scientific data, which is NASA satellite data,” Simmons said.

“Long-term global warming effect”

Michael Diamond, an assistant professor at Florida State University’s College of Earth, Ocean and Atmospheric Sciences who was not involved in the study, said the IMO regulation “like other regulations will have a long-term warming effect on the Earth’s climate.” He said he agreed with that. Air pollution is no different, as is the significant improvement in air quality seen over China since 2013. ”

In an email to CBC News, Diamond said he agrees that aerosol cooling masks about a third of the warming caused by greenhouse gases.

“However, it is important to emphasize that if we also reduce concentrations of short-lived greenhouse gases such as methane, we are not doomed to experience that ‘hidden’ warming while cleaning up air pollution. ”

The authors suggest that there are only three ways to stop this rapid warming.

• Rising global prices for greenhouse gas emissions, including carbon taxes.
• Cooperation between Eastern and Western countries “in response to the needs of the developing world.”
• Efforts to reduce the Earth’s radiation imbalances. This may involve some form of geoengineering.

Geoengineering efforts could include solar radiation management, which bounces sunlight back into space, such as spraying salt-laden droplets into the air from yachts. This may in turn cause cooling.

However, the authors noted that vigorous research is needed to avoid unintended consequences.

“There are ways to do it other than just releasing aerosols into the stratosphere,” Hansen said. “Rather than describing these efforts as ‘threatening’ geoengineering, we must recognize that we are now geoengineering the Earth.”

The paper’s authors also highlight the need for further research, including satellite observations, and the potential impact of such large-scale energy imbalances and what policies to reduce the threat to people around the world. He pointed out that it is necessary to tell them what steps should be taken.

“Even if there is uncertainty… that’s the reason for the decision.” [the effect of fewer ship tracks] “It’s even more serious because if there’s uncertainty, we may be underestimating what’s going on,” Simmons said.