Past greenhouse gas emissions may raise sea levels by nearly two feet, study finds

By Dana Drugmand

Heat-trapping emissions released over more than a century and a half by the world’s largest fossil fuel and cement producers are projected to cause global sea levels to rise about one to two feet through the year 2300, even if future emissions are drastically cut, according to new peer-reviewed research.

The study, published March 18 in the journal Environmental Research Letters, is the first to measure how past greenhouses gas emissions from fossil fuel companies may contribute to future long-term sea level rise, one of the consequences of human-caused climate change, according to the authors.

“This research contributes to the growing body of work that quantifies how fossil fuel producers’ past emissions will harm future generations,” Delta Merner, co-author of the study and associate director of the Science Hub for Climate Litigation at the Union of Concerned Scientists, said in a statement. “Island and coastal communities will bear the disproportionate brunt of the impacts of sea level rise over time, including infrastructure damage, habitat loss, saltwater intrusion, increased flooding, economic burdens and forced displacements.”

The researchers also found that nearly half (37% to 58%) of present-day surface air temperature rise and about one-third (24% to 37%) of global mean sea level rise to date can be attributed to the historical emissions of the 122 biggest oil, gas, coal, and cement producers, known as the ‘Carbon Majors.’ The study builds on previous analyses examining how emissions stemming from these companies’ products contribute to climate change impacts including surface warming, sea level rise, and drying conditions that help fuel wildfires.

The study further examined what the impacts on surface warming and sea levels would have been if the Carbon Majors had cut emissions by phasing out production at earlier periods in time, such as after 1950, when at least some companies first became aware that their products would impact the climate system, and after 1990, when the international community had begun to address climate change.

“Across all scenarios, we find that the world would have been cooler and the sea levels lower if fossil fuel emissions had been phased out earlier,” Shaina Sadai, the lead author of the study, explained in a blog post.

Had fossil fuel emissions stopped after 1990, for example, the study estimated that future long-term sea level rise attributable to the Carbon Majors’ past emissions would have been about 6 to 14 inches – lower than the 10 to 21 inches now expected.

Research that looks at the impacts of failing to rein in emissions is important for advancing efforts to hold polluters responsible, said Jennifer Jacquet, a professor at the Rosenstiel School of Marine, Atmospheric, and Earth Science at the University of Miami, who was not involved in the study.

“As our world changes significantly for the worse as a result of climate change, I expect we will try to hold accountable those most responsible for those changes — both in terms of the carbon pollution but also the information pollution — in the courts and in the global market, where this kind of study will be relied upon,” said Jacquet.

Global average sea level is currently at its highest since satellite records began in 1993, and the rate of sea level rise has doubled over that time, according to a new report from the World Meteorological Association. That report notes that atmospheric concentrations of carbon dioxide and other heat-trapping gases are the highest they have been in the last 800,000 years. Last year was the warmest in the 175-year observational record, according to the report.

Despite these indicators of a worsening climate crisis, the US is ramping up fossil fuel production under the new Trump administration while attacking climate science and clean energy and reversing federal climate policies. Trump, who has previously called climate change a hoax, is pulling the US out of the Paris Climate Agreement, and his administration has targeted agencies that do critical climate science and weather forecasting work with deep cuts, including the National Oceanic and Atmospheric Administration (NOAA). A NOAA office in Hawaii that serves as the main support for the Mauna Loa Observatory, which monitors atmospheric carbon dioxide concentrations, may have its lease cancelled as part of these cuts.

With global commitments already falling short of what is needed to reach net zero emissions by 2050, according to the United Nations, changes in the US government’s stance on climate change could put the world  further off track, said Sadai.

“Every delay [in action to mitigate climate change], even just a couple of decades, is going to come with long-term consequences,” she said.

(Featured image by Point Normal on Unsplash.)