Dr. Kevin Trenberth is one of the world's foremost authorities on climate change. He is a distinguished scholar at the National Center for Atmospheric Research, worked for the World Climate Research Programme (WCRP) and has published more than 600 articles on climatology. Yet despite these impeccable credentials, as Trenberth spoke with Salon about his recent paper in the Journal of Climate Action, Research and Policy, an unmistakable tone of frustration crept into the scientist's voice. It was that of an expert who is not being listened to by the broader public, despite having something extremely important to say.
"Climate change is clearly well underway and represents a major, even existential threat that is not being adequately addressed," Trenberth writes. "Improvements are much needed in expressing why and how the climate is changing from human activities."
"We really should think more about it in terms of global heating rather than warming."
He asserts that when it comes to fixing climate change, humanity is missing a key point, one that he has repeatedly emphasized throughout his career: Warming and heating are not the same thing. As Trenberth explained both in his paper and in his interview with Salon, if our species does not soon fully grasp both this fact and its implications, the consequences will be disastrous.
It all comes down to a statistic known as EEI, or Energy Earth Imbalance, that measures the difference between the solar energy that reaches Earth and the amount which returns to space.
"Carbon dioxide is a greenhouse gas, and greenhouse gases are those which trap the infrared radiation that would otherwise be escaping to space," Trenberth told Salon, adding that the "general rule of thumb" is to classify any molecule with more than two atoms in it as a greenhouse gas. This includes carbon dioxide (CO2), water vapor, methane (CH4) and the various CFCs, also known as fluorocarbons.
These gases trap heat that would normally escape back into space — creating an EEI that could prove detrimental to humanity's future. While temperature is a part of this imbalance, there are other aspects of it too that cannot be measured solely with a thermometer.
"In this case, we really should think more about it in terms of global heating rather than warming," Trenberth said. "Heating and warming are synonyms, in some sense, but not always. Sometimes 'heating' relates more to temperature change rather than simply the temperature itself, and that's where some of the confusion arises."
In his paper, Trenberth elaborates on why this confusion is bad for humanity.
"The United Nations, and especially the Intergovernmental Panel on Climate Change (IPCC) in their Summary for Policy Makers, focus on global temperature targets rather than broader facets of climate change including EEI, and do not always adequately discriminate between temperature and heating," Trenberth wrote. "This also has consequences for future climate if or when heating is brought under control by cutting emissions. Improvements are needed in expressing how the climate is changing by properly accounting for the flow of energy through the climate system."
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"There is a greater risk of heavy rains and flooding as a result, but in the places where it's not raining, then things dry out. There is a greater risk of drought and wildfire, and heat waves as a consequence of that."
If humanity reaches net zero in terms of greenhouse gas emissions, Trenberth pointed out, the planet will still be be much hotter than our recent past and present, while the nature of our climate will still be very different.
"At that point, there is no longer this close relationship between heating and temperature," Trenberth observed. "The temperature maybe stalls, doesn't go up anymore or not quite so much," but other issues caused by overheating such as problems with the water cycle will persist. Those problems will, in turn, lead to extreme weather events impacting millions of people.
Other experts who spoke to Salon agreed with Trenberth's assessment.
"The basic premise — that greenhouse gas increases are causing changes in the hydrological cycle and various types of weather extremes — is well-founded," Dr. Michael E. Mann, a professor of earth and environmental science at the University of Pennsylvania, said in an email. "I think the paper is mostly just suggesting a different way for scientists to frame the climate crisis, i.e. rather than emphasizing the warming, better explain how the warning is symptomatic of a whole range of changes, including an intensified hydrological cycle and increases in various types of weather extremes."
Dr. Shiv Priyam Raghuraman from the University of Miami also told Salon that he "largely agree(s) with the paper," adding that his own 2021 paper for the journal Nature Communications "shows that this heating, known as Earth's Energy Imbalance (EEI), is increasing due to human activities."
Raghuraman also shared Trenberth's concern about people not paying enough attention to this aspect of climate science.
"A positive EEI, i.e., a surplus of heat in the Earth system, manifests as many symptoms such as global warming, less sea ice and land ice, a more powerful hydrological cycle, etc," Raghuraman pointed out. "The paper advocates not focusing on just the global warming part but also paying attention to the entire planetary heating."
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Trenberth was not shy about how humanity will suffer if the planet does not fully heal from its positive EEI. His paper focuses on the water cycle because it is the "best example, or the simplest example" that can be used to illustrate how this is the case.
"If you have extra heat, a lot of that heat goes into evaporating moisture at the surface, and that puts more moisture into the atmosphere," Trenberth said. "It rains harder. There is a greater risk of heavy rains and flooding as a result, but in the places where it's not raining, then things dry out. There is a greater risk of drought and wildfire, and heat waves as a consequence of that."
None of these extreme weather events will come as a surprise to those who have been following climate change — but the exact reason why they are occurring might be. If Trenberth's paper does what the scientist hopes, policymakers and ordinary people alike will better understand how climate change is changing the weather and be able to react accordingly.
As Trenberth and other experts agree, the stakes could not be higher.
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