Princeton and GFDL scientists say “Lower than 1% probability” that the rise in Earth’s vitality imbalance occurred naturally.
The earth’s energy balance is in the red, leading to higher temperatures, rising sea levels, floods, droughts, more severe snowstorms and hurricanes, and more deadly extreme events.
PICTURE: SHIV PRIYAM RAGHURAMAN, A GRADUATE STUDENT IN ATMOSPHERIC AND OCEANIC SCIENCES IN PRINCETON, REPORTED IN TODAY’S EDITION OF NATURAL COMMUNICATIONS THAT THE “ENERGY IMPROPERIAL EQUALITY” IS EQUAL TO THE EARTH. In other words, there is a greater than 99% chance that our planet’s rising temperatures are caused by human activity. Show more CREDIT: MORGAN KELLY, HIGH MEADOWS ENVIRONMENTAL INSTITUTE
Sunlight in, reflected and emitted energy out. That is the basic energy balance of our planet. When the earth’s clouds, oceans, ice caps and land surfaces send as much energy back into space as the sun shines down on us, our planet is in balance.
But this system has been out of whack for decades. Sunlight keeps streaming in, and the earth is not releasing enough, either as reflected solar radiation or as emitted infrared radiation. The extra heat trapped around our globe – around 90% of which is stored in the ocean – adds energy to global climate systems and manifests itself in many ways: higher temperatures, rising sea levels, floods, droughts, stronger snowstorms and hurricanes and even more deadly extreme events.
While climate scientists have warned for half a century that this was the inevitable result of adding too much carbon dioxide into the atmosphere, so-called climate deniers continue to claim that the changes observed could be a coincidence – just natural fluctuations.
“Previously, scientists believed that from the brief observational records we could not infer whether the increase in imbalance was human or climatic ‘noise’,” said Shiv Priyam Raghuraman, a PhD student in Atmospheric and Marine Sciences (AOS) at Princeton . “Our study shows that even with the given observational data, it is almost impossible to achieve such a large increase in imbalance just by the earth making its own vibrations and variations.”
He and his co-authors used satellite observations from 2001 to 2020 and found that the Earth’s “energy imbalance” was increasing. Raghuraman worked with David Paynter of the Geophysical Fluid Dynamics Laboratory (GFDL), a NOAA-funded national laboratory on the Forrestal campus in Princeton, and V. “Ram” Ramaswamy, GFDL Director and Senior Lecturer in Earth Sciences and AOS. together at Princeton University. Your paper appears today in Nature Communications.
“It is exceptionally unlikely – with a probability of less than 1% – that natural variations in the climate system can explain this trend,” Raghuraman said.
So what caused the growing energy imbalance?
“We always think: ‘Increasing greenhouse gases means capturing more infrared heat’ – the classic greenhouse effect is getting bigger,” said Raghuraman. “That’s right, but the downside is that the resulting warmer planet is now also emitting more infrared heat into space, negating the effects of greenhouse gas heating. Instead, much of the increase in imbalance is due to the fact that we receive the same amount of sunlight but reflect less, as increased greenhouse gases cause changes in cloud cover, fewer aerosols in the air reflect sunlight – the US and Europe – and sea ice is decreasing. “(Bright white sea ice reflects much more sunlight than sea water, so that the earth reflects less when the sea ice melts.)
In addition, Princeton and GFDL researchers found that oceans store 90% of this excess heat. Because of this close relationship between growing energy imbalances and ocean warming, Earth’s energy imbalance has important links to ocean health, sea level rise, and global warming. Researchers hope that tracking historical trends in this energy imbalance and understanding its components will improve the models of future climate change that drive policy making and mitigation efforts.
“The satellite records provide clear evidence of a human-influenced climate system,” they said. “The knowledge that human activities are responsible for the acceleration of planetary heat absorption requires significant political and societal measures to reduce anthropogenic greenhouse gas emissions in order to contain a further increase in the earth’s energy imbalance.”
“Anthropogenic Drive and Response Results in an Observed Positive Trend in Earth’s Energy Imbalance,” by Shiv Priyam Raghuraman, David Paynter and V. Ramaswamy, appears in the current issue of Nature Communications (DOI: 10.1038 / s41467-021-24544-4). The research was supported by the National Oceanic and Atmospheric Administration, Future Investigators in NASA Earth and Space Science and Technology (Award 80NSSC19K1372), Princeton University’s High Meadows Environmental Institute, and the Mary and Randall Hack ’69 Research Fund.
10.1038 / s41467-021-24544-4
Computer simulation / modeling