Earth Is Trapping 'Unprecedented' Amount of Heat, Says NASA

Left to its own devices, Earth’s climate typically takes thousands of years to change. Thanks to human activities, however, what previously took millennia now is taking only decades, suggests a new joint study by NASA and the National Oceanic and Atmospheric Administration (NOAA). Published this month in the journal Geophysical Research Letters, it finds the Earth is retaining twice as much heat now as it did in the early 2000s.

Specifically, scientists used two different means to measure and assess the Earth’s energy imbalance, which is the amount of radiative energy that the planet absorbs from the sun relative to the amount of thermal infrared radiation that it emits into space. The first was NASA’s Clouds and the Earth’s Radiant Energy System (CERES), a suite of satellite sensors that measure the amount of energy entering and leaving the Earth’s atmosphere. The second was Argo, a global network of ocean floats that measure the retention of energy in the ocean. Both revealed a positive energy imbalance, which means Earth is retaining more energy than it’s releasing.

That causes the planet to heat up. By a lot, it turns out: Data from both CERES and Argo show that Earth’s energy imbalance in 2019 was double what it was in 2005, just 14 years prior.

“The two very independent ways of looking at changes in Earth’s energy imbalance are in really, really good agreement, and they’re both showing this very large trend, which gives us a lot of confidence that what we’re seeing is a real phenomenon and not just an instrumental artifact,” said NASA scientist Norman Loeb, lead author of the study and principal investigator for CERES at NASA’s Langley Research Center in Hampton, Va. “The trends we found were quite alarming in a sense.”

Scientists blame rapid heating on a mix of human and natural causes. On the one hand, they observe, increases in greenhouse gas emissions from human activities—for example, driving, deforestation, and manufacturing—have trapped outgoing heat in the atmosphere that Earth would otherwise emit into space. That causes changes in snow and ice melt, water vapor, and cloud cover, which in turn creates even more warming.

On the other hand, scientists also note a concurrent change in the Pacific Decadal Oscillation (PDO), a natural pattern of climate variability in the eastern Pacific Ocean. During the time period in question, the PDO—which is like a longer-term El Niño—switched from a cool phase to a warm phase, which likely exacerbated Earth’s positive energy imbalance.

“It’s likely a mix of anthropogenic forcing and internal variability,” Loeb said. “And over this period they’re both causing warming, which leads to a fairly large change in Earth’s energy imbalance. The magnitude of the increase is unprecedented.”

The increase is as impactful as it is unprecedented.

“It’s excess energy that’s being taken up by the planet, so it’s going to mean further increases in temperatures and more melting of snow and sea ice, which will cause sea level rise—all things that society really cares about,” Loeb told CNN, adding that accelerated warming will likely produce “shifts in atmospheric circulations, including more extreme events like droughts.”

Because 90% of the excess energy from an energy imbalance is absorbed by the ocean, yet another consequence will be ocean acidification from higher water temperatures, which will impact fish and marine biodiversity, CNN points out.

“My hope is the rate that we’re seeing this energy imbalance subsides in the coming decades,” Loeb continued in his CNN interview. “Otherwise, we’re going to see more alarming climate changes.”

Unfortunately, it’s impossible to predict what those changes might be or when they’ll occur, stress Loeb and his colleagues, who describe their research as “a snapshot relative to long-term climate change.” Still, the science is getting better all the time. By using it to measure the severity of global warming, scientists at NASA and NOAA hope to inform and influence actions that will stop or reverse human-induced climate change before it’s too late to do so.

“The lengthening and highly complementary records from [space- and ocean-based sensors] have allowed us both to pin down Earth’s energy imbalance with increasing accuracy, and to study its variations and trends with increasing insight, as time goes on,” said Gregory Johnson, Loeb’s co-author on the study and physical oceanographer at NOAA’s Pacific Marine Environmental Laboratory in Seattle. “Observing the magnitude and variations of this energy imbalance are vital to understanding Earth’s changing climate.”