Earth’s energy is out of balance; planet to warm more if imbalance persists or increases, paper warns
Photo: iStock_ Human-induced climate change is skewing Earth’s energy balance and oceans are bearing the brunt of the heat accumulation, according to a new study. About 89 per cent of the warming in the last 50 years has been absorbed by the ocean and the rest by the land, cryosphere and atmosphere.
About 381 zettajoules (ZJ) of heat accumulated on the planet from 1971-2020 due to anthropogenic emissions, according to the study published in journal Earth System Science Data. One ZJ is equal to 10 to the power of 21 joules.
This roughly equals a heating rate (Earth Energy Imbalance or EEI) of approximately 0.48 watts per square metre.
About 89 per cent of the accumulated heat is stored in the ocean, six per cent on land, a per cent in the atmosphere and about four per cent available for melting the cryosphere, the findings showed.
Source: Earth System Science Data
EEI is the difference between incoming and outgoing solar radiation. It is an indicator of climate change that provides an estimate of how much, how fast, and where the Earth’s climate is warming, as well as how this will evolve in the future, the paper read.
“The heat gain in the Earth system results in, directly and indirectly, triggered changes in the climate system, with a variety of implications for the environment and human systems,” the researchers wrote.
Researchers from several institutions updated the Earth’s heat inventory from a 2020 study to monitor climate change and provide community-based recommendations.
The experts calculated that between 2006 and 2020, the EEI was 0.76 watts per square metre with a variable of ±0.2. The Earth, they said, will keep gaining energy, increasing planetary warming if the energy imbalance continues to exist or increases.
Heat accumulated on land drives up ground surface temperatures. This, experts said, may increase soil respiration, which triggers the decomposition of soil organic matter and plant litter by soil microbes, releasing carbon dioxide in the process.
Higher soil respiration will likely decrease soil water, depending on climatic and meteorological conditions and factors.
Heat storage within inland water bodies has increased to roughly 0.2 ZJ since 1960. For permafrost thawing, it was about 2 ZJ.
The accumulation of heat in inland water increases lake water temperatures. This makes conditions ripe for algal blooms. Permafrost heat content could inject methane and carbon dioxide into the atmosphere, the researchers warned.
The upper ocean (0–300 and 0–700 metres depth) has taken up a major fraction of heat, according to the new estimates.
Source: Earth System Science Data
The heat content from the surface to the bottom between 1960-2020 was roughly 0.14 watts per square metre. In the most recent period (2006-2020), the heat content was estimated to be approximately 0.68 watts per square metre, the data showed.
During 2006–2020, ocean warming rates for the 0–2,000 metres depth reached record rates of roughly 1.03 watts per square metre.
The troposphere, the lowest layer of the atmosphere of Earth, measuring 8-14 kilometres in thickness, is also warming up due to increased heat accumulation.
The upper troposphere in the tropics has warmed faster than the near-surface atmosphere since at least 2001, the researchers noted.
The cryosphere — the frozen water part of the Earth system — gained roughly 14 ZJ of heat from 1971–2020.
Half of the uptake triggered the melting of grounded ice, while the remaining half is linked to the melting of floating ice (ice shelves in Antarctica and Greenland, Arctic Sea ice).
Antarctic Ice Sheet, including the floating and grounded ice, contributed about 33 per cent to the total cryosphere heat gain.
Arctic sea ice stood second, having contributed 26 per cent. Melting glaciers and the Greenland ice sheet was responsible for 25 per cent and 17 per cent. The Antarctic Sea ice accounted for about 0.2 per cent, according to the paper.
We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.
.png)
Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.