`Less than 1% probability' that Earth's energy imbalance increase
occurred naturally

Date:
July 28, 2021
Source:
Princeton University
Summary:
Sunlight in, reflected and emitted energy out. That's the
fundamental energy balance sheet for our planet -- and for decades,
it has been out of balance. The extra energy manifests as higher
temperatures, rising sea levels, floods, droughts, more powerful
blizzards and hurricanes, and deadlier extreme events. Not only
is the imbalance growing, but there's a 99% chance that the growth
is due to human activity, calculated a team of researchers.



FULL STORY ========================================================================== Sunlight in, reflected and emitted energy out. That's the fundamental
energy balance sheet for our planet. If Earth's clouds, oceans, ice caps
and land surfaces send as much energy back up to space as the sun shines
down on us, then our planet maintains equilibrium.


==========================================================================
But for decades, that system has been out of balance. Sunlight continues
to pour in, and Earth isn't releasing enough, either as reflected solar radiation or as emitted infrared radiation. The extra heat trapped
around our globe - - some 90% of which is stored in the ocean --
adds energy to worldwide climate systems and manifests in many ways:
higher temperatures, rising sea levels, floods, droughts, more powerful blizzards and hurricanes, and deadlier extreme events.

While climate scientists have warned for a half-century that this was the inevitable result of adding too much carbon dioxide to the atmosphere,
so- called climate deniers have continued to suggest that the observed
changes might be a fluke -- just natural variation.

"Until now, scientists have believed that because of the short
observational record, we can't deduce if the increase in the imbalance
is due to humans or climatic 'noise,'" said Shiv Priyam Raghuraman,
a graduate student in atmospheric and oceanic sciences (AOS) at
Princeton. "Our study shows that even with the given observational
record, it is almost impossible to have such a large increase in the
imbalance just by Earth doing its own oscillations and variations."
He and his co-authors used satellite observations from 2001 to 2020 and
found that Earth's "energy imbalance" is growing. Raghuraman worked with
David Paynter of the Geophysical Fluid Dynamics Laboratory (GFDL), a NOAA-funded national laboratory located on Princeton's Forrestal Campus,
and V. "Ram" Ramaswamy, director of GFDL and a lecturer with the rank
of professor in geosciences and AOS at Princeton University. Their paper appears today in Nature Communications.

So what has caused the growing energy imbalance? "We always think,
'Increasing greenhouse gases means trapping more infrared heat' -- the
classic greenhouse effect becomes larger," said Raghuraman. "This is
correct, but the flip side is that the resulting warmer planet now also radiates more infrared heat away to space, so the greenhouse gas heating
impact is cancelled. Instead, much of the imbalance increase comes from
the fact that we are receiving the same amount of sunlight but reflecting
back less, because increased greenhouse gases cause cloud cover changes,
less aerosols in the air to reflect sunlight -- that is, cleaner air
over the U.S. and Europe -- and sea-ice decreases." (Bright white sea
ice reflects much more sunlight than sea water, so as sea ice melts,
Earth is becoming less reflective.) In addition, the Princeton and GFDL researchers noted that oceans store 90% of this excess heat. Because
of this close relationship between the growing energy imbalance and
ocean heating, the Earth's energy imbalance has important connections
to marine health, sea-level rise and the warming of the global climate
system. The researchers hope that tracking the historical trends in this
energy imbalance and understanding its components will improve the models
of future climate change that drive policymaking and mitigation efforts.

"The satellite record provides clear evidence of a human-influenced
climate system," they said. "Knowing that human activity is responsible
for the acceleration of planetary heat uptake implies the need for
significant policy and societal action to reduce anthropogenic greenhouse
gas emissions to curb further increases in Earth's energy imbalance." ========================================================================== Story Source: Materials provided by Princeton_University. Original written
by Liz Fuller- Wright. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Shiv Priyam Raghuraman, David Paynter, V. Ramaswamy. Anthropogenic
forcing and response yield observed positive trend in Earth's
energy imbalance. Nature Communications, 2021; 12 (1) DOI:
10.1038/s41467-021- 24544-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210728150340.htm

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