Human Emissions Will Delay Next Ice Age by 50,000 Years, Study Says
The phrase “ice age” may bring to mind woolly mammoths, saber-toothed cats and perhaps Sid the sloth from the animated films. It certainly doesn’t suggest ideal conditions for us distinctly-not-woolly humans.
New research suggests that the impact of humans on the planet is pushing back when the Earth might descend into its next ice age.
While the Earth might have naturally cycled back into an ice age in 50,000 years’ time in the absence of emissions, we’re unlikely to see one for at least 100,000 years because of the CO2 we put into the atmosphere.
The findings highlight the huge impact that humans are having on the planet, say scientists not involved in the study.
Around 12,000 years ago, the Earth emerged from its last ice age. As the vast ice sheets that covered much of the northern hemisphere receded, human civilization blossomed, making the most of the relatively mild conditions that we still enjoy today.
In the new study, published in Nature, researchers have worked out a formula for what triggers an ice age to start. The timing is based on two principal factors, they say: the amount of the sun’s energy the northern hemisphere receives during summer and the levels of CO2 in the atmosphere.
The amount of energy the Earth gets from the sun fluctuates naturally over many thousands of years because of subtle variations in the Earth’s position and orbit around the sun. These are known collectively as as Milankovitch Cycles.
Running simulations with an Earth System model, the researchers find that if atmospheric CO2 were still at pre-industrial levels, our current warm “interglacial” period would tip over into a new ice age in around 50,000 years’ time.
But CO2 emissions from human activity in the past, and those expected in the future, mean the next ice is likely to be delayed to 100,000 years’ time, the researchers say.
No Practical Importance
This may sound like good news—nobody wants another ice age anytime soon—but it isn’t a reason to thank fossil fuels, says lead author Dr. Andrey Ganopolski from the Potsdam Institute for Climate Impact Research. He tells Carbon Brief:
“We do not believe that the fact that anthropogenic CO2 emission can additionally postpone the next ice age …has any practical importance—this is rather an illustration of not so well-known fact that anthropogenic climate change will last not hundreds, but hundreds of thousand years.”
This is a point that Prof Michel Crucifix from the Université catholique de Louvain picks up in an accompanying News & Views article. Even though the industrial revolution is only a few centuries old, human-caused emissions will keep atmospheric CO2 levels elevated for many thousands of years, he says:
“[A]nthropogenic CO2 will still be in the atmosphere in 50,000 years’ time, and even 100,000 years, which is enough to prevent any glaciation.”
As for holding off the next ice age, the damaging impacts of climate change will be felt long before then, says Prof Richard Allan, professor of climate science at the University of Reading, who wasn’t involved in the study:
“[The next ice age is] not worth worrying about compared to immediate concerns about damaging human-caused climate change expected over the coming decades if no action is taken to mitigate this likelihood.”
“This study further confirms what we’ve suspected for some time, that the CO2 humans have added to the atmosphere will alter the climate of the planet for tens to hundreds of thousands of years.”
“It is both remarkable and a little scary to think that, in a short space of time, humans have been able to modify the climate system in such a dramatic and profound way.”
The researchers also looked back into the Earth’s history, and found that we narrowly missed descending into an ice age a few hundred years ago.
Natural CO2 levels during the most recent interglacial periods have been at around 280 parts per million (ppm), but have been as low as 240ppm in the more distant past.
Running their model for these different levels of atmospheric CO2, the researchers found that an ice age could have been triggered if CO2 had been at the lower level of 240ppm.
A recent study suggested that land clearance and early agriculture by humans around that time could be the reason for the extra 40ppm in the atmosphere. But Ganopolski and his co-authors say the changes to land use are unlikely to have caused such a large increase in CO2.
Avoiding the ice age was just down to luck, says Ganopolski:
“What we show in our paper is that we escaped the glacial inception naturally, thanks to a proper combination of Earth’s orbital parameters and natural CO2 concentration.”
So although humans aren’t behind this icy near-miss, it seems we are having a substantial impact on when the next ice age does finally appear.
YOU MIGHT ALSO LIKE
A grim new assessment of the world's flora and fungi has found that two-fifths of its species are at risk of extinction as humans encroach on the natural world, as The Guardian reported. That puts the number of species at risk near 140,000.
- Climate Crisis Could Cause a Third of Plant and Animal Species to ... ›
- World Leaders Urged to 'Act Now' to Save Biodiversity - EcoWatch ›
- Bumblebees Face Extinction From the Climate Crisis - EcoWatch ›
- Plant Extinction Is Happening 500x Faster Than Before the Industrial ... ›
EcoWatch Daily Newsletter
As human activity transforms the atmosphere, flowers are changing their colors.
- The Best Plants to Attract Pollinators, by Region - EcoWatch ›
- Corals Turn Bright Neon in Last-Ditch Effort to Survive - EcoWatch ›
- Hummingbirds Live in a More Colorful World, Study Confirms ... ›
By Sharon Zhang
Back in March, when the pandemic had just planted its roots in the U.S., President Donald Trump directed the Environmental Protection Agency (EPA) to do something devastating: The agency was to indefinitely and cruelly suspend environmental rule enforcement. The EPA complied, and for just under half a year, it provided over 3,000 waivers that granted facilities clemency from state-level environmental rule compliance.
A rare celestial event was caught on camera last week when a meteoroid "bounced" off Earth's atmosphere and veered back into space.
- Asteroid Could Strike Earth Before Election Day But Won't Cause ... ›
- Water May Have Originated on Earth, Study Finds - EcoWatch ›
By Bob Jacobs
Hanako, a female Asian elephant, lived in a tiny concrete enclosure at Japan's Inokashira Park Zoo for more than 60 years, often in chains, with no stimulation. In the wild, elephants live in herds, with close family ties. Hanako was solitary for the last decade of her life.
Hanako, an Asian elephant kept at Japan's Inokashira Park Zoo; and Kiska, an orca that lives at Marineland Canada. One image depicts Kiska's damaged teeth. Elephants in Japan (left image), Ontario Captive Animal Watch (right image), CC BY-ND
Affecting Health and Altering Behavior<p>It is easy to observe the overall health and psychological consequences of life in captivity for these animals. Many captive elephants suffer from arthritis, obesity or skin problems. Both <a href="https://doi.org/10.11609/JoTT.o2620.1826-36" target="_blank">elephants</a> and orcas often have severe dental problems. Captive orcas are plagued by <a href="https://doi.org/10.1016/j.jveb.2019.05.005" target="_blank">pneumonia, kidney disease, gastrointestinal illnesses and infections</a>.</p><p>Many animals <a href="https://doi.org/10.1016/j.neubiorev.2017.09.010" target="_blank">try to cope</a> with captivity by adopting abnormal behaviors. Some develop "<a href="https://doi.org/10.1016/j.applanim.2017.05.003" target="_blank" rel="noopener noreferrer">stereotypies</a>," which are repetitive, purposeless habits such as constantly bobbing their heads, swaying incessantly or chewing on the bars of their cages. Others, especially big cats, pace their enclosures. Elephants rub or break their tusks.</p>
Changing Brain Structure<p>Neuroscientific research indicates that living in an impoverished, stressful captive environment <a href="https://doi.org/10.1016/j.jveb.2019.05.005" target="_blank" rel="noopener noreferrer">physically damages the brain</a>. These changes have been documented in many <a href="https://doi.org/10.1002/cne.903270108" target="_blank" rel="noopener noreferrer">species</a>, including rodents, rabbits, cats and <a href="https://doi.org/10.1006/nimg.2001.0917" target="_blank" rel="noopener noreferrer">humans</a>.</p><p>Although researchers have directly studied some animal brains, most of what we know comes from observing animal behavior, analyzing stress hormone levels in the blood and applying knowledge gained from a half-century of neuroscience research. Laboratory research also suggests that mammals in a zoo or aquarium have compromised brain function.</p>
This illustration shows differences in the brain's cerebral cortex in animals held in impoverished (captive) and enriched (natural) environments. Impoverishment results in thinning of the cortex, a decreased blood supply, less support for neurons and decreased connectivity among neurons. Arnold B. Scheibel, CC BY-ND<p>Subsisting in confined, barren quarters that lack intellectual stimulation or appropriate social contact seems to <a href="https://doi.org/10.1590/S0001-37652001000200006" target="_blank" rel="noopener noreferrer">thin the cerebral cortex</a> – the part of the brain involved in voluntary movement and higher cognitive function, including memory, planning and decision-making.</p><p>There are other consequences. Capillaries shrink, depriving the brain of the oxygen-rich blood it needs to survive. Neurons become smaller, and their dendrites – the branches that form connections with other neurons – become less complex, impairing communication within the brain. As a result, the cortical neurons in captive animals <a href="https://doi.org/10.1002/cne.901230110" target="_blank">process information less efficiently</a> than those living in <a href="https://doi.org/10.1002/dev.420020208" target="_blank">enriched, more natural environments</a>.</p>
An actual cortical neuron in a wild African elephant living in its natural habitat compared with a hypothesized cortical neuron from a captive elephant. Bob Jacobs, CC BY-ND<p>Brain health is also affected by living in small quarters that <a href="https://doi.org/10.3233/BPL-160040" target="_blank">don't allow for needed exercise</a>. Physical activity increases the flow of blood to the brain, which requires large amounts of oxygen. Exercise increases the production of new connections and <a href="http://dx.doi.org/10.1126/science.aaw2622" target="_blank">enhances cognitive abilities</a>.</p><p>In their native habits these animals must move to survive, covering great distances to forage or find a mate. Elephants typically travel anywhere from <a href="https://www.elephantsforafrica.org/elephant-facts/#:%7E:text=How%20far%20do%20elephants%20walk,km%20on%20a%20daily%20basis." target="_blank">15 to 120 miles per day</a>. In a zoo, they average <a href="https://doi.org/10.1371/journal.pone.0150331" target="_blank" rel="noopener noreferrer">three miles daily</a>, often walking back and forth in small enclosures. One free orca studied in Canada swam <a href="https://doi.org/10.1007/s00300-010-0958-x" target="_blank" rel="noopener noreferrer">up to 156 miles a day</a>; meanwhile, an average orca tank is about 10,000 times smaller than its <a href="https://www.cascadiaresearch.org/projects/killer-whales/using-dtags-study-acoustics-and-behavior-southern" target="_blank" rel="noopener noreferrer">natural home range</a>.</p>
Disrupting Brain Chemistry and Killing Cells<p>Living in enclosures that restrict or prevent normal behavior creates chronic frustration and boredom. In the wild, an animal's stress-response system helps it escape from danger. But captivity traps animals with <a href="https://doi.org/10.1073/pnas.1215502109" target="_blank">almost no control</a> over their environment.</p><p>These situations foster <a href="https://doi.org/10.1037/rev0000033" target="_blank">learned helplessness</a>, negatively impacting the <a href="https://doi.org/10.1155/2016/6391686" target="_blank" rel="noopener noreferrer">hippocampus</a>, which handles memory functions, and the <a href="https://doi.org/10.1016/j.neuropharm.2011.02.024" target="_blank" rel="noopener noreferrer">amygdala</a>, which processes emotions. Prolonged stress <a href="https://doi.org/10.3109/10253899609001092" target="_blank" rel="noopener noreferrer">elevates stress hormones</a> and <a href="https://doi.org/10.1523/JNEUROSCI.10-09-02897.1990" target="_blank" rel="noopener noreferrer">damages or even kills neurons</a> in both brain regions. It also disrupts the <a href="https://doi.org/10.1016/j.neubiorev.2005.03.021" target="_blank" rel="noopener noreferrer">delicate balance of serotonin</a>, a neurotransmitter that stabilizes mood, among other functions.</p><p>In humans, <a href="https://doi.org/10.1006/nimg.2001.0917" target="_blank" rel="noopener noreferrer">deprivation</a> can trigger <a href="https://doi.org/10.3389/fnins.2018.00367" target="_blank" rel="noopener noreferrer">psychiatric issues</a>, including depression, anxiety, <a href="https://doi.org/10.3389/fnins.2018.00367" target="_blank" rel="noopener noreferrer">mood disorders</a> or <a href="https://doi.org/10.1177/1073858409333072" target="_blank" rel="noopener noreferrer">post-traumatic stress disorder</a>. <a href="https://doi.org/10.1007/s00429-010-0288-3" target="_blank" rel="noopener noreferrer">Elephants</a>, <a href="https://doi.org/10.1371/journal.pbio.0050139" target="_blank" rel="noopener noreferrer">orcas</a> and other animals with large brains are likely to react in similar ways to life in a severely stressful environment.</p>
Damaged Wiring<p>Captivity can damage the brain's complex circuitry, including the basal ganglia. This group of neurons communicates with the cerebral cortex along two networks: a direct pathway that enhances movement and behavior, and an indirect pathway that inhibits them.</p><p>The repetitive, <a href="http://dx.doi.org/10.1016/j.bbr.2014.05.057" target="_blank">stereotypic behaviors</a> that many animals adopt in captivity are caused by an imbalance of two neurotransmitters, dopamine and <a href="https://doi.org/10.1016/j.neubiorev.2010.02.004" target="_blank" rel="noopener noreferrer">serotonin</a>. This impairs the indirect pathway's ability to modulate movement, a condition documented in species from chickens, cows, sheep and horses to primates and big cats.</p>
The cerebral cortex, hippocampus and amygdala are physically altered by captivity, along with brain circuitry that involves the basal ganglia. Bob Jacobs, CC BY-ND<p>Evolution has constructed animal brains to be exquisitely responsive to their environment. Those reactions can affect neural function by <a href="https://www.penguinrandomhouse.com/books/311787/behave-by-robert-m-sapolsky/" target="_blank">turning different genes on or off</a>. Living in inappropriate or abusive circumstance alters biochemical processes: It disrupts the synthesis of proteins that build connections between brain cells and the neurotransmitters that facilitate communication among them.</p><p>There is strong evidence that <a href="https://doi.org/10.1523/JNEUROSCI.0577-11.2011" target="_blank">enrichment</a>, social contact and appropriate space in more natural habitats are <a href="https://doi.org/10.1111/j.1748-1090.2003.tb02071.x" target="_blank" rel="noopener noreferrer">necessary</a> for long-lived animals with large brains such as <a href="https://doi.org/10.1371/journal.pone.0152490" target="_blank" rel="noopener noreferrer">elephants</a> and <a href="https://doi.org/10.1080/13880292.2017.1309858" target="_blank" rel="noopener noreferrer">cetaceans</a>. Better conditions <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5543669/" target="_blank" rel="noopener noreferrer">reduce disturbing sterotypical behaviors</a>, improve connections in the brain, and <a href="https://doi.org/10.1038/cdd.2009.193" target="_blank" rel="noopener noreferrer">trigger neurochemical changes</a> that enhance learning and memory.</p>