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In the midst of what has already been an abnormally long period of warming, scientists have announced that human-induced climate change could push back the next ice age for at least 100,000 years.
In a study published this Wednesday in the journal Nature, researchers from the Potsdam Institute for Climate Impact Research make clear that anthropogenic carbon emissions, even in moderate future scenarios, could significantly delay the development of ice sheets across the Northern Hemisphere.
Without "a considerable drop in CO2 concentration," the report outlines, it is "very unlikely" that we will see a glacial period in the near future.
"This illustrates very clearly that we have long entered a new era," wrote Hans Joachim Schellnhuber, co-author of the article and the director of the institute. "In the Anthropocene, humanity itself has become a geological force," he said, proposing that the new epoch be referred to as the "Deglacial."
Over the past million years, glacial periods have generally been spurred by reduced solar radiation — insolation — in northern altitudes during summer months. But in the Holocene, the period beginning at the end of the last ice age, some 12,000 years ago, scientists made an unexpected observation: minimal solar radiation in the summer, as is currently the case, without any signs of an impending ice age.
This observation, according to an institute scientist was the motivation behind their most recent study. As they worked to "crack the code of glacial inception," attempting to explain when and under what conditions the planet enters into an ice age, they found that anthropogenic emissions, not only levels of solar radiation, have now become a permanent variable in that equation.
"It is unprecedented to avoid an entire glacial cycle," said Kelly Levin, a senior associate and climate change expert with the World Resources Institute. "Through the burning of fossil fuels and the cutting down of trees, we have altered everything we have come to know – we have made a fingerprint that will last 100,000 years."
Absent human forces, institute scientists estimate that the beginning of the next glacial period would be no sooner than 50,000 years from now, but that with anthropogenic contributions of cumulative CO2 emissions estimated between 1,000 and 1,500 gigatons of carbon, that period could be repressed by at least 100,000 years.
The UN's Intergovernmental Panel on Climate Change has estimated that cumulative emissions will exceed 1,000 gigatons of CO2, but even if these emissions total 500 gigatons, which is slightly above present day value, the evolution of Northern Hemisphere ice sheets will be affected by tens of thousands of years.
This is due, in large part to the "extremely long lifetime of anthropogenic CO2" in the atmosphere, according to researcher and co-author on the study, Ricarda Winkelmann.
In the past, glaciers have been credited with leaving behind much of the fertile land in the Northern Hemisphere, while glacial packs currently provide a major water source for many populations.
"They are making an important point, which is that humans have become a geologic force," said Lonnie Thompson, a professor of geological sciences at Ohio State University, in response to the study. "At no time in Earth history has there been 7.3 billion people on Earth and that number will likely grow to 10 billion by 2050."
While previous studies have shown that global warming could delay the next ice age, the institute's study is considered an important landmark in the body of research aiming to better quantify our impact on geologic patterns.
Moving forward, both Thompson and Levin believe that the research lays bare the importance of human decision-making and the impact on forces once thought to be beyond our realm of influence.
"Certainly the choices we make today and in the next 20 to 30 years will determine just how great a 'force of nature' we will become going forward," said Thompson. Echoing his sentiment, Levin added that the study acts as a "warning sign that we are entering an unprecedented era."
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