One-Third of Humanity Could Live in Sahara-Level Heat by 2070
If nothing is done to reduce greenhouse gas emissions, one third of humanity could live in conditions as hot as the Sahara Desert by 2070.
This sobering conclusion, published in The Proceedings of the National Academy of Sciences Monday, was based on an international study of the climate conditions humans have preferred over the past 6,000 years and how the climate crisis might alter them.
"The numbers are flabbergasting. I literally did a double take when I first saw them," study coauthor Tim Lenton of Exeter University told The Guardian. "I've previously studied climate tipping points, which are usually considered apocalyptic. But this hit home harder. This puts the threat in very human terms."
We also show that these conditions deviate strongly from the moderate temperatures under which the majority of peop… https://t.co/qQBDYSazZW— Jens Svenning (@Jens Svenning)1588622591.0
The researchers first set out to determine if humans had a "climate niche," or ideal temperature range they tend to settle in, much like other animals, The New York Times explained. They found that, throughout human history, we have consistently chosen locations with a relatively narrow temperature range.
The majority of people now live in places with a mean temperature of 50 to 60 degrees Fahrenheit while a smaller number live in places with a mean of 68 to 77 degrees. Most human settlements from 6,000 years ago were placed in areas with the same mean temperatures, the researchers found.
"We didn't think that would be the case," study coauthor Marten Scheffer, a professor of complex systems sciences at Wageningen University in the Netherlands, told The New York Times.
This human vulnerability to climate extremes is bad news for the future. In a business-as-usual scenario, 3.5 billion people will live in areas with a mean temperature above 84 degrees Fahrenheit or 29 degrees Celsius within 50 years.
"This would bring 3.5 billion people into near-unlivable conditions," study coauthor Jens-Christian Svenning of Aarhus University in Denmark told iNews.
The countries most at risk from extreme heat are India, Nigeria, Pakistan, Indonesia and Sudan. In India, more than 1.2 billion people could be exposed to these temperatures.
"I think it is fair to say that average temperatures over 29C are unlivable," Scheffer told The Guardian. "You'd have to move or adapt. But there are limits to adaptation. If you have enough money and energy, you can use air conditioning and fly in food and then you might be OK. But that is not the case for most people."
The scientists said their findings were another argument for climate action, noting that, if emissions are reduced, the number of people exposed to these temperatures would decrease to around one billion, according to The New York Times.
"The good news is that these impacts can be greatly reduced if humanity succeeds in curbing global warming," Lenton told USA TODAY. "Our computations show that each degree warming (Celsius) above present levels corresponds to roughly 1 billion people falling outside of the climate niche. It is important that we can now express the benefits of curbing greenhouse gas emissions in something more human than just monetary terms."
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By Katherine Kornei
Clear-cutting a forest is relatively easy—just pick a tree and start chopping. But there are benefits to more sophisticated forest management. One technique—which involves repeatedly harvesting smaller trees every 30 or so years but leaving an upper story of larger trees for longer periods (60, 90, or 120 years)—ensures a steady supply of both firewood and construction timber.
A Pattern in the Rings<p>The <a href="https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/coppice-standards-0" target="_blank">coppice-with-standards</a> management practice produces a two-story forest, said <a href="https://www.researchgate.net/profile/Bernhard_Muigg" target="_blank">Bernhard Muigg</a>, a dendrochronologist at the University of Freiburg in Germany. "You have an upper story of single trees that are allowed to grow for several understory generations."</p><p>That arrangement imprints a characteristic tree ring pattern in a forest's upper story trees (the "standards"): thick rings indicative of heavy growth, which show up at regular intervals as the surrounding smaller trees are cut down. "The trees are growing faster," said Muigg. "You can really see it with your naked eye."</p><p>Muigg and his collaborators characterized that <a href="https://ltrr.arizona.edu/about/treerings" target="_blank">dendrochronological pattern</a> in 161 oak trees growing in central Germany, one of the few remaining sites in Europe with actively managed coppice-with-standards forests. They found up to nine cycles of heavy growth in the trees, the oldest of which was planted in 1761. The researchers then turned to a historical data set — more than 2,000 oak <a href="https://eos.org/articles/podcast-discovering-europes-history-through-its-timbers" target="_blank" rel="noopener noreferrer">timbers from buildings and archaeological sites</a> in Germany and France dating from between 300 and 2015 — to look for a similar pattern.</p>
A Gap of 500 Years<p>The team found wood with the characteristic coppice-with-standards tree ring pattern dating to as early as the 6th century. That was a surprise, Muigg and his colleagues concluded, because the first mention of this forest management practice in historical documents occurred only roughly 500 years later, in the 13th century.</p><p>It's probable that forest management practices were not well documented prior to the High Middle Ages (1000–1250), the researchers suggested. "Forests are mainly mentioned in the context of royal hunting interests or donations," said Muigg. Dendrochronological studies are particularly important because they can reveal information not captured by a sparse historical record, he added.</p><p>These results were <a href="https://www.nature.com/articles/s41598-020-78933-8" target="_blank">published in December in <em>Scientific Reports</em></a>.</p><p>"It's nice to see the longevity and the history of coppice-with-standards," said <a href="https://www.teagasc.ie/contact/staff-directory/s/ian-short/" target="_blank">Ian Short</a>, a forestry researcher at Teagasc, the Agriculture and Food Development Authority in Ireland, not involved in the research. This technique is valuable because it promotes conservation and habitat biodiversity, Short said. "In the next 10 or 20 years, I think we'll see more coppice-with-standards coming back into production."</p><p>In the future, Muigg and his collaborators hope to analyze a larger sample of historic timbers to trace how the coppice-with-standards practice spread throughout Europe. It will be interesting to understand where this technique originated and how it propagated, said Muigg, and there are plenty of old pieces of wood waiting to be analyzed. "There [are] tons of dendrochronological data."</p><p><em><a href="mailto:email@example.com" target="_blank" rel="noopener noreferrer">Katherine Kornei</a> is a freelance science journalist covering Earth and space science. Her bylines frequently appear in Eos, Science, and The New York Times. Katherine holds a Ph.D. in astronomy from the University of California, Los Angeles.</em></p><p><em>This story originally appeared in <a href="https://eos.org/articles/tree-rings-reveal-how-ancient-forests-were-managed" target="_blank">Eos</a></em> <em>and is republished here as part of Covering Climate Now, a global journalism collaboration strengthening coverage of the climate story.</em></p>
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While President Joe Biden's top climate envoy John Kerry told world leaders at a virtual climate summit that the U.S. will fulfill its commitment to provide financial support to developing countries as they grapple with the deadly consequences of a warming planet, campaigners are urging the U.S. to follow the lead of European Union officials who on Monday pledged to stop subsidizing fossil fuels and instead invest in a just transition toward clean energy.
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