Groundbreaking Study Reaffirms Human Impact on Climate
A groundbreaking new study, published in Nature Geoscience, has found that global temperatures were warmer between 1970 and 2000 than any other 30-year period in the last 1,400 years.
The research, compiled by 73 scientists from 28 institutions worldwide, is the most comprehensive reconstruction of global temperatures to date. It used corals, ice cores, tree rings, lake and marine sediments, historical records, cave deposits and climate archives to help establish temperature trends over the last 2,000 years.
The researchers aimed to chart change not just of the globe itself, but also of climate change in seven continental regions, studying more than 500 different sets of temperature records from all continents except Africa, where the evidence is still incomplete.
And while results could vary widely across continents, the research did confirm that a long period of cooling, between 1580 and 1880, was halted by a sharp reversal in the late nineteenth century. It also confirmed that the 30-year period between 1970 and 2000 was the warmest on land in at least 1,400 years.
While the research found that natural variability, such as volcanic eruptions and changes in solar irradiance can, and has, imprinted on the global climate systems to cause cooling historically, it once again affirms that these natural causes of climate variability do not and cannot explain the most recent period of global warming.
The timing of the warming period correlates directly with an increase in carbon emissions from human activity over the same period and broadly confirms an ever-growing message from climate scientists: climate change is happening, it is caused by humans and billions of people will fall victim to it without urgent action.
For example, the latest briefing from the World Meteorological Organisation (WMO) warns that scientific consensus that global climate is due to human activity is strong and should not be ignored, and the upcoming Intergovernmental Panel on Climate Change fifth report is expected to further bolster this overwhelming consensus.
The WMO reported that global average temperatures have risen an estimated 0.6°C (1.1°F) over the course of the 20th century, and continue to climb. They found 2001-2010 to be the warmest decade since satellite records began, 2010 the warmest year, and no year since 1985 having recorded a below average mean temperature.
The latest study is an important contribution to this growing body of research. It looked in detail at the differences in temperature change between individual continents and also provided temperature information for each year–creating a more detailed reconstruction than previous studies over the same time period.
Lead author Professor Darrell Kaufman, Northern Arizona University in Flagstaff said:
Previous attempts to reconstruct temperature changes focused on hemispheric or global scale averages, which are important, but overlook the pronounced regional-scale differences that occur along with global changes. A key aspect of the consortium effort was to engage regional experts who are intimately familiar with the evidence for past climate changes within their regions.
Looking in this detail at how the Earth’s past temperatures have changed, the researchers say they are more able to separate the effects of human activity from fluctuations that occur naturally–something they say is vital to being able to track future projections on climate change.
Visit EcoWatch’s CLIMATE CHANGE page for more related news on this topic.
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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:firstname.lastname@example.org" 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>
Earth's ice is melting 57 percent faster than in the 1990s and the world has lost more than 28 trillion tons of ice since 1994, research published Monday in The Cryosphere shows.
By Jewel Fraser
Noreen Nunez lives in a middle-class neighborhood that rises up a hillside in Trinidad's Tunapuna-Piarco region.