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Human-driven climate change meets 'gold standard' of scientific certainty
New statistical analyses show that human-driven climate change is a virtual certainty.
- While it's difficult to find people who deny climate change is happening, some still argue that humans are not climate change's primary cause.
- By applying peer-reviewed statistical methods to 40 years' worth of satellite data, researchers have determined that the evidence of human-driven climate change has passed the gold standard of scientific certainty: the five-sigma level.
- This threshold is used in particle physics to determine the existence of new particles; now, it's being used to definitively state that humans are the cause of climate change.
As if there were any reason to doubt the 97% of climate scientists who believe that climate change is driven by human activities, now more data has confirmed what we already knew. The fact that the five most recent years have been the five warmest in 139 years, the fact that global temperatures have risen by 0.8°C since 1880, and the fact that arctic sea ice is decreasing by 12.8% per decade are definitively attributable to human-driven climate change.
The new certainty comes from a recent article by Benjamin Santer of the Lawrence Livermore National Laboratory and colleagues. The article, published in Nature Climate Change, looked at three of the most relied-on satellite datasets used to conduct climate science: Specifically, the Remote Sensing Systems (RSS), the Center for Satellite Applications and Research (STAR), and the University of Alabama in Huntsville (UAH) datasets.
The researchers were looking through the datasets for a specific signal—that is, the "thumbprint" of human-induced climate change—in the noise of the data—the general variance in the climate. They found that the likelihood that the current change in climate is derived from human activities has surpassed the "gold standard" of statistical significance, or the five-sigma level.
For most, the fact that the researchers detected the fingerprint of human-driven climate change at the five-sigma level probably means exactly nothing. Sigma refers to a standard deviation—a measurement of how spread out a value is from the mean or average. Another way of thinking about it is that the sigma levels correspond to how likely it is that a given observation actually matches what one is looking for versus how likely it is that the observation has arisen from random chance.
Generally, the five-sigma level, or five standard deviations, is used in particle physics as the threshold before a discovery can be declared. Because many of the observations from particle physics can occur by chance rather than from, say, a newly discovered type of particle, physicists tend to set the bar high. When an observation meets the five-sigma level, it means that only once out of 3.5 million times could the observation have occurred by chance. This threshold was used to declare the discovery of the Higgs boson and the first detection of gravitational waves.
Now, lead author Santer claims that the three biggest datasets on climate change show that human-driven climate change has reached the five-sigma level: There is a one in 3.5 million chance that our climate is changing because of some other reason than human activities. "The narrative out there that scientists don't know the cause of climate change is wrong," said Santer in an interview with Reuters. "We do."
This graph depicts the signal-to-noise ratio found in the three datasets over time. The signal refers to human-driven climate change, while the noise refers to the general variance in our climate.
The RSS (red) and STAR (blue) datasets showed that the evidence for human-driven climate change has passed the five-sigma level a while ago, but the UAH (green) dataset only passed this threshold recently. (Santer et al., 2019)
Making use of 40 years of satellite data
Santer and colleagues' work was based on the previous work by Klaus Hasselmann, who developed a statistical approach for attributing climate change to various sources. Hasselmann's original work was developed in 1979, however, only a year after the first satellites began collecting data on global temperature. By modifying Hasselmann's approach and applying it to the 40 years of satellite data we now have access to, Santer and colleagues could track the growing likelihood of human-driven climate change.
Because of variations in satellite instrumentation, condition, and configuration, not all three datasets showed the same level of confidence in human-driven climate change. As Santer writes, "In two out of three datasets, fingerprint detection at a 5σ [five-sigma] threshold—the gold standard for discoveries in particle physics—occurs no later than 2005, only 27 years after the 1979 start of the satellite measurements." In 2016, the third dataset from the UAH satellite also showed that the fingerprint of human activity in climate change passed the five-sigma threshold. In the conclusion of his article, Santer summarized these findings as succinctly as possible: "Humanity cannot afford to ignore such clear signals."
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Richard Feynman once asked a silly question. Two MIT students just answered it.
Here's a fun experiment to try. Go to your pantry and see if you have a box of spaghetti. If you do, take out a noodle. Grab both ends of it and bend it until it breaks in half. How many pieces did it break into? If you got two large pieces and at least one small piece you're not alone.
But science loves a good challenge<p>The mystery remained unsolved until 2005, when French scientists <a href="http://www.lmm.jussieu.fr/~audoly/" target="_blank">Basile Audoly</a> and <a href="http://www.lmm.jussieu.fr/~neukirch/" target="_blank">Sebastien Neukirch </a>won an <a href="https://www.improbable.com/ig/" target="_blank">Ig Nobel Prize</a>, an award given to scientists for real work which is of a less serious nature than the discoveries that win Nobel prizes, for finally determining why this happens. <a href="http://www.lmm.jussieu.fr/spaghetti/audoly_neukirch_fragmentation.pdf" target="_blank">Their paper describing the effect is wonderfully funny to read</a>, as it takes such a banal issue so seriously. </p><p>They demonstrated that when a rod is bent past a certain point, such as when spaghetti is snapped in half by bending it at the ends, a "snapback effect" is created. This causes energy to reverberate from the initial break to other parts of the rod, often leading to a second break elsewhere.</p><p>While this settled the issue of <em>why </em>spaghetti noodles break into three or more pieces, it didn't establish if they always had to break this way. The question of if the snapback could be regulated remained unsettled.</p>
Physicists, being themselves, immediately wanted to try and break pasta into two pieces using this info<p><a href="https://roheiss.wordpress.com/fun/" target="_blank">Ronald Heisser</a> and <a href="https://math.mit.edu/directory/profile.php?pid=1787" target="_blank">Vishal Patil</a>, two graduate students currently at Cornell and MIT respectively, read about Feynman's night of noodle snapping in class and were inspired to try and find what could be done to make sure the pasta always broke in two.</p><p><a href="http://news.mit.edu/2018/mit-mathematicians-solve-age-old-spaghetti-mystery-0813" target="_blank">By placing the noodles in a special machine</a> built for the task and recording the bending with a high-powered camera, the young scientists were able to observe in extreme detail exactly what each change in their snapping method did to the pasta. After breaking more than 500 noodles, they found the solution.</p>
The apparatus the MIT researchers built specifically for the task of snapping hundreds of spaghetti sticks.
(Courtesy of the researchers)
What possible application could this have?<p>The snapback effect is not limited to uncooked pasta noodles and can be applied to rods of all sorts. The discovery of how to cleanly break them in two could be applied to future engineering projects.</p><p>Likewise, knowing how things fragment and fail is always handy to know when you're trying to build things. Carbon Nanotubes, <a href="https://bigthink.com/ideafeed/carbon-nanotube-space-elevator" target="_self">super strong cylinders often hailed as the building material of the future</a>, are also rods which can be better understood thanks to this odd experiment.</p><p>Sometimes big discoveries can be inspired by silly questions. If it hadn't been for Richard Feynman bending noodles seventy years ago, we wouldn't know what we know now about how energy is dispersed through rods and how to control their fracturing. While not all silly questions will lead to such a significant discovery, they can all help us learn.</p>
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In a recent study, researchers examined how Christian nationalism is affecting the U.S. response to the COVID-19 pandemic.
- A new study used survey data to examine the interplay between Christian nationalism and incautious behaviors during the COVID-19 pandemic.
- The researchers defined Christian nationalism as "an ideology that idealizes and advocates a fusion of American civic life with a particular type of Christian identity and culture."
- The results showed that Christian nationalism was the leading predictor that Americans engaged in incautious behavior.
A pastor at the chapel of the St. Josef Hospital on April 1, 2020 in Bochum, German
Sascha Schuermann/Getty Images<p>Christian nationalists, in general, believe the U.S. and God's will are tied together, and they want the government to embody conservative Christian values and symbols. As such, they also believe the nation's fate depends on how closely it adheres to Christianity.</p><p style="margin-left: 20px;">"Unsurprisingly then, in the midst of the COVID‐19 pandemic, conservative pastors prophesied God's protection over the nation, citing America's righteous support for President Trump and the prolife agenda," the researchers write.</p><p style="margin-left: 20px;">"Correspondingly, the link between Christian nationalism and God's influence on how COVID‐19 impacts America can be seen in proclamations about God's divine judgment for its immorality―with the logic being that God is using the pandemic to draw wayward America <em>back </em>to himself, which assumes the two belong together."</p><p>The logical conclusion to this kind of thinking: America can save itself not through cautionary measures, like mask-wearing, but through devotion to God. What's more, it stands to reason that Christian nationalists are less likely to trust the media and scientists, given that these sources are generally not concerned with promoting a conservative, religious view of the world.</p><p>(The researchers note that they're unaware of any research directly linking Christian nationalism to distrust of media sources, but that they're almost certain the two are connected.)</p>
Predicted values of Americans' frequency of incautious behaviors during the COVID‐19 pandemic across values of Christian nationalism
Perry et al.<p>In the new study, the researchers examined three waves of results from the Public and Discourse Ethics Survey. One wave of the survey was issued in May, and it asked respondents to rate how often they engaged in both incautious and precautionary behaviors.</p><p>Incautious behaviors included things like "ate inside a restaurant" and "went shopping for nonessential items," while precautionary behaviors included "washed my hands more often than typical" and "wore a mask in public."</p><p>To measure Christian nationalism, the researchers asked respondents to rate how strongly they agree with statements like "the federal government should advocate Christian values" and "the success of the United States is part of God's plan."</p><p>The results suggest that, compared to other groups, Christian nationalists are far less likely to wear masks, socially distance and take other precautionary measures amid the COVID-19 pandemic.</p><p style="margin-left: 20px;">"Christian nationalism was the leading predictor that Americans engaged in incautious behavior during the pandemic, and the second leading predictor that Americans avoided taking precautionary measures."</p><p>But that's not to say that religious beliefs are causing Americans to reject mask-wearing or social distancing. In fact, when the study accounted for Christian nationalist beliefs, the results showed that Americans with high levels of religiosity were likely to take precautionary measures for COVID-19.</p>
Limitations<p>Still, the researchers note that they're theorizing about the connections between Christian nationalism and COVID-19 behaviors, not documenting them directly. What's more, they suggest that certain experiences — such as having a family member that contracts COVID-19 — might change a Christian nationalist's behaviors during the pandemic.</p><p style="margin-left: 20px;">"Limitations notwithstanding, the implications of this study are important for understanding Americans' curious inability to quickly implement informed and reasonable strategies to overcome the threat of COVID‐19, an inability that has likely cost thousands of lives," they write.</p>
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