This story is a roundup of articles from The Conversation's archives.
As cold weather settles in across North America, some communities have already started up their snowplows, while others keep watchful eyes on the forecast. Snow and ice can wreck travel plans, but they also play important ecological roles. And frozen water can take amazing forms. For days when all talk turns to winter weather, we spotlight these five stories from our archives.
1. The Strange Forms Water Can Take
Beyond snowflakes and icicles, frozen water can behave in surprising ways. For example, during very cold snaps, lakes can appear to steam like a sauna bath.
As Colorado State University atmospheric scientist Scott Denning explains, this happens because the liquid water in the lake can't be colder than the freezing point — about 32 degrees Fahrenheit. As water evaporates from the relatively warm lake into the cold dry air, it condenses from vapor (gaseous water) to tiny droplets of water in the air, which look like steam.
When it gets extremely cold, ice can form on the ocean's surface. Waves break it up, so the water starts to look like an undulating slurpee. "For anyone willing to brave the cold, it's wild to stand by the shore and watch the smoking slushy sea with its slow-motion surf," Denning writes.
2. How Road Salt Tames Ice
When a big storm is forecast, utility trucks often will head out to pre-treat streets and highways, typically spraying rock salt or saltwater solutions. But contrary to popular belief, salt doesn't melt ice.
Water freezes at 32 degrees Fahrenheit, but mixing it with salt lowers its freezing point. "The salt impedes the ability of the water molecules to form solid ice crystals," explains Julie Pollock, assistant professor of chemistry at the University of Richmond. "The degree of freezing point depression depends on how salty the solution is." When dry salt is spread on ice, it relies on the sun or the friction of car tires to melt the ice, then keeps it from re-freezing.
Pulses of salt can harm plants, water bodies and aquatic organisms when it washes off of roads — especially during spring runoff, which can carry huge doses. Researchers are working to find more benign options, and are currently studying additives including molasses and beet juice.
3. Why Trees Need Snow
Snow may seem like nothing but trouble, especially if you have to shovel it. But it's also a valuable resource. In the Northeast, environmental scientists Andrew Reinmann and Pamela Templer have found that winter snow cover acts like a blanket, protecting tree roots and soil organisms from the cold.
In experimental forest plots where Reinmann and Templer removed snow from the ground, they have observed that
"…frost penetrates a foot or more down into the soil, while it rarely extends more than two inches deep in nearby reference plots with unaltered snowpack. And just as freeze-thaw cycles create potholes in city streets, soil freezing abrades and kills tree roots and damages those that survive."
Climate change is shortening northeast winters and decreasing snowfall, with serious effects on forests. "Losing snowpack can reduce forest growth, carbon sequestration and nutrient retention, which will have important implications for climate change and air and water quality all year-round," Reinmann and Templer predict.
4. Frozen Reservoirs
Today’s #snowpack on Montgomery Pk in northern White Mtns CA, seen from down in Benton Valley. Very good snow for J… https://t.co/PrFvN50V7G— Laura Cunningham (@Laura Cunningham)1559786481.0
Snow is even more valuable in western states, where many communities get large shares of their drinking water from snowpack that lingers at high altitudes well into the warm months. Here, too, warming winters mean less snow, and scientists are already observing "snow droughts."
Adrienne Marshall a research fellow studying hydrology and climate change at the University of Idaho, defines a snow drought as a year with snowpack so low that historically it would only happen once every four years or less.
"Today, back-to-back snow droughts in the western U.S. occur around 7% of the time," she writes. "By mid-century, if greenhouse gas emissions continue to increase, our results predict that multiyear snow droughts will occur in 42% of years on average."
Snowpack is also melting earlier in the spring, which means less water is available in summer. These changes are affecting cities, farms, forests, wildlife and the outdoor recreation industry across the West year-round.
5. Can We Make It Snow?
If nature doesn't deliver as much snow as we need, what about helping it along? Many western states and agencies have tried to do just that for years by cloud-seeding — adding particles to the atmosphere that are thought to serve as artificial ice crystals, promoting the formation of snow.
There's just one hitch: No one has proved it actually works. Nonetheless, "Western states need water, and many decision-makers believe that cloud seeding can be a cost-effective way to produce it," write atmospheric scientists Jeffrey French and Sarah Tessendorf.
In a 2018 study, French, Tessendorf and colleagues used new computer modeling tools and advanced radar to see whether they could detect ice crystals forming on silver iodide particles injected into clouds. They hung imaging probes from the wings of research planes, which flew in and out of the seeded areas of clouds. Sure enough, in those zones ice crystal formation increased by hundreds, leading to the formation of snow. No such results occurred in non-seeded regions.
More research is needed to see whether cloud seeding can change water balances over large areas. And ultimately, even if that proves to be true, another question will remain: Whether it's worth the cost.
Reposted with permission from The Conversation.
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EcoWatch Daily Newsletter
By Julia Conley
A new campaign unveiled this weekend by the nonprofit organization Fossil Free Media aims to expand on the goals of the fossil fuel divestment movement, cutting into oil and gas companies' profit margins through their public relations and ad campaigns.
<div id="1dcf1" class="rm-shortcode" data-rm-shortcode-id="d5e39a5a3812bc2589ba8aa0563756e0"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1330177734799208465" data-partner="rebelmouse"><div style="margin:1em 0">PR and ad companies' work for the fossil fuel industry is pushing the planet past the breaking point.… https://t.co/wOuDBM26ne</div> — Clean Creatives (@Clean Creatives)<a href="https://twitter.com/cleancreatives/statuses/1330177734799208465">1605974060.0</a></blockquote></div>
<div id="21b90" class="rm-shortcode" data-rm-shortcode-id="bdc23e69ff18075b4fb5df6d4939b9f5"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1330205383848288257" data-partner="rebelmouse"><div style="margin:1em 0">Porter Novelli isn't some small shop: they've got offices and clients in 60 countries and are part of @Omnicom, the… https://t.co/iw0BCmrdzx</div> — Jamie Henn (@Jamie Henn)<a href="https://twitter.com/jamieclimate/statuses/1330205383848288257">1605980652.0</a></blockquote></div><p>"It's a BIG deal that they're dropping fossil fuel clients—let's make sure it's the drop that starts a flood," wrote Henn. </p>
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By Jason Farley
COVID-19 has disrupted our daily lives, and it is poised to completely disrupt the holiday season. As people make holiday plans and think about ways to reduce the risks to their loved ones, a strategy is essential.
Are masks really necessary at family gatherings?<p>If you're gathering with friends and family who don't live in your home, yes. Just because you're with people you know doesn't mean you're safe from the coronavirus. Infection rates are <a href="https://coronavirus.jhu.edu/data/new-cases-50-states" target="_blank" rel="noopener noreferrer">higher now than they have ever been</a> in the U.S., and <a href="https://youtu.be/ehdgceGzQxs" target="_blank" rel="noopener noreferrer">small gatherings have been a source</a> of viral spread. All it takes is one infected person who doesn't know they have the coronavirus to infect others.</p><p>Remember, people can be <a href="https://medical.mit.edu/covid-19-updates/2020/07/how-long-symptom-onset-person-contagious" target="_blank" rel="noopener noreferrer">contagious two to three days</a> before symptoms show – that's one thing that makes this virus so hard to stop. And it's why, even if you feel fine, you should wear a mask.</p><p>The Centers for Disease Control and Prevention now estimates that when both people are wearing masks, the <a href="https://www.cdc.gov/coronavirus/2019-ncov/more/masking-science-sars-cov2.html" target="_blank">likelihood of infection is low</a>.</p>
Who am I protecting when I wear a mask?<p>In a word: everyone. The coronavirus <a href="https://theconversation.com/aerosols-are-a-bigger-coronavirus-threat-than-who-guidelines-suggest-heres-what-you-need-to-know-142233" target="_blank">spreads through respiratory droplets</a> that you send out into the air when you talk, sing or even just breathe. The tiniest of these droplets can float on air currents for long periods.</p><p>Face masks stop many of those droplets, reducing the amount of virus in the air. That lowers your chances of getting infected, and it also lowers the chances that you'll infect someone else.</p><p><a href="https://www.cdc.gov/coronavirus/2019-ncov/more/masking-science-sars-cov2.html" target="_blank">Studies of people who had prolonged exposure</a> to others with COVID-19 have demonstrated how masks can reduce the chance of the virus spreading. In general, <a href="https://www.cdc.gov/coronavirus/2019-ncov/more/masking-science-sars-cov2.html" target="_blank" rel="noopener noreferrer">well-fitted cloth masks</a> made up of multiple layers can stop most large droplets and at least half of the tiny ones. Plastic <a href="https://doi.org/10.1101/2020.10.05.20207241" target="_blank" rel="noopener noreferrer">face shields</a> alone are far less effective. <a href="https://www.washingtonpost.com/health/2020/08/13/cdc-mask-guidance-masks-valves/" target="_blank" rel="noopener noreferrer">Face masks with valves or vents</a> might be good for construction work, but they don't stop the wearer from breathing out virus into the air.</p>
Can I reuse a mask and when should I replace it?<p>Reusable masks should be kept clean and dry. We're moving into cold and flu season, and noses get drippy. A rule of thumb: Anytime a mask is wet to the point that you can discern the wetness, it's time for a new one if it's disposable, or it's time to clean your reusable mask.</p><p>Wetness allows viruses to more easily move through paper or fabric because it allows the threads to move and may reduce the electrostatic charge in the masks that add extra protection with some fabrics.</p><p>In general, you can use a mask that stays clean and dry for about a week before you need to wash or discard it.</p>
How should I clean a cloth mask?<p>Washing your mask is like washing your clothes. You know when it is time.</p><p>In general, <a href="https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-to-wash-cloth-face-coverings.html" target="_blank">cleaning your mask weekly</a> should be sufficient. If odors develop before then, it's a good idea to wash it sooner. Odor generally means bacterial buildup.</p><p>Cleaning your mask by hand with soap and water is your best option. Using a general detergent on a gentle cycle in the washing machine is also fine, but that may increase the risk of damage, depending on the quality of the material. COVID-19 is not a hardy virus. Any soap or detergent should work fine. There's no need for special chemicals, bleach or harsh soaps.</p><p>Be careful to remove any inserts before washing. Inserted filters are generally not washable.</p><p>Air drying masks works best. Remember, masks should be completely dry before use. So be sure to have a replacement mask handy while the one you just washed dries.</p><p>Sunlight is always a great source of heat to dry your mask. Also, sunlight has ultraviolet radiation, which has been shown to <a href="http://doi.org/10.1111/php.13293" target="_blank" rel="noopener noreferrer">eliminate coronavirus</a> and is also known to have antibacterial properties.</p>
Can I wear the mask below my nose?<p>Wearing your mask below your nose is, frankly, ridiculous.</p><p>Think about it. If you are breathing through your nose and only covering your mouth, you are effectively eliminating the point of the mask. Properly wearing a mask requires covering both your nose and mouth at all times.</p><p>Studies show that wearing a proper cloth mask or surgical mask while exercising <a href="http://doi.org/10.1513/AnnalsATS.202008-990CME" target="_blank">doesn't affect the flow of oxygen</a> or carbon dioxide in any detectable way. So, unless you have serious heart and lung problems, that isn't an excuse.</p>
How do I safely remove my mask if I’m going to eat or drink?<p>When you <a href="https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-to-wash-cloth-face-coverings.html" target="_blank">take your mask off</a>, remove it carefully by the straps without touching anything else and put it somewhere safe, like wrapped in paper in a purse, bag or pocket. Then wash your hands or use hand sanitizer. When you put it back on, wash your hands again.</p>
So, how can I have a safe holiday gathering?<p>The safest way to celebrate this year is to do so with members only within your household. The <a href="https://www.cdc.gov/coronavirus/2019-ncov/daily-life-coping/holidays.html" target="_blank" rel="noopener noreferrer">CDC is now stressing that point</a>, as well. If you do celebrate with friends and relatives from outside your household, you need an action plan to reduce the risk of exposure.</p><p>Here are five recommendations:</p><ul><li>Limit the number of people – fewer people means fewer opportunities for exposure, and you'll have more room to spread out.</li><li>Require masks when not eating or drinking.</li><li>Use physical distancing when eating. Try to seat people <a href="https://doi.org/10.1136/bmj.m3223" target="_blank" rel="noopener noreferrer">at least 6 feet apart</a>. Eat outside if you can.</li><li>Consider being tested for COVID-19 before traveling or gathering. It's not a guarantee, but it can help flag illnesses. Remember to self-isolate between the test and the event.</li><li>Be prepared to self-isolate for 14 days after traveling or participating in any event that involves people from outside your home.</li></ul><p>[<em>Research into coronavirus and other news from science</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-corona-research" target="_blank" rel="noopener noreferrer">Subscribe to The Conversation's new science newsletter</a>.]</p><p><em>The map has been updated with New Hampshire announcing a mask mandate effective Nov. 20.</em></p><p><em>Jason Farley is a professor, infectious disease-trained epidemiologist and nurse practitioner at the Johns Hopkins University School of Nursing.<br></em></p><p><em>Disclosure statement: Jason Farley, PhD, MPH, ANP-BC, FAAN receives funding from the National Institutes of Health on the Rapid Acceleration of Diagnostics for COVID-19 and Becton Dickinson for studies on SARS-CoV-2 diagnostics.</em></p><p><em>Reposted with permission from <a href="https://theconversation.com/why-face-masks-belong-at-your-thanksgiving-gathering-7-things-you-need-to-know-about-wearing-them-150130" target="_blank">The Conversation</a>. </em></p>
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By Tara Lohan
How much of U.S. energy demand could be met by renewable sources?
According to a new report from the Institute for Local Self-Reliance, the answer is an easy 100%.
Graphic: ILSR, Energy Self-Reliant States 2020