Blue Sharks Are True Globalists, Tagging Data Shows
Blue sharks are among the widest-ranging shark species in the oceans. We know this partly because from 1962 to 2013, 117,962 blue sharks were tagged as part of the ongoing Cooperative Shark Tagging Program.
This partnership between the commercial fishing industry, the U.S. government, recreational fishermen and academic research scientists is the longest-running tagging program in the world. Since its launch in 1962, participants have tagged hundreds of thousands of sharks representing 35 different species.
A dart tag, one type used in the Cooperative Shark Tagging Program. NOAA
More than half (51%) of the animals tagged were blue sharks (Prionace glauca) – a total of 117,962 individual sharks. This is probably because blues are abundant: They are found in all of the world's oceans, as far north as Alaska and as far south as Chile, but rarely venture near shore.
Unlike some other sharks, blues are not a prized commercial species, likely because most people think they taste disgusting. That makes fishermen willing to tag and release them instead of harvesting them.
Each tag attached to a shark carries an identification number and contact information, so that recaptures can be reported and matched to data collected during the initial tagging. The data show that these sharks really move. One traveled a record-breaking 3,997 nautical miles from waters off Long Island, New York, where it was first tagged, to the south Atlantic where it was recaptured – a distance longer than the Great Wall of China.
The sharks were caught in all seasons throughout their range, in tropical waters warmer than 68 degrees Fahrenheit (20 degrees Celsius) and temperate waters, which range from 50°-68°F (10°-20°C). In more tropical climates, blue sharks occupy waters as deep as 1,150 feet (350 meters), which are cooler than water near the surface. Their ability to inhabit a wide range of depths enables them to move around as seasons and water temperatures change.
Tagging data confirm that blue sharks migrate incredibly long distances, with some even crossing the equator from the North Atlantic to the South Atlantic. All of this movement allows them to mix and mingle with individuals throughout their range. This tells scientists that all blue sharks in the Atlantic Ocean are part of one mating pool, and can be considered one big population, rather than smaller separate groups.
The fact that blue sharks range so widely suggests that an event in one part of the Atlantic, such as an oil spill, could potentially affect the number of mating pairs across the population. This could reduce the number of blue sharks in the next generation and lead to a decline in their population throughout the Atlantic. It could also reduce their genetic diversity and make the survivors more prone to mortality from disease.
About 7% of the tagged blue sharks (8,213) were recaptured later, sometimes after more than a decade. One shark was recaptured nearly 16 years after it was first tagged. Scientists estimated that this shark was between 8 and 11 years old at the time it was tagged, based on its size. That original age estimate would have made the shark 24 to 27 years old when it was recaptured, which falls within the current estimated range of maximum age for the species.
Thanks to tagging data, scientists have learned a lot about the ecology of several species, including smooth dogfish and sandbar sharks. As a scientist pursuing a career in marine conservation, I look forward to more wondrous discoveries about these marvelous animals.
Reposted with permission from The Conversation.
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For some combat veterans, the Fourth of July is not a time to celebrate the independence of the country they love. Instead, the holiday is a terrifying ordeal. That's because the noise of fireworks – loud, sudden, and reminiscent of war – rocks their nervous system. Daily fireworks in many U.S. cities in recent weeks have no doubt been interfering with the sleep and peace of mind of thousands of veterans.
What Is PTSD?<p><a href="https://theconversation.com/veterans-refugees-and-victims-of-war-crimes-are-all-vulnerable-to-ptsd-130144" target="_blank">PTSD</a> can occur when someone is exposed to extreme exposure traumatic experience. Typically, the trauma involves a threat of death, serious injury, or sexual violence. Along with war veterans, it happens to refugees; to victims of gun violence, rape and other physical assaults; and to survivors of car accidents and natural disasters like earthquakes or tornadoes.</p><p>PTSD can also happen by witnessing trauma or its aftermath, often the case with <a href="https://www.psychiatry.org/patients-families/ptsd/what-is-ptsd" target="_blank">first responders</a> and <a href="https://www.psychologytoday.com/us/blog/the-many-faces-anxiety-and-trauma/202006/invisible-wounds-the-frontline-heroes" target="_blank">front-line workers</a>.</p><p>All this adds up to tens of millions of Americans. Up to 30% of combat veterans and first responders, and 8% of civilians, <a href="https://www.ptsd.va.gov/professional/treat/essentials/epidemiology.asp" target="_blank">fulfill the diagnostic criteria for PTSD</a>. And that criteria is not easily met: symptoms of PTSD include nightmares, flashbacks, intrusive trauma memories, difficulty sleeping, avoidance of reminders of trauma, negative emotions, and what we call "hyperarousal symptoms."</p>
Fireworks Can Trigger Flashbacks<p>Hyperarousal, a core component of PTSD, occurs when a person is hyper-alert to any sign of threat – constantly on edge, easily startled and continuously screening the environment.</p><p>Imagine, for instance, stepping down the stairs in the dark after hearing a noise; you're worried an intruder might be downstairs. Then a totally unpredictable loud sound explodes right outside your window.</p><p>For people with PTSD, that sound – reminiscent of gunfire, a thunderstorm or a car crash – <a href="https://theconversation.com/veterans-refugees-and-victims-of-war-crimes-are-all-vulnerable-to-ptsd-130144" target="_blank">can cause</a> a panic attack or trigger flashbacks, a sensory experience that makes it seem as if the old trauma is happening here and now. Flashbacks can be so severe that combat veterans may suddenly drop to the ground, the same way they would when an explosion took place in combat. Later, the experience can trigger nightmares, insomnia or worsening of other PTSD symptoms.</p><p>Those of us who set off fireworks need to ask ourselves: Are those few minutes of fun worth the hours, days, or weeks of torment that will begin for some of our friends and neighbors – including many who put their lives on the line to protect us?</p>
Who Else Is Affected?<p>Millions of others, though not diagnosed with PTSD, may similarly be affected by fireworks. <a href="https://adaa.org/about-adaa/press-room/facts-statistics" target="_blank">One in five Americans</a> have an anxiety disorder, many with symptoms of hyperarousal. Also impacted are those with autism or developmental disabilities; they find it difficult to cope with the noise, or just the drastic change from life routines. Then there are people who have to work, holiday or not: nurses, physicians and first responders, who have to be up at 4 a.m. for a 30-hour shift.</p><h3>How to Reduce the Negative Impact</h3><p>There are ways to reduce how fireworks affect others:</p><ul><li>For those with PTSD, the unexpected nature of fireworks is probably the worst part. So at least make it as predictable as possible. Do it in designated areas during designated times. Don't explode one, for instance, two hours after the designated time window. And avoid setting them off <a href="https://www.theguardian.com/society/2018/jul/04/fireworks-ptsd-fourth-of-july-veterans-shooting-survivors" target="_blank">on the 3rd</a>. People are less prepared then.</li><li>If you're aware that a veteran or trauma survivor lives in the neighborhood, move the noise as far as possible from their home and give them prior warning. Consider putting a sign in your front yard noting the time you'll set the fireworks.</li><li>Remember, it doesn't have to be super loud to make it fun. Consider using <a href="https://thehill.com/opinion/energy-environment/504964-its-time-for-silent-fireworks" target="_blank">silent fireworks</a>. And you don't have to be the one who lights the fireworks. Simply enjoy watching while your city or township does it safely.</li></ul>
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By Jeff Berardelli
For the past year, some of the most up-to-date computer models from the world's top climate modeling groups have been "running hot" – projecting that global warming may be even more extreme than earlier thought. Data from some of the model runs has been confounding scientists because it challenges decades of consistent projections.
International Effort to Evaluate Climate Models<p>For the past 25 years the international community has been evaluating and comparing the world's most sophisticated climate models produced by various teams at universities, research centers, and government agencies. The effort is organized by the World Climate Research Programme under the United Nations World Meteorological Organization.</p><p>Climate models are complicated computer programs composed of millions of lines of code that calculate the physical properties and interactions between the main climate forces like the atmosphere, oceans, and solar input. But models also go a lot further, incorporating other systems like ice sheets, forests, and the biosphere, to name a few. The models are then used to simulate the real-world climate system and project how certain changes, like added pollution or land-use changes, will alter the climate.</p><p>Every few years there is a new comprehensive international evaluation called the Coupled Model Intercomparison Project (CMIP). In the sixth such effort, known as CMIP6 and now under way, experts are reviewing about 100 models.</p><p>Information gleaned from this effort will act as a scientific foundation for the U.N.'s Intergovernmental Panel on Climate Change (IPCC) next major assessment report, scheduled for release in 2021. The goal of the report – the sixth in 30 years – is to inform the international community about how much the climate has changed, and, importantly, how much change can be expected in coming decades.</p>
A Conundrum Emerges<p>Over the past year, the CMIP6 collection of models being reviewed threw researchers an unexpected curveball: a significant number of the climate model runs showed substantially more global warming than previous model versions had projected. If accurate, the international climate goals would be nearly impossible to achieve, and there would be significantly more extreme impacts worldwide.</p><p>A foundational experiment in every report addresses "sensitivity": If you double levels of carbon dioxide (CO2) that were in the air before the Industrial Revolution, how much warming do the models show? This doubling is not expected for a few more decades, but it is a quick way to communicate the critical role of greenhouse gases in changing the climate.</p><p>The amount of CO2 in the atmosphere has increased by 35% since the 1800s because of the burning of fossil fuels. As a result, global temperatures have already increased by more than 2 degrees Fahrenheit.</p><p>In the first IPCC assessment report, published in 1990, the answer to that question about the impact of doubling carbon dioxide gave a fairly wide range of results – between 2.7-8 degrees F of global warming. Since then, four more assessments issued six to seven years apart reached nearly the exact same conclusion on sensitivity.</p><p>But that sensitivity may, for the first time, change significantly in next year's assessment. Why? Because starting last year, numerous models in the CMIP6 collection displayed even bigger spikes in temperature upon doubling of CO2 concentrations. We're in serious trouble if the climate sensitivity falls in the mid or upper range of the previous assessments. But if the new, higher estimates are correct, the impacts on civilization would be catastrophic.</p>
In the above CarbonBrief interactive visualization, the bars offer a comparison in the range of sensitivity in the CMIP5 models (gray) and CMIP6 models (blue).
New and Encouraging Evidence Is Emerging<p>At first, scientists were uncertain whether the new model runs were on to something, so the international modeling community dug in to produce multiple studies. The results are not yet conclusive, but a gradual collective sigh of relief seems to be materializing.</p><p>"Evidence is emerging from multiple directions that the models which show the greatest warming in the CMIP6 ensemble are likely too warm," explains Dr. Gavin Schmidt, director of NASA's Goddard Institute for Space Studies.</p><p>For example, <a href="https://www.earth-syst-dynam-discuss.net/esd-2020-23/" target="_blank">a study</a> released April 28 evaluated the past performance of the models making up the CMIP6 ensemble. The team assigned weights to each model based upon historical performance of their warming projections, weighing the poorer performing models less. By doing so, both the mean warming and the range of warming scenarios in the CMIP6 ensemble decreased, meaning the warmest models were the ones with weaker historical performance. This result supports a finding that a subset of the models are too warm.</p><p>That conclusion is supported by another new study evaluating one particular model – the Community Earth System Model (CESM2) – that showed greater warming. Using that model, the researchers simulated the climate in the early Eocene era, about 50 million years ago, when rainforests thrived in the Arctic and Antarctic. The CESM2 simulated a historical climate that seems way too warm compared with what is known about that era from geological data, indicating that the model is likely also too warm in its future projections.</p><p>Two other recent studies of the CMIP6 models being evaluated use clever analysis methods to <a href="https://www.google.com/url?q=https://www.earth-syst-dynam-discuss.net/esd-2019-86/&sa=D&ust=1589209938203000&usg=AFQjCNHYwFB-1KqndGfJ4sXdrrm9DpbLaQ" target="_blank">narrow the range</a> of future warming projections and also <a href="https://www.google.com/url?q=https://advances.sciencemag.org/content/6/12/eaaz9549&sa=D&ust=1589209938203000&usg=AFQjCNEhKY1YZ19qgjSZ_hJM14JmzqXOXw" target="_blank">reduce the projected warming</a> of the CMIP6 models by 10 to 15%.</p><p>Through the intensive research spurred by the CMIP6 climate-sensitivity curveball, scientists have been able to turn a confounding challenge into a confidence builder, providing even greater certainty than they had before in both the abilities of the climate science community and in the computer models used. Moreover, the experience has helped unearth uncertainties remaining in the modeling process.</p><p>Experts conclude much of this uncertainty probably lies in the complexity of clouds. "We have been looking as a community at why the models with greater warming are doing what they are doing – and it's tied to cloud feedbacks in the southern mid-latitudes mostly," explains Schmidt.</p><p>In fact, <a href="https://advances.sciencemag.org/content/6/26/eaba1981" target="_blank">a new study</a> addressing the increased sensitivity was published in Science Advances stating, "Cloud feedbacks and cloud-aerosol interactions are the most likely contributors to the high values and increased range of ECS [sensitivity] in CMIP6."</p>
Understanding the Complexity of Clouds<p>It's long been known in climate modeling circles that cloud processes and interactions are a potential weak link for climate modeling. That reality has been brought front and center by the urgent challenges posed during this CMIP6 evaluation period, but the current evaluation of models also provides an opportunity for discovery and improvement.</p><p>Cloud complexity comes from the reality that clouds have a multitude of sizes, altitudes, and textures. Some clouds cool Earth by providing shade, reflecting sunlight back into space. Others act like a blanket, trapping heat and warming the world.</p><p>Given that about <a href="https://www.nasa.gov/vision/earth/lookingatearth/icesat_light.html" target="_blank">70% of the globe</a> is covered by clouds at any given time, it's no surprise that they play an integral role in regulating the climate. The challenge is to figure out which types of clouds will increase, which will decrease, and what the net effect will be on cooling or warming as the climate changes.</p><p><a href="https://www.nature.com/articles/s41561-019-0310-1" target="_blank">One study</a> last year reached an alarming conclusion: Left unchecked, the release of CO2 into the atmosphere may lead to a tipping point where shallow low clouds disappear – leading to runaway, catastrophic warming of nearly 15 degrees F. While scientists see that outcome as only a remote possibility, it drives home the urgent need to better understand clouds.</p><p>"We have a saying at NOAA: It isn't rocket science – it's much, much harder than that," quips Dr. Chris Fairall, ATOMIC's lead investigator. "One of the major problems for modeling is there is not clean separation of scales." The photo below is one that Fairall took from the NOAA P-3 aircraft.</p>
Investigating the Secrets of Clouds<p>To address the urgent question about the dynamics and role of clouds in a warming world, NOAA and European partners launched their ongoing research effort unprecedented in scale. The U.S. contribution, ATOMIC – short for Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign – is an international science mission that was featured recently on "<a href="https://www.cbsnews.com/video/study-aims-to-examine-links-between-climate-change-and-clouds/" target="_blank">CBS This Morning: Saturday</a>."</p>
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