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Record Heat Means Hurricanes Gain Ferocity Faster
By Tim Radford
But Hurricane Harvey, which in 2017 assaulted the Gulf of Mexico and dumped unprecedented quantities of rain to cause devastating floods in Texas, happened because the waters of the Gulf were warmer than at any time on record. And they were warmer because of human-driven climate change, according to a second study.
Both studies examine the intricate machinery of a natural phenomenon, the tropical cyclone. Researchers from the Pacific Northwest National Laboratory looked at how fast four of 2017's hurricanes—Harvey, Irma, Jose and Maria—intensified: episodes in which maximum wind speed rose by at least 25 knots, which is more than 46 kilometers (approximately 29 miles), per hour within a 24-hour period. They report in Geophysical Research Letters that they combed through 30 years of satellite data from 1986 to 2015 to find a pattern.
Researchers have repeatedly warned that hurricane hazard must increase with global warming, driven by profligate human combustion of fossil fuels that dump greenhouse gases in the atmosphere. Hurricanes will hit higher latitudes and deliver more damage within the Gulf of Mexico. But climate change is only part of the answer.
The latest study did not find that storms were intensifying rapidly more often than usual. But the researchers did find that when a storm grew at speed, it became much more powerful within a 24-hour period than such storms did 30 years ago: wind speeds had gained 3.8 knots or seven kilometers (approximately 4.3 miles) an hour for each of the three decades.
And although hurricanes are driven by the warmth of the upper ocean, the researchers decided that rather than overall ocean warming, in this case the biggest factor was a natural cycle called the Atlantic Multidecadal Oscillation, which in its present phase tends to make ocean waters warmer in the central and eastern Atlantic—the spawning ground for Irma, Jose and Maria.
Warmest on Record
But when Harvey hammered the Texas coast in August 2017, the waters of the Gulf of Mexico were warmer than they had ever been. And scientists from the National Center for Atmospheric Research (NCAR) report in the journal Earth's Future that they calculated the rate of evaporation as the hurricane winds raced over the water and compared it with the levels of precipitation over the city of Houston.
To make a hurricane happen at all, ocean temperatures need to reach 26°C (approximately 79°F). When Harvey gathered its strength and its moisture, the Gulf waters had tipped 30°C.
"We show, for the first time, that the volume of rain over land corresponds to the amount of water evaporated from the unusually warm ocean," said Kevin Trenberth, a senior scientist with NCAR. "As climate change continues, we can expect more supercharged storms like Harvey."
Reposted with permission from our media associate Climate News Network.
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A central player in the fight against the novel coronavirus is our immune system. It protects us against the invader and can even be helpful for its therapy. But sometimes it can turn against us.
How does our immune system react to the coronavirus?<p>The coronavirus is — like any other virus — not much more than a shell around genetic material and a few proteins. To replicate, it needs a host in the form of a living cell. Once infected, this cell does what the virus commands it to do: copy information, assemble it, release it.</p><p>But this does not go unnoticed. Within a few minutes, the body's immune defense system intervenes with its innate response: Granulocytes, scavenger cells and killer cells from the blood and lymphatic system stream in to fight the virus. They are supported by numerous plasma proteins that either act as messengers or help to destroy the virus.</p><p>For many viruses and bacteria, this initial activity of the immune system is already sufficient to fight an intruder. It often happens very quickly and efficiently. We often notice only small signs that the system is working: We have a cold, a fever. </p>
Is there an immunity? How long does it last?<p>The good news is that it is very likely there is an immunity. This is suggested by the proximity to other viruses, epidemiological data and animal experiments. Researchers <a href="https://www.biorxiv.org/content/10.1101/2020.03.13.990226v1" target="_blank">infected four rhesus monkeys,</a> a species close to humans, with SARS-CoV-2. The monkeys showed symptoms of COVID-19, the disease caused by the coronavirus, developed neutralizing antibodies and recovered after a few days. When the recovered animals were reinfected with the virus, they no longer developed any symptoms: They were immune. </p><p>The bad news: It is not (yet) known how long the immunity will last. It depends on whether a patient has successfully developed neutralizing antibodies. Achim Hörauf estimates that the immunity should last at least one year. Within this year, every new contact with the virus acts as a kind of booster vaccination, which in turn might prolong the immunity.</p><p>"The virus is so new that nobody has a reasonable immune response," says the immunologist. He believes that lifelong immunity is unlikely. This "privilege" is reserved for viruses that remain in the body for a long time and give our immune system a virtually permanent opportunity to get to know it. Since the coronavirus is an RNA (and not a DNA) virus, it cannot permanently settle in the body, says Hörauf.</p><p>The Heidelberg immunologist <a href="https://www.klinikum.uni-heidelberg.de/immunologie/immunologie" target="_blank">Stefan Meuer</a> predicts that the novel coronavirus will also mutate like all viruses. He assumes that this could be the case in 10 to 15 years: "At some point, the acquired immunity will no longer be of any use to us because then another coronavirus will return, against which the protection that has now been formed will not help us because the virus has changed in such a way that the antibodies are no longer responsible. And then no vaccination will help either."</p>
How can we take advantage of the antibody response of the immune system?<p>Researchers are already collecting plasma from people who have successfully survived an infection with SARS-CoV-2 and are using it to treat a limited number of patients suffering from COVID-19. The underlying principle: <a href="https://www.dw.com/en/coronavirus-drugs-can-antibodies-from-survivors-help/a-52806428" target="_blank">passive immunization.</a> The studies carried out to date have shown positive results, but they have usually been carried out on only a few people.</p><p>At best, passive immunization is used only when the patient's own immune system has already started to work against the virus, says Achim Hörauf: "The longer you can leave the patients alone with the infection before you protect them with passive immunization, the better." Only through active immunization can one be protected in the long term. At the same time, it is difficult to recognize the right point in time.</p><p>PCR (polymerase chain reaction) tests are currently used to find out whether a person is infected with the coronavirus. With the help of PCR, it is not possible to tell whether or not there is reproducible viral RNA; it is just a proof of whether the virus is still present, dead or alive. A PCR test cannot tell us whether our immune system has already intervened, i.e. whether we have had contact with the virus in the past, have formed antibodies and are now protected. Researchers are therefore working on tests that check our blood for the presence of antibodies. They are already in use in Singapore, for example, and are nearing completion in the USA. With the help of these tests, it would finally be possible to gain an overview <a href="https://www.dw.com/en/corona-confusion-how-to-make-sense-of-the-numbers-and-terminology/a-52825433" target="_blank">of the unclear case numbers.</a> In addition, people who have developed antibodies against the virus could be used at the forefront of health care, for example. An "immunity passport" is even under discussion.</p>
Is it possible to become infected and/or ill several times with the coronavirus?<p>"According to all we know, it is not possible with the same pathogen," says Achim Hörauf. It is possible to become infected with other coronaviruses or viruses from the SARS or MERS group if their spike proteins look different. "As far as the current epidemic is concerned, it can be assumed that people who have been through COVID-19 will not become ill from it for the time being and will not transmit the virus any further," he says.</p>
How long before you're no longer contagious?<p>A study <a href="https://www.nature.com/articles/s41586-020-2196-x" target="_blank">carried out on the first coronavirus patients in Germany</a> showed that no viruses that are capable of replication can be found from day eight after the onset of symptoms, even though PCR can still detect up to 100,000 gene copies per sample. This could change the current quarantine recommendations in the future.</p><p>According to the Robert Koch Institute, patients can currently be discharged from hospital if they show two negative PCR samples from the throat within 24 hours. If they have had a severe case of the disease, they should remain in domestic isolation for another two weeks. For each discharge, whether from hospital or home isolation, they should have been symptom-free for at least 48 hours.</p>
Why do people react differently to the virus?<p>While some people get off with a mild cold, others are put on ventilators or even die of SARS-Cov-2. Especially people with <a href="https://www.dw.com/en/coronavirus-who-is-particularly-at-risk-and-why/a-52710881" target="_blank">pre-existing conditions</a> and older people seem to be worst-affected by the virus. Why? This is the hottest question at the moment.</p><p>It will still take a very, very long time to understand the mechanistic, biological basis for why some people are so much more severely affected than others, virologist Angela Rasmussen told <em>The Scientist</em>. "The virus is important, but the host response is at least as important, if not more important," her colleague Stanley Perlman told the magazine.</p><p>Stefan Meuer sees a fundamental survival principle of nature in the different equipment and activity of our immune systems: "If we were all the same, one and the same virus could wipe out the entire human species at once. Due to the genetic range, it is quite normal that some people die from a viral disease while others do not even notice it. "</p><p>Achim Hörauf also suspects immunological variants that could be genetically determined. Since interstitial pneumonia is observed with the coronavirus, the focus is probably on an overreaction of the immune system. However, it is also possible that each person affected may have been loaded with a different dose of the virus, which in turn leads to different outcomes. And finally, it makes a difference how robust the body and lungs are: Competitive athletes simply have more lung volume than long-time smokers. </p>
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