Nå frykter de at menneskeskapte klimaendringer kan føre planeten inn på en lignende sti.Fredrik Lie1 time sidenDEL

Det er rundt 250 millioner år siden omtrent 90 prosent av alt liv i sjøen og 70 prosent av livet på land ble utryddet i «Perm-trias-utdøingen», ofte kjent som «den store døden». Forskere har lenge trodd at den katastrofale hendelsen ble utløst av massive vulkanutbrudd, men akkurat hvordan det skjedde har lenge vært litt uklart, skriver AP.

I en utgave av tidsskriftet Science, som kommer ut på torsdag, vises en ny studie der det er brukt komplekse datasimuleringer for å finne ut hva som skjedde etter at vulkanutbruddene. Utbruddene førte til at nivåene av karbondioksid økte til et nivå mer enn 12 ganger høyere enn det vi har i dag.

Tappet vannet for oksygen

Utbruddene førte til at temperaturen i vannet steg med omtrent elleve grader, noe som tappet sjøvannet for mye oksygen. Dette førte til masseutryddelsene i havet, spesielt i områdene langt fra ekvator. Artene som tilhørte områdene rundt ekvator var mer vant til varmere, oksygentappet vann.

En av forskerne bak rapporten, Justin Penn, forteller at vannet mister oksygen når det blir varmt, på samme måte som en brusboks mister kullsyren.

Forskerne har sett på et dusin moderne arter, for å se hvordan de reagerer på varmere, oksygentappet vann for å forstå hva som skjedde den gangen.

– Det kan skje igjen

Selv om vi mennesker ikke varmer opp Jorden på langt nær like mye som vulkanutbruddene gjorde for 250 millioner år siden, mener forskerne vi øker risikoen for at noe lignende kan skje igjen.

– Vi risikerer virkelige katastrofer i fremtiden, sier medforfatter i studien Curtis Deutsch ifølge AP.

Han mener katastrofen for 250 millioner år siden viser «nesten nøyaktig hva som ligger framfor oss ved slutten av den stien vi er på».

– I realiteten gjør vi det samme mot Jordens klima og hav.

Det siste århundret har kloden blitt rundt en grad varmere grunnet drivhuseffekten. Forskere advarer mot at temperaturen kan ha steget med tre grader eller mer innen slutten av århundret med mindre utslippene kuttes radikalt og fort.

– Vi er omtrent en tiendel på veien til den store døden. Når vi 3-4 grader oppvarming vil livet i vannet være i stor fare, sier Deutsch til The Guardian.

Studien viser at dersom utslippet av karbondioksid fortsetter slik som nå, vil kloden oppleve 30 til 50 prosent av utrydningsnivået man så i den store døden innen år 2300.

Forsker ved the University of Mary Washington, Pamela Grothe sier til The Guardian

Dec 5th, 2018 2 min read

Edwin J. Feulner, Ph.D.@EdFeulner

FounderEdwin J. Feulner is the founder and former president of The Heritage Foundation.

KEY TAKEAWAYS

The author of 1968’s “The Population Bomb” was another gloom-and-doom prophet who made so many failed predictions over the years that it’s almost hard to keep count.

Climatologists lay out four possible future trajectories for the environment. Alarmists seized on the worst one. It’s also the least likely.

It’s time for the global-warming crowd to realize, once and for all, that civilization isn’t ending – not in 1985 and not in 2100. And those are the cold facts.Copied

“Civilization will end within 15 or 30 years unless immediate action is taken against problems facing mankind.”

Sounds dire. A reaction to the National Climate Assessment published the day after Thanksgiving? No. Harvard biologist George Wald made that claim in 1970.

So if Wald had been correct, just about everything would have crumbled to ruin sometime between 1985 and 2000.

Wald, however, wasn’t alone. He and others came up with some incredibly over-the-top predictions as the 1960s came to a close.

“Earth Day” founder Denis Hayes, for example, didn’t hedge his bets: “It is already too late to avoid mass starvation.” Or take Paul Ehrlich (please). The author of 1968’s “The Population Bomb” was another gloom-and-doom prophet who made so many failed predictions over the years that it’s almost hard to keep count.

“Population will inevitably and completely outstrip whatever small increases in food supplies we make,” he said in a 1970 interview. “The death rate will increase until at least 100-200 million people per year will be starving to death during the next 10 years.”

Off by about 180 degrees. Food production spiked in the ensuing years. And starvation on such a massive scale never materialized, thank God.

Many other examples could be cited (I haven’t even touched on predictions by global-warming luminaries such as Al Gore), but I hope the point is clear: Take sky-is-falling claims with a large grain of salt.

Particularly because they never seem to go out of style. You’d think, given the track record I’ve just referred to, that doomsayers would learn to temper their warnings, at least a little bit. But no. We see the same trend at work with the National Climate Assessment.

“Global greenhouse gas emissions is expected to cause substantial net damage to the U.S. economy throughout this century,” we read in the 1,700-page report.

How substantial? As The New York Times noted: “All told, the report says, climate change could slash up to a tenth of gross domestic product by 2100, more than double the losses of the Great Recession a decade ago.”

Sounds awful, to put it mildly. Then again, so did the first Earth Day predictions. And these latest claims are just as plausible, according to climate expert Nicolas Loris.

“The study … calculates these costs on the assumption that the world will be 15 degrees Fahrenheit warmer,” he writes. “That temperature projection is even higher than the worst-case scenario predicted by the United Nations Intergovernmental Panel on Climate Change.
“In other words, it is completely unrealistic.”

So where do these Chicken Little claims come from? In the report, climatologists lay out four possible future trajectories for the environment. Alarmists seized on the worst one.

It’s also the least likely. It assumes a combination of bad factors will somehow coincide — that global population will climb at the fastest-possible rate (about double the current amount), that technology will develop at the slowest-possible rate, and that world poverty will increase massively, along with energy use and emissions.

Would it be responsible to assume the best-case scenario? Of course not. But assuming the worst-case is no better. In fact, considering the policy changes that believers wind up pushing as a result – such as huge carbon taxes and giant subsidies for dubious “green” projects — it’s even less responsible.

Not that the alarmists need an excuse like the National Climate Assessment to make bad recommendations. Even before it came out, the Intergovernmental Panel on Climate Change had proposed a carbon tax of between $135 and $5,500 per ton of carbon emissions by the year 2030.

“An energy tax of that magnitude would bankrupt families and businesses, and undoubtedly catapult the world into economic despair,” Mr. Loris writes.

If the doomsayers want to spread pessimism, that’s their business. But the rest of us shouldn’t have to pay for it.

It’s time for the global-warming crowd to realize, once and for all, that civilization isn’t ending – not in 1985 and not in 2100. And those are the cold facts.

This piece originally appeared in The Washington Times

Anthony Watts / 2 hours ago December 6, 2018