Clear signs from the coral reef

In January of this year, Australia experienced the hottest summer for a long time, with record high temperatures and Bush fires. In February, the winter temperatures have increased in Alaska to unusual heights. In March, the cyclone Idai parts of Mozambique, Malawi, and Zimbabwe, devastated; according to the UN weather organisation WMO quite possibly one of the worst weather disasters ever in the southern hemisphere. And now, in April, reports scientists from the disastrous state of the Great Barrier Reef: Perhaps it will never recover all of the Heat bleaching of the past few years.

Dramatic coral bleaching

Long, you could dismiss many of the signs of the changes in the world as individual cases, as a warning. Now it starts to be noticeably uncomfortable in the world, and partly irreversible.

The shows, in particular, the current study from the Great Barrier Reef, the largest coral reef in the earth. In the years 2016 and 2017, there were back-to-back Mass bleaching, in which many of the corals lost due to warm water, your algae-roommate and were seriously damaged. Now a Team led by Terry Hughes of James Cook University in Queensland, has studied the corals to recover. Their findings, in the last week, published in "Nature" summarized lead author of Hughes in a simple sentence: "Dead coral't have children."

Normally, coral polyps produce according to Bleaching huge larvae swarms, to replace the dead coral. This process seems to be in front of Australia, however, severely and permanently disrupted. Almost 90 percent of the settlement rate of the young decreased coral, according to the researchers, compared to previous levels in the section. Apparently, there are not enough surviving adult corals, which can produce new larvae.

"For us, all this is no Surprise, but the continuation of a trend."Mojib Latif, climate researcher

Also, the species composition has changed. Because the previously dominant corals of the genus Acropora have been hit particularly hard, settled for the first time, mainly Pocillopora, which survived the bleach better. This genus, however, is much less diverse, and increasingly, also, different. Acropora send sperm and eggs on the trip, the first find in the water to each other and to vast distances, until they settle down. Pocillopora produce, however, most ready-to-larvae, which settle in the vicinity. This difference is likely to change the unique reef.

Only when the current young Acropora corals are sexually Mature, have the area a Chance to really relax. But this will take many years. It is almost certain that in this time, the more Bleaching will occur. Finally, the average distance between such episodes has decreased in the last decades, from 25 years to less than 6 years and will continue to shrink. All of this gives rise to the fear that the Great Barrier is Reef never to return to his old Form.

"For us, all this is no Surprise, it will only continue in the long-term Trend," says the climate researcher Mojib Latif of the Geomar in Kiel about all the horror stories of the past few months. From a scientific point of view, one should not be surprised if the real and permanent consequences of climate change are starting to pile up, says Latif.

It is not a great deal

Finally, the 1.5-degree had not been taken-aim just to the Paris agreement: "This is the point at which the probability of a jump increases that irreversible events." From this temperature, we were no longer removed very far. By about one degree the earth has warmed since pre-industrial times already. In the most recent report of the IPCC on the 1.5-degree target, the warming, the area in which the risks for threatened Ecosystems, and extreme weather climbing events.

Beyond the 1.5 degree, then damage is also global, severe and collapse of large ice sheets is more likely. This temperature is achieved according to the climate models, so, or so by 2040.

If emissions were immediately reduced radically, it could stagnate the warming after that. Otherwise, it goes to the top. It is the climate policy is ultimately in the Hand. So far, the emissions are rising despite all the promises.

"coral reefs or the ice sheet of Greenland could be more sensitive than we thought."Johan Rockström

Johan Rockström is the Director of the Potsdam Institute for climate impact research and is known worldwide for his Work on the natural stability limits of the planet. He also says: "The 1.5 degrees is just a number, that's a limit."

What happens when one approaches such a limit, one can observe today; for Rockström, this is disturbing. Unlike Latif, he sees the reality, rather, on the outskirts of the forecasts. "In the past 15 years, the changes were somewhat faster than predicted. Coral reefs, or the ice sheet of Greenland could be more sensitive than we thought," he says. Although researchers have warned against all of these risks for a long time. But maybe this is the threshold at which the pace of change accelerated, achieved, even earlier than expected.

trees in the Antarctica

Meanwhile, the concentration of CO2 in the atmosphere is not as high as last about three million years ago, in the Pliocene. How different, however, at that time, the earth and the climate looked like, researchers have in the past week reported on a meeting of the Royal Meteorological Society in London: The climate was on average 2 to 4 degrees warmer than today, the temperature was 14 degrees higher in the Arctic, the sea level is 15 meters, Greenland was probably free of ice, and, as fossils show, there were trees in Antarctica.

this Is the future of the planet? Maybe. "It is a question of the time scale," said Alan Haywood, Paläoklimatologe from the University of Leeds and one of the speakers in London. "Some of the components of the earth system, such as the surface temperature, react very quickly to CO2. Other answers very slowly, such as ice sheets, Vegetation or the depth of the ocean."

But even these begin now to respond: The Arctic ice cover goes back rapidly, Greenland's glaciers are shrinking, even the Antarctic is changing. These long-term processes to strengthen the climate change, for example, because ice-free regions to absorb much more heat. If the concentration of CO2 long enough to be as high as it is today, comes out at the end of the warm Pliocene climate. This means that Even if the miracle manage to keep the warming in this century to under 1.5 degrees, could it be that the earth is warming then. To prevent this, you would have to escape the atmosphere, perhaps a lot of CO2.

The Transition to the next climatic stage has already begun. This is hard to miss, even on the Great Barrier Reef. "It is nothing to what might happen in the future. It is happening right now," says coral researcher Terry Hughes.

(editing Tamedia)

Created: 11.04.2019, 18:14 PM