Consequences of coral bleaching. Lizard Island. Photo by Dorothea Bender-Champ for ARC Centre of Excellence for Coral Reef Studies
The energy and climate newsreel: Oceans too warm, carmakers cheating, and criticism of transportation plan
On Friday, the climate agreement was solemnly signed in New York (Climate: Agreement solemnly signed). In doing so, countries pledge to limit global warming to well below 2 degrees, but better to 1.5 degrees.
Scientists have been warning for some time that this half degree Celsius could make a decisive difference. A new paper now highlights some differences: two degrees of warming by 2100, compared to 1.5 degrees, will mean a ten-centimeter increase in sea level, will cause heat waves, and will severely threaten all coral reefs, according to some of the findings published Thursday by a team of European climate scientists. Particularly in the case of extreme weather events in the tropics, half a degree could be decisive.
“In the case of heat-related extremes, the additional increase of 0.5 degrees Celsius marks the difference between events that are at the limits of current natural variability and a new climate regime, especially in tropical regions”, explains the lead author Carl Schleussner. In the Mediterranean region, an average temperature increase of 1.5 degrees would reduce the availability of water by 10%, and by 2 degrees by 20%.
Crop losses in Central America and West Africa were twice as high under a 2-degree scenario as under a 1.5-degree scenario. Corals had little chance of survival with a 2 degree climate warming, with a lower temperature rise some species may have been able to adapt. Coral reefs are not only tourist attractions, they also provide important services in coastal protection.
Lizard Island. Image: Dorothea Bender-Champ for ARC Centre of Excellence for Coral Reef Studies
93 percent of Great Barrier Reef corals damaged
The seriousness of the effects of rising water temperatures can already be seen clearly in the current coral bleaching on the Great Barrier Reef off the coast of Australia. About 93% of the corals are damaged according to an inventory of the ARC Centre of Excellence, the northern part of the reef is most affected.
“North of Port Douglas we already measure an average mortality of almost 50% of bleached corals. In some reefs, the mortality rate is likely to exceed 90%. When bleaching reaches this serious level, almost all coral species are affected, including the old, slow-growing ones that, once lost, will take decades to recover”, explains Andrew Baird of the ARC Centre.
Lizard Island. Picture: Dorothea Bender-Champ for ARC Centre of Excellence for Coral Reef Studies
In the central part of the reef, coral bleaching is about the same as in 1998 and 2002. There was a good chance that the corals would survive and regain their color as temperatures dropped, said Terry Hughes, chairman of the National Coral Bleaching Taskforce. The bleaching is worst where the water temperature has been the highest for a long time. The high temperatures this year are again due to a strong El Nino phenomenon combined with global warming.
Not only off the Australian coast the sea temperatures are too high, but also in the Arctic. As a result of the mild winter, sea ice physicists from the Alfred Wegener Institute fear a strong loss of ice this summer, which could be comparable to that in 2012.
“The particularly warm winter in the Arctic has led to very slow formation of new sea ice in many areas. If we compare the sea ice thickness map of the past winter with that of 2012, we can see that we are currently experiencing ice conditions similar to those of spring 2012 – in some cases even much darker ice”, said AWI sea ice physicist Marcel Nicolaus. North of Alaska, the ice thickness is less than one meter, where the ice layer should normally be 1.5 meters thick. In the summer sun the ice will therefore melt quickly.