By Tim Radford
Researchers now know the difference half a degree can make. They can tell you why 1.5°C warming would be better than a 2°C climb in average global temperatures, because even half a degree Celsius could mean greater extremes of heat, more overwhelming rainfall and longer spells of warm weather.
And they know all this because they've seen it happen in the recent past. There is enough evidence, they say, in the observational record for the last half century to underline the importance of even half a degree.
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Scientists from Germany and Switzerland outline the argument and identify the evidence in the journal Nature Climate Change.
In the last two centuries, the ratio of carbon dioxide, the result of extravagant fossil fuel use since the Industrial Revolution, has risen from around 280 parts per million to 400 ppm, and average global temperatures have risen around 1°C during that time.
The researchers matched temperature and climate records for the years 1960 to 1979 and 1991 to 2010, a period when the thermometer averages climbed by a whole half a degree.
They found that the intensity of extreme rainfall had increased by nine percent over that period. The coldest winters were measurably less cold, and half of the global land mass had experienced changes of what they called "warm spell duration" of more than six days.
It is not that perceptible global warming made these extremes happen—extremes happen anyway—but the researchers think it made them more likely. By raising the temperature, humans loaded the climate dice.
"The hottest summer temperatures increased by more than 1°C in a quarter of global land areas, while the coldest winter temperatures warmed by more than 2.5°C," said Peter Pfleiderer, a scientist with the Potsdam Institute for Climate Impact Research and for Climate Analytics.
And his colleague Carl-Friedrich Schleussner said, "As we're moving increasingly outside of the range of natural climate variability, we have to expect that impacts on agriculture, human and biological systems will be more pronounced."
There is no certainty that the world's nations can meet the Paris target and contain global warming, and limit climate change, because enough carbon dioxide has been emitted to take air temperatures over land to that level already.
The next decade could be critical, which is why researchers feel they need the evidence in as clear a form as possible.
"One of the pressing questions for scientists today is whether we know that limiting warming to 1.5°C instead of 2°C would make a difference in the future. We have to rely on climate models to predict the future, but given we now have observational evidence of around 1˚C warming, we can also look at the real life impacts this warming has brought," Schleussner said.
And the third signatory, Erich Fischer of ETH Zurich, said, "Communicating abstract quantities like differences in global mean temperature is difficult.
"With the warming the world has already experienced, we have an actual record of warming to study, and we can see very clearly that a difference of 0.5˚C of warming really does matter."
Reposted with permission from our media associate Climate News Network.
Sweden's reindeer have a problem. In winter, they feed on lichens buried beneath the snow. But the climate crisis is making this difficult. Warmer temperatures mean moisture sometimes falls as rain instead of snow. When the air refreezes, a layer of ice forms between the reindeer and their meal, forcing them to wander further in search of ideal conditions. And sometimes, this means crossing busy roads.
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By Aaron W Hunter
A chance discovery of a beautifully preserved fossil in the desert landscape of Morocco has solved one of the great mysteries of biology and paleontology: how starfish evolved their arms.
The Pompeii of palaeontology. Aaron Hunter, Author provided<h2></h2><p>Although starfish might appear very robust animals, they are typically made up of lots of hard parts attached by ligaments and soft tissue which, upon death, quickly degrade. This means we rely on places like the Fezouata formations to provide snapshots of their evolution.</p><p>The starfish fossil record is patchy, especially at the critical time when many of these animal groups first appeared. Sorting out how each of the various types of ancient starfish relate to each other is like putting a puzzle together when many of the parts are missing.</p><h2>The Oldest Starfish</h2><p><em><a href="https://www.biorxiv.org/content/10.1101/216101v1.full.pdf" target="_blank" rel="noopener noreferrer">Cantabrigiaster</a></em> is the most primitive starfish-like animal to be discovered in the fossil record. It was discovered in 2003, but it has taken over 17 years to work out its true significance.</p><p>What makes <em>Cantabrigiaster</em> unique is that it lacks almost all the characteristics we find in brittle stars and starfish.</p><p>Starfish and brittle stars belong to the family Asterozoa. Their ancestors, the Somasteroids were especially fragile - before <em>Cantabrigiaster</em> we only had a handful of specimens. The celebrated Moroccan paleontologist Mohamed <a href="https://doi.org/10.1016/j.palaeo.2016.06.041" target="_blank" rel="noopener noreferrer">Ben Moula</a> and his local team was instrumental in discovering <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031018216302334?via%3Dihub" target="_blank" rel="noopener noreferrer">these amazing fossils</a> near the town of Zagora, in Morocco.</p><h2>The Breakthrough</h2><p>Our breakthrough moment came when I compared the arms of <em>Cantabrigiaster</em> with those of modern sea lilles, filter feeders with long feathery arms that tend to be attached to the sea floor by a stem or stalk.</p><p>The striking similarity between these modern filter feeders and the ancient starfish led our team from the University of Cambridge and Harvard University to create a new analysis. We applied a biological model to the features of all the current early Asterozoa fossils in existence, along with a sample of their closest relatives.</p>
Cantabrigiaster is the most primitive starfish-like animal to be discovered in the fossil record. Aaron Hunter, Author provided<p>Our results demonstrate <em>Cantabrigiaster</em> is the most primitive of all the Asterozoa, and most likely evolved from ancient animals called crinoids that lived 250 million years before dinosaurs. The five arms of starfish are a relic left over from these ancestors. In the case of <em>Cantabrigiaster</em>, and its starfish descendants, it evolved by flipping upside-down so its arms are face down on the sediment to feed.</p><p>Although we sampled a relatively small numbers of those ancestors, one of the unexpected outcomes was it provided an idea of how they could be related to each other. Paleontologists studying echinoderms are often lost in detail as all the different groups are so radically different from each other, so it is hard to tell which evolved first.</p>
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