The manmade changes pushing the planet toward a critical transition
Nature changes gradually—until it doesn’t. As the changes in an ecosystem pile up, they can push the system past a “critical threshold,” and then the change can become extremely fast (in relation to geological timescales) and unstoppable. And in a review in the journal Nature, researchers suggest that the same thing is happening to the whole world: Humans could be driving Earth’s biosphere towards a tipping point beyond which the planet’s ecosystems will collapse abruptly and irreversibly.
This global ecosystem collapse has occurred before, most recently about 12,000 years ago with the last transition from a glacial period to the current interglacial (i.e., warm) period, say the review authors. Over the relatively short period of 1,000 years, fluctuations in the Earth’s climate largely killed off about half the large mammal species, along with birds, reptiles, and a few smaller mammal species. The millennium-long shift was triggered by rapid global warming, and once this warming pushed the planet past its tipping point, the end of the 100,000-year-old ice age became inevitable, giving way to the current 11,000-year-old interglacial era.
It’s easy to see how overwatering our crops would deplete the groundwater supply and cause land nearby to sink, but could it cause sea level to rise on a global scale? Yes, according to a model published in Nature Geosciences, that attributes 42% of the sea-level rise over the past half century to groundwater use.
Ninety percent of readily available freshwater is underground, and water used for drinking or crop irrigation must, of course, be brought above ground. That water then evaporates or flows into rivers, entering the water cycle and eventually the oceans, making them deeper.
The Fukushima Daiichi power plant in 1975, seen from above.
As of this weekend, when Tomari Nuclear Power Plant was shutdown for maintenance, every last one of Japan’s 54 nuclear plants have Japan has been taken offline. Although the shutdowns are supposed to be temporary, after the power utilities’ mismanagement of the Fukushima disaster last year, the Japanese public has registered increasing distrust for official reassurances that nuclear power can be safe. These shutdowns could conceivably become permanent.
The world’s major economies all use nuclear power to some extent, and Japan, which got about 30% of its power from reactors, was one of the heavier users before the the Fukushima meltdown. Now, public opinion there and the world over has soured toward nuclear power, to the extent that Germany has officially announced plans to abandon nuclear completely by 2022.
In addition to rising temperatures, wildly fluctuating weather, and higher sea levels, global climate change is triggering a spike in the acidity of the oceans, as the carbon dioxide in the atmosphere reacts with seawater. In an attempt to see whether anything like the projected climb in acidity has happened before and what we can expect the results to be, scientists have been looking into the geological record and recently published their findings in Science. Poring over the carbon isotopes in ancient rock, the fossilized bodies of long-extinct creatures, and the chemical compositions of those bodies, they looked as far back—300 million years—as we have fairly reliable geological records. They found that for the track we’re on, there really is no good analog in the past: even the extreme extinction events of the Permian-Triassic Mass Extinction, which killed 96% of marine species, and the Paleocene-Eocene Thermal Maximum, which likewise caused huge extinctions in the oceans, happened after slower rises in acidity than we will see. It’s hard to say how much of those massive extinctions was due to acidification and how much was due to related factors, like warming. But we already know that we’re looking at some pretty serious effects in the future, and this confirms that we’re heading into uncharted territory .
Image courtesy of Repoort / flickr
If you could watch a movie of the planet over the last several million years, you’d see the ice caps advance and retreat: The planet’s climate moves in cycles, with ice ages and interglacial periods alternating. But looking at previous interglacials similar to our own, geophysicists now think that the current mostly ice-less period may be longer than it would have been had a certain species not invented the combustion engine. Specifically, it looks like with amount of greenhouse gases we’ve already spewed into the atmosphere, the next ice age will be delayed. And before you decide that’s a good thing, at the rate we’re currently going, we’re not just pushing off the glaciers for a few geologically insignificant years: the team says that the atmospheric concentration of CO2 would to be at most 240 parts per million (ppm) before glaciation would kick in. Right now, it’s 390 ppm, with no signs of dropping and many signs of continuing to rise. When (and how) the planet’s self-regulation system will kick in isn’t clear, but the long, increasingly hot trip probably isn’t going to be pretty.
Read more at the BBC.
Image courtesy of NASA / Wikipedia
The most important climate meeting of the year, the UN Framework Convention on Climate Change’s Convention of Parties in Durban, South Africa, has just concluded, with the US envoy “relieved” by the results, but developing countries frustrated by the failure of developed nations to take greater responsibility for emissions. At Nature News, Frank MacDonald, a veteran reporter who has attended nearly every Convention of Parties meeting since they began in 1992, recounts his experiences as a spectator on the edge of the climate poker game:
Nearly 20 years ago, as I wandered as a newspaper reporter from tent to tent at the Global Forum in Rio de Janeiro’s Flamingo Park, with young, idealistic environmental activists milling about, I couldn’t help thinking of Dale Arden’s line from the film Flash Gordon, a decade before: “Flash, Flash, I love you, but we only have 14 hours to save the Earth!”
Brazil’s 1992 Earth Summit was in full swing, and when it closed it even seemed that we would manage to save the world from global warming, and species extinction too. After all, delegates at the United Nations Conference on Environment and Development — as it was officially known — had just adopted two conventions to stave off these threats.
A naled, or aufeis, in the flesh. Er, ice.
It sounds like science fiction, but, like so many science fiction-ish ideas in the age of radical adaption to climate change, it’s real: Mongolia is launching a $750,000 geoengineering project to freeze vast quantities of the Tuul River in order to cool its capital city of Ulan Bataar during the sweltering summer, and to provide drinking water as the ice melts, as well. While specifics about exactly how the cooling will work are scarce, details about the freezing process are not, as it will mimic a natural process that already occurs on rivers in the north.
California birds are getting slightly bigger, according to a study published in Global Change Biology in which researchers measured and weighed 33,000 birds over the past 40 years. The increases were small, but significant: in the last 25 years robins have grown 0.2 ounces in mass and 1/8th of an inch in wing length, for example. But the finding runs counter to the only other long-term study measuring avian size in North America, which found that birds in Pennsylvania have shrunk slightly over recent decades. And it seems to disagree with other recent suggestions that animals may shrink in a warming world: Bergmann’s rule holds that animals generally get bigger as they get farther away from the equator, because larger animals are better able to retain heat.
[Originally published 9/16] Greenland glaciers have had a hard time of it lately, what with all the warming and disintegrating, and in their latest edition, the folks at the Times Comprehensive Atlas of the World have decided to illustrate the island’s new look: as you can see above, lots and lots less white. The warming has even created a new island off the east coast: look closely just under the “Gr” in “Greenland Sea,” and you can see the words “Uunartoq Qeqertoq (Warming I.)”
If we are looking at a radically reshaped world in the next hundred years or more, maybe atlases will have to be more like dictionaries from here on out, recording the dynamic nature of their subject matter.
[Update 9/19: Scientists at the UK's Scott Polar Institute have written a letter to the Times saying that the image above is inaccurate; less ice has melted in the last 15 years than the atlas's image shows. The atlas's publishers, HarperCollins, respond that they created the image using data from the US National Snow and Ice Data Center, and that it represents not only changes due to warming but also "much more accurate data and in-depth research" than had previously been available. Regardless of the causes, however, the image doesn't resemble current satellite images, the Scott Polar group says. Check out a comparison of the images here. What do you think?]