(Shorter edition this week, sorry)
It’s summer in the Northern hemisphere, and although weather and climate are different things, it’s hard to stop thinking about climate change when there are spectacular displays of warming happening very quickly right before our eyes, such as this:
Greenland ice sheet melted at unprecedented rate during July. The Greenland ice sheet melted at a faster rate in July than at any other time in recorded history. It happened so fast, that NASA scientists at first thought that there was an error in the satellite readings. The readings showed that the area of melted ice sheet surface went from 40% to 97% of the ice sheet surface melted over just 4 days, from July 8th to July 12th, as measured by 2 satellites. Usually ~half of the ice sheets melts every summer in Greenland. This extremely unusual massive melt came just a few days after a huge iceberg (as big as Manhattan) broke off from the Petermann Glacier. If multiple events like this happen in the next coming years, the pattern will be significant because it will contribute to raising sea levels. About one-fifth of the annual sea level rise (3 mm/year) is attributed to the melting of the ice sheet in Greenland.
But even though this melting event certainly looked pretty scary, climate science is very complex and it is good to keep things in perspective by looking at different studies:
Signs of Hope Emerge for Greenland Ice. A team of Danish scientists has used aerial photographs to produce digital elevation models of the Greenland ice sheet. This method, unlike satellite information which dates back only to the past decade, was used to extended the time record of recent dynamic ice loss to 1985. They have determined that two dynamic ice loss events have happened relatively recently, on the northwestern Greenland Ice Sheet margin, one from 1985 to 1993 and another from 2005 to 2010. Their findings were published in Science (see abstract here). The implications are that these events are short-lived and dynamic and that the melting rate can vary a lot, with rapid melts and rapid freezes, and that the situation may not be as dire in terms of sea-level changes in the near future, because these are predicted based only on the current melting rate. The article states that the mass change of the northern Greenland Ice Sheet is the result of predictable surface processes over short time scales, and that both the spatial and temporal variability in ice sheet dynamics will need to be modeled in order to predict future sea level changes due to these events, and they suggest that the analysis of historical aerial photographs can be extended back into the 1930s and 1940s, to create better models and explain the pattern further. The article concludes that such analysis could become “the new observational standard for the temporal and spatial variability of the ice sheet response” and that it could lead to a higher confidence level in terms of calculating the future ice sheet contribution to sea-level rise.
And while all this ice melting was happening, an even more extraordinary event occurred:
Koch-funded study finds that anthropogenic global warming is real. The amazing part is not that a scientific study concluded that global warming is real, that the rate at which has been modeled to occur is actually pretty accurate, and that man-made CO2 emissions are the main culprit. What is extraordinary about this is that the Koch brothers, the major funders of disinformation in this field, funded the study! And the head of the Koch-funded study used to be one of the most prominent, best-known climate change skeptic, Richard A. Muller, Physics Professor at the University of California, Berkeley, who even wrote a NYT piece on why he is no longer a climate change skeptic! He led a study, the Berkeley Earth Surface Temperature project, which concluded that the average temperature of the earth’s land has risen by two and a half degrees Fahrenheit over the past 250 years, including an increase of one and a half degrees over the most recent 50 years. They also concluded that these increases result from the human emission of greenhouse gases. They have published the study online at this site, Berkeley Earth Surface Temperature.
And while we are talking about climate change and events that affect climate, such as massive volcanic eruptions, it turns out that we cannot blame our cousins’ extinction on a volcano:
Neandertals Didn't Bite the Volcanic Dust. Scientists have speculated that a super-massive volcanic eruption that occurred ~40,000 years ago near what is now Naples, Italy, known as the Campanian Ignimbrite, had something to do with demise of the Neandertals. The eruption showered ash over central and Eastern Europe, and it happened in combination with a sharp cold spell that hit the Northern Hemisphere, and cooled the area by 2°C for up to 3 years. But a new analysis of microscopic volcanic glass particles (known as cryptotephra) concludes that the event happened after the Neandertals had almost disappeared. It appears that modern humans are still the number one suspects when it comes to doing the Neandertals in, since they arrived in Europe around the time of the Campanian Ignimbrite explosion. The problem with those dates is that they are all plus minus a few thousand years, so the timing is critical. If Neandertals began disappearing before the eruption, it could not be responsible for their extinction; if their demise began at the same time or shortly afterward, the correlation with climate might still hold. The new analysis relies on deposits of cryptotephra from 4 central European caves where stone tools both from Neandertals and modern humans, have been found, and from a modern human site in Libya. The results show that the cryptotephra lie on top of the transition from Neandertal to modern human stone tool types at all four central European sites, meaning that Campanian Ignimbrite occurred after modern humans had replaced Neandertals in those sites. Analysis of other climatic indicators further confirmed the contemporaneousness of the volcanic explosion with the sharp cold spell, meaning that it too, could not have caused the Neandertals’ disappearance from central Europe. Unfortunately, cryptotephra could not be found in Western Europe, therefore it cannot be ruled out that Neandertals survived there even post explosion and cold spell, in limited numbers and likely already on the verge of extinction.
And while we are on the subject of extinct humans, the genomes of some modern day Africans have made our ancestral tree possibly even bushier:
Genomes of modern African hunter-gatherers suggest a previously unk.... A new article in the prestigious journal Cell describes the complete genomic sequence of 5 members of three African hunter-gatherer populations, the Hadza, the Sandawe (both from Tanzania) and the Pygmies from Cameroon. These populations are considered to be some of the most ancient human lineages. Some stretches of DNA sequence (~2.5 % of the genome) from these populations do not look like any other human sequence decoded until now, and this hints at an admixture with an ancient African ancestor, now extinct, possible the African equivalent of the European Neandertals. Of course, this is all based on a statistical analysis on a genomic scale, and another interpretation could be given once more genomes from other human populations worldwide are characterized. In the meantime, the NYT's Nicholas Wade has chosen to write on this, and gave his article an unfortunate title: Genetic Data and Fossil Evidence Tell Differing Tales of Human Origins. As you can imagine, creationist sites on the web are already saying this means human evolution is disproved. What it means is that the fossil record so far shows no African equivalent of a Neandertal. And a few paleoanthropologists are a bit miffed at the geneticists for "jumping to conclusions" with respect to the existence of this previously unknown African forebear. In reality, the genomic data hints at the existence of this ancestor, does not prove it. It's all normal science fare, and it does not disprove human evolution, if at all, it just makes our tree bushier. Besides this, the genomes of these African populations yielded some other interesting data, such as a gene variation that would explain the pygmies short stature and precocious puberty, and some interesting variants regarding the cannabinoid receptor in the Hadza (who by the way, smoke a lot of pot).
There is really no good segue from the human genome into the next story, so I’m just making one up for your enjoyment. The next story is about wine and beer, and we could perhaps say that we haven’t really become human until we started making fermented beverages to sooth our spirits and embolden our story-telling capabilities. So there. No humans, no wine. And it turns out that no wasps, no wine or beer. I bet you did not know this. I didn’t.
Thank the European wasp for beer and wine. Wine and beer need Saccharomyces cerevisiae (in plain English, yeast) to be produced. This wonderful yeast, which we also use to make bread, pizza, etc. has been with us for ~9,000 years but we still know very little about wild yeast strains. We know that wild strains of S. cerevisiae grow on ripe grapes and some berries. But where do they live in the winter when there are no fruits? A team of Italian scientists thought about the European wasp, because they love feeding on grapes, and because females hibernate through the winter, already fertilized, so they can start up colonies in the spring. Wasps feed their larvae by regurgitating food, so if yeast hid in the wasps’ guts, they would get passed to the new generation and then to the grapes again. And bingo, when they analyzed the guts of wasps in the winter, and in summer, and in spring, they found several strains of S. cerevisiae. They were mostly wine strains but also bread strains, and others. As a control, they looked in the guts of bees and found no yeast. Other animals may be carriers, too, but it’s not known whether they last through the winter like in the wasps. The Italian scientists think that the wasps also help start the fermentation process directly in the grape, and the complex flavors of wines would simply not be the same if we relied on winemakers adding yeast later. It makes you think about how so many things in nature are so interconnected in wonderful ways. So tonight, when you are enjoying the wonderful bouquet and flavor of your Chianti, thank the lowly wasps, and don’t get so annoyed by their threatening presence next time you see one flying around.
And the Olympic Games are ongoing right now, so I could not avoid but point you to an excellent article in Nature on how the abilities of Olympians could be enhanced if there were no restrictions on the use of pharmacological agents, and in the future, potentially genetic or surgical enhancement.
Superhuman athletes. Performance enhancers have become so prevalent, and doping scandals so ubiquitous, that there are some people who think restrictions should be lifted and everything done out in the open, under medical supervision. This is of course, debatable; I’m actually undecided on this. The best-known performance enhancers are anabolic steroids, that can result in >30% performance enhancement. They are not without risks; they can cause high blood pressure, thickening of the heart valves, decreased fertility and libido, chest hair in women and shrunken testicles in men. Other enhancements, such as EPO, a growth factor involved in the production of red blood cells, can thicken the blood and contribute to stroke occurrence. As far as genetics, we are now beginning to understand the gene variants behind some extraordinary performances, for example, there are mutations that make the EPO receptor more efficient, or muscles bigger and stronger. Drugs that activate genes that increase the ratio of ‘slow-twitch’ to ‘fast-twitch’ fibers in muscle have shown to increase the endurance of mice by 70%. And finally, there is orthopedics. Right now, this branch of medicine is not very good at fixing broken bones and joints, and usually athletes that undergo surgery are never back to being the same as before. But this will change as we will learn to make ligaments, tendons, and may be repair joints in the lab. Mechanical prosthetics will be seen for the first time in London 2012. Oscar Pistorius from South Africa, a Paralympic gold medalist who is an amputee and has cheetah-style prosthetic lower legs, was approved this month to run in the 2012 Olympics. Pistorius’s prosthetic legs lack the stiffness of a human ankle and they do not generate the same force as they hit the ground, so he has to pump his legs faster to compensate. It’s clear that what might look like an advantage, is not really and advantage. But the future is a different story. I’m going to be rooting for Pistorius for sure.