April 24, 2008
The closest living relatives of Tyrannosaurus rex are birds such as chickens and ostriches, according to research published today in Science (and promptly reported in the New York Times). Paleontologists used material discovered in a chance find in 2003 to pin down the link.
The dinosaur-ness of birds has been suspected for many years based on anatomical similarities, but the new research is the first molecular evidence. For decades, dinosaurs were thought to be reptiles: big ones, to be sure, but basically cold-blooded, slow-moving, and dim-witted. The movie Jurassic Park popularized the idea of dinosaurs as quick, smart and birdlike. (The movie’s ideas had been proposed in the 1970s–a book by paleontologist Robert Bakker, called The Dinosaur Heresies, nicely conveys this change in thinking and the controversy that accompanied it.)
To get molecular evidence about dinosaurs, you need some actual molecules–a tall order for a group of animals that died out 65 million years ago. But in 2003, scientists Jack Horner and Mary Schweitzer discovered some unfossilized material inside a T. rex bone by a combination of luck, desperation, and sharp eyes (see Smithsonian, May 2006). Faced with flying a giant femur out of a remote Montana field site, they broke the bone in half so it would fit inside their helicopter. If they’d had a larger helicopter, we might never have known.
Unlike in Jurassic Park, the real-life researchers couldn’t recover any DNA from the ancient remains. But they did retrieve molecules of collagen, a structural protein that appears in slightly different forms in many animals. They compared the dinosaur version with 21 living animals, including humans, chimps, mice, chickens, ostriches, alligators and salmon. T. rex‘s collagen proved to be most similar to chickens and ostriches; its next closest match was to alligators.
Chickens and ostriches are only distantly related to each other, so the research says little about what kind of birds might be the closest relatives of the famous carnivore. The scientists noted that answering that question would require data from more molecules than just collagen. Whether they are currently cracking into any more giant fossils in search of material was not divulged.
(Images courtesy Science)
April 17, 2008
One of the most talked-about outcomes of climate change is global sea-level rise–perhaps because the effects are straightforward and tangible: If sea level rises by this much, wipe this much of Florida (Bangladesh, Venice, Vancouver, Togo, the U.K., etc.) off the map. That’s a lot more immediate than envisioning the effect of a 3 degree rise in temperature on, say, the location of the world’s intertropical convergence zones.
Records show that on average, sea level has risen by about 1.7 millimeters (the thickness of a quarter) per year over the last century, for a total of more than 6 inches so far. But like many natural records, a graph of sea-level rise over time gives you a jittery line. Sea-level rise accelerated around 1930, slowed in 1960, and sped up again around 1990.
That is, until a correction arrived last week, when two Taiwanese scientists, writing in the journal Science, calculated that worldwide dam construction in the 20th century had kept nearly 11,000 cubic kilometers of water from reaching the ocean. The effect of all that withholding has been to slow the ocean’s rise by about 0.55 millimeters, or nearly a third of the total, per year.
The researchers went on to trace the timeline of dam construction, using a database of more than 29,000 of the world’s largest dams. They allowed for contradictory effects such as reservoirs not filling completely, water seeping into the ground below and small dams not being reported in the database. When they were finished, they added up the dam volumes year by year and superimposed the amounts on the historical, jagged graph of observed sea level rise.
The result: a much straighter line. It seems that the great dam-building bonanzas of the 1950s through the 1980s changed the Earth’s runoff patterns enough to be felt (admittedly, somewhat minutely) at sea level. Without dams, sea level would have risen at an average 2.46 millimeters per year. You can take this news as good or bad.
Good: it means sea-level rise may not have accelerated as sharply in recent years as it seems to have done. Bad: scientists can’t account for where all the rising seawater is coming from, and these new numbers mean there’s even more water to be accounted for. Which reminds me: new models suggest melting ice could raise sea levels by 4 feet this century, New Scientist reports. That’s nearly three times more than in the worst-case estimates from the Intergovernmental Panel on Climate Change.
April 11, 2008
It was just three years ago that Hurricane Rita stormed the Texas coastline, mere weeks after Katrina flattened Louisiana. While New Orleans struggles to rebuild, Texas seems to have forgiven, forgotten, and embraced the sunny weather. The Houston Chronicle reports that development values along the state’s picturesque Gulf Coast have tripled since Rita.Though real estate agents may be celebrating, the trend is causing consternation among insurance companies, which would be called upon to cover the region’s $64 billion of development should another bad hurricane season get Texas in its sights. At present, the Texas Windstorm Insurance Association has just $1.4 billion on hand for such an eventuality.
The Chronicle article gives a breakdown of how insurance firms might cover the remainder. But the upshot is that after such a payout, many insurance companies might stop selling insurance in the hurricane-prone areas entirely, leaving homeowners (anything but) high and dry.
But what’s the chance of another bad hurricane season? Well, hurricanes are fueled by warm water. And though the ocean is unruly, over the long term it’s slowly warming along with the atmosphere. That’s likely to make hurricanes more intense, a conclusion long argued by MIT’s Kerry Emanuel and covered on an insurance news site just three weeks before Katrina struck. Here’s one powerful industry, at least, that’s sitting up and taking notice of the problem – even if it’s largely by raising premiums or getting out of the market.
April 1, 2008
A few weeks ago we wished Darwin a happy 199th, so here’s three cheers for the Keeling Curve (above) passing the big 5-0.
Described by the Scripps Institution of Oceanography, in only a bit of a stretch, as âone of the iconic images of science, rivaling the double helix or Darwinâs sketches of finches,â? the Keeling Curve is an unassuming sawtooth tracing a steepening path up a piece of graph paper. Itâs also the longest continuous record of atmospheric carbon dioxide levels we have.
In 1958, Charles David Keeling began taking extremely precise measurements from an observatory 11,000 feet up on Mauna Loa, Hawaii. He had recently developed a new measurement method accurate to within 1 part per million (ppm). (Watch the pioneering scientist gleefully pouring liquid nitrogen barehanded into his equipment. He mentions he got interested in his field because it was a chance to build gadgets.)
The work is still going strong, and the Curve now charts a slow and unflinching rise in the carbon dioxide levels in the air, from an already-elevated 315 ppm in 1958 to some 380 ppm today. Keeling’s equipment was so precise, he later said, that the rise was already detectable with just 2 or 3 years of data.
As a representation of the natural world, the Keeling Curve is remarkable for its decorum. Pretty much any other historical record, from the temperature at your local airport to the vicissitudes of Wall Street, is a hysterical EKG of peaks and valleys, as each irregular day passes into the next. By contrast, the Keeling Curve looks like the work of an obsessive with an Etch-a-Sketch. The instrumentâs location helps, stuck high into the atmosphere in the middle of the worldâs biggest ocean, far from smokestacks and tailpipes.
In the absence of noise, any variation on the graph means something. That sawtooth pattern reflects passing seasons in the Northern Hemisphere, where most of the worldâs vegetated land is. During summer, plants take up carbon dioxide to grow, putting a roughly 6-ppm dent in atmospheric CO2 levels. During northern winters, decaying matter releases carbon dioxide back into the atmosphere, and the Keeling Curve peaks again.
Notice anything else? The line is getting steeper. That means that carbon dioxide isn’t just accumulating – we’re adding more upon more each year. You could seek out appendices full of statistics on car ownership and megawatt production to calculate this, but the gist is right here on this graph.
And as Keeling noticed while plotting results a decade or so ago, the size of the sawtooths is getting bigger. Thatâs an ominous indication of a subtle shift: slightly more plant growth each year, a result of longer growing seasons stemming from earlier springs and later falls.
So while we’re at it, let’s save a birthday cheer for Keeling, who died in 2005. This year would have marked his 80th birthday.
(Scripps atmospheric scientist Ralph Keeling – Dave Keeling’s son)