Image by trillbilly

A house in Bermuda with a white roof.

In an interview with the British newspaper The Independent, Chu said:

“If you look at all the buildings and make all the roofs white, and if you make the pavement a more concrete-type of color than a black-type of color, and you do this uniformly … It’s the equivalent of reducing the carbon emissions due to all the cars in the world by 11 years.”

Let’s tackle energy conservation first. On a hot day, you’ll be much cooler wearing a white shirt than a dark shirt. This is because light colored objects reflect more sunlight. Dark objects absorb more sunlight than light colored objects; the absorbed light then radiates away from the object (or is emitted from the object) as heat. Your dark shirt is absorbing sunlight, and then releasing it as heat, which makes you feel hotter.

Image by Cool Roof Rating Council

A white roof reflects more light and radiates less heat than a dark roof.

A dark roof on a building is like a dark shirt. The roof absorbs sunlight, and then radiates heat into the building. The temperature inside the building increases, and we use energy - in the form of air conditioning - to cool the building. Paint the roof white (or use a reflective material, like white tiles), the roof absorbs less sunlight, less heat is radiated into the building, the temperature inside the building doesn’t increase as much and we don’t need to use as much energy to cool the building. That’s how painting a roof white conserves energy. In the United States, the California state government has become a leader in encouraging the use of white roofs or cool roofs.

White roofs may also reduce global warming.

When sunlight is absorbed by a roof, the roof heats up and radiates heat in the form of  infrared light, which is invisible to humans (it has a longer wavelength than red light). Infrared light is emitted from the roof and reaches the atmosphere, where it is absorbed by gases and re-emitted as infrared light - a continuous cycle of absorption and emission that traps heat in the atmosphere and increases the temperature of the Earth. Gases that absorb and radiate infrared light are called greenhouse gases - these include water vapor, carbon dioxide and ozone.

Atmospheric gases don’t absorb much visible light, which is why sunlight reflected from a white roof - visible light - can travel through the atmosphere and escape into outer space.

Image by redskunk

These principles also apply to car roofs.

Incidentally, light is also absorbed by the Earth - the ground, the soil - and returned to the atmosphere as infrared light, where it is trapped as heat. This is the greenhouse effect. We can’t paint the Earth white to reduce global temperatures, but nature has helped us out a bit, in the form of ice. Polar ice caps and glaciers are like big, white roofs - they reflect much of the incoming sunlight back into the atmosphere and out into space. Scientists and policymakers are concerned that melting ice will expose land, decreasing the amount of sunlight reflected back into space and increasing the amount absorbed by the Earth and trapped in the atmosphere as heat.

Researching this post I have found no reason why we should not be painting our roofs white (or using reflective tiles). Can you think of a reason not to do this? People might complain about having to look at a white roof, but does an aesthetic concern outweigh conserving energy and reducing global warming?

In a victory for science and for diplomacy, the U.S. and U.K. governments cooperated to rescue an endangered sea turtle.

Wilhelmina - nicknamed Willy - is a Kemp’s ridley sea turtle (Lepidochelys kempii) who wandered from the turtles’ normal habitat, along the Gulf of Mexico and the North American Atlantic coast, and wound up in Devon in the United Kingdom in 2007.

The English waters are usually too cold for Kemp’s ridleys to survive, but Willy was lucky. She was taken to the Weymouth Sea Life Centre and nursed back to health. The BBC reported that Willy is only the second Kemp’s ridley found alive in the United Kingdom.

On April 23 Willy was flown to the United States, where she’ll spend several weeks at a sea turtle sanctuary in North Carolina before being released into the wild.

My colleague Jock Whittlesey and the environment office at the U.S. Embassy in London helped coordinate Willy’s return to the United States - you can read about their efforts on Jock’s blog.

According to the National Oceanic and Atmospheric Administration, the endangered Kemp’s ridley is the smallest marine turtle in the world (weighing on average 45 kg) and displays a unique, synchronized nesting behavior:

Large groups of Kemp’s ridleys gather off a particular nesting beach near Rancho Nuevo, Mexico, in the state of Tamaulipas. Then wave upon wave of females come ashore and nest in what is known as an “arribada,” which means “arrival” in Spanish.

There are many theories on what triggers an arribada, including offshore winds, lunar cycles, and the release of pheromones by females. Scientists have yet to conclusively determine the cues for ridley arribadas. Arribada nesting is a behavior found only in the genus Lepidochelys (which includes only the Kemp and olive ridley sea turtles).

Fishing gear, primarily shrimp trawls, are the greatest threat to Kemp’s ridleys.

I don’t know why Wilhelmina was given the nick name Willy. Was it in honor of the movie ‘Free Willy?’ As a tribute to the hero of the Scottish comic strip Oor Wullie?

Despite having a less convoluted birth canal, Neandertals felt the difficult pangs of childbirth just like modern humans do, according to a recent study of a female Neandertal pelvis unearthed in Israel more than 70 years ago.

Unlike our ape and monkey relatives, human babies are about the same size as the birth canal, making for a “difficult” passage, the two male authors write. (How’s that for an understatement?)

In fact, the human birth canal is twisted, wider than it is long in some places, and longer than it is wide in others. This means that babies must twist as they make their egress: entering the birth canal sideways, the baby must rotate so its head is down, and then rotate again to allow its shoulders to pass.

When did the ape’s birth canal evolve into the twisted, and painful, human version? Timothy Weaver and Jean-Jacques Hublin used CT scans to reconstruct a birth canal from pelvic bone fossil fragments from a Neandertal and compared this to data from pelvic bones from modern humans.

Weaver and Hublin’s reconstruction suggest that the Neandertal’s birth canal was less twisted than that of modern humans. But the pelvic area in Neandertals and modern humans is similar, suggesting that even though Neandertal babies didn’t have to twist as much during delivery, their size relative to the birth canal was close enough to insure a painful passage.

The results mean that changes in childbirth probably occurred “quite late in human evolution, during the last few hundred thousand years.”

A word of caution - this type of research relies on intact fossils. The pelvis survives very poorly, which is why scientists must rely on sophisticated reconstruction techniques. The current study is based on bone from a single Neandertal, making it difficult to take normal variations present within a species into account.

You know the cliché that science knows no borders? The current study was written by a scientist in the United States and one in Germany - examining a specimen discovered in Israel by a British archaeologist - using imaging technology developed by scientists from South Africa and the United Kingdom (one of whom worked in the United States).

Source: “Neandertal birth canal shape and the evolution of human childbirth” by Timothy D. Weaver and Jean-Jacques Hublin published April 20 online in PNAS (doi: 10.1073/pnas.0812554106).