Scientists Just Discovered A New Key Reason Why Cities Get So Hot
Posted in Main Blog (All Posts) on July 14th, 2014 11:08 pm by HL
Scientists Just Discovered A New Key Reason Why Cities Get So Hot
Scientists have long been aware of the “urban heat island” effect — the tendency of large cities to get 1.8 to 5.4°F warmer than surrounding areas in the day, and 22°F warmer at night.
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Sunset in London during the summer time.
CREDIT: Shutterstock
Scientists have long been aware of the “urban heat island” effect — the tendency of large cities to get 1.8 to 5.4°F warmer than surrounding areas in the day, and 22°F warmer at night. The assumption has been that this was because all the concrete and other structures stored up heat, and the lack of vegetation reduced evaporation.
But a new study published last week in Nature says that’s not entirely right: convection, or the movement of air through the city, plays a big role in the daytime. The lack of vegetation and the presence of urban structures still matters, but because of their effect on air movement rather than on evaporation: “The ‘rougher’ surfaces of the vegetation triggers turbulence, and turbulence removes heat from the surface to the atmosphere,” said Lei Zhao, a doctoral student at the Yale School of Forestry and Environmental Studies, and the study’s lead author. “But where there is a smoother surface, there is less convection and the heat will be trapped in the surface.”
Interestingly, this effect on convection actually played much different roles depending on whether a city is found in wetter or drier climates. In dry areas like the American southwest, vegetation is shorter and scrubbier, which makes the rural areas far less adept at dissipating heat. As a result, urban areas actually become comparably more efficient at releasing heat back into the atmosphere, making the cities about 1.5°F cooler. But in wetter climates, urbanization reduces the efficiency of convection by as much as 58 percent.
The study examined 65 different cities in the U.S. and Canada, using satellite data of land surface temperatures and vegetation cover. The researchers then applied various climate models to the data to tease out the contributions of different variables — such as radiation, convection, evaporation, heat storage, and human-generated heat — to the heat island effect.
“One of the major barriers to mitigating the effects of UHI [urban heat island effect] is the lack of quantitative attribution of the contributing factors,” continued Zhao.
One unfortunate take-away from the study is that managing convection effects will be largely impossible, since it would require massive alterations to the height and structural design of buildings in cities throughout the country. An alternative possibility the researchers brought up was changing “albedo” — the amount of solar radiation reflected back out to space from various city surfaces like rooftops and roads — to reduce the absorption of heat in cities. Studies have shown that while both white roofs and “green” roofs — ones planted with vegetation or gardens — have various advantages, the white roofs tend to to the best job of reflecting heat, which also comes with energy savings from the reduced need for cooling. It’s an approach to climate adaptation that multiple American cities are already taking on of their own accord.
Another concern is the danger of future heat waves, and how those will interact with the convection problems in some cities. “There is a synergistic relationship between climate conditions and the urban heat island,” said Xuhui Lee, the Sara Shallenberger Brown Professor of Meteorology at the Yale School of Forestry and Environmental Studies, and another one of the study’s authors. “This relationship suggests that the urban heat island will exacerbate heat wave stress on human health in wet climates where temperature effects are already compounded by high humidity.”
“This is a huge concern from a public health perspective.”
A recent study by Climate Central showed that U.S. summers are already warmer than in the 1970s, and by the end of this century Boston could be seeing the same kinds of summers that Miami sees now. Another recent granular study of the risks climate change poses throughout the American economy warned that heat waves could have significant impacts on both human safety and worker productivity by 2100, especially in the eastern half of the country.
About 3.5 billion people, or more than half the global population, already live in cities according to the World Health Organization. And by 2050, the group projects that portion will rise to 70 percent of the people on Earth living in urban areas.
Update
This post has been edited for clarity.
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How Bad Medicine Is Sweeping The Country, One State At A Time
In most states, health decisions are determined by politicians instead of doctors.
The post How Bad Medicine Is Sweeping The Country, One State At A Time appeared first on ThinkProgress.
CREDIT: Flickr Creative Commons via Stephen Melkisethian
In the majority of this country, Americans’ medical care is determined by politicians instead of by doctors. That’s because a wave of anti-choice legislation has completely reoriented the women’s health landscape, ensuring that medical professionals are forced to ignore their best judgment in order to remain compliant with the law, according to a new report from the National Partnership for Women & Families.
“Politics are taking over our exam rooms and that is a dangerous, disturbing trend,” the National Partnership’s president, Debra L. Ness, noted in a statement released to coincide with the new findings. “More and more, lawmakers across the country are enacting laws that mandate how health care providers must practice medicine.”
Ness’ group argues that four different anti-abortion restrictions — unnecessary ultrasound requirements, biased counseling sessions, mandatory waiting periods, and regulations on the abortion pill — fall into a broad “bad medicine” category. Even though there’s no scientific evidence to justify those policies, they’re incredibly common. Thirty three states currently have at least one of those laws on the books, and 16 states have enacted all four types:
CREDIT: National Partnership for Women & Families
For instance, 26 states require abortion patients to wait 24, 48, or even 72 hours before receiving medical care. That forces their doctors to delay a time-sensitive procedure regardless of their professional opinion about whether the abortion should wait. A growing number of states are passing laws that require doctors to follow an outdated protocol for administering the abortion pill, which actually forces them to violate current practice and give their patients an unnecessarily high dosage of the medication. And ultrasound and counseling laws — which are each in place in more than 20 states — often make doctors present their patients with implicit anti-abortion messages that communicates they’re making the wrong choice, even if they’d rather not approach the medical procedure that way.
“It is time to take politics out of the exam room and return abortion care to women and their health care providers,” the report concludes.
Indeed, doctors have been speaking out about these type of state laws for years. Medical professionals frequently testify against proposed state-level abortion restrictions, pointing out they’ll unfairly intrude into the doctor-patient relationship. The American College of Obstetricians and Gynecologists, the biggest group of OB-GYNs in the country, has officially come out against state-level abortion laws that interfere with their work. “Nowhere is legislative interference more rampant than in the world of women’s health care,” the group’s senior director of government affairs pointed out last year.
But the state legislators who are insistent on limiting abortion services tend to disregard medical professionals’ opinions. Even when lawmakers admit they’re not qualified to make decisions about women’s health, that’s not necessarily enough to stop them from imposing new laws in this area. A particularly clear example of this dynamic was recently evident in Ohio: After a state legislator there introduced a measure to limit low-income women’s access to certain types of contraception based on the false assertion that they can induce abortion, he acknowledged, “This is just a personal view. I’m not a medical doctor.”
The National Partnership for Women & Families isn’t the only organization working to highlight this issue. Last month, the Center for Inquiry, a secular humanist organization that works to promote scientific reason, launched a new campaign to fight to keep junk science out of government. The “Keep Health Care Safe and Secular” project hopes to encourage more Americans to fight back against the laws that limit women’s access to health services. Similarly, NARAL Pro-Choice America sometimes uses the slogan “Politicians Make Crappy Doctors.”
The push to keep abortion-related laws grounded in scientific fact has also made its way to Congress. Last year, a group of Senate Democrats unveiled the Women’s Health Protection Act of 2013, a measure that stipulates new abortion regulations shouldn’t require doctors to go against their best judgment. That measure — a somewhat historic piece of proactive legislation within a political environment focused on limiting abortion rights — will go before a Senate committee on Tuesday.
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