By Candice Leigh Helfand

HOUSTON (CBS Houston) — Memories of last summer’s scorching-hot conditions were brought back this week with a heat wave that’s pushing temperatures toward 100 degrees in much of the northeastern United States.

And according to Victor Murphy, the climate service program manager for the National Oceanic and Atmospheric Administration’s southern headquarters, Texas is also very likely to experience a hotter-than-normal summer this year.

“It looks like for summer time … Texas is running a probability of about two-to-one odds of having above average temperatures,” he said.

An info-graphic provided to CBS Houston by Murphy (shown below) also indicates a likelihood of above-average temperatures for much of the continental United States over the course of the next three months.

High temperatures herald a host of dangers – especially for the very young and very old.

But Andrew Carleton, a professor of geography and a climatologist at Penn State University, warned of smaller, more concentrated zones of elevated temperatures called urban heat islands that contain threats all their own.

“[U]rban areas are becoming places where increasing numbers of people are moving to. The areas are getting bigger, creating an urban heat island effect,” he told CBS Houston. “The buildings and streets trap heat, which contributes to heat waves in urban areas. Mortality rates could particularly increase in [those] areas.”

Carleton attributed the rise in danger to higher overnight temperatures, which can negatively affect sleeping habits and leave city residents weakened – especially those without air conditioning.

The concept of an urban heat island in nothing new. In fact, the phenomenon has been studied since the early 19th century, though it was not formally named until later on.

However, the overall heating of the Earth, caused in part by greenhouse gas emissions and shifts in wind patterns and pressure belts due to the melting of the icecaps, and the equally steady rise in urban populations combine to exacerbate their effects.

The Natural Resources Defense Council also warned against the potentially fatal nature of modern-day heat waves, citing the urban heat island effect as part of the problem and noting the lack of tree shade as another contributing factor.

release published by the NRDC said that, on average, extreme heat is to blame for 400 deaths per year.

“[A]n estimated 1,800 die from illnesses made worse by heat – including heat exhaustion, heat stroke, cardiovascular disease, and kidney disease,” the release added.

Rural areas will also feel the burn as the seasons change.

The Farmers’ Almanac predicted staggering temperatures in all areas of North America for the upcoming summer season, which officially started Wednesday.

“Look for a hot spell just about everywhere in late June, with temperatures soaring into the 100s in many areas, followed by stormy weather that will hopefully cool things down,” an article on its website stated. “The heat will remain turned up across North America in July, with unsettled conditions, thunderstorms, and another exceptional heat wave toward the middle of the month.”

However, there is some hope on the horizon, as experts expect relief from the record-breaking heat experienced last summer.

“We don’t have severe drought conditions. The heat was related to how dry it was, and there wasn’t a lot of water in the ground … to cool it off,” David Brown, regional climate services director for the NOAA, told CBS Houston.

“The 2011 drought obviously affected warm temperatures last year, as well as El Nino and La Nina,” Brown added. “There are also cyclical patterns in temperature.”

On a longer timeline, most climatologists agree that the Earth will continue to steadily get warmer. But the gradual nature of the phenomenon could prove to be a blessing of sorts, as humans may be able to adjust to higher temperatures over time.

“For health reasons, it is good that the rate of temperature increase is gradual – the largest number of deaths from heat occur when the weather is so hot that people are not used to it,” Texas A&M University meteorology professor John Nielsen-Gammon noted to CBS Houston. “I am hopeful that as temperatures become warmer, people will gradually get used to them, so a heat wave with 110 [degree] temperatures in the middle of the century, while more common, won’t cause as many deaths as a similar heat wave today.”

On another optimistic note, Brown added that “[e]ven with a warmer summer … if that does pan out, there will still be days where it’s cool.”

There will be still be adverse effects from global warming, however. Carleton noted the danger of what he called “positive feedback” – the ironic name given to the process by which higher temperatures and greenhouse gases reciprocally affect each other.

“Greenhouse gas traps heat, and as temperatures start to rise … more moisture can be stored in the air as well. Water vapor is also a greenhouse gas, and quite a potent one,” he explained. “And higher humidity tends to make heat worse.”

“If temperatures do continue to warm as they have been, what that will mean … is an increased stress on agriculture, cattle, electricity production,” Brown explained. “It’s one of the biggest areas of focus in weather and climate science, is how long-term trends impact people, the economy and ecosystems.”

nws Climatologist: Urban Heat Islands Could Increase Mortality Rates

Graphic showing a three-month temperature projection for North America. Orange areas indicate zones likely to experience above-average temperatures. (Credit: National Oceanic and Atmospheric Administration)

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