When it comes to thinning the human herd, heat is one of the most effective killers on the planet. It's quiet and it's sneaky, with its death tolls often going nearly unnoticed until the worst of the sultriness has passed.
Centuries ago, we humans hid in the shadows to escape long-lasting summer heat waves. In these more modern times, we shield ourselves with buildings and blasts of air-conditioning units. But the sun has a way of making our contemporary technologies look weak and powerless.
In 2003, a three-week heat wave hung over Europe. Power companies couldn't supply enough energy to keep up with the demand for air conditioners. Utility lines simply melted. The heat began to rise in apartments and offices across the continent, and the results were catastrophic.
Elderly people with poor mobility, higher levels of poverty and poorer health began dying in droves. If they had air conditioning at all, their units failed in the scorching heat and then they perished in their stifling residences. Officials found more than 15,000 people just in Paris, and across Europe the death toll was around 70,000 [source: Gannon].
Heat kills by stressing your body to the breaking point, raising your heart rate and respiration and then often triggering secondary effects such as heart attack or stroke. Once your body temperature shoots past 104 degrees Fahrenheit (40 degrees Celsius), you'll have a harder time recovering. This is especially true for older people. After days or weeks of high heat, these vulnerable populations die quickly, all thanks to awful, ceaseless heat exposure.