EXTREME HEAT © 2011 Tomás Gianelli / Flickr / CC BY-NC 2.0 As you might expect, extreme heat is one of the most direct and easiest to understand effects of man-made climate change. “If you warm up the planet, you’re going to have more frequent and intense heat waves,” Dr. Michael Mann explained to Climate Reality . Perhaps unsurprisingly, 17 of the 18 hottest years on record have occurred this century. Extreme heat elevates the rate of death from illnesses like heart attack, heat stroke, organ failure, and more. The journal Nature Climate Change reports that potentially deadly extreme heat is a growing concern, and will likely become more frequent and will occur over a larger portion of the planet in the coming decades. According to a study published in the journal last year , “Around 30 percent of the world’s population is currently exposed to climatic conditions exceeding this deadly threshold (where daily mean surface air temperatures and relative humidity become deadly) for at least 20 days a year. By 2100, this percentage is projected to increase to ~48 percent under a scenario with drastic reductions of greenhouse gas emissions and ~74 percent under a scenario of growing emissions. An increasing threat to human life from excess heat now seems almost inevitable, but will be greatly aggravated if greenhouse gases are not considerably reduced.” 14