Global warming made headlines across the world. The Department of Defense called it a national security threat “that requires a broader, whole-of-government response.” Here are some of the reasons why: The Atlantic hurricane season was the most destructive one in history. Three massive Category 4 or 5 storms — Harvey, Irma and Maria — brought high winds, water and damage to the Gulf Coast and Caribbean. The dollar cost of these mighty storms has already passed $200 billion, and we aren’t through calculating the bill for rebuilding Puerto Rico’s infrastructure from the ground up. The United States wasn’t the only place where extreme rainfalls wreaked havoc. Storms in Africa and the Indian subcontinent claimed thousands of lives this summer. The year 2017 will replace 2016 as the hottest year in recorded history, just as 2016 did 2015 last year. This is the first time this has occurred since the current warming trend began in the 1970s. Unusually heavy rains followed by exceptionally hot weather created perfect conditions for the spectacularly huge fires that are currently incinerating hundreds of thousands of acres in Southern California. But this year saw more than the usual number of fires all across the West, as well as Canada, Brazil and southern Europe. And the gigantic Larsen C Ice Shelf became an iceberg in July; it is bigger than Delaware and has enough ice to cover all 50 states in 4.5 inches of ice. Closer to home, in Carroll County, we’re seeing temperatures almost 3 degrees above average this month, and that includes last Saturday’s snowy chill.