Last week the United States Department of Agriculture (USDA) released a new plant-hardiness zone map for the United States. Does the new USDA map offer proof that the climate is warming? No, it does not. Do temperatures shift warmer and colder over time? Of course they do. The temperatures over large regions fluctuate and hopefully always will. Just like the previous USDA map released in 2012, the new USDA map does not represent the new normal for climate.
The USDA website notes: “Climate changes are usually based on trends in overall average temperatures recorded over 50-100 years. Because the (new map) represents 30-year averages of what are essentially extreme weather events (the coldest temperature of the year), changes in map zones are not reliable evidence of whether there has been global warming.”
