“A picture is worth 1,000 words.” It’s a cliché for a reason – graphics are incredibly powerful. I saw the graphic below on Climate Central and was struck by how adeptly it demonstrates the recent and dramatic rise in temperature in the U.S. Take a look.
This chart works off of the assumption that, without the occurrence of global warming, the number of record high and record low temperatures should be relatively equal each year. This seems like a reasonable assumption, although I am not a climatologist and therefore cannot say definitively that it is correct. But if we accept this assumption, we can conclude that an increase in record high temperatures that is not matched by an equal number of record lows is indicative of a warming planet. Certainly natural variability in the Earth’s climate could cause the ratio to lean slightly in one direction or the other, but over time the ratio between record highs and lows should average out to 1:1.
The charts above are telling a different story. We see that in the 1950’s, record temperatures were nearly equal in both directions. But, in the last few years, we have seen a dramatic favoring of warmer temperatures. With recent heat waves, it may come as no surprise that the last three years have been unusually warm. Although it’s not just the last three years that have been seeing an increased number of record high temperatures. According to this chart, the last three decades have seen more record highs than record lows, and the decade from 2000-2009 saw record highs beat out record lows 2:1. While number of record temperatures set doesn’t necessarily demonstrate the degree of warming, I do think it is reasonable to conclude that the climate is indeed warming.
And, it is warming at an unnatural rate. We know that Nature tends to work slowly, evolving over hundreds, or even thousands, of years. But here, we are seeing significant change over the course of just a few years. This type of change is not natural.
I do see a flaw with this model, however. The balance between record highs and lows could remain intact so long as the temperature breaks records in both directions an equal number of times. So, we could have a record hot summer with temperatures consistently hitting above the 100-degree mark and a record cold winter with temperatures barely rising above freezing, and the balance could remain at 50/50. But, climate change doesn’t just involve warming – it includes a greater occurrence of extreme weather occurrences. Current data reveals that the global climate is, in fact, warming, and most predictions of future extreme weather events are based on a global warming scenario. The above graphic supports these conclusions, and I agree with them. But, pictures can also be deceiving, and I think graphics like those above require us to take a deeper dive to make sure we are seeing the whole picture.