Any time it’s hot or hotter than average, the subject of global warming invariably arises. The usual question I hear is: Is this global warming (or climate change)? The answer I give is that global warming is not causing hot weather but almost certainly intensifying it.
In other words, think of the greenhouse gases building up in the atmosphere from human activities as steroids. Just like steroids can help a baseball player hit a ball farther and hit more home runs in a season, greenhouse gases are performance enhancers when it comes to hot weather. These gases from fossil fuel combustion and other sources add a little heat to the atmosphere or “juice” it up - loading the dice to make hot weather and hot weather records more likely as long as they continue accumulating in the atmosphere.
Extending the analogy, just like any single homerun can not solely be attributed to a baseball players’ steroid use since it ignores natural ability (and past performance prior to use of performance enhancers), a single hot day can’t be exclusively explained by global warming (as it ignores natural weather variability and past hot days/heat waves; see Andrew Freedman’s column which further explores this analogy).
The graphic below, produced by the NationalCenter for Atmospheric Research (NCAR), offers another way to think about the hot weather and climate warming link: the warming shifts our distribution of temperatures to the right toward more hot weather and hotter extremes, and decreases cold weather.
“A relatively small shift in the average produces a large change in extremes,” said NCAR scientist Jerry Meehl. “If you shift the whole distribution a little to the right you have more extreme heat. The tail on the far right moves into uncharted territory, breaking new heat records.”
Interested in evidence that this shift towards a hotter climate is real? NCAR supported research recently found record high daily temperatures in the United States are outpacing record low daily temperatures by a ratio of 2 to 1.
UPDATE (4:10 p.m.): CapitalClimate reports through the first week of June, high temperature records have outnumbered cold temperature records in the U.S. by over 10:1.
According to our projections, large areas of the globe are likely to warm up so quickly that, by the middle of this century, even the coolest summers will be hotter than the hottest summers of the past 50 years.