How A Western Heatwave Is Setting Disturbing Records

My fingers shouldn’t be typing this. It was 116 degrees Fahrenheit in Sacramento, California this week. In case that is not bizarre enough on its own, consider this tweet from the National Weather Service in Sacramento:

Such record-breaking heat happened in September (not July). Here are four startling weather-climate aspects of the ongoing heatwave in the American West.

Record-Breaking Summer Temperatures in September

September itself is the first thing that catches my eye. The U.S. National Weather Service predicted temperatures for September 6 and 7 that could break records by as much as 3 to 5 degrees. Typically, temperature records are broken by smaller increments. This heatwave is shattering records during September, which is traditionally not the warmest month at these locations. Salt Lake City, for example, experienced its hottest 5 September days on record this week according to numerous reports. Referring back to Sacramento, its maximum temperature typically peaks much earlier in the summer (see graphic below), and that value is no where near 116 degrees F. The spike that you see in the graphic below is well beyond the record maximum (red line).

Heat Domes Of High Pressure

Another fascinating aspect of the heatwave is the meteorology itself. Heatwaves are typically associated with strong areas of high pressure or anti-cyclonic flow, and this one is no different. Heat is trapped in domes of high pressure and as the NOAA SciJinks website reminds us, “High-pressure systems force air downward.” The sinking air warms by something called ‘adiabatic compression’, and rain-producing clouds are suppressed. Studies suggest that blocking associated with high pressure and mid-latitude heatwaves will continue to be problem in our ongoing and future climate system (more on this later). The NOAA Weather Prediction Center forecast discussion said, “The dominant and anomalous upper-level ridge parked over the central Great Basin responsible for the ongoing western U.S. heat wave is anticipated to finally begin dissolving on Thursday and offer a cooling trend for areas experiencing record shattering September heat.” Unfortunately, the run of upper 90s to values in excess of 110 degrees F will continue until the high weakens.

‘DNA’ Of Climate Change

A third jaw-dropping aspect of the heatwave is that it is consistent with long-term expectations about changing climate. Attribution studies are maturing to the point that they can detect the “DNA” of climate change in current extreme weather events. Yes, we know. Weather events are naturally-occurring, but they are now modified by human-activities. Grass is naturally-occurring too, but it grows differently when soil is fertilized. It is not “either/or.” It is “and.”

Scholarly studies continue to warn that climate change has increased the frequency and intensity of mega-heatwaves like the September 2022 event or the one in Europe weeks ago. By the way, 104 degrees F is not normal in London and explains why such places are devastated by extreme heat. The Pacific Northwest (U.S.) and Canadian heatwave of 2021 is another example. Like the United Kingdom, many of homes in that region do not have air conditioning. A 2021 study concluded the magnitude of that heatwave was basically “impossible” without climate change. A more recent study published in Environmental Research Letters also found that the likelihood of heatwaves is 10 more likely in some locations.

Working amid heatwaves

The final aspect of the current heatwave is the human story. While many schools and businesses have closed during the extreme heat, I wonder how many workers are still in agricultural fields or in construction zones. The Central Valley of California provides a large percentage of fruits, vegetables, and nuts consumes by us all. Yet, there is brutal heat in that region right now. How many workers are being subjected to that heat? How many homeless or poor communities have insufficient options to cool themselves or seek medical attention for heat-related illnesses? How will the energy grid hold up?

These are questions facing our new climate reality and ultimately why it matters.