I’ll be doing a few more of these types of posts down the road…looking at “big” picture type stuff using data that helps to tell the story about how things are changing with regards to the climate and also, depending on where the data takes me. to how things are not changing.
So with summer arriving over the weekend I thought it would be interesting to see where the data goes with regard to our changing summers in KC. Are they hotter, cooler…little changed from when you were growing up. Are we getting drier or wetter? Maybe things haven’t changed as much as you may think…perhaps more than you think. Let’s see where the actual data takes us.
So are summers getting hotter in KC?
Well maybe not in the big scheme of things…take a look at the data for the average summer temperatures going back to 1920. Almost 100 years worth of data. I’ve inserted a moving 30 year average as well.
We know some summers are hotter and some are cooler…nothing new there for our area. It’s hoped that over the course of 30 years or so that these hotter and cooler seasons sort of average out and you get a better baseline of what’s going on…
So the chart above from 1920 through last summer shows essentially NO change with the 30 year moving average. 76.5° at the start of the data and 76.5° at the end of the data.
IF I just looked at the last 30 years of data…there’s actually been a tiny decrease in the average summer temperature in KC.
A couple of notes…data for the period before 1972 or so was for the Downtown area (where ever the weather station was set-up-it moved around a few times). Since the early 70s it’s been up at KCI. There are obvious siting issues with this…Downtown’s retain heat…KCI for a couple of decades was in the boonies…now land use is creeping closer and closer to the KCI area as we know. This can affect temperatures in some fashion. Also for the purpose of this conversation summer is the 3 month period from June 1st to August 31st. Meteorological summer as we say.
Now let’s break this down…and strictly look at the high temperatures…
Again lots of ups and downs…but in the last 100 years there has been about a 1.2° increase in the highs for KC…when I exam the data though in the last 30 years…there is very little change in the highs for the summer months on average.
When I look at the overnight lows…the data is also interesting…and actually shows a .5° decrease in the overnight low temperatures in KC and in the last 30 years a 3/10ths of a degree drop in overnight lows.
To tell you the truth I was expecting not a lot of change in some of this data but I was expecting an increase in the overnight lows. Again the siting issues from Downtown to KCI could be playing a role in some of the above information. So let’s look at the data in the last 50 years…and yes there has been a subtle increase in the overnight lows.
What is somewhat interesting though is that we’re seeing more above average days during the summer months. This data takes into account the decades from the 70s through the 2010s.
You can see that clearly from the 90s through the 2010s we’re on the uptick for overall warmer than average days. As a matter of fact this next more specific chart, with data to 2018, reveals that we are indeed averaging about 2-3 hotter than average days in the summer season.
Again this is KC focused data above. The thing about the changing climate is that you have to look locally…regionally…nationally…hemispherically, and worldwide to get a comprehensive idea what’s going on.
That’s why I found this next chart more interesting…it shows how the summer temperatures have changed in the USA since 1970. For us here in the Plains and the upper Midwest, there hasn’t been a lot of change and in some cases the summers are actually getting slightly cooler…but for areas towards the south as well as east and west…well it’s quite a different story.
So what’s the takeaway from this data. Summers in KC aren’t really changing a lot. We have our hot ones…our “less” hot ones…and everything in between BUT in the big scheme of things summers haven’t really changed a lot over the course of the many years. We remember the brutal ones…the dustbowl 30s…a few of the summers in the 50s…a couple in the 80s and some since but while they were noteworthy, we’ve also had counter-balances to these hotter summers as well. Hence the minor changes in the moving 30 year averages.
What about the rain situation?
This is trickier because as we know most of the rains around here in the summer months are convectively driven and you can get wild swings from town to town in convection. One towns 4″ is another towns “trace” of rain. You hope over time…things try to even out somewhat.
It’s with that backdrop that I show you this data…again we’ll go back to 1920 as a starting point.
Disregard that last data point on the right side…that is for the 1st 2 weeks of this summer so obviously it’s low.
What we have seen though is an overall increase in the summer rain…almost an inch worth from the moving average back in 1920 to current. 1″ of rain is a pretty significant increase when we only get about 14″ of rain in the summer season.
IF we break it down to the last 30 years…there has been about a 1.1″ increase in the rains here in KC for a summer season. Again that is pretty significant. So the summers are trending wetter.
This may not be surprising because there is widespread belief that as the climate/atmosphere warms…that warmth in the atmosphere has the ability to retain more water vapor. This water vapor can lead to heavier rains (when it does rain). That is something that I think we’ve noticed as a broad generality here in KC. We talk the talk about severe weather with tornadoes etc…but in reality KC is a flood city.
So take a look at this…it shows the tendency to get heavier rain (2″+) in KC…and notice the trends in the last 70 years…a doubling of incidents. That is significant.
We are also a city that loves our roads…and our pavement…so the flooding aspect of things needs to take into account the use of terrain. When we had the devastating flooding a few years ago along 435 in JOCO…part of that was a direct result of all the pavement down there that has been put in. Pavement and flooding is not a good combination. There are other issues as well but it doesn’t change the fact that we are seeing, at times, heavier downpours when it does rain during the summer months as the data above shows.
So the summers are getting “wetter” on average in terms of the amounts of rain…and the ferocity of the downpours.
Hope you enjoyed this look at summer trends in KC.
The feature photo today is from Aaron Smith…