Warm Season, Cool Climate Graphics!

Deep into the heat of summer, with occasional thunderstorm relief, there is a burst of color and buzz of activity in native gardens and prairies all around the Chicago region. I’m reminded that the cool season grasses have tapered off and “tagged in” a warm season period of productivity. Later this fall, we will see a reversal as cool season species once again take center stage. One of my favorite things about prairies is that the growing season is fully utilized!

What will happen to this interplay between grasses as the growing season expands with climate change? Will it be “warm season” longer? Will some grass species adapt? Will the plant species composition change? Simple as those questions are, the answers are hard to come by – even as we are inundated by climate projections and ecological research results. We can start by examining recent weather patterns and ecological responses, looking for trends, and then combine this information with climate projections. Still overwhelming? One method for grasping a large amount of information easily is with creative and robust visual graphs.

Let’s use as our source of robust graphics and combine it with some high level climate projections for an example.

According to their website, “offers detailed reports of the typical weather for 150,165 locations worldwide.” Their graphs show a single weather factor’s average value (temperature, precipitation, etc.) in a variety of graphical plots. My favorite plots are on an hourly timescale for the year – in an easy to digest and understand format.

Here’s a plot showing average hourly temperatures for Tampa, FL:

The time of year is plotted horizontally, in months, and the time of day is plotted vertically, in hours. The colors represent the temperature range, and shading shows the daylight and nighttime hours. Once you examine it and learn the format, it’s a great deal of useful information all in one graph from which you can easily make some observations. Seasonally, it’s the hottest part of the summer right now, with little relief at night, and really hot for the majority of the afternoon. The only time it gets “cold” is early mornings in January. They have no concept of a polar vortex!

OK, now let’s use this same graph for our region and combine it with some high level climate projections. It has been reported through the National Climate Assessment that we are getting much warmer and the report provides a range of temperature increases and maps to show those changes. A helpful way to think about those increases is this graphic from the Chicago Wilderness Climate Action Plan for Nature, illustrating how much warmer our summers would be by comparing it to other locations in the US:

Using this graph/map, let’s select a city for a location in the mid-century projection area – only 30 years away now. We will use this city to compare the average temperatures to Chicago now and use it as a proxy to see where we may be headed. St Louis, MO should work fine!

Here are the graphs of the average hourly temperatures for Chicago and St. Louis:

A quick review of these two plots and two things jump out – the summer and winter temperatures. Again, we are using the St. Louis plot as a proxy for what Chicago may experience by 2050. The summer temperatures get hotter, mostly in the afternoons, and the summer heat expands into May and September. Winters get milder with some of the freezing temperatures disappearing. This is really helpful for a quick assessment, but before I move on, I want to remind you that 1) it’s an approximation and 2) the climate projections analogy used in the Climate Action Plan for Nature uses this method for approximating summer, not winter.

Returning to the above questions, and now using this method, let’s try to answer some of them. Will it be “warm season” longer? By 2050, it seems the answer is a confident “yes”. Will some grass species adapt? Will the plant species composition change? Ah, now those are probable “yes” answers, but it seems more analysis would be in order. I’ll throw it back to you with this tantalizing suggestion – check out the Growing Season and Growing Degree Days plots! Enjoy.

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