Weather & Climate

Does snow in April mean global warming is not happening?

This week, much of Indiana got to see some snow falling as we were hoping that winter weather was behind us.  It is not unusual for some to ask when this sort of event happens how “global warming” could be real when things are feeling so cold.  The start of my answer is pointing out the word “global”.  While Indiana was experiencing below-normal temperatures this past week, many other places around the earth were experiencing above (if not much above) normal temperatures.  When averaged across the planet, that global temperature is still showing increasing trends.  The other part of the answer is about variability.  Every year, there are going to be days that are cooler than normal and days that are warmer than normal.  When averaged over a month, season, or year, temperatures have been increasing.  Finally, our daytime high temperatures may not be showing a noticeably strong trend (though, there is even a slight warming trend that has been occurring), but nighttime low temperatures have been warming at a greater rate.  Therefore, if our average daily temperature is an average of the daily maximum and minimum temperature, if just one of those is increasing, then the average will increase.

Will these cooler temperatures and risk for snow continue this spring?  Climate outlooks at this point are favoring above-normal temperatures (Figure 1) and forecasts for the next 10 days suggest a strong warming with high temperatures in the upper 70s and lower 80s as early as next week.  Perhaps our last snow date of the season is behind us.  Even precipitation should stay near-to-above normal over the next several weeks (Figure 2) – offering the potential for abnormally dry conditions in our northern counties to not worsen.

With the recent cold spell, growing degree-day accumulations have slowed down this past week, but total accumulations are still ahead of where things were last year (Figures 3 and 4).