Have you ever heard someone say, “Wow, it is so cold outside, how can folks be talking about global warming?”
Based on this statement, we can tell that the person is confusing weather and climate. For starters, what happens outside on any one day is weather. Weather is the state of the atmosphere at a place and time. With weather we experience variations from day to day and place to place. Climate is the long-term average of the weather over a period of at least 20 to 30 years, derived from accumulating GHGs in our atmosphere. Climate is what we expect, weather is what we get.
Famously, in February 2015, Oklahoma Sen. James Inhofe brought a snowball to the Senate floor. This was supposed to be evidence that global warming was not occurring. How could the planet be warming when it was cold enough outside to create a snowball? This is just one example of people confusing weather and climate. Note that this incident was in February, the middle of winter for the eastern part of the United States. A snowball in winter should not be considered an abnormal event, but rather it should be something to be expected at that time and place.
Some of the results of a warming world can lead to weather outcomes that seem odd and counterintuitive. This can create confusion for someone that is only looking at the weather event and does not consider the climate issues that go along with it. For instance, a warming world can lead to bigger snowstorms. How can this be? Shouldn’t we have less snow if the world is warming? What also needs to be considered is that warmer air holds more water vapor. With this in mind, let’s consider a winter storm approaching Maryland. If our atmosphere is currently holding more water vapor than normal, then an approaching storm will have more potential for a bigger snowfall than we would see without the warmer air and greater amount of water vapor.
One of the ways that can help us separate weather and climate is looking at the frequency of setting new, daily temperature records. This can be new records for daily high temperatures, low temperatures or highs for minimum temperature. The third category is particularly interesting. We are increasingly seeing days when the low temperature for a day does not get as low as normal. This is particularly challenging in summer, when people and ecosystems don’t get as much nighttime relief from extreme heat. Any individual new daily record is an example of weather. However, we are seeing more monthly and all-time temperature records, and this indicates that there is a change in the climate.
Another example of a pattern that indicates climate change is from the daily temperature highs and lows. Over time we are seeing more new high temperature records than new low temperature records. If the climate were stable, we should expect a roughly equal number of high and low temperature records. However, between 2000 and 2010, the last full decade with data, the ratio of new highs to new lows averaged 2-to-1. Another example of the changing climate is that in the 1960s, Frederick averaged 20 days above 90 degrees contrasted with 49 days above 90 degrees in 2019. This shows us that the climate is warming.
It can be easy to focus on individual weather events and not see the big picture. What we wear on any one day does not represent our entire wardrobe. The performance of our retirement savings on any one day does not represent how our savings will grow over decades. Just like these events, we need to be careful not to focus too much on any one weather day. We need to consider the climate impacts that are and will continue to occur over decades.
As you venture outside in summer or winter, think about trends over weeks to months and contrast that with previous years. Do you recall so many blistering days in previous summers? Or, has it been warmer longer into the fall and even into the winter than in the past? Are your backyard plants blooming earlier than normal? That’s the Frederick climate we now experience and think how much different it could be in the future.