1.1 Weather vs. Climate

Such the case arises far too often when people confuse weather and climate.¹ It happens all the time; typically among people in the general public, journalists at media outlets, and politicians on both sides of the political spectrum.¹

Surly, the two can’t be that different if it causes a lot of confusion, right?

Well, despite some similarities between the two terms, weather and climate are actually vastly different. The main difference between the two is time.²

Weather

Almost any time there is an extreme weather event, whether that is a heatwave, cold wave, tornado, or hurricane, people cite these individual events as evidence that the climate is becoming more extreme because of human activities.¹

The issue with this mindset is that any single weather event tells us nothing about climate change or long term trends.¹

Extreme weather has likely occurred on Earth since the atmosphere formed over four billion years ago, and it has most certainly occurred for as long as we’ve had documentation, not just “official” observations since the late 1800s.¹ It is for this reason that we will continue to see extreme weather events in the future.¹

As I explained in the introduction, weather is “the state of the atmosphere at any given time and/or place.” In other words, weather is simply short term atmospheric conditions, like a daily rain or snowfall measurement, the high and low temperature, wind speed and direction, cloud cover, humidity, and so forth.¹ ³

Climate

Unlike weather, which is short term, climate is conversely long term. Both can change, but on vastly different timescales. Indeed, a single location’s (or any number of locations’) climate describes the weather conditions that can be expected over a long period of time.¹ ²

The old time saying often goes as follows: “climate is what you expect, weather is what you get.”¹ ² This statement is for the most part, true.¹ ²

Though contrary to the saying, “normal” or “average” weather rarely occurs simply because averages are arithmetically based; they don’t exist in reality. Averages are just the mean of a data distribution; in which while there are mostly normal weather conditions, there are also an abundance of extremes to take into account.¹ ² ³

Traditionally, this “long period of time” is a fixed set of 30 years.¹ ² This is called the “climatic average” and it can be used on a global scale or just for a single location.² While climatic averages are only mathematically based calculations, they are are actually useful because they are used as a reference point, not to mention they keep up-to-date with current and/or recent atmospheric conditions. The current set of averages cover the period 1981 to 2010. In 2021, it will be updated to cover the period 1991 to 2020.²

Averages can be calculated by hand, but most of the time, they are computer-generated.¹ ² Statistics like temperature and precipitation are summed up, then divided by 30 (for 30 years) for not only single days, but also, single months, meteorological seasons, or for the entire year.² ³ Occasionally, metrics like wind speed, wind direction, and atmospheric pressure will be computed into averages, but generally are left alone.²

While 30-year averages are conventional in meteorology, they aren’t always necessary in all fields of science.¹ In geology, climatology, and paleoclimatology, much longer time periods are used, ranging from decades to millions, if not billions of years.¹

REFERENCES

[1] “Weather versus Climate.” ATMO336 – Fall 2016. 2016. Accessed October 10, 2019. http://www.atmo.arizona.edu/students/courselinks/fall16/atmo336/lectures/sec1/climate1_new.html.

[2] “Climate vs. Weather.” National Weather Service. Accessed October 10, 2019. https://www.weather.gov/jetstream/climate_v_wx.

[3] Haby, Jeff. “AVERAGE RAINFALL, WEATHER AND CLIMATE.” Weather Prediction Education. Accessed October 10, 2019. http://www.theweatherprediction.com/habyhints2/550/.