Exploring Change
Understanding change through interactive data visualizations
Weather and Climate -
What’s the difference?
When we talk about “climate change”, it’s easy to confuse climate with another common concept - weather. Weather refers to short-term atmospheric conditions, like whether tomorrow will be sunny or windy. While extreme weather events may be an indicator of climate change, the weather conditions during any given day, week, or month should not be viewed as reflecting long-term trends.
Climate refers to the weather of a particular region averaged over a much longer period of time - typically multiple decades. Averaging shorter-term data (such as temperatures over an entire summer) and using these averages in a longer-term comparison (such as every summer over the course of 50 years) allows us to capture larger trends using a vast amount of information. On this website, Visualizing Change presents many of the long-term data sets with a “weather” and “climate” view. You can toggle between them to explore the differences in weather and climate.
What is a baseline and why do we use it?
In order to make long-term climate data meaningful and informative, we need to establish a frame of reference. In other words, while we can make observations about the weather without historical context, we can’t understand how these observations reflect the climate without comparing them to something. To create a reference period, which we call a “baseline”, we average data from typically a 30-year timespan. By averaging so much information, we ensure that the baseline isn’t substantially changed by unusual or extreme weather events. To better understand how the choice of baseline impacts our analysis of long-term climate data, try using the data visualizations to alter the length and period of the baseline.
After we choose a baseline, it’s convenient to treat that average baseline value as “zero”. This way, when we compare values or trends to the baseline, it’s much more obvious how they compare. In the “climate” view of our data on this website, you’ll notice that the values are not absolute, but are rather expressed as the numerical difference from the average during the chosen baseline period.
If you would like to see the data represented in greater detail, or if you would like information on a specific, shorter time period, simply click on the “weather” view.