1.4: Global Warming vs. Climate Change

One last tool… two very important definitions

The last tool needed is the definitions of Global Warming and Climate Change, which can be summarized in Figures \(\PageIndex{1}\) and \(\PageIndex{2}\).

Figure \(\PageIndex{1}\): Global Average Temperature Anomalies, with respect to the 1951-1980 average temperature. (Public Domain; via NASA/GISS). Alternative description of image.

Figure \(\PageIndex{1}\) is essentially the entire definition of Global Warming, which is the increase in global average temperatures! The graph shows global mean temperature anomalies (deviations from the mean) from 1880 to the present, relative to the 1951–1980 base period. While there is some year-over-year variability, global temperatures have increased notably, with the warmest temperatures occurring in recent years. Let's answer the following few questions based on Figure \(\PageIndex{1}\).

14. While there is some variation from year-to-year, in general, Global Mean Temperature Anomalies have:
    1. Increased since 1880
    2. Decreased since 1880
    3. Haven’t changed since 1880
15. While there is a noticeable change in temperatures from 1880 to 2025, a warming trend becomes very noticeable after approximately:
    1. 1940
    2. 1960
    3. 1900
16. In fact, 2024 was the warmest year on record with a temperature anomaly of approximately:
    1. 0.3°C
    2. 0.5°C
    3. 1.0°C
    4. 1.2°C

So yes, over the past 145 years, there has certainly been an upward trend in the average temperature. So yes, Global Warming is real! However, a comparison between Figure \(\PageIndex{1}\) and Figure \(\PageIndex{2}\) shows a flaw in the concept of Global Warming. Before we delve into that concept, let's consider a scenario: Rather than giving you the grade that you individually earned in this class, your instructor instead takes the class average and gives everyone that same grade! Take a moment and let that thought sink in. How do you feel about that? Is that fair? Is that accurate? Of course not!

But that’s exactly what the concept of Global Warming does: It essentially uses one number (global average temperature anomaly) to define the entire state of Earth’s Climate. That is extremely misleading and allows people to make pseudoscientific claims, such as “it’s cold outside… so global warming must be fake!” Figure \(\PageIndex{2}\), on the other hand, provides a more nuanced view of Earth’s temperature anomalies (Legend: Redder means warmer, Bluer means Colder).

Figure \(\PageIndex{2}\): Temperature Anomalies for 2022 with respect to the 1991-2020 base period. (Public Domain; NOAA via National Center for Environmental Information). Alternative description of image.

Let's answer the following true or false questions based on Figure \(\PageIndex{2}\).

17. Everywhere on Earth experienced above-average temperatures in 2025.
    1. True
    2. False
18. Some locations such as the Central United States, the Equatorial Pacific Ocean, and the North Atlantic, experienced cooler-than-average temperatures.
    1. True
    2. False

This dichotomy underscores the importance and usefulness of the term Climate Change, or, more formally (for this course), Anthropogenic Climate Change. Climate Change refers to changes in average atmospheric conditions (temperature, precipitation, etc.) for a given region. It considers the fact that not everywhere on Earth is warming. Some places are, in fact, cooling. While Figure \(\PageIndex{1}\) shows that 2025 was a very warm year, Figure \(\PageIndex{2}\) shows that some locations on Earth were not warmer than average, and some were even cooler than average! So we can’t simply summarize the entire state of Earth in a single graph or number, even if that may be more convenient.

The purpose of this course will be to introduce you to the numerous data sources, such as Carbon Dioxide and Methane Concentrations, and the tools that climate scientists use to analyze and predict changes in Earth’s Climate. Because this is an introductory level course, much of what we do is very simplified, but should still be sufficient to give you a taste of how Climate Science works! A few last questions to complete this introductory Investigation.

19. Wrapping things up: What do you think you are going to enjoy about this class?
20. What do you think you may struggle with?
21. What are some ways your instructor can help?