Teaching Essential Principle Four

Climate varies over space and time through both natural and man-made processes.

kenai fjords
Calving glacier in Kenai Fjords National Park, Alaska. Satellite image by GeoEye.

Teaching this principle is supported by seven key concepts.

Click here to see them.

  1. Climate is determined by the long-term pattern of temperature and precipitation averages and extremes at a location. Climate descriptions can refer to areas that are local, regional, or global in extent. Climate can be described for different time intervals, such as decades, years, seasons, months, or specific dates of the year.
  2. Climate is not the same thing as weather. Weather is the minute-by-minute variable condition of the atmosphere on a local scale. Climate is a conceptual description of an area's average weather conditions and the extent to which those conditions vary over long time intervals.
  3. Climate change is a significant and persistent change in an area's average climate conditions or their extremes. Seasonal variations and multi-year cycles (for example, the El Niño Southern Oscillation) that produce warm, cool, wet, or dry periods across different regions are a natural part of climate variability. They do not represent climate change.
  4. Scientific observations indicate that global climate has changed in the past, is changing now, and will change in the future. The magnitude and direction of this change is not the same at all locations on Earth.
  5. Based on evidence from tree rings, other natural records, and scientific observations made around the world, Earth's average temperature is now warmer than it has been for at least the past 1,300 years. Average temperatures have increased markedly in the past 50 years, especially in the North Polar Region.
  6. Natural processes driving Earth's long-term climate variability do not explain the rapid climate change observed in recent decades. The only explanation that is consistent with all available evidence is that human impacts are playing an increasing role in climate change. Future changes in climate may be rapid compared to historical changes.
  7. Natural processes that remove carbon dioxide from the atmosphere operate slowly when compared to the processes that are now adding it to the atmosphere. Thus, carbon dioxide introduced into the atmosphere today may remain there for a century or more. Other greenhouse gases, including some created by humans, may remain in the atmosphere for thousands of years.

What does this principle mean?

These key ideas build an understanding of the differences between weather and climate. It also covers climatic processes that cause natural climate variability, and abrupt climate change, which can be triggered by naturally occurring dynamics. Understanding climate variability such as the El Niño/Southern Oscillation is critically important in helping scientists tease apart natural variation from human-induced climate change. In this principle the human impact on the climate through burning of fossil fuels is clearly differentiated from naturally occurring climate relevant processes.

Why are these topics important?

Students frequently conflate weather with climate. While related, weather occurs over short (hours to days) time scales, and climate occurs over seasons and longer time spans. Because of these common confusions, it is especially important to clarify topics such as:

  • A spell of unusually cold or warm weather neither negates nor confirms human-caused climate change. Climate is defined as a long-term pattern with naturally occurring variability.
  • The climate has changed throughout the history of Earth, to varying degrees, over different time periods and due to different causes.
  • Human-caused warming is not the same thing as Earth's "natural" warming. Scientists use many lines of evidence to differentiate human-caused changes from natural cycles.
  • Weather and climate can both vary to a large degree over very small distances.

What makes this principle challenging to teach?

The confusion between weather and climate and how they both are studied, modeled and forecast is a common one. Though connected, weather events occur over minutes to hours to weeks, while climate happens over months, seasons, years and into millennia. Both can change abruptly, but the reasons for the changes can be very different.

Understanding natural climatic processes that drive multi-year cycles (like the El Niño/Southern Oscillation) requires an understanding of basic climatic patterns and processes as well as feedback effects. Once students have reached an understanding of the complexity of the climate system they will be able to understand that global warming doesn't necessarily result in warming at every location but that some (few) places might experience a net cooling despite the global trend of rising temperatures. Likewise, the occurrence of brief periods of cooling during a long-term trend of warming does not negate the fact that the climate is indeed warming.

Moreover, the difference between past fluctuations in the climate and today's human-accelerated warming is a key issue. Because this is nuanced, it can be especially challenging to present the distinctions. Examining climate trends over different times scales can help reveal the recent and abrupt warming that is the signature of human-driven changes. There is an abundance of scientific evidence that can be used to help students understand how the climate can change as a result of both natural causes and human causes.

How can I use this principle in my teaching?

The two most basic cycles–the diurnal cycle and the annual cycle–are great places to begin exploring variability of weather and climate over time and space. Beyond these basic concepts, students can learn about climate variation on longer time scales, and how some changes are cyclic and others are not. These topics also afford the opportunity to present the key differences between weather and climate

It can be difficult to describe processes that operate on different time scales. Specific strategies that can help students understand this are using visualizations and teaching with simulations. Both of these approaches allow students to "observe" a process at work and get an overview of complex processes and relevant feedback loops.

  • Middle school students who are grounded in the seasons and daily observations of weather have a good foundation to understand variations of the climate over a local and regional scale. See Changes Close to Home
  • In high school, students are somewhat more acquainted with the wider world and can compare seasonal and longer term variations from one region to another, such as with the activities Exploring Regional Differences in Climate Change or Normal Climate Patterns. They can also examine data about heating and cooling days and synthesize these with energy consumption data. High school students are also ready to understand more complex climatic processes and feedback effects. They are ready to build an initial understanding of the difference between the natural variations of climates and the human-induced climate change.
  • In the introductory undergraduate curriculum, students can plot cycles of various lengths. The concepts of the magnitude and frequency of cyclic events can be used to clarify differences between them. This approach is illustrated by this Carbon Dioxide Exercise. This topic also presents an opportunity to integrate the idea of the process of science and how scientists work to further our understanding of complex processes.
  • Upper-level college students may be engaged by the key differences between human-caused climate change and normal cycles. These students can study findings such as the isotopic signature of fossil fuel emissions, or investigate recent climate data in detail from different parts of the world. One example is this activity about Global Temperatures.

Credit: CLEAN