EarthLabs for Educators > Climate Series Intro

Preparing to Teach a Climate EarthLabs Module

Introduction


Studies about weather and climate and the ways in which they shape life on Earth have long had a place in the school curriculum. Today, as we struggle to understand the surprisingly new ways in which weather and climate are influencing our lives, the need for an informed citizenry is greater than ever. The most recent set of four EarthLabs Climate modules will play a key role in helping students deepen their understanding of how our climate system works. Like their climate-related EarthLabs predecessors (Drought; Hurricanes; etc.), the new modules address weather and climate not simply as atmospheric processes but in the context of the interconnected Earth system, which includes the planet's oceans, landmasses, biosphere, and cryosphere (Earth's frozen places), as well as the atmosphere.

Although the main focus of the four new climate modules is climate literacy, it is impossible to ignore climate change when one looks seriously at climate data, something that students do in each of the new modules.

A brief introduction to the new modules (below) is followed by some classroom implementation suggestions and science background notes that can help you address student questions and support student learning across all of the EarthLabs Climate modules.


Climate and the Cryosphere

Water is unique among Earth's natural materials. In addition to the essential role it plays in supporting life, it covers a large portion of our planet and has a freezing/melting point that is fairly close to Earth's average temperature. This results in water being present in both liquid and solid forms on Earth's surface, depending on location. Relatively small changes in Earth's average temperature dramatically increase or decrease the amount of Earth's snow and ice. Earth's average temperature today is just 4° to 5° C warmer than it was during the last glaciation, when a large area of the northern United States was buried under 3 to 4 kilometers of ice.

This dynamic cryosphere does not simply react to Earth's climate; it also plays a key role in shaping it. In this module, students learn about the dynamic nature of Earth's land and sea ice, how the cryosphere and our climate shape one another, and what scientists are discovering about Earth's climate by studying ice that was formed hundreds of thousands of years ago.


Climate and the Biosphere

When you go outside, do you see cactus or willow trees? White pine or southern yellow pine? What you see depends on the climate in your region. The distinction between weather and climate is often misunderstood, but the native plants we find in any location are good indicators of climate; they are adapted to and dependent upon the long-term average atmospheric conditions (climate) and not on the day-to-day, often quite variable conditions (weather).

It is solar energy that drives our planet's weather processes, so any change in Earth's energy balance is likely to result in climate change. This module addresses these topics in detail, as well as the differences between weather and climate, the various temporal and spatial scales at which climate processes occur, and the relationship between climate and our planet's biosphere (in particular, the plants life on Earth).


Climate and the Carbon Cycle

Earth is sometimes called the water planet, but carbon is no less essential in shaping the nature of the planet or life on Earth. It is present in the atmosphere, the biosphere, the rocky parts of Earth, and Earth's waters, and it cycles through both the living and non-living elements of the planet at extremely different rates. Plants can remove carbon from the atmosphere (photosynthesis) and release it back (respiration) in a matter of seconds or minutes, while coal can store it for millions of years before, through combustion, CO2 is cycled into the atmosphere. But it's the amount of carbon in the atmosphere that plays a major role in Earth's climate, and consequently, on the nature of life on Earth.

This module helps students deepen their understanding of the carbon cycle, the feedback loops that add such complexity to the Earth system, and the critical role that atmospheric carbon plays in shaping the planet, from the greenhouse effect and Earth's climate to life in the oceans. Is it time to start calling Earth the Carbon Planet?


Climate Detectives

This module takes students on a virtual expedition on the ocean drilling research vessel JOIDES Resolution. After students have met the science crew and toured the ship they learn how to inspect and analyze the sediment cores that the ship recovers from hundreds of meters below the sea floor in order to collect data about paleoclimate conditions that existed in the area. Their final challenge is to make use of the knowledge and skills they have acquired in the module by doing their own analysis of the sediments, microfossils, oxygen isotopes, and Earth's magnetic field for a core recovered from the Gulf of Alaska. Students use this proxy data to sketch a record of climate conditions and climate change that occurred millions of years ago, and in the process they develop a sense for how science is done, the role of proxy data, and how we know what we know.


In the Classroom


Student Prerequisite Knowledge: The Earth System

All students should read Earth System: The Basics (Microsoft Word 2007 (.docx) 151kB Jun6 12) before starting one of the Climate modules. It is short and introduces basic Earth system concepts, processes, and vocabulary in simple terms. Our climate system appears as an atmospheric process, but it is driven by solar energy and results from interactions among all components of the Earth system, including the oceans and land, the biosphere, the atmosphere, and Earth's frozen waters—the cryosphere.


Launching a Climate Module

Key practices advocated by A Framework for K-12 Science Education and the Next Generation Science Standards include students asking, refining, and answering their own questions, and developing their conceptual models of scientific phenomena. In support of these practices, we encourage you to launch any one of the climate modules by asking students the following set of questions and recording their responses, without judgment, on large sheets of paper for future reference. This can be done on a day prior to starting the module, or immediately prior to starting the first Lab of the module.

  • "What is climate?"
  • "What is the Cryosphere (or Biosphere, or Carbon Cycle)?
  • "What is the relationship between Climate and the Cryosphere (or Biosphere, or Carbon Cycle)?
  • "What effect does climate have on our lives...right here, where we live?"
  • "What questions do you have about climate or about the Cryosphere (or Biosphere,or Carbon Cycle), or about the relationship between them?"
Over the course of the module, return to these questions to see how students are:
  • refining their understanding of the terms and concepts
  • developing answers to some of their own questions
  • developing new questions to add to the list
  • refining their conceptual model of the relationship between climate and the Cryosphere (Biosphere, Carbon Cycle)

Crosscutting Themes

Each of the four Climate Literacy modules has a set of clearly defined objectives. You'll find them on the Educator web site as well as on the Student web site for each module. There are also four major themes that cut across all three modules, themes that appear in different contexts in each of the modules, and that are essential to the development of climate literacy. They are described below.

1. The Earth System

Each of the modules in this series addresses climate and climate literacy in the context of the Earth system. If students are familiar with the basic Earth system ideas, they will better understand the references to reservoirs, flux, residence time, and other Earth system concepts as they work through a module, and ultimately they will have a deeper understanding of our planet's climate. Be sure to carefully read the brief paper "Earth System: The Basics (see link above), and take every opportunity to highlight Earth system dynamics as you implement the module. This paper is also included in the Student web site of each module.


2. Time Scales and Rates of Change

The time scales and rates of change associated with Earth system and climate processes can be challenging to comprehend. How do we grasp a process that takes 10,000 years to complete, or put into context an event that took place millions of years ago? One goal of the Climate Literacy modules is to help strengthen student understanding of these larger-than-life time frames, which often involve rates of change that can seem extremely slow but that nevertheless produce dramatic results.

Here is one simple example of slow change that most of us can relate to. If your soup needs some salt, you are likely to want to make that change quickly by turning the saltshaker upside down and giving it a few shakes. However, the soup will get just as salty if you shake that same amount of salt into your hand and then add it to the soup one grain at a time, but that might take 15 minutes. If you added one grain of salt each hour, or one grain a day, or month, or year, the soup would eventually get just as salty—the change will be the same (if you kept the soup from evaporating, and lived long enough!)—but it would take significantly longer to get there. And along the way, if you sample the soup once in a while, it's unlikely you'd notice the change because it is so gradual.

Natural Earth system processes, like the examples of salting the soup, happen at very different rates. A tornado can develop quite quickly, like shaking the salt directly into the soup. Other processes, such as the changes in Earth's tilt and orbit that usher in a new ice age, happen so gradually that we cannot really sense the coming change in the human lifespan. It's like adding the salt a single grain per year. Ultimately the change can be dramatic, but noticing the incremental change along the way (in the context of a human lifetime) is not likely to happen.


3. Spatial Scales

Earth system and climate processes occur at various spatial scales, but as with time scales, some are more difficult to grasp than others. We can observe local processes, but understanding their impact when they occur at the global scale (e.g., the decay of leaves) is beyond what our perceptions can readily imagine.

In addition, climate can be defined at any spatial scale that is pertinent to our interest. If we are planting a garden along the south wall of a house, the microclimate of those few square meters becomes very important to understand. Climate can also be defined at the local, regional, continental, and global scales. Scientists who study the global climate depend on data that is collected from thousands of stations as well as satellite instruments.


4. How do we know what we know?

Throughout the Climate Literacy modules, be sure to highlight the data scientists use to support their claims as well as the instruments and procedures scientists use to collect that data. Science is the set of practices used to support the study of the natural world. To appreciate and trust the work of science, students need some understanding of the practices scientists use to build new knowledge. Those practices include collecting and analyzing data. Data can take many forms, and can include direct evidence in the form of photographs, satellite data, field samples, and real-time measurements of temperature, atmospheric carbon dioxide levels, etc. Scientists have also learned how to interpret proxy data—data that provide indirect but compelling evidence of Earth conditions or processes that occurred thousands or possibly millions of years ago. For example, the presence of fossilized pollen in a location provides direct evidence of the existence of plant species in that general location, but it also provides indirect evidence of that location's climate at some point in the distant past.


Classroom Discussions

Discussions provide students with important opportunities for formulating, consolidating, and communicating their thoughts—processes that are key to the scientific enterprise. They also provide students with opportunities for critical thinking as they discuss and evaluate ideas they have read or heard, or as they analyze the results of a lab experience. Take full advantage of the opportunities for classroom discussions, both those that are highlighted in the curriculum as well as others that present themselves during the module. It is time well spent. Suggestions for focusing each classroom discussion are provided on the Educator's pages under Teaching Notes and Tips.

You'll find plenty of articles and studies on the Web that address the growing consensus that discussion plays a key role in the science classroom. Links to two resources are provided here.

A Primer on Productive Classroom Conversations

Talk Science Primer

Talking Science


Climate-Related Misconceptions

Climate and climate change involve complex processes that are poorly understood by many. Yet these topics are being widely discussed, and understandably there is a lot of confusion and misinformation about them. While uncovering the specific misconceptions of your own students is a valuable thing to do, it is also helpful to understand what some of the more commonly held misconceptions are. The resource Realities vs. Misconceptions About the Science of Climate Change (Acrobat (PDF) 429kB Jun6 12) not only identifies several of the commonly held misconceptions about climate and climate change, it also provides a wealth of accurate background information related to those poorly understood topics.


Classroom Materials, Equipment, and Computer Software

The Lab Overview page on the Educator web site includes a list of software, equipment, and materials that will be used in each lab of the module. Please check this carefully before you start teaching the module. Gather the necessary equipment and materials necessary for the hands-on labs, and make arrangements to install any required software on school computers. Doing this ahead of time will save you valuable class time (and potential headaches) later on.


Student Access to Computers

While the entire EarthLabs curriculum is computer-based, it is not necessary for students to have continuous access to a computer. The Lab Overview page on the Educator web site indicates those class periods when student access to a computer and the Internet is a high priority. Even if your students have unlimited access to computers, you should decide when it makes most sense to use a single classroom computer and projector (e.g., to show a video), when you'll want students working on their own computers, and when it's best to have no computers available (e.g., provide printed copies of lab procedures to your students vs. having them follow procedures from a computer screen).


Science Notes


Weather vs.Climate

In a nutshell, the difference between weather and climate is time scale.

Weather is the set of short-term conditions that exist in the atmosphere over periods of minutes, hours, or days, or possibly across weeks. Weather includes atmospheric conditions such as air temperature, precipitation, wind speed, humidity, and fog.

Climate is a statistic: it is defined by the average weather for a date and location across much longer time scales. How long? Organizations such as the National Climatic Data Center define climate statistically by averaging the previous 30 years of weather, but longer time periods can also be used.

Climate can be defined at whatever spatial scale is relevant: if you are thinking about where to locate a garden, you may select a patch of ground along the south side of your house because the "micro-climate" there is generally warmer than elsewhere on your property. If you were planning to move to a new city, you would be more interested in the climate for the region in which the city exists. Likewise, climate can be defined for a country, a section of a continent, or even for the globe.

One folksy way of describing the difference between weather and climate is found in the saying: "Climate is what you expect; weather is what you get."

The trees and plants that are native to a location are those that have adapted to, and that depend on its climate, even if they can endure the daily or weekly fluctuations of weather that are associated with that climate.

In the graph below the light green band indicates the long-term temperature averages for each day in May. For example, averaging the lowest temperature for May 15 across the previous 30 years of weather results in 54 degrees F, and averaging the highest temperature for May 15 across the previous 30 years of weather results in 75 degrees F. That range between 54 and 75 is indicated by the light green bar above May 15.

The graph also shows us that several days in May, 2014 (beginning and middle of the month) were colder than the average of the past 30 years, but most days in May were warmer than the 30-year average.

The pink and violet represent the highest and lowest temperature ever recorded for each date in May.

Springfield, MO, May 2014 i


Natural Climate Variability vs.Climate Change

Natural Climate Variability is defined as changes in local or regional climate that may persist across periods of weeks, months, years, or even a couple of decades, but that do not exceed the 30-year time period across which climate is normally measured. These departures from the normal climate result from temporary changes in the natural system such as ocean currents, jet stream location, fluxes in solar radiation and other large scale fluctuations in phenomena that determine climate. Many of these changes are periodic and have been given names such as El Niño, La Niña, and the Arctic Oscillation.

Climate Change is usually defined by change that persist for longer than a 30-year time period. Climate change has natural causes, such as cyclical changes in the shape of Earth's orbit, the tilt of Earth's axis, and the orientation of Earth's axis, all of which influence the amount of solar energy that is absorbed by Earth. For more information about these orbital changes, see the next section, Natural Climate Change and the Milankovitch Cycles.These long-term changes result in the gradual development or retreating of glacial periods, or warming periods during which Earth is free of ice. Scientists have identified periods of global warming and cooling across millions of years of Earth history using evidence from ice cores and from sediment cores extracted from below the world's oceans.


Natural Climate Change and the Milankovitch Cycles

(Source: Climate and the Cryosphere; Erin Bardar)

We know that Earth's climate has been highly variable over time, but what processes are behind these climatic swings?

Serbian astrophysicist Milutin Milankovitch is credited for developing one of the most significant theories relating changes in Earth's orbit to long-term changes in climate, including ice ages. Milankovitch's theory is based on cyclical variations in three aspects of Earth's orbit that result in changes to the seasonality and location of solar radiation reaching Earth:

  1. Changes in the obliquity (tilt) of Earth's axis
    Earth is slightly tilted—that's why we have seasons. As Earth orbits the sun, one hemisphere will be tilted toward the sun for a period of time (summer) and tilted away from the sun six months later (winter). Today, Earth's rotational axis is tilted at about 23.5 degrees from vertical. However, this tilt oscillates between 22.1 and 24.5 degrees on a 41,000-year cycle. Variations in the obliquity (tilt) of Earth's rotational axis result in changes in the severity of seasonal changes. When the tilt is larger, the extremes between summer and winter temperatures are greatest. When the tilt is smaller, the average temperature difference between winter and summer is less drastic. It is believed that it's actually these periods of smaller tilt that promote the growth of ice sheets. When Earth's axis is less tilted, winters are relatively warmer and summers are relatively cooler. This means that there is more moisture in the air in winter and therefore more snowfall. It also means that there is less summer melting, so more of the winter snow accumulation will last through the warmer months.

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  2. Variations in the shape of Earth's orbit (eccentricity)
    The gravitational pull of other planets orbiting the sun causes the shape of Earth's orbit to be elliptical rather than perfectly circular. Eccentricity (e), which ranges from 0 to 1, is a measure of how much an ellipse deviates from a perfect circle (how flattened the circle is). An orbit with an eccentricity of 0 is perfectly circular, and an orbit with an eccentricity of 1.0 is a parabola (no longer a closed orbit). The shape of Earth's orbit ranges from nearly circular (e = 0.005) to slightly elliptical (e = 0.058) and back again about every 100,000-400,000 years. Changes in eccentricity are important to determining periods of glaciation because they determine the distance between the Earth and sun, and therefore how much radiation is received at the Earth's surface during different seasons. When the orbit is nearly circular, the distance between the Earth and sun (and therefore the amount of solar energy reaching Earth) remains relatively constant throughout the year. However, when the orbit is more elliptical, the distance between the Earth and sun (and the amount of energy reaching Earth) fluctuates between seasons, resulting in slightly warmer or cooler temperatures. Today, Earth's orbit has an eccentricity of 0.017.

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  3. Changes in Earth's "Wobble" (Precession)
    Earth's axis of rotation behaves like a spinning top that is slowing down, wobbling in a circle over time. Earth's axis wobbles between pointing at Polaris (what we now call the North Star) and pointing at the star Vega (which would then be considered to be the North Star). Every year, this wobble causes Earth to travel slightly farther than one full orbit each year. This means that on today's date next year, Earth will be a little bit further in its orbit than it is right now. This is called precession. Earth's axis completes a full cycle of precession approximately once every 26,000 years. Because Earth's orbit isn't perfectly circular, the distance between the Earth and sun (and the average temperature) will be slightly different each year on the same date. Precession can cause significant changes in climate due to greater contrast in seasons. For example, when Earth's axis is pointed at Vega, the winter solstice in the northern hemisphere coincides with Earth being at its farthest distance from the sun (aphelion), and the summer solstice coincides with Earth being at its closest distance from the sun (perihelion). Just like with variations in obliquity and eccentricity, the more drastic seasons brought on by precession will impact glaciation.

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Greenhouse Gases and Climate

Every object that has a temperature above absolute zero (-273 C or -459 F) emits electromagnetic radiation. Really hot objects emit more of the shorter, higher energy wavelengths (such as visible light, ultraviolet light, x-rays, and gamma rays) and cooler objects emit more of the longer, lower energy wavelengths (such as infrared radiation, microwaves, and radio waves). If you heat up a metal rod it will first emit or radiate the longer wavelengths, such as infrared radiation, which we can sense as heat but that is not visible to our eyes. Heat up that rod enough and it will start to glow because it is emitting shorter wavelength radiation (visible light) that our eyes can detect, in addition to the infrared radiation that we can feel but not see.

electromagnetic spectrum

The Big Picture

The Sun is hot enough to radiate mostly high energy, shorter wavelength radiation (mostly visible light) although it also radiates wavelengths across most of the electromagnetic spectrum. The high energy visible light passes through Earth's atmosphere largely without interacting with it, and when that solar energy reaches Earth much of it is absorbed by and warms Earth's surface.

Although Earth is warmed by the Sun, its temperature is low enough that it radiates only long wave, lower energy radiation (infrared radiation). In contrast to the radiation coming from the Sun, that long wave infrared radiation does get absorbed by and warm some of the gases in the atmosphere, the so-called greenhouse gases. Those greenhouse gases (carbon dioxide, methane, water vapor, ozone, nitrous oxide) make up only a tiny fraction of Earth's atmosphere, which is mostly nitrogen and oxygen, but once those greenhouse gases are warmed–which means the molecules move more rapidly–they not only re-radiate that energy, they also collide with and transfer their energy to the non-greenhouse gases, thereby warming all of the gases in atmosphere. That warmed atmosphere radiates its energy in all directions. Some is radiated up and is lost to space, but some is radiated back toward Earth. In fact, the amount of energy that Earth's atmosphere radiates back toward Earth is greater than the amount of energy Earth receives directly from the sun. Without greenhouse gases Earth would radiate most of its heat directly back to space and would have an average temperature of about -19 C (-2.2 F) vs. the present average of about 15C (59 F).

Eventually the atmosphere releases its energy, but the process of slowing down its escape back into space has a significant impact on Earth's temperature.

More Details

What is the difference between oxygen or nitrogen, which together make up close to 99% of the atmosphere, and a greenhouse gas? The main difference is geometry, or the structure of the molecules. Watching this amusing video, featuring Dr. Scott Denning from Colorado State University, will give you more details about how atmospheric gases have different capacities for absorbing radiation.

loading the player


Climate and Feedback Loops

Throughout the EarthLabs modules you'll find references to the Earth system, the interconnected set of sub-systems or spheres (atmosphere, hydrosphere, biosphere, geosphere, cryosphere) that exchange energy and matter and that interact to form our planet's environment. Some examples of these interactions are: 1) volcanic eruptions move matter and energy from the geosphere into the atmosphere and the hydrosphere; 2) decaying plants and animals (biosphere) result in chemical changes to the atmosphere and to the geosphere. The resource Earth System: The Basics (Microsoft Word 2007 (.docx) 151kB Jun6 12) provides a simple overview of this very complex Earth system with its interacting elements.

The two examples above are simple and correct, but they are also incomplete. Often changes in one sphere of the Earth system continue to trigger changes in other spheres in a "falling dominos" fashion, and those sequential changes can circle or loop back around to influence the process that started the change. Such loops are called feedback loops. These feedback loops are one of the key features that lead scientists to describe the Earth system as a "complex system". One of the goals of the EarthLabs Climate modules is to introduce students to the concept of the complex system.

There are two basic types of feedback loops: one type works to moderate or balance an initial process, and the other type tends to amplify or reinforce the initial process. In a nutshell, each time you circle around a balancing feedback loop, the effect reverses itself, tending toward equilibrium, and each time you circle around a reinforcing feedback loop, the effect remains the same, tending toward change. Here are examples of each type.

Balancing Feedback Loop*

Balancing Feedback Loop

The driver of the loop, which is the driver for most Earth system processes, is solar energy. Solar energy is absorbed by Earth, which warms it and causes evaporation.

Loop #1

  • Evaporation
  • Leads to increased water in the atmosphere
  • Leads to increased cloud cover
  • Leads to increased Albedo (reflection of solar energy into space by clouds or other reflective surfaces)

Increased albedo (less solar energy absorbed by Earth) leads to:

Loop #2

  • Decreased evaporation
  • Leads to decreased water in the atmosphere
  • Leads to decreased cloud cover
  • Leads to decreased Albedo (reflection of solar energy off clouds)

Decreased albedo (more solar energy absorbed by Earth) leads to:

Loop #3

  • Increased evaporation
  • Leads to increased water in the atmosphere
  • Leads to increased cloud cover
  • Leads to increased Albedo (reflection of solar energy off clouds)

This reversal between increased evaporation and decreased evaporation happens with every loop and defines the Balancing Feedback Loop. Balancing feedback loops act to maintain the stability of the planet.

Reinforcing Feedback Loop*

Reinforcing Feedback Loop

Again, the driver of this loop is solar energy. Water vapor, which is a known "greenhouse gas", acts to help Earth retain heat in the atmosphere that would otherwise radiate directly into space. (It is the lack of this greenhouse gas in the atmosphere above deserts that leads to such dramatic cooling of deserts once the sun sets.)

Loop #1

  • Evaporation
  • Leads to increased water in the atmosphere
  • Leads to increased greenhouse effect
  • Leads to increased atmospheric temperature

Increased atmospheric temperature leads to:

Loop #2

  • Increased evaporation
  • Leads to increased water in the atmosphere
  • Leads to increased greenhouse effect
  • Leads to increased atmospheric temperature

Increased atmospheric temperature leads to:

Loop #3

  • Increased evaporation
  • Leads to increased water in the atmosphere
  • Leads to increased greenhouse effect
  • Leads to increased atmospheric temperature

This constant reinforcing of a trend happens with every loop and defines the Reinforcing Feedback Loop. Reinforcing feedback loops act to change the equilibrium of the planet.

The Complex Earth System

Solar energy constantly drives a vast number of feedback loops, both balancing and reinforcing, in the Earth system, making that system incredibly complex. It is beyond the scope of the Climate Earthlabs modules to untangle the many competing balancing and reinforcing feedback loops and look for a net result. The only purpose is to make you and your students aware of these two basic types of feedback loops and to look for and recognize them as they appear in the Climate EarthLabs modules.

* The terms "balancing feedback loop" and "reinforcing feedback loop" were proposed by Dr. Kim Kastens in her blog Going Negative on "Negative" Feedback, which appears in Earth and Mind: The Blog. The examples of the two types of feedback loops were also drawn from Dr. Kastens' blog post.

The common name used for "balancing feedback loops" is "negative feedback loops", and the common name for "reinforcing feedback loops" is "positive feedback loops". We agree with Dr. Kastens that those common names can lead to confusion since the terms positive and negative commonly refer to "good" and "bad" and can incorrectly suggest that the feedback loops have good or bad effects.


Anomaly Maps and Graphs

Anomaly Maps and Graphs don't show actual measurements for weather variables. Instead they show the difference or anomaly between a recent average and the long-term average for a selected period of time, referred to as a base period.

Anomaly maps typically use dot size or color to represent the difference between a given period and the base period. That base period is typically 30 years on maps. Notice that in the anomaly map below, most places on Earth had a warmer average temperature in 2011 than they had during the 1971-2000 base period. The temperature increases in 2011 were greatest in northern Asia.

anomaly map_NOAA

Below is a different type of anomaly map, one that uses shades of color instead of dot sizes to indicate the magnitude of the departure from the long-term average. The base period for this NOAA map is more recent. It compares the November, 2012 average temperatures for the US against the average of all 30 Novembers between 1981-2010.

anomaly map_NOAA-us

Anomaly graphs sometimes use a longer base period than the maps. In the example below, the base period is the 100-year period 1901-2000. The average global temperature for the base period is used as the zero line on the graph. Notice in the graph below that long term trends, such as the 1880-1910 cooling period or the 1910-present warming period often have shorter-term temperature reversals embedded within them. These irregularities highlight the fact that the factors that combine to create Earth's climate are numerous and varied; their interactions are complex, and they can cause short-term reversals during longer-term trends that are being driven by persistent factors.

anomaly graph_NOAA