The purpose of this activity is to measure the aerosol optical thickness of the atmosphere (how much of the sun's light is scattered or absorbed by particles suspended in the air). Students point a GLOBE sun photometer at the sun and record the largest voltage reading they obtain on a digital voltmeter connected to the photometer. Students observe sky conditions near the sun, perform the Cloud, Optional Barometric Pressure (optional) and Relative Humidity Protocols, and measure current air temperature. Intended outcomes are that students will understand the concept that the atmosphere prevents all of the sun's light from reaching Earth's surface and they learn what causes hazy skies. Supporting background materials for both student and teacher are included.

The purpose of the resource is to meaure the alkalinity of a water sample. Students will use an alkalinity kit to measure the alkalinity in the water at their hydrology site. The exact procedure depends on the instructions in the alkalinity kit used.

The purpose of this resource is to observe when selected bird species first arrive at your study site, and to count the numbers until few or none of these birds are seen. Students select a common and easily identifiable bird species in their region and observe when the bird species first arrives. Students use binoculars or telescopes to scan a study site and count how many they see. They continue to observe every other day until few or none of the selected species can be seen.

The purpose of this resource is to continuously measure soil and air temperature at one site. Students install four temperature probes; three are placed in the soil at three different depths and one is placed in an instrument shelter. Students use a data logger to record readings from the probes every 15 minutes. Students transfer the data to their school computers for analysis and submission to the GLOBE database.

The purpose of this resource is to develop an understanding of plants' response to light. Students will do simple investigations to observe plant responses to light.

The purpose of this resource is to measure and classify the plant life at a Land Cover Site to help determine the MUC classification.

The purpose of this resource is to quantitatively evaluate the accuracy of a classification system. Students sort birds into three possible classes based on each bird's beak: carnivores, herbivores, and omnivores. Students compare their answers with a given set of validation data.

The purpose of this resource is to observe budburst on selected trees at a Land Cover or Phenology Site. All students will learn about hummingbird natural history and ecology. Students will learn how to identify and age male and female Ruby-throated Hummingbirds and to observe migration and feeding behavior. Students will learn how to make connections among hummingbird behavior and weather, climate, food availability, seasonality, photoperiod (day length), and other environmental factors.

The purpose of this activity is to build an instrument that can be used to measure water temperature. Students construct a soda-bottle thermometer, which is similar to the thermometer used by GLOBE schools. Both are based on the principle that most substances expand and contract as their temperature changes. This experiment also demonstrates the principle of heat transfer. The intended outcome is that students will understand why and how a standard thermometer works.

The purpose of this resource is to measure the bulk density of each horizon in a soil profile. In the field, students collect three soil samples from each horizon in a soil profile using a container with a measured volume. In the classroom, students weigh the samples, dry them, and weigh them again to determine their dry mass and water content. Students then sieve the dry soil samples and measure the mass and volume of any rocks and material with dimensions greater than 2 mm. Students use the Bulk Density Data Sheet to calculate the soil bulk density for each sample.

The purpose of this activity is to introduce students to the concept of relative air mass and demonstrate how solar elevation angle affects the intensity of sunlight that reaches an observer on the ground. Students work in teams to calculate air mass using simple geometry. Teacher background materials are included.

The purpose of this resource is to have students observe their lilac plants and identify the five phenophases (first leaf, full or 95% leafed, first bloom, full bloom and end of bloom) for each lilac plant. During the growing season, students will observe their lilac plants and identify the five phenophases (first leaf, full or 95% leafed, first bloom, full bloom and end of bloom) for each lilac plant.

The purpose of this activity is to observe the type and cover of clouds including contrails. Students observe which of ten types of clouds and how many of three types of contrails are visible and how much of the sky is covered by clouds (other than contrails) and how much is covered by contrails. Intended outcomes are that students learn how to make estimates from observations and how to categorize specific clouds following general descriptions for the categories. They will learn the meteorological concepts of cloud heights, types, and cloud cover and learn the ten basic cloud types. Supporting background materials for both student and teacher are included.

The purpose of this activity is to explore the connections between cloud type, cloud cover, and weather and stimulate student interest in taking cloud type observations. Students observe cloud type and coverage and weather conditions over a five-day period and correlate these observations. Students make and test predictions using these observations. The intended outcome is that students learn to draw inferences from observations and use them to make and test predictions.

The purpose of this resource is to deepen students understanding of the Earth as a system, and their appreciation for the value of diagrams as tools. Students visit a study site, where they observe and recall their existing knowledge of air, water, soil, and living things to make a list of interconnections among the four Earth system components. They make predictions about the effects of a change in a system, inferring ways these changes affect the characteristics of other related components.

The purpose of this resource is to develop familiarity with interactions among the major components of the Earth system at the global scale. Students brainstorm about the nature of connections between their region and others, across oceans and on different continents. On a black-line map of the world, they trace possible pathways of water and wind currents from their part of the continent to other continents, and identify what the wind and water carry. Then they write about the possible effects of activities in other regions on their region, and the possible effects of activities in their regions, on others.

The purpose of the resource is to produce a land cover type map from the digital file of a Landsat satellite image using MultiSpec software.

The purpose of this resource is to help students articulate and integrate their existing knowledge about the air, water, soil, and living things by viewing them as interacting parts of a system. Students visit a study site, where they observe and recall their existing knowledge of air, water, soil, and living things to make a list of interconnections among the four Earth system components. They make predictions about the effects of a change in a system, inferring ways these changes affect the characteristics of other related components.

The purpose of this activity is to construct a model that will provide students with a visual representation of parts per billion. Students work in teams to construct cubes of different volumes and to compare them to get a feel for parts per million by volume and parts per billion by volume. The intended outcome is that students gain a feeling for the small quantities of gases, such as ozone, present in the Earth's atmosphere.