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Collaborative Learning through Environmental and Aerosol Research

LIVING IN THE MODERN WORLD, OUR SOCIETY CONTINUES TO FACE MANY GLOBAL ISSUES — from human disease and hunger to pollution and climate change.  Science plays a critical role in helping us learn about how these issues affect our world and how we might go about fixing them. Every day, scientists work to better understand the issues that face us. However, these problems are large, complex, and complicated—meaning we have to work together to figure them out!  No one scientist can solve these issues alone, but together, teams of scientists can work together to build the knowledge that we need to work through these challenges. Starting with an observation, researchers formulate a scientific question that they can study in a controlled manner—in this way, scientists answer one question at a time, until we can understand how the bigger issue works.

The CLEAR Project will help you to learn about small particles in our atmosphere, called aerosols, which come from both natural sources and from human pollution. By participating in the CLEAR program, teams of students will have the opportunity to contribute to the research effort of CAICE by working on their own research study. CAICE researchers are working to understand how these particles in our atmosphere impact our environment and climate change. Now, you are part of this effort too—welcome to the team!

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What are aerosols?

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Aerosols & Health

Aerosols & Climate

The climate of our planet is influenced by a number of factors: the sunlight, the gases in our atmosphere, and the aerosol particles, among other factors. Aerosol particles have a complicated role in our climate and have both direct and indirect effects. The direct effects are based on the aerosol particles themselves, and the indirect effects are based on the ability of aerosol particles to help clouds form. Aerosol particles can impact the temperature of our planet as well as the probability of rain, among other things. Although the role of aerosols on climate is complex, CAICE researchers and other scientists are working to better understand the impact of aerosols on our climate.

Direct Aerosol Effect. Aerosols can scatter light from the sun away from the earth, causing a cooling effect.

The direct aerosol effect is based on the ability of the particulate matter to absorb sunlight or scatter it back into space. How does this work? The light radiation from the sun travels to the earth, where it provides the planet with a source of heat that drives our planet’s climate. However, not all of the light radiation from the sun reaches the earth’s surface. This is because aerosol particles (and the clouds that they help form) scatter about 25% of the sun’s radiation back into space. Because less of the sun’s radiation reaches the ground, this results in a cooling effect. To read more about light scattering, continue on to the next page.

Direct Aerosol Effect. Aerosols can scatter light from the sun away from the earth, causing a cooling effect.

Indirect Aerosol Effects

Because aerosol particles play an important role as the seeds for cloud formation, the amount and properties of the aerosol particles in the atmosphere can affect our planet’s climate in two major ways. These are called the indirect aerosol effects because they depend on the aerosols ability to form clouds. These indirect aerosol effects mainly influence the climate through changing the temperature and tendency for rain.

The Twomey effect describes the indirect aerosol effects on temperature. As a cloud forms, the water vapor will be distributed among all of the available CCN (particles). When many CCN are present, the water will be distributed among more particles, resulting in smaller, more numerous water droplets. Based on your knowledge of light scattering, are smaller or larger droplets more efficient at scattering light back where it came from?

How would the number of droplets affect how much light is back-scattered? The Albrecht effect describes the indirect aerosol effects on precipitation. In clouds that form from many CCN, the water droplets are smaller and more lightweight. Therefore, they are less likely to fall out of the cloud as rain. In clouds that form from few CCN, the water droplets are bigger and heavier, so they are more likely to cause rain.

Check out the figure to the right to see how these two effects influence the properties of clouds.

Indirect Aerosol Effects. When there are few particles in the air, the water vapor is condensed to give larger droplets which results in clouds that are less reflective and more likely to cause rain. When there are many particles in the air, the water vapor is spread across all of the droplets, which results in whiter, more reflective clouds that are less likely to cause rain.

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Designing Experiments

Taking the time to design a good experiment is a key component of doing good science! You must carefully think through each aspect of the experiment to make sure that your experiment helps you answer the scientific question that you wish to answer. The following information will help you design your own scientific study to explore the world around you, such as an experiment with the CLEAR-CAICE! It is important to think through each step thoroughly in order to make sure that the experiment that you design answers the question you want to answer in an unbiased, scientific way.


An Example of Experimental Design — Water Pollution In the city of Farmtown, CA, there are several farms that are next to the Blue River. Sally, Diego, and Monique are environmental researchers that want to examine pollution in the Blue River. Nitrate and phosphate are both chemical substances that are found in the fertilizers used for farming. Sally, Diego, and Monique have an instrument that can measure the concentrations of nitrate and phosphate in water samples. These are the steps they take to design an experiment with this instrument, according to the steps outlined on the previous page.

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