Satellite image of aerosol (particulate) pollution over Beijing, China. Click on image for full size (219 Kb) NASA image courtesy the MODIS Rapid Response Team

Little particles in the atmosphere called aerosols may be small but they have the ability to change climate. These tiny particles are a natural part of the atmosphere, coming from erupting volcanoes, sea salt, and wildfires. However, since the start of the Industrial Revolution additional aerosols have been added to the atmosphere as fossil fuels are burned. This air pollution is having an impact on Earth’s climate. These effects are complex, however, because different types of aerosols affect climate in different ways.

The amount and type of aerosols in the atmosphere has an impact on the albedo of our planet - the amount of solar energy that is reflected back out to space. Different types of aerosols have different effects on albedo. Aerosols like sea salt have a high albedo so they reflect solar radiation back out into space. Aerosols like black carbon have a low albedo and reflect very little solar energy.

Aerosols help clouds form and clouds have an impact on climate. The millions of little droplets of water that make up a cloud each need a little particle, like an aerosol, to condense upon. When more aerosols are released into the atmosphere, either from a natural event like a volcanic eruption or from burning of fossil fuels, the types and numbers of clouds that appear in the sky can change. The number and type of clouds overhead affects the amount of solar energy that makes its way to the Earth surface and the strength of the greenhouse effect. The amount of precipitation that falls in the region is affected too.

Also, climate is affected when the additional aerosols change chemical reactions that are going on in the atmosphere. Some reactions cause the little aerosols to grow larger, increasing their ability to either reflect sunlight away or absorb it. Scientists are actively studying how chemical reactions in the atmosphere are affected by aerosols.

Scientists think that over most of the last century the overall effect of the added aerosols was to reduce the amount of global warming. Today, however, as new technologies have allowed factories, power plants, and automobiles to release less air pollution into the atmosphere, the amount of aerosols has dropped. That’s a good thing since air pollution is a problem for human health. But it has also stopped dampening the global warming which means the pace of warming is likely to increase.

Satellite image of particulate pollution over Beijing, China. Click on image for full size (219 Kb) NASA image courtesy the MODIS Rapid Response Team

There are little particles in the atmosphere that are so small and light they can float in air. These particles are called aerosols. They may be small but they have the ability to change climate.

Some aerosols are a natural part of the atmosphere - coming from erupting volcanoes, sea salt, and wildfires. However, burning of fossil fuels like coal, oil, and gas has let lots more aerosols loose in the air. Aerosols are a part of air pollution. They are dangerous to human health and they also dampen the effect of global warming.

Aerosols in the atmosphere can change the amount of solar energy that is reflected away from Earth. Different types of aerosols react differently when hit with sunlight. Sea salt particles reflect sunlight back out into space. Black carbon particles from burning of wood or fossil fuels absorb most of the sunlight that hits them.

Aerosols help clouds form and clouds have an impact on climate. The millions of little droplets of water that make up a cloud each need a little particle, like an aerosol, to condense upon. More aerosols can create more clouds. Different types of clouds may have different impacts on climate and this is a topic that scientists are still exploring. But in general, clouds reflect incoming solar radiation back out to space.

Scientists think that over most of the last century the overall effect of the added aerosols was a reduced amount of global warming. Today, however, as new technologies have allowed factories, power plants, and automobiles to release less air pollution into the atmosphere, the amount of aerosols has dropped. That’s a good thing since air pollution is a problem for human health. But it has also means that the pace of global warming is likely to increase.

This is a photograph of pollution over Beijing, China. Click on image for full size (219 Kb) NASA image courtesy the MODIS Rapid Response Team

There are little particles in the atmosphere that are so small and light they can float in air. These particles are called aerosols. They may be small but they have the ability to change climate.

Some of them are natural. They come from erupting volcanoes, sea salt, and wildfires. Other aerosols are let loose in the air when fossil fuels like coal, oil, and gas are burned for energy. They are a part of air pollution, which is bad for people’s health. They also lower the amount of global warming.

Aerosols in the atmosphere can change the amount of sunlight that is reflected away from Earth. Light colored particles reflect sunlight back out into space. Dark particles absorb most of the sunlight that hits them.

Aerosols help clouds form. The millions of little droplets of water that make up a cloud each need a little particle, like an aerosol, to condense upon. Clouds have an impact on climate. In general, clouds reflect incoming solar radiation back out to space.

Scientists think that over most of the last century overall effect of the added aerosols was a reduced amount of global warming. Now that we are making our air cleaner so that it is healthier for people to breath, the pace of warming will likely increase.