Heat from the Sun supplies our planet with much-needed warmth. But over the past 150 years more heat has been retained by Earth as the amount of heat-trapping greenhouse gases in the atmosphere has grown. Click on image for full size (69 Kb) Courtesy of USGS Astrogeology Research Program

A factor that has an affect on climate is called a “forcing.” Some forcings, like volcanic eruptions and changes in the amount of solar energy, are natural. Others, like the addition of greenhouse gases to the atmosphere, are caused by humans.

The Sun Affects Climate
The heat on Earth comes from the Sun, so climate can change if there is a change in the amount of solar energy that gets to Earth. Changes to the cycle of solar activity, called the 11-year solar cycle, can produce small but noticeable impact on climate. Recent climate change is too large to be caused by solar activity. On timescales of tens of thousands to hundreds of thousands of years, changes in the way Earth orbits the Sun can cause changes to climate.

Volcanic Eruptions Affect Climate
When volcanoes erupt they spew more than hot red lava and ash. Tiny particles called aerosols wind up in the atmosphere too. These tiny particles, made of sulfur dioxide, get into the stratosphere and reflect solar radiation back out to space. This causes cooling. The effect is temporary, lasting usually only a year or two.

Greenhouse Gases Affect Climate
Only a small portion of the molecules that are in Earth’s atmosphere are greenhouse gases, yet they have a strong affect. These gases trap heat through a process called the greenhouse effect. While greenhouse gases are a natural part of the atmosphere, their quantities have increased over the past 150 years due to burning of fossil fuels and decrease in the amount of forests which naturally take up the greenhouse gas carbon dioxide during photosynthesis.

Snow and Ice Affect Climate
The cryosphere, the frozen part of the Earth including snow and ice, has an impact on Earth’s climate. Because snow and ice are light in color, they have a high albedo – the ability to reflect most solar radiation back out to space. When snow and ice melt as Earth’s climate warms, less energy is reflected; this causes even more warming.

There are also other aspects of our planet that have an impact on climate too. Scientists are actively studying the impact of clouds on climate and the effect of aerosols on climate. Melting Arctic sea ice could change ocean circulation, producing a regional impact on climate. This is also an area of active research.

Heat from the Sun supplies our planet with much-needed warmth. But over the past 150 years more heat has been retained by Earth as the amount of heat-trapping greenhouse gases in the atmosphere has grown. Click on image for full size (69 Kb) Courtesy of USGS Astrogeology Research Program

Some of the factors that have an affect on climate, like volcanic eruptions and changes in the amount of solar energy, are natural. Others, like the addition of greenhouse gases to the atmosphere, are caused by humans. Some of the main ones are listed below.

The Sun Affects Climate
Climate can change if there is a change in the amount of solar energy that gets to Earth. Changes to the cycle of solar activity, called the 11-year solar cycle, can cause a small impact on climate, too small to be the cause of recent climate change. Over thousands of years, changes in the way Earth orbits the Sun can cause large changes in climate.

Volcanic Eruptions Affect Climate
When volcanoes erupt they spew more than hot red lava and ash. They release tiny particles made of sulfur dioxide into the atmosphere too. These particles get into the stratosphere and reflect solar radiation back out to space. This causes cooling. The cooling is temporary, lasting usually a year or two.

Greenhouse Gases Affect Climate
Greenhouse gases have a strong affect on climate. These gases trap heat through a process called the greenhouse effect. While greenhouse gases are a natural part of the atmosphere, the amount has increased over the past 150 years as fossil fuels have been burned and the amount of forests, which naturally take up the greenhouse gas carbon dioxide during photosynthesis, has shrunk.

Snow and Ice Affect Climate
Because the snow and ice of the cryosphere are light in color, they have a large albedo – the ability to reflect most solar radiation back out to space. When snow and ice melt as Earth’s climate warms, less energy is reflected and this causes even more warming.

There are also other aspects of our planet that have an impact on climate too. Scientists are studying the impact of clouds and the impact of aerosols on climate. Scientist are studying the oceans too because melting Arctic sea ice could change ocean circulation, causing regional climate to change.

Heat from the Sun supplies our planet with warmth. But over the past 150 years the amount of heat that is trapped by Earth has increased, causing global warming. Click on image for full size (69 Kb) Courtesy of USGS Astrogeology Research Program

The Sun
Climate can change if there is a change in the amount of solar energy that gets to Earth. A change in the solar cycle can impact climate. The effect is too small to be the reason that global warming that is happening now. Over thousands of years, changes in the way Earth orbits the Sun can cause big changes in climate too.

Volcanoes
When volcanoes erupt they spew more than lava and ash. They also release tiny particles so small that you can’t even see them. These particles get into the stratosphere and reflect solar radiation away from Earth. This shades the planet, causes cooling. After a year or two the little particles fall out of the air and the climate warms up again.

Greenhouse Gases
Greenhouse gases trap heat through a process called the greenhouse effect. Greenhouse gases are a natural part of the atmosphere. But the amount of them has grown over the past 150 years as fossil fuels are burned.

Snow and Ice
Because snow and ice are light in color, they have a high albedo. That means they reflect most of the solar energy that gets to them back out to space. When snow and ice melt as Earth’s climate warms, less energy is reflected and this causes even more warming.

There are also other parts of our planet that have an impact on climate too. For example, scientists are studying the impact of clouds and aerosols on climate.