View All Pages

HICC - Causes of Climate Change Lesson

EnvSci_Lesson_TopBanner.png

Causes of Climate Change

But Why?

For the past two centuries, climate has been relatively stable. People placed their farms and cities in locations that were in a favorable climate without thinking that the climate could change. But climate has changed throughout Earth's history, and a stable climate is not the norm. In recent years, Earth’s climate has begun to change again. Most of this change is warming because of human activities that release greenhouse gases into the atmosphere. The effects of warming are already being seen and will become more extreme as temperatures rise.

Short Term VS Long Term

Climate change can be described as either short term or long term depending on how the change comes about. 

Short Term Climate Change

Short-term changes in climate are very common and will cycle climate in a predictable pattern. The largest and most important of these is the oscillation between El Niño and La Niña conditions. This cycle is called the ENSO (El Niño Southern Oscillation). The ENSO drives changes in climate that are felt around the world about every two to seven years.

Let’s Review

  • El Niño and La Niña are opposite phases of what is known as the El Niño-Southern Oscillation (ENSO) cycle.
  • The ENSO cycle is a scientific term that describes the fluctuations in temperature between the ocean and atmosphere in the east-central Equatorial Pacific.
  • La Niña is sometimes referred to as the cold phase of ENSO.
  • El Niño as the warm phase of ENSO. El Niño events change global climate patterns.
  • Some regions receive more than average rainfall, including the west coast of North and South America, the southern United States, and Western Europe.
  • Drought occurs in other parts of South America, the western Pacific, southern and northern Africa, and southern Europe.
  • These deviations from normal surface temperatures can have large-scale impacts not only on ocean processes, but also on global weather and climate.
  • El Niño and La Niña episodes typically last nine to 12 months, but some prolonged events may last for years. La Niña events occur on average every two to seven years. Typically, El Niño occurs more frequently than La Niña.

Long Term Climate Change

Long term climate change refers to changes in climate that have long withstanding affects globally – 1000s of years or more. There are many processes that can cause the climate to change. These include:

  • The amount of energy the Sun produces over years.
  • The positions of the continents over millions of years.
  • The tilt of Earth's axis and orbit over thousands of years.
  • Catastrophic events, such as a large asteroid impact.
  • Greenhouse gases in the atmosphere, caused naturally or by human activities.

 

Let’s look at the factors affecting climate change a little closer:

Changes in Atmospheric Greenhouse Gas Levels

How to Greenhouse Gases Work?

Since greenhouse gases trap the heat that radiates off the planet’s surfaces what would happen to global temperatures if atmospheric greenhouse gas levels decreased? What if greenhouse gases increased? A decrease in greenhouse gas levels decreases global temperature and an increase raises air temperature.

Greenhouse gas levels have varied throughout Earth's history. For example, CO2 has been present at concentrations less than 200 parts per million (ppm) and more than 5,000 ppm. But for at least 650,000 years, CO2 has never risen above 300 ppm, during either glacial or interglacial periods.

CO2 levels during glacial [blue] and interglacial [yellow] periods.

Are CO2 levels relatively high or relatively low during interglacial periods?

Current carbon dioxide levels are at 392 ppm, the highest level for the last 650,000 years. BP means years before present.

 Late Pleistocene Glacial Cycles

Adding and Removing CO2

Natural processes add and remove CO2 from the atmosphere

  • Processes that add CO2
    • volcanic eruptions
    • decay or burning of organic matter
  • Processes that remove CO2
    • absorption by plant and animal tissue

Try the questions below to see if you have grasped the concept:

Fossil fuel use has skyrocketed in the past few decades; more people want more cars and industrial products. This has released more CO2 into the atmosphere.

Burning tropical rainforests, to clear land for agriculture, a practice called slash-and-burn agriculture, also increases atmospheric CO2. By cutting down trees, they can no longer remove CO2 from the atmosphere. Burning the trees releases all the CO2 stored in the trees into the atmosphere.

40% more CO2 in the atmosphere.

There is now nearly 40% more CO2 in the atmosphere than there was 200 years ago, before the Industrial Revolution. About 65% of that increase has occurred since the first CO2 measurements were made on Mauna Loa Volcano, Hawaii, in 1958.

Carbon dioxide concentration at Mauna Loa Observatory. Global CO2 emissions are rising rapidly. The industrial revolution began 1850 and industrialization has been accelerating.

So if the Earth’s climate is always in a state of fluctuation what is the big deal? Why should we care? How do we know that the climate is actually changing?

Causes of Climate Change Challenge

Before You Go, You Need To Know

The following key points are from this explore section of the lesson. You must know the following information before moving to the next lesson. This is just a summary of the key points.

  • Differentiate between short-term climate change and long-term climate change
  • Differentiate between El Nino and La Nina
  • Explain how Greenhouse gasses raise and lower temperatures
  • Explain how human activity has increased CO2 levels and temperatures over the last 100 years

EnvSci_LessonBottomBanner.png

IMAGES CREATED BY GAVS  OR OPEN SOURCE