Human causes of Climate Change

There are human and physical causes of climate change.

1. Enhanced Greenhouse Effect

This refers to the human influence on the greenhouse effect.

Since the Industrial Revolution began around 1750, humans have contributed to the warming of the planet by adding Co2 and other heat-trapping gases into the atmosphere. Human activities, such as the burning of fossil fuels and changes in land use, release large amounts of CO₂, causing concentrations in the atmosphere to rise. Human activities currently release over 30 billion tons of CO₂ into the atmosphere every year.

2. CFCs – Another group of greenhouse gases includes the chlorofluorocarbons (CFCs). CFCs have been responsible for depleting the ozone layer as they attack and destroy ozone molecules. The ozone layer helps keep out harmful ultraviolet rays that cause sunburn to skin and damage to plants. Holes in the ozone layer caused by CFCs, which can be found in aerosols, fridges and making foam plastics, let harmful ultraviolet radiation in and contribute to the greenhouse effect. Remember – CFCs do not occur naturally in the atmosphere – they are synthetic compounds that only originate from human sources.

3. Nitrous oxide from fertilizers– they are used in agriculture but also the burning of fossil fuels and organic matter. Remember nitrous oxide is a harmful greenhouse gas which traps heat in the atmosphere.

4. Methane – methane is much more potent than Co2 despite having a shorter lifespan. Human causes of methane release include decomposing organic matter (landfills, sewage) and from natural gas extraction (methane escapes during oil and gas extraction (e.g. fracking) operations and is released into the atmosphere).

5. Deforestation – trees  are the lungs of the planet and store carbon.Forests in areas such as the Congo and the Amazon represent some of the world’s largest carbon stores on land. But when forests are logged or burnt, that carbon is released into the atmosphere, increasing the amount of carbon dioxide and other greenhouse gases and accelerating the rate of climate change. So much carbon is released that they contribute up to one-fifth of global man-made emissions, more than the world’s entire transport sector.

Evidence of Climate Change

Before we explain the different kinds of evidence demonstrating climate change is happening, we have to define what climate change is. Climate change is a large-scale, long-term shift in the planet’s weather patterns (temperature, precipitation, winds and other factors) or average temperatures. Earth has had tropical climates and ice ages many times in its 4.5 billion years. Since the last ice age, which ended about 11,000 years ago, Earth’s climate has been relatively stable at about 14 °C. However, in recent years, the average temperature has been increasing. The climate has always been changing, but overall average global temperature have been increasing.

Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era — and of human civilization.

The graph above shows that average temperatures have been increasing. For your Higher exam, you maybe asked to interpret climatic trends on a graph. It is important you are able to provide as much detail about what is happening. What is the line showing? Can I back my answer up with statistics? Are there any obvious trends?

Evidence of Climate Change

Scientific evidence for warming of the climate system is unequivocal.

– Intergovernmental Panel on Climate Change

We always hear about climate change on the news, but how do we know it is happening? Let’s first look at clues coming from our changing landscapes. These vital signs refer particularly to evidence of global warming.

1. Sea level rises – the most commonly referred to vital sign. Satellite measurements and samples tell us that the Global Mean Sea Level (GMSL) has risen by 4 to 8 inches (10 to 20 centimeters). This is attributed to rising global temperatures which have caused melting of the polar ice caps and melting ice caps. The oceans absorb 80% of the additional heat trapped by the greenhouse gases. To help you visualise this, think of the oceans as large, vast sponges soaking up the heat. Water expands when it is heated up, so warmer waters need more space.
2. Look at the graphs and data! The planet’s average surface temperature has risen about 2.0 degrees Fahrenheit (1.1 degrees Celsius) since the late 19th century (a good statistic for your answers!). The year 2016 was the warmest year on record.
3. Ice sheets are shrinking in size – The thickness of the Arctic sea ice is rapidly declining and the the Greenland and Antarctic ice sheets have decreased in mass.
4. Glaciers are retreating (moving back) – Almost everywhere in the world including the Himalayas, Andes and Alaska.
5. Extreme weather patterns – Not only are there more heat waves, but a strong characteristic of climate change occurring is the number of extreme weather patterns. Global warming causes droughts, for example. The length of the UK growing season is increasing, winters are getting wetter and summers drier.

 

Collecting the Evidence

There are various ways you can collect the evidence.

1. Ice cores – scientists can take samples from ice caps (like a slushie drink). These samples are called ice cores. Looked inside the ice cores are trapped air and little bubbles of carbon dioxide which are preserved year after year with more snowfall. These samples can tell us about subtle changes in temperatures from decades back.
2. Rocks and Fossils – these can tell us about the climate from thousands of years ago. Limestone found in Yorkshire would have been formed on the bottom of a warm seabed millions of years ago.
3. Weather recordings – instruments like thermometers can accurately record temperatures in remote settings.
4. Tree rings – their growth layers, appearing as rings in the cross section of the tree trunk, record evidence of floods, droughts, insect attacks, lightning strikes, and even earthquakes that occurred during the lifespan of the tree. Each year a new tree ring is added. Thick rings are a sign of favorable climate, abundant rainfall, and good growing conditions. Thin rings indicate poor growing conditions and lack of rain, as well as natural disasters such as droughts, floods, and volcanoes.

 

 

Climate Change – Greenhouse Effect

The below revision notes intend to help you with your revision and understanding of the course.

Greenhouse Effect

When fossil fuels are burned (for example by industry and vehicles) gases are released into the atmosphere. These gases include methane, carbon dixoide and water vapour). These gases have always been present in the atmosphere, but scientists agree that their concentration is increasing as more fossil fuels are burned. These gases basically stop heating from escaping back into space. Remember, the ability of the atmosphere to capture some of the Sun’s heat is essential for life on earth. However, too much heat is bad news…

These gases form a blanket around the Earth trapping heat inside the atmosphere, much like a greenhouse. This is called the greenhouse effect and the resulting increase in temperatures is called global warming.

The diagram above shows what happens when electromagnetic radiation at most wavelengths from the Sun enters the Earth. The energy is absorbed, scattered and reflected by clouds and the Earth’s surface . The Earth absorbs the radiation at short wavelengths and emits it as long wavelengths. The reflection is called the albedo effect.

The below tables shows the sources of these gases. You can see that cattle-ranching also causes the release of methane. Many scientists believe that cattle-ranching is a primary cause of global warming.

Greenhouse gas	Natural source	Man-made source
Methane	Decomposing plant material	Rice paddy fields, cattle, coal mines
Water vapour	Evaporation from oceans, lakes and rivers	Burning hydrocarbon fuels
Carbon dioxide	Respiration by plants and animals,forest fires, volcanoes	Making cement,burning fossil fuels