Human Causes Climate Change

Temperature and Greenhouse Gasses

Human Causes Climate Change, figure 1

These graphs show an increase over time. Both the Carbon Dioxide Concentration and Temperature Anomaly have given a steady increase over time.

Enhanced Greenhouse Effect

Human Causes Climate Change, figure 1

The sun naturally warms the earth through the natural greenhouse effect, whereby some gasses trap heat in the earth’s atmosphere.

The enhanced greenhouse effect mean that there are more of these gasses, which trap more heat in the atmosphere.

Greenhouse Gasses

Carbon Dioxide: is the most potent of the greenhouse gasses, and is given off by burning fossil fuels (coal, gas, petrol).

Methane: is the second most important greenhouse gas. It is more potent than CO2, but exists in far lower concentrations in the atmosphere.

Nitrous Oxide: exist mainly due to human activity, and have very low concentrations.

Human Activity

Carbon dioxide: Humans increase the amount of CO2 in the atmosphere by burning wood, petrol and other sources for energy. This releases more CO2, this process is made worse by the fact that plant life (like trees), which takes up CO2 during the process of photosynthesis, is being destroyed by deforestation.

Methane is released into the atmosphere by human sources (rice cultivation, livestock farming, and decomposition in landfills). These currently account for approximately 70 percent of total annual emissions, leading to substantial increases in concentration over time.

Nitrous Oxide is released by agricultural (farming) and industrial activities.

The main drivers of global warming:

Human Causes Climate Change, figure 1


  • The EU, USA and Japan emit 33% of all carbon dioxide emissions.
  • China alone emits 29% (and rising) with Russia and India each emitting more than 5%.


What happens if the temperature increases by 2 degrees?

The ten hottest years on record have occurred since 1998 (2005, 2010 and 2014 as the hottest!) In 2012 we had half the level amount of sea ice as 1979, this in turn has melted ice caps, caused the oceans to expand and therefore the average sea level has risen.

Human Causes Climate Change, figure 1

There has been an increase of extreme weather events, Iceland’s hottest summer on record was in 2008, where temperatures hit 26.2 degrees.

The change of behaviour of animals is another impact. There are 1,200 Polar Bears in Hudson Bay, Canada. Usually they hunt on the ice during Spring and put on 50-75% of their body fat in these months. But due to global warming, ice in Hudson Bay melts 3 weeks earlier now meaning less chance for the bears to feed. On average they come onto shore 10kg lighter!


These graphs show evidence for climate change from four different factors. Why are we uncertain about the future of climate change?

Human Causes Climate Change, figure 1

It is not possible to make accurate prediction about the possible consequences of climate change because:

  • We don’t know the extent of the changes- because human enhanced climate change hasn’t occurred before.
  • Future projections are mixed- because we don’t know what will happen to future greenhouse gas emissions.
  • We don’t know what will happen to the future population of the world.
  • We don’t know what will happen to the future economic growth patterns of the world.
  • However, for some it is possible to make accurate predictions about the consequences of climate change:
  • We have a wide range of predictions from scientists.
  • We can make a ‘best guess’ of warming at 3.5oC and a sea level rise of 40cm by 2100.
  • We can use evidence of past climate change to construct what might happen.

In conclusion therefore…

  • We can provide a range of predictions. Based on ‘what if’ scenarios.
  • We can provide a range of consequences assuming that climate change follows previous patterns.
Explain how the enhanced greenhouse effect works.
Your answer should include: Fossil / Fuels / Human / Activity / Greenhouse / Gasses
Describe the human activities that increase the amount of greenhouse gasses in the atmosphere.
Your answer should include: Farming / Agriculture / Industry / Fossil / Fuels / Deforestation
Explain the impacts of a human induced changing climate.
Your answer should include: Sea / Level / Rise / Increased / Temperature / Melting / Ice / Caps / Glaciers / Extreme / Weather
In your opinion, do we have a good grasp on the future scenarios of climate change? Use evidence in your answer.
Your answer should include: Projections / Predictions / Scenario / Population / Agriculture