Climate change

• Over the last few years scientists have become increasingly convinced that climate change created by mankind has the potential to alter our world forever
• The driving force behind earth's climate

  Energy from the Sun
• Energy travels from the Sun

  1. In the form of shortwave infrared radiation

  2. Some doesn't get through the Earth's atmosphere

  3. Lots of it does and is absorbed by the land and oceans, warming them

  4. The Earth re-radiates the energy back in the form of long wave infrared radiation
• Greenhouse gases


  Gases in the Earth's atmosphere that trap some of the long wave infrared radiation, acting like an invisible insulating blanket around the Earth
• The greenhouse effect is Perfectly Natural and if the greenhouse gases weren't there at all global temperatures would be 20 to 30 degrees Centigrade colder than they are now, probably too cold for life on Earth to survive
• Delicate balance


  Between how much energy reaches Earth and how much is returned into space
• If the balance changes it has a profound effect on global climate
• There have always been natural variations in climate since long before humans evolved
• Climate system varies naturally

  1. Over many millions of years

  2. Over many thousands of years

  3. Due to how the Earth and solar orbit varies

  4. Due to where the continents lie
• Factors affecting how much energy we get from the Sun

  • Volcanic eruptions blasting sulfur dioxide gas into the atmosphere, creating aerosols that reflect energy from the Sun making the Earth cooler
• Everyone agrees there are lots of different natural factors that affect the earth's climate
• Changes over the last 300 years


  • World's population has increased from 650 million to 6.5 billion
  • Technological advances including the Industrial Revolution
  • Increased fossil fuel use, now 3/4 of UK energy comes from fossil fuels
• Rapidly developing countries like China and India have big populations that are rapidly increasing and want to have the same lifestyle changes as the developed world
• Fossil fuels


  When burned, produce a gas called carbon dioxide (CO2)
• The human race is now producing quite incredible quantities of carbon dioxide, over 7 gigatons a year
• Carbon dioxide


  One of the greenhouse gases found naturally in the atmosphere, but extra CO2 from burning fossil fuels is making the insulating blanket around the earth too effective, trapping more energy and heating up the earth's climate
• Until recent times, a lot of the Earth's carbon dioxide has been absorbed into plants and trees during photosynthesis, keeping it locked away
• Forests, especially the Amazon rainforest, are being cut down, reducing this carbon dioxide absorption and releasing more into the atmosphere, speeding up climate change
• It's hard for scientists to predict exactly how much global average temperatures will increase in the future, as it depends on human behaviour and how much we're willing to cut back on fossil fuel use
• Even small temperature changes of 2-6°C could have very big effects on the planet, as this is a rate of change unprecedented in human history
• Positive feedback mechanisms


  • Processes triggered by climate change that then produce further changes, amplifying the effects
• Climate change is increasingly being seen as a moral issue, not just a scientific one, with political and economic consequences that make it controversial
• Some people claim climate change caused by humans isn't happening or that humans play a tiny role compared to natural forces, often due to vested interests or reluctance to change behaviour
• The UN's Intergovernmental Panel on Climate Change (IPCC) reviewed thousands of scientific papers and concluded that most of the increase in global temperatures since the mid-20th century is very likely due to human-generated greenhouse gases
• The IPCC said there is plenty we can do to avoid the worst effects of climate change and save much of what is precious