What is climate change, global warming and the Greenhouse Effect?

Climate change, sometimes termed global warming, is the gradual warming of the atmosphere, oceans and land since the Industrial Revolution. Air, land and ocean measurements including Antarctic ice core records go back hundreds of thousands of years showing that global average temperatures are closely correlated with increased concentrations of carbon dioxide (CO₂), a 'greenhouse gas', in the atmosphere. Water vapour (H₂O), methane (CH₄), nitrous oxide (N₂O) and ozone are also termed 'greenhouse gases' because they reflect the Sun's energy back to the Earth's surface, instead of allowing it to escape back out into space. NASA has a very good website which tracks the Earth's 'vital signs'.

The Greenhouse effect involves atmospheric science, which is a complex subject, however we should focus on long-term changes rather than daily temperatures in any specific place or time. 

What are the causes of climate change?

Carbon dioxide concentrations in the atmosphere since the 1800s have risen, at least in part due to human industrial activity, to 417 parts per million (this is the highest level for 800,000 years!).

What are the effects of climate change?

The global average temperature has increased by 1.17 degrees centigrade since 1880. In terms of global effects, the arctic ice minimum has reduced by 13.1% per decade and the ice sheets are down by 428 billion metric tons per year, with sea levels rising by 3.4mm per year. The IPPC (Intergovernmental Panel on Climate Change) collates the latest body of evidence in the Sixth Assessment Report and Working Group 1.

How are weather and the climate related?

Weather and climate are often confused, but they're inherently related. Climate refers to global averages (temperatures and other statistics) measured over decades or centuries, whereas weather refers to short-term day-to-day meteorological changes (eg temperature, pressure, wind, rain and humidity). Long-term global warming leads to extreme and more intense weather events due to the increased solar energy absorbed in the oceans, land and atmosphere. The UK Met Office offers a good explanation of climate change. Why not install a personal weather station and measure the changes for yourself?

Further reading

The Royal Society outlines climate change evidence and causes. You may also find the BBC's 'Climate Change: The Facts' documentary useful and interesting.