Climate change has been happening for centuries and is nothing new. Phenomena such as Ice Ages and the Medieval Warm Period are the direct results of natural climate change, which is caused by variations in the Earth’s orbit, variations in solar activity, the behaviour of sea currents, volcanic activity and continental drift – among other things. The average global temperature in 1000 AD may actually have been warmer than in 2000AD, while in 1600AD it was most definitely a lot cooler.
Global warming is a specific type of climate change whereby the average global temperature increases over time. It doesn’t necessarily have to be man-made – it could be the result of natural climate change – though many believe that recent global warming trends could be the result of human activity.
The distinction between climate change and global warming is the source of many arguments in the scientific community. We know for certain that the global average temperature has risen by close to 1C since the 19th century, but this has possibly happened before.
What we don’t know for certain is whether this trend is part of the natural cycle of climate change or is the result of man-made global warming.
Part of the problem stems from the fact that our knowledge of climate change itself is incomplete. Since the beginning of the 20th century scientists have kept fairly accurate thermometer readings of temperatures at various points around the world and plotting trends in global temperature changes is relatively straightforward. This is how we are able to say with some certainty that temperatures have risen in this period.
But to get past climate data we need to employ methods that are often more unreliable. Isotope analysis of ice cores taken from glaciers, for example, can reveal something about temperatures as far back as the formation of the glacier.
The average temperature over a season affects the concentration of certain oxygen isotopes in the ice and by analysing this concentration against the age of the ice we can plot fluctuations in the temperature at a specific location.
Dendrochronology works in a similar way – a core is taken from a tree and the size of the tree rings can help determine the temperature when the tree ring was formed. There are other geological methods as well.
However, they all have a number of things in common – they require interpretation and they only provide us with a general average temperature over a period of time and tell us nothing of the temperature on individual days or how temperatures fluctuated within that period.
As such, many scientists still argue about the true extent of climate change. Some researchers have shown that the global warming trend in the 20th century has happened before, around the Medieval Warm Period of 1000AD.
Others have shown that the warming period at the end of the 20th century is unprecedented, making a clear case for the influence of industry in creating the global warming effect.
Whatever the cause, climate change is different from global warming in that global warming is a kind of climate change, while man-made global warming is a still-debated phenomenon that may or may not be occurring.
We know that climate change has been happening for millennia, we know that global warming has been occurring over the last century, but we do not know what the causes of the recent warming trend are.