Climate change is one of the most talked about and controversial subjects in today’s world. Although it is big news, it is still an area which causes scientists problems and great debate. There is evidence which says yes, global warming is happening as a direct consequence of human activity, but also evidence which suggests that this is a natural warm spell which has been witnessed many times throughout the history of the earth, after all we are still recovering from the last ice age which ended around 12,000 years ago and moving into a natural interglacial period. The last 1000 years has varied in temperature greatly, for example the Northern Hemisphere was about 1^oC warmer than present at the time the Vikings invaded (800 – 1300). This meant they could grow crops and settle on the Shetland Islands and Southern Greenland, a period known as the medieval Warm Period. The little ice age followed between 1645 and 1715 (there are great variations between dates for this event) where temperatures fell significantly, but this event was dominated by three smaller temperature variations.

It is important to point out the difference between weather and climate change. Weather is the localised conditions which change hour by hour, day by day and sometimes quite rapidly. Climate change is the weather patterns we would expect over a longer period of time such as seasonal changes.

The causes of climate change have mainly been put down to increases in human activity such as burning fossil fuels as a result of the increase in the use of cars, to name a few. The one big cause associated with climate change and global warming is carbon dioxide (CO₂). CO₂ levels have increased by about 38% since the industrial revolution, with 20% of this occurring in the last twenty years (since about 1990). This increase in CO₂ may not be caused by only human activity though, because there is a natural CO₂ cycle, which has fluctuated throughout geological time. The current climate conditions could be down to a natural increase in CO₂ but the influence of increased human activity may have increased its effects and accelerated it. The more CO₂ we put into the atmosphere, the more heat from the Sun gets trapped in our atmosphere, causing warming.

Today global temperatures are 0.8^oC above the normal average. This rise in temperatures is reportedly melting our ice caps and glaciers fairly quickly and leading to sea level rise, but thermal expansion in actually the main reason for this rise. The melting of the ice caps is only adding a small amount to this. A slow rise in sea level has been witnessed over the last 100 years. Temperatures are also affected by cyclic climate systems. Natural cyclic climate events add to climate change. El Niño and La Niña are climate patterns which affect the Tropical regions of the Pacific Ocean. El Niño is associated with unusually warm sea temperatures. La Niña is associated with unusually cold sea temperatures. The effect of these climate patterns affects the weather on a global scale. Recent events, such as the worst floods in decades to hit Australia, suggest that extreme weather events such as floods are increasing due to warming. The Australian floods are believed to have been caused by an unusually cold La Niña event which has cooled the sea waters of the western Pacific but warmed the waters in the east Pacific, near Australia. This rise in sea temperatures off the coast of Australia has caused more intense rainfall than normal for this time of year. Rainfall in the western Pacific therefore is lower than average. This particular La Niña event was the strongest one to occur in the last half a century. Changes such as increased floods and droughts are typical of climate change and the warming of the Earth.

If the climate continues to warm, the effects of it will increase. This can include a large rise in sea level and extreme weather events such as hurricanes and storms are likely to be stronger. Changes in the climate will lead to problems with ecosystems because flowers may bloom earlier but the insects which usually thrive around these flowers may arrive later leading to the collapse of the ecosystems.

Every scientist will have a different view on the causes and effects of climate change, as will every non-scientist; your opinion will be different to mine. There are new discoveries being made all the time as well as older theories being altered. Nobody is 100% sure about what is really happening. In the future we are able to have a good guess at what may happen, but nobody can know for certain. In the end it is down to the Earth and how it is going to cope with further increases in human activity. The Earth will find a way of naturally balancing itself, as it has done in the past. All we know is that global warming and climate change is happening but what is going to happen in the future? Nobody knows.