The topic of climate change is very current, widely discussed and of relevance to everybody on the planet but what exactly is climate change? After all, the earth’s climate is not a static phenomenon and has changed innumerable times over history. Timescales are sometimes long when people look at climatic changes – ice ages have come and gone spanning time periods of tens of thousands of years – whereas other climatic phenomenon are far more temporary such as the brief and irregular impacts of El Ninos. So why are people more concerned nowadays about the apparent changes we are seeing and what is causing those changes?
The evidence would seem to suggest that since emerging from the last great ice age (about 11,000 years or so ago) the climate of the planet had remained relatively stable and that global temperatures have hovered around an average of about 14⁰C. However the majority of the scientific community hass agreed that this ‘normal’ average temperature has started to rise quite rapidly and it is felt that this sudden rise in temperature is not simply a temporary glitch but is a trend which, if left unattended, is likely to continue with very serious consequences for the planet and mankind.
If the fact that temperatures are increasing is relatively incontrovertible, the causes that lie behind this rise is a topic of very great debate and controversy. The most commonly accepted view concerning the root causes of global warming would seem to be the based around the affect of increased levels of greenhouse gasses in the atmosphere. Whilst it is true that greenhouse gasses exist naturally in the atmosphere ( water vapour, carbon dioxide, methane for example) it is also felt that human activities have been very much responsible for the rising levels of greenhouse gasses we now find in the environment. Such activities as the burning of fossil fuels (oil and coal predominantly) and massive levels of deforestation where the forests are replace with pasture for the grazing of cattle are pointed to as key contribitors.
Although methane has a stronger effect, there is much less methane in the atmosphere than there is carbon dioxide and it is therefore felt that carbon dioxide is the biggest problem. (Carbon dioxide can stay in the atmosphere for up to 100 years and levels have increased by almost 40% in the past 250 years.)
It is commonly accepted that the earth’s temperature has increased by about three-quarters of one percent in the past 100 years and this increase has coincided with unusual levels of extreme sets of weather conditions – heat waves and droughts as well as unprecedented levels of rainfall.
Some of the other sections on the site look at these issues in more detail.