What does Global Warming mean?
Global warming is the increase in the Earth’s temperature caused mainly by greenhouse gas emissions from human activity. Here is a quick and simple definition of global warming.
But let’s take our definition one step further: the greenhouse effect is the warming that occurs when certain types of gases in the atmosphere retain heat. Sunlight shines onto the earth’s surface, where it is absorbed and then returned to the atmosphere as heat. In the atmosphere, greenhouse gases retain some of this heat and the rest escapes into space. The more greenhouse gases there are, the more heat is retained. To give you an idea, this is the same principle as the windows of a greenhouse.
Greenhouse gases were discovered in 1824, when the scientist Joseph Fourier calculated that the Earth would be much colder if we had no atmosphere. Thus, this famous greenhouse effect is essential for us, as it allows the Earth’s climate to be habitable. Without it, many scientists estimate that the Earth would be 15 degrees Celsius colder. Then, in 1895, the Swiss chemist Svante Arrhenius made the discovery of greenhouse gas when he realised that human activity could increase the greenhouse effect due to its large production of carbon dioxide.
Many climate sceptics argue that the Earth has always experienced periods of warming and cooling and that there is nothing new about this. However, while the start of their argument is a good one, they forget one essential and important fact:
Temperatures have never risen so rapidly and sharply.
Global average temperature and concentrations of carbon dioxide (one of the main greenhouse gases) have fluctuated over a cycle of hundreds of thousands of years as the Earth’s position relative to the sun has varied. As a result, the different ice ages have occurred. However, over thousands of years, GHG emissions to the atmosphere have been offset by naturally absorbed GHGs. Therefore, GHG concentrations and temperature have been fairly stable. This stability has allowed human civilisation to develop in a consistent climate. Occasionally, other factors have a brief influence on global temperature. Volcanic eruptions, for example, emit particles that temporarily cool the Earth’s surface. However, these do not have an effect that lasts more than a few years. Other cycles, such as El Niño, also occur briefly and in predictable cycles. Humans have now increased the amount of carbon dioxide in the atmosphere by more than a third since the industrial revolution. Such significant changes have historically occurred over thousands of years but are now occurring in just a few decades.