The Reality of Global Warming
The two previous articles addressed global warming and its relationship to climate change, but is it real and what are the causes?
Scientists attribute the global warming, observed since the mid-20th century, to particular gases in the atmosphere that trap and prevent heat from radiating from Earth. This is known as the Greenhouse Effect. While the most abundant greenhouse gas in the atmosphere is water vapour:
- it is short lived,
- it increases with global warming caused by the other greenhouse gases (GHG) and
- according to the American Chemical Society this feedback can amplify the warming effect of other greenhouse gases.
Of the gases that remain semi-permanently in the atmosphere, the most significant GHG is carbon dioxide (CO2). But other GHG are methane and nitrous oxide. Base levels of carbon dioxide are released through natural processes such as breakdown of plant material, volcanic eruptions and bushfires, but according to NASA the human activities of burning fossil fuels (coal, oil and gas, over the last century are mainly responsible for increasing the levels of CO2.
NASA’s chart below shows the current level of CO2 compared to levels over the last 800,000 years determined from ice cores. While CO2 levels have fluctuated in long-lasting cycles, the current spike is a clear breakout beyond any previous cycle.
This chart, and the Berkeley Earth temperature chart in the first article of the series, both show a rapid increase in the last 50 years. The 2014 IPCC report (p. 47) concluded that the probability that the last 50 years of global warming have been caused mostly by human activities is greater than 95 per cent. This is known as anthropogenic global warming.
The next article in the series will address humanity’s contribution to climate change.