What is climate change?
There are several periods identified by climatologists of changes in earth’s climate over extensive time period – oscillation between broadly cold and warmer weather (glacial and interglacial periods). What we want to know is whether this current period of warming is natural or not? Scientific evidence suggests that it is independent of what might be expected in a natural cycle.
This is linked to the GHG emissions and the increased absorption of these gases into the atmosphere (they become trapped and heat the earth). Earth absorbs solar energy and heats up – it starts to radiate heat which is trapped in its atmosphere – heat radiating from the earth encounters greenhouse gas molecules and is absorbed. Examples of greenhouse gasses are carbon dioxide, methane, nitrous oxide, water vapour, dichloflorormethane and trichloroflouromethane.
The rate of warming for most of the 20th century was slightly below 0.1 deg C, however, in the last couple of decades this has increased to 0.2 C – this is nearly ¼ of the observed change in temperature between today and the last ice age.
Relatively fixed factors determine climate over years eg: orbit and rotation. These will change over time and affect temperature. Primarily it is the burning of fossil fuels and deforestation that have resulted in what can be called a human induced warming effect on the earth.
Global warming potential is a calculation of the increase in greenhouse effect caused by the release of a kg of the gas, relative to that produced by the equivalent of CO2. While the above shows that gases other than carbon have greater potential to increase warming – they are being released at lower rates
These complexities create problems for decisions making due to uncertainty because there is a lack of information on what the extent of the problem will be in the short, medium, and longer terms. This has implications for policies in terms of reduction targets eg: how much to reduce to avoid significant costs while sacrificing minimum wealth.
The fact that the costs-benefits are not spread evenly around the globe has implications for developing and developed countries because different regions will experience different outcomes of rising temperatures. Combined with uncertainty, the result is that any international agreement is difficult to come to because the exact spread of costs- benefits is unknown.