As a scientist, and one who has studied Biology, global warming has dominated the scientific stage for some time and will continue to do so for many years to come. The debate about whether it is real and whether it is man-made is not one which will be discussed here, but what we will discuss is what could be the possible causes of man-made climate change, also known as enhanced global warming.
What is global warming?
As humans we are very reliant upon the insulating effect of the layer of gases that makes up our atmosphere. Without that effect the temperatures would be much lower, water would be inaccessible and it’s highly likely that most, if not all, life wouldn’t exist on the planet. Therefore when we use words like greenhouse effect, we are really talking about an increased greenhouse effect rather than that we, man, have created from scratch on our own.
The definition of global warming is the increase in the average temperature of the Earth. That includes air temperatures, sea temperatures and the temperature of the land, so that on average the entire planet would warm. In the last century or so, since the beginning of the industrial revolution, temperatures have already increased by 0.8°C. Much of the increase in temperature is thought to have occurred in the last twenty or thirty years, indicating that the effects of humans on the planet and global temperatures are accelerating.
Different projections carried out by the IPCC (Intergovernmental Panel on Climate Change) estimate that temperatures could increase by up to 6°C in the situation where the most emissions are made. Such increases in temperatures could have disastrous consequences as although environments have, and will continue to, adapt over time to slow changes in conditions, such a rapid change will mean the environment cannot adapt quickly enough and so human activities such as food production could be compromised.
The causes of Global warming
The main accepted causes of man made global warming refer to increases in the concentration of greenhouse gases. There are other, not man-made, factors which could be causing it such as changes in the amount of solar radiation, volcanic eruptions and changes in the earth’s orbit.
The main greenhouse gases are carbon dioxide, water vapour, ozone and methane. These gases cause the greenhouse effect by effectively preventing the solar radiation from “leaving” the planet. Since the industrial revolution we have been producing large amounts of greenhouse gases, increasing the total amount in the atmosphere. The concentration of gases such as carbon dioxide has increased by around a third, which is a huge amount considering it has occurred in only a couple of hundred years.
We know what past concentrations were from records taken from ice cores. To take ice cores we drill down into thick ice and can analyse the gases that dissolved when the water froze. The ice was formed by layers of snow falling on top of each other, building the layers up over time. We know roughly how much depth relates to each year so we can work out the concentration of gases over time, even before humans existed on the planet in any big form.
Volcanic eruptions are one of the largest natural producers of greenhouse gases. A large eruption can release thousands of tonnes of gases into the atmosphere which can actually have an effect on the atmosphere over time. Usually during a volcanic eruption large amounts of particulates are released, which reflect the solar radiation back into space. This can cause a reduction in global temperatures, which can sometimes mask the effect of the increased greenhouse gases.
However greenhouse gases last for up to several hundred years in the atmosphere, meaning that the effect of the volcano can be felt for much longer than that of the particulates. The life of the particulates can be as short as a couple of days, as rain will bring the particulates onto the ground.
These particulates can have a particular effect on Polar Regions when they deposit on the ground. Natural white snowy conditions reflect much of the energy back into the atmosphere, slowing the melting of snow and ice. When the dark particulates drop onto the ground, they make the surface slightly darker, increasing the amount of energy absorbed by the ground. This increase is thought to be able to cause increased melting of snow, potentially increasing the rate of polar ice melting.
Changes in the earth’s orbit
Changes in the earth’s orbit would obviously not be caused by man, but it could have an effect on our planet. The distance from the earth to the sun is astronomical, yet we can still feel the sun on our face, which demonstrates the huge amount of energy it outputs. Therefore a small change in the orbit of the earth, bringing us closer or further away from the sun, could affect the temperature of the planet.
If the earth become closer to the sun, then the increased about of solar radiation reaching the planet could increase the temperature of the planet. The earth has always varied between states of being in an ice age which is defined as the continuous existence of ice at the poles year round, and periods of warming when there is not year round ice. This has happened for billions of years and therefore is not a result of human engineering.
We do not know the exact change in distance which was to cause the ice age and warm climatic periods of the planet. We also do not know how quickly such changes occurred, although it is expected that it took centuries or millennia rather than a few decades.
Working out the potential causes of man-made global warming is a challenge that will take science decades, if not centuries to figure out. What has been discussed may change tomorrow if a new discovery is made about the behaviour of greenhouse gases, or how the sun warms the planet or some other reason. Basically, it is known that the planet is warming, and the above reasons are widely accepted as the reasons because of it. As scientists we are always looking for the alternative theories and so the above is likely to change.
What do you think about climate change? Got any viewpoints? Please write a comment below.