2000s >> 2007 >> no-1240-december-2007

Global warming – what is it?

Global warming is an increase in mean global temperature, which is an average of temperatures taken in various parts of the world at near surface level on land and sea. Its now about 14.6º Celsius (about 58º in old money). On a mild December day in Britain it could be more or less that temperature outside. But of course this is a pure coincidence. In most other parts of the world the temperature today will have been quite different. Thats because its an average. Actually, the absolute figure is pretty meaningless, which is why commentators generally fix a base year and compare changes since that year.

More or less reliable statistics have existed only since 1880 and these show that the average global temperature in 2000 was 0.5ºC higher than in 1900. But this was not a continuous rise. It rose from the 1900s to 1940s, then fell in the 1950s and 1960s, and has been rising since the 1970s. The average temperature in the 70s was 14.01. Today its about 14.6, a rise of 0.6º. So, while it is not accurate to say (as some do) that temperatures have been rising since 1900 or since the industrial revolution, the world does seem to be currently warming even though a century, let alone a few decades is the equivalent of a second in geological time over which changes in global temperatures (Ice Ages and Warm Periods) are measured.

Changes in the Earths temperature also mean changes in the Earths climate or, rather, since theres no such thing as a single Earth climate, in the climates of the different parts of the world. When the Earth warms up this means, for instance, that the polar ice caps decrease in size and that glaciers everywhere retreat. Which is happening now.

So, it can be accepted that we are living in a period when the Earth is warming at least temporarily and that this is resulting in climate change.

The big question is: what is causing this? We know that in the past the Earth has warmed and cooled and that this has been due to natural phenomena such as volcanic activity, changes in the intensity of solar radiation or changes in the Earths tilt towards the Sun or its orbit round the Sun. Some scientists are suggesting that this is the case now, that the Earth is just warming up after the Little Ice Age that lasted from 1500 to 1850 and which may partly have been caused by a reduction in solar radiation.

But the majority of scientists take the view, to quote from a recent report of the Intergovernmental Panel on Climate Change (IPCC) which groups hundreds of scientists, specialists in their field, from all over the world:

Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.

Burning fossil fuels releases the greenhouse gas, carbon dioxide (CO2), into the
atmosphere. CO2 is called a greenhouse gas because, though it does not prevent heat from the Sun reaching the Earth, it prevents some of it from radiating back. Which is a good thing actually, since we need this. Without any greenhouse gases in the atmosphere the average world temperature would be minus 18C.

At the time of the industrial revolution and for thousands of years before the average amount of CO2 in the atmosphere has been estimated as about 280 parts per million or ppm (in other words, out of every million molecules in the air 280 were CO2, not much: 0.00028%). In 1958 when this was first measured (as opposed to estimated from other data) it was 315. In 2000 it was 367. Today it is near 380 and rising. A word of caution is in order here. CO2 is not the only greenhouse gas in the atmosphere. There are others, especially methane (which is a product of agriculture). Total greenhouse gas presence in the atmosphere is measured in terms of CO2 equivalent. Today this is about 430 ppm. And this is the figure that is generally referred to in discussions on the subject. Its as well to be aware that when this figure is quoted not all of it is made up of CO2, but is a figure for all greenhouse gases. CO2 equivalent is about 15 percent higher than the figure for CO2 alone.

Socialists are not scientists so all we can do is to exercise critical thinking while taking into account what the majority of scientists in the field have concluded, knowing that they could be wrong.

The majority of scientists in the fields involved have concluded that the undeniable rise in average global temperatures has been caused since at least the 1970s by the rise in the amount of CO2 in the atmosphere due to the burning of fossil fuels. In other words, that it is man-made or anthropogenic as they put it in their language.

What is not clear scientists are still arguing about it is what precise temperature rise is caused by the emission of a given extra amount of CO2. This of course is a key ratio since more and more CO2 is being released into the atmosphere by the continued burning of coal, oil and gas.

If you assume the climate sensibility of CO2 to be low, then the rise in average global temperature at particular levels will be low. If you consider its climate sensibility to be high, then by 2100 the rise could be 2, 3 or 4ºC. A 3 or 4º rise could cause huge problems: sea levels rising by a third to a half a metre (one or two feet), more stormy weather, more forest fires, more droughts and desertification.

So, without necessarily subscribing to the higher figures put forward by the more engaged scientists, it can be accepted that it is desirable to cut back on CO2 emissions. The question we look at in this issue is how likely is this to happen under capitalism given its competitive and anarchic nature?

Leave a Reply