C – CARBON DIOXIDE
Okay, so we are now well into our alphabetic A–Z journey throughglobal warming. C for Carbon Dioxide is one of the main playersin the global-warming problem. Carbon dioxide, chemical symbolCO2, is a chemical compound composed of one carbon and twooxygen atoms.1
CO2 is present in the Earth’s atmosphere at a low concentration, about 0.038 per cent by volume, and is one of many gases that make up Earth’s atmosphere (see Chapter G). CO2 is measured in parts per million by volume of air (ppmv). Atmospheric CO2 derives from many natural sources, including volcanic eruptions, the combustion of organic matter, the respiration of living aerobic organisms, and unfortunately from manmade (anthropogenic) sources, which we all know from the news is being linked to global warming and climate change.
Since the Industrial Revolution, particularly the mid – nineteenth century, the burning of fossil fuels for energy to provide electricity, power factories and homes, and for all our transport needs, has released massive amounts of CO2 into the atmosphere. Not only the burning of fossil fuels, but changes in the use of the land for agriculture and deforestation (looked at in the next chapter), have further added to global manmade CO2 levels.
According to the WWF some twenty-nine gigatons, which is 29,000,000,000 metric tons of CO2, were, in 2004 alone, added to the atmosphere from burning coal, oil and gas. If we go back 250 years or so, to pre-industrial times, usually taken to be approximately 1750, CO2 levels in the atmosphere stood at about 280 parts per million by volume (ppmv). However, levels of the gas have been increasing steadily ever since.
How do we know this?
Well, pioneering scientist Charles Keeling (1928–2005) started taking atmospheric CO2 measurements in 1958 from Mauna Loa volcano in Hawaii. Those measurements have been recorded and are now known as the Keeling curve. Charles Keeling was the professor of oceanography at the Scripps Institute of Oceanography (SIO), in San Diego, USA. He followed the work of another eminent scientist and director of the SIO, Roger Revelle. Dr Revelle was instrumental in creating the Geophysical Year in 1958, and SIO’s first programme looking at atmospheric CO2 back in 1956.
Monthly CO2 measurements were collected from a height of 3,397 metres (11,140 feet) at the Mauna Loa Observatory situated on the slopes of Earth’s largest volcano, Mauna Loa, which was
chosen for its remoteness from populations and vegetation, so as not to skew the readings.
Measurements have been taken over a fifty-nine-year period, between 1958 and present, and show an increase in CO2 levels of 70 ppmv from about 315 ppmv to approximately their current level of 385 ppmv. The effects of CO2 in the atmosphere can even be measured on a cyclical basis, and this can be seen in the saw-toothed Keeling graph. Because there is a greater land area, and thus far more plant life in the northern hemisphere (as mentioned in Chapter A) compared to the southern hemisphere, there is an annual fluctuation of about five ppmv peaking in May and reaching a minimum in October. This corresponds to the northern hemisphere growing season. The amount of CO2 in the atmosphere drops towards spring, when uptake by the plants and trees by photosynthesis is greatest. The opposite occurs in winter when the plants die off and CO2 levels rise again.2
Continuous readings in this way have been taken only since 1958. However, scientists have discovered that prior to the industrial era, circa 1750, CO2 levels stood at about 280 ppmv, and this data has been revealed from air trapped in ice core records, taken from both the Antarctic and Arctic.3 Perhaps most startling is the fact that CO2 levels are now about eighty-five ppmv higher than at any time during the last 650,000 years. Records from ice-core records go back that far and have shown atmospheric CO2 levels to range from 180-300 ppmv during that period. The level of CO2 in our atmosphere now stands at 385 ppmv, and is increasing steadily.4 , 5 , 6
The Keeling curve has become one of the most recognisable images in modern science, as it shows with no uncertainty the effects of humankind’s fossil-fuel pollution of Earth’s atmosphere.
CO2 levels have increased by thirty-seven per cent since preindustrial times and have been increasing by an average of almost 1.4 ppmv a year since measurements began in 1958 – although some months the figure has been higher, sometimes lower. In the last ten years, the average increase appears to be about 1.9 ppmv each year, which indicates the rate of increase is increasing. This is looked at further in Chapter I.
Where does all the CO2 go?
It is estimated that about fifty per cent is absorbed by the oceans and land (soil, plants, trees etc.) in equal amounts, and fifty per cent remains in the atmosphere. The oceans absorb vast amounts of CO2 and act as a major sink/store for the gas, just as do the forests of the Amazon. However, the oceans take a relatively long time to absorb the CO2 that is pumped into the atmosphere, and
therefore the effects of current CO2 levels may not be reflected by the oceans for some time to come. The oceans can sustain many times more CO2 than the atmosphere can. According to NOAA the oceans have taken up about 118,000,000,000 metric tons of CO2 from human sources (anthropogenic CO2) between 1800 and 1994. This equates to about forty-eight per cent of all manmade CO2, which would be enough to push atmospheric CO2 up by an additional fifty-five ppm.
Why is carbon dioxide such a problem?
Basically global-warming theory predicts that increasing amounts of CO2 (and other gases) in the atmosphere tend to enhance the greenhouse effect and thus contribute to global warming. Despite
CO2 being present in the atmosphere in small concentration, natural CO2 levels are a very important component of Earth’s atmosphere. As mentioned earlier, CO2 is one of Earth’s natural
greenhouse gases and it helps the Earth maintain its temperature by trapping some of the sun’s heat, which would otherwise escape back into space. If this did not happen the Earth would be some 30°C (54°F) cooler and have an average temperature of about -18°C (-0.4°F) – pretty chilly, unless of course you are a penguin!
CO2 is also essential for life on Earth. Photosynthesis, the process by which plants and trees absorb CO2 and produce oxygen, could not occur without it. In the distant past volcanoes were the main source of Earth’s CO2, and there are still lots of active volcanoes on Earth, such as Mount Etna and Stromboli in Italy, which have been erupting continuously for thousands of years. Erupting volcanoes are just part of Earth’s natural CO2 cycle, and the CO2 they emit will eventually be absorbed back into the oceans and the land.
CO2 is only one of the gases that make up the Earth’s atmosphere that are collectively referred to as greenhouse gases. As we shall see in later chapters, the higher the level of greenhouse gases of which manmade CO2 is a component, the higher the Earth’s temperature is likely to be. The effects of higher temperatures could be catastrophic, as we shall be reminded throughout this book.
We will now look at deforestation, which is a continuing problem, and which destroys the Earth’s rainforests ability to soak up CO2. The rainforests destruction also adds to CO2 levels as dead and decaying trees release their stores of carbon back into the atmosphere that were taken out over many decades of growth.
CARBON DIOXIDE 2012 UPDATE.
So, what’s the position with CO2 levels now? Well, they have continued to increase and now stand at 393 ppm. Click on the following link to be taken to the NOAA website which gives a graph taken from the Mauna Loa data. An increase of 10 ppm in the four years since this book was first written.
A record-setting 30.6 billion tons of carbon dioxide was added to the atmosphere in 2010. That’s a 45 per cent increase in the global annual release of carbon dioxide by humans since 1990, reports the International Energy Agency. According to the Guardian report, Professor Lord Stern of the London School of Economics, the author of the influential Stern Report into the economics of climate change for the Treasury in 2006, warned that if the pattern continued, the results would be dire. “These figures indicate that [emissions] are now close to being back on a ‘business as usual’ path. According to the [Intergovernmental Panel on Climate Change’s] projections, such a path would mean around a 50% chance of a rise in global average temperature of more than 4C by 2100,” he said. “Such warming would disrupt the lives and livelihoods of hundreds of millions of people across the planet, leading to widespread mass migration and conflict. That is a risk any sane person would seek to drastically reduce.”
In 2011, reports Reuters, global CO2 emissions rose a further 3.2 per cent to 34.83 billion tons, with China making the largest contribution to the rise.
In 2012, CO2 emissions were again forecast to rise to 35.6 billion tonnes – ScienceDaily.
Many scientists have long suspected that rising levels of carbon dioxide and the global warming that ended the last Ice Age were somehow linked, but establishing a clear cause-and-effect relationship between CO2 and global warming from the geologic record has remained difficult.
A new study, funded by the National Science Foundation and published in the journal Nature, identifies this relationship and provides compelling evidence that rising CO2 caused much of the global warming.
Despite biofuels being developed for jet-engines, recent predictions for aircraft CO2 emissions show they will double or triple by 2050. Currently global aircraft emissions contribute around 2-3 per cent of carbon dioxide emissions. More worryingly, global emissions are set to increase by 43 per cent by 2035 as fossil fuels remain the number one energy source and coal becomes the number one fuel. Carbon capture and storage technology is unlikely to keep up with the pace of coal burning energy production.
The bad news is that CO2 levels are continuing to rise, forcing Earth’s temperature up as they do. Greenhouse gases, of which CO2 is just one, will be looked at further in chapter G.
➢ CO2 is just one of Earth’s greenhouse gases and makes up just 0.038 per cent by volume of atmospheric gas.
➢ Levels of CO2 have increased from 280 to 393 ppmv since circa 1750, an increase of thirty seven per cent, mainly as a result of burning fossil fuels.
➢ CO2 is a global-warming gas and current levels are higher than at any time in the last 650,000 years.
➢ Professor Charles Keeling started taking measurements of CO2 from Mauna Loa Observatory in Hawaii, and they show an increase from 315 to 393 ppm since 1958.
2 NASA, http://www.visibleearth.nasa.gov, the Keeling curve.
3 Stern Review on The Economics of Climate Change, Part I.
5 Real Climate, http://www.realclimate.org.