One of the few areas of the global warming debate which seems to | be universally accepted is that there is clear proof that levels of j| atmospheric carbon dioxide have been rising ever since the Ü beginning of the industrial revolution. The first measurements of CO2 concentrations in the atmosphere started in 1958 at an altitude of about 4,000 metres on the summit of Mauna Loa mountain in Hawaii. The measurements were made here to be remote from local sources of pollution. What they have clearly shown is that atmospheric concentrations of CO2 have increased every single year since 1958. The mean concentration of approximately 316 parts per million by volume (ppmv) in 1958 rose to approximately 369 ppmv in 1998 (see Figure 3). The annual variations in the Mauna Loa observatory are mostly due to CO2 uptake by growing plants. The uptake is highest in the northern hemisphere springtime; hence every spring there is a drop in atmospheric carbon dioxide which unfortunately does nothing to the overall trend towards ever higher values.
This carbon dioxide data from the Mauna Loa observatory can be combined with the detailed work on ice cores to produce a complete
3. Indicators of the human influence on the atmosphere composition during the industrial era record of atmospheric carbon dioxide since the beginning of the industrial revolution. What this shows is that atmospheric CO2 has increased from a pre-industrial concentration of about 280 ppmv to over 370 ppmv at present, which is an increase of 160 billion tonnes, representing an overall 30% increase. To put this increase into context, we can look at the changes between the last ice age, when temperatures were much lower, and the pre-industrial period. According to evidence from ice cores, atmospheric CO2 levels during the ice age were about 200 ppmv compared to pre-industrial levels of 280 ppmv - an increase of over 160 billion tonnes - almost the same CO2 pollution that we have put into the atmosphere over the last 100 years. This carbon dioxide increase was accompanied by a global warming of 6°C as the world freed itself from the grips of the last ice age. Though the ultimate cause of the end of the last ice age was changes in the Earth's orbit around the sun, scientists studying past climates have realized the central role atmospheric carbon dioxide has as a climate feedback translating these external variations into the waxing and waning of ice ages. It demonstrates that the level of pollution that we have already caused in one century is comparable to the natural variations which took thousands of years.
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