Although the controversy about who or what is causing the ever-increasing concentration of carbon dioxide in the atmosphere is scientifically closed by the overwhelming evidence, the second controversy is still being debated hotly. This is whether the extra carbon dioxide is causing any further warming of the Earth's atmosphere and surface.
This diagram shows the variation of the CO2 concentration in the atmosphere (green) since 1900 as is shown on the previous page. It also shows the record of the global average temperature (red). This comparison is the source of much of the controversy raging about whether the extra CO2 has caused, is causing, further warming of the atmosphere/surface system. The correlation between the two sets of data is by no means clear although the correlation coefficient is a respectable 0.87.
Temperature anomalies are calculated from thousands of temperature records and are quoted as deviations from the mean temperature of the global system from 1961-1980.
To a seasoned eye it would seem that there was a small decrease in temperature from 1900-1910 and this was followed by a sustained rise until 1942. From then there was a small reduction in temperature until about 1976. In the final stage, which brings the records up-to-date, there was another sustained rise, but since the extreme anomaly of 1998 there has been little change. These comments should be taken with some caution since the changes are very small compared to those occurring in the CO2 record.
The average temperature of the Earth's surface is in the region of 15oC which in absolute terms is 15 + 273.2 = 288.2 K on the Kelvin scale. So, the overall increase in temperature of about 0.8oC represents a change of only 0.28% whereas the CO2 concentration has changed by about 30% in the same time.
We should mention that in the early seventies some climatologists were predicting the onset of a cooling period, possibly leading us into the next iceage. The same set of people are today predicting 'dangerous' warming. In the last three years there has been a cooling of the planet.
It is clear that in the relationship of warming to CO2 concentration other factors must be participating. The most quoted other factor is that concerned with mechanisms that alter the amount of solar radiation affecting the atmosphere/surface system. This matter is dealt with at a later stage.