The chart on trend in atmospheric CO2 has been seen in every newspaper. In early May, concentration of CO2 was above 400 parts per million (ppm) for the first time in 4.5 million years. This could allow some alarmist articles. But once they are read every one of us goes back to its usual business. The main challenge of the planet does not change our everyday life, expecting that someone else will take care of it and will be able to change the future.
The first chart shows the trend in atmospheric C02 from May 1974 to May 2013. For the fist time last week the level is above 400 ppm. This indicator is a measure of CO2 accumulation in the atmosphere and most part of it come from human activity. This measure is an important element in the comprehension of climate change. Accumulation of CO2 in the atmosphere increases the greenhouse effect which is then a source of higher temperature. As long as this measure remains on an upward trend, higher temperature can be forecast without uncertainty. That’s why it is important.
On the chart there is a purple line which is a weekly average of daily data. It fluctuates a lot due to seasonal effects. The red line is the 52 week average. From May 1974 to now it’s a straight line. The situation seems to be deterministic.
But looking at the situation more closely we see that things are getting worse. The second chart below shows the 10 year average of annual change of CO2 concentration. We see that from the 60’s the regime has changed.
For the 10 years to 2012, annual change was of 2.1 ppm on average. On the first measure from 1959 to 1968, the average was only 0.8. Annual change has been multiplied by a factor 2.6 in 50 years. (Observations at the Mauna Loa Observatory, Hawaii, have started in 1958)
We see on the chart that the change in regime is clear and that there is a real acceleration in CO2 accumulation in the atmosphere.
For the moment, the 400 ppm level is still but hardly compatible with a forecast of an increase of 2°C compared to the pre-industrial period. This 2°C was the target in Copenhagen summit in December 2009 where no agreement was found. This 2°C target was one for which damages to the planet were not too dramatic.
If the atmospheric CO2 concentration exceeds the threshold of 400 ppm then we can expect higher temperatures in the future, higher than the 2°C. The main current risk is to overshoot it.
Efforts on energetic transition in Europe are too limited, in the US the use of fossil energies with shale oil and gas has increased and in emerging countries there is a huge need of fossil energies to support strong growth. Nothing here can let us suppose that upward trends will change rapidly.
In a recent report, the World Bank said that it was less and less reasonable to work on the 2°C hypothesis and that we all have to think and to imagine a world with a 4°C increase. This report says that it is a hypothesis on which we have to work on just to try to avoid converging to it. (The report is available here)
We have already knowledge on what could happen with higher temperatures but their impact will be on a larger scale with risks of disruption as there is not necessarily linearity in the consequences.
Five points have to be kept in mind on this issue
- The average temperature will be higher but this increase will be heterogeneous. Some regions will have much higher increase than the average. We can expect from that that populations will move.
- Water availability will be an important one. Its quality will be challenge too. The water distribution will be unequal. This could accelerate population migrations
- Large-scale climate events (heat waves, hurricanes,..) will be more numerous and at a higher frequency
- Sea level will be higher which will be problematic in countries which are currently at this level. Sea water acidification will have adverse consequences for marine organisms and ecosystems
- Food production will decrease with temperature above the threshold of 3°C. Until then production will grow with temperature
These conditions will create a large disruption and will be probably larger than expected after reading the five points above as population will continue to grow. The United Nations expects 9 billions people in 2050 and close to 10 billions at the end of this century (see here).
Deep population movements have to be expected, as well as health care problem and probably deep changes on political systems as all these conditions will imply a new geography.
Everything is in place to converge to these conclusions – For the moment trends will not be changed. But as it is for the future we first take care on the current situation. That’s probably wrong in a long term vision of the world.