CO2 levels reached 403.64 ppm in October 2017, a rise of 2.07 ppm above October 2016. This has triggered amplifying feedbacks from land and oceans. It is becoming clear the only way to avert environmental and nuclear catastrophes is to down-draw atmospheric CO2 using budgets on a scale currently only available to the military.
Efforts to reduce atmospheric CO2-emissions have been failing. It is imperative that reductions in CO2 concentrations take place if global temperature rises of 4 degrees Celsius and higher, with calamitous consequences, are to be avoided. A new book titled “Drawdown: 100 Solutions to Reverse Global Warming” (Penguin Books, 2017), edited by Paul Hawken, considers a range of ways to reduce CO2 in the atmosphere by 2050. Those methods, in billion tons (GtCO2 equivalent), are as follows:
- Wind turbines -146 GtCO2
- Tropical forests regrowth -89 GtCO2
- Solar farms -64 GtCO2
- Rooftop solar -43 GtCO2
- Silvo pasture -47 GtCO2
- Planet-rich diet -78 GtCO2
These methods would reduce emissions by close to 40 per cent. However, the slow nature of some of these methods and the urgent need to arrest global heating require urgent down-draw. More direct and immediate measures are called for if the atmospheric CO2 levels and thereby global heating are to be contained.
Such measures include streaming of air through basalt, as in Iceland, developing extensive sea weed farms, as in South Korea, biochar farming, “sodium trees” (NaOH sequestration of CO2) and other methods.
James Hansen estimates that, if such methods are used, it would cost between $150 and $350 to draw-down one tonne CO2. Thus it would cost between $600-$1400 billion per year to remove one year’s emissions from the atmosphere. This is below the scale of global military expenditure of $1700 billion in 2016.
The scale and rate of modern climate change has been greatly underestimated. Since 1750, human industry has released a total of over 2000 billion tonnes of CO2 with a consequent rise of atmospheric CO2 from about 280 to over 403 ppm. The growth of atmospheric methane to 1845 ppb at a rate of ~10 ppb per year adds an equivalent of 46 ppm CO2 (assuming forcing by 1.0 ppb CH4 is equivalent to fording by 25 ppb CO2) That means that the current CO2 equivalent effect is approximately 449 ppm (403+46 ppm). That level of CO2, is a level similar to levels estimated for the Pliocene 2 age,6-5.3 million years ago Then the Greenland and west Antarctic ice sheets did not exist and sea levels were about 25±12 meters above those at present. A rise of sea level to Pliocene levels, though lagging behind temperature change, would inundate coastal and low river valleys, where the bulk of population and agriculture reside and where civilization has risen in the first place.
Good Planets are hard to come by.
Dr Andrew Glikson, Earth and Paleo-climate science, ANU School of Anthropology and Archaeology, ANU Climate Change Institute, ANU Planetary Science Institute; Honorary Associate Professor, Geothermal Energy Centre of Excellence, University of Queensland