The ALP has come up with a new policy: net-zero carbon emissions by 2050. It’s been encouraged by public opinion. It had to come up with something, what with its pro-coal stance on Adani and the challenge of comprehending the bushfires.
On the surface this sounds promising. However, the promise is a tactic, inconsistent with the science, for a number of reasons. Here are two:
1. By 2050, at the current CO₂ rise rate of about 2.5 parts per million per year, CO₂ levels will be far in excess of 500ppm, or 600ppm CO₂-equivalent when methane and nitrous oxide are taken into account. This would push global temperatures to 2 degrees and higher.
2. Australia’s current coal export is more than four times the domestic combustion. However, according to ALP frontbencher Joel Fitzgibbon, Labor will not harm the coal industry to meet its 2050 net zero target. Than means large-scale coal mining would continue.
Let me expand.
Both the government and the opposition claim they are listening to the science but, whether combusted in Australia or exported, the greenhouse gases all go into the same worldwide atmosphere.
Temperature-rise projections already suggest that the supposed 1.5 degrees (above mean pre-industrial temperatures) bar defined in Madrid will be exceeded, while the uppermost threshold of 2 degrees would be calamitous.
Once atmospheric concentration thresholds are exceeded, the atmosphere generates amplifying feedbacks from the land and ocean. These include the replacement of sea ice, land ice and snow surfaces by open water surfaces, methane release from permafrost (and now from coal seam gas drilling), desiccated vegetation, extensive fires on several continents, and reduced CO₂ absorption by warming oceans.
Given the long atmospheric residence time of CO₂, the rise in concentration of greenhouse gases becomes irreversible and so is the rise in global temperatures.
According to NASA, the consequences of current global warming include:
1. “Extreme heatwaves will become widespread at 1.5 degrees warming. Most land regions will see more hot days, especially in the tropics.”
2. “At 1.5 degrees about 14% of Earth’s population will be exposed to severe heatwaves at least once every five years, while at 2 degrees warming that number jumps to 37%.”
3. “Risks from forest fires, extreme weather events and invasive species are higher at 2 degrees warming than at 1.5 degrees warming.”
4. “Ocean warming, acidification and more intense storms will cause coral reefs to decline by 70-90% at 1.5 degrees warming, becoming all but non-existent at 2 degrees warming.”
If global warming is to be arrested, a sharp reduction in fossil fuel combustion is essential and attempts at CO₂ drawdown are required.
Carbon sequestration in soil (the biochar method) has significant potential — applying pyrolysis of residues of crops, forestry and animal waste. Biochar helps soil retain nutrients and fertilisers, reducing release of greenhouse gases such as N₂O.
Replacing slash-and-burn agriculture with a slash-and-char method and the use of agricultural and forestry wastes for biochar production could provide a CO₂ drawdown of approximately 8ppm or more in half a century.
However, in itself, the biochar method may not be capable of constraining atmospheric CO₂ rise, currently at about 2.57ppm per year (the fastest rate recorded for the last 56 million years).
Apart from abrupt reductions in emissions, additional methods are required.
Every potentially effective method needs to be urgently applied on a global scale before temperatures rise irreversibly to 2 degrees and higher.
Andrew Glikson is a visiting fellow in the Research School of Earth Sciences at the ANU College of Science.