The Intergovernmental Panel on Climate Change (IPCC), a United Nations body for assessing the science related to climate change, released its most recent report (AR6) in August.
The report does not make for pleasant reading, as even IPCC’s most ambitious model of emission scenarios offers less than a 50 per cent probability that global warming can be kept under 1.5 degrees C, the threshold beyond which consensus scientific opinion is that more dire climate change consequences will be upon us.
Global greenhouse gas emissions accumulated since 1850 are now estimated at 2,400 billion tonnes of carbon dioxide, and IPCC estimates that each additional 1,000 tonnes is likely to increase global temperatures by 0.27 to 0.63 degrees C. To have a 50 per cent chance of keeping global warming below the threshold of 1.5 degrees C, the upper limit of “allowable” greenhouse gas additions is 500 billion tonnes, which is about the equivalent of 10-15 years of emissions at current rates.
IPCC reckons that carbon dioxide emissions have the greatest negative impact on global warming (about 0.75 degrees since 1850). Methane is a close second (about 0.5 degrees). There is at least 100 times more atmospheric carbon dioxide as atmospheric methane and, on an annual basis, more than ten times as much carbon dioxide enters the atmosphere than methane. However, here are big differences between the two gases: methane is a far more potent greenhouse gas but, luckily, the half-life of atmospheric methane is less than 10 years whereas carbon dioxide can linger in the atmosphere for over 100 years. Consequently, from a governmental policy perspective, the first priority should be to stop methane from entering the atmosphere.
Surprisingly, there are also emissions of gases that have a positive impact on global warming, notably nitrogen oxides and sulphur dioxide. The former is produced by burning fossil fuels. Although emissions of nitrogen oxides have had a beneficial impact on global warming, estimated by IPCC at 0.2 degrees C since 1850, breathing high levels of nitrogen oxides has a very negative impact on human health, and can be fatal. Similarly, although the emissions of sulphur dioxide have had a beneficial impact of global warming, estimated by IPCC at 0.5 degrees C since 1850, high concentrations of SO2 can cause inflammation and irritation of the respiratory system, and causes acid rain. SO2 emissions are associated with the burning of coal in electric power plants, and the burning of heavy fuel oils in marine vessels (now being mitigated through the substitution of low sulphur fuels and the use of exhaust scrubbers).
The production of methane is associated with production and transportation of fossil fuels, with the raising of livestock, and with landfills. Production of carbon dioxide is mostly associated with the burning of fossil fuels.
Governments are already tightening regulations, and companies engaged in production and transportation of oil and gas are eliminating sources of leaks. Satellite identification of methane sources helps to pinpoint troublespots.
Beef production has been identified as a primary source of methane emissions. Beef production also consumes other resources, such as land, and huge volumes of fresh water. Governments could reduce this source of methane by imposing an environmental tax on the sale of beef products. Beef producers and consumers would howl from one end of the country to the other. Unfortunately, there are no easy solutions to climate change. We must change our ways, or climate change will change us. The choice is ours.