Why We Should Be Even More Alarmed About the Climate Emergency Than We Are Now.

A scientific paper, published in Nature Scientific Reports in July 2020, should have been more widely read than it has been (it has been cited 54 times). Its topic is 'Atmospheric CO2 during the Mid-Piacenzian Warm Period and the M2 glaciation', and it's by E. de la Vega et al.

The Piacenzian, for those who don't know, is the last age of the Pliocene Epoch. The study focused on the period 3.35-3.15 million years ago (Mya), in other words covering 200,000 years (200 ky). The Earth was then in the same solar orbital configuration as it is today.

During this period, atmospheric CO2 rose to a maximum of 428 ppm = 829 mg/m^3 = 3,340.25 GtCO2 (billion tonnes of CO2). Mean annual global near-surface atmospheric temperature, however, was +3 °C above the pre-industrial (1750) Holocene norm, and sea-levels 20 metres higher than they are today.

If such conditions were reproduced now, the impact would be catastrophic, with all coastal and many riverine cities inundated, and large parts of the planet rendered uninhabitable. There would also be severe consequences in terms of extreme weather events, and global food production, already badly affected by the impact of monoculture, intensive use of artificial fertilisers and chemical pesticides, which destroy soil fertility and kill insect pollinators, would decline precipitously.

Water shortages, a problem now, would become far worse, although that might seem paradoxical: it would be a case of 'Water, water everywhere,/But not a drop to drink.' No desalination effort would be sufficient to deal with this.

Last month, the US NOAA recorded 424 ppm of CO2 at the Maunakea Observatories in Hawaii - just 4 ppm short of the 428 ppm maximum of the Piacenzian. The figure for 22nd June 2023, according to CO2 earth, was 423.52 ppm, just a fraction below last month's figure - but well within seasonal variability, and 2.8 ppm above the 420.72 ppm of the year before.

E. de la Vega et al warn that: 'at present rates of human emissions, there will be more CO2 in Earth's atmosphere by 2025 than at any time in at least the last 3.3 million years.'

Last year, according to Statista, the world emitted 37.49 GtCO2. If we take May's 424 ppm = 3,309.032 GtCO2, we only need 31.28 GtCO2 more to equal the 428 ppm maximum of the Piacenzian, so de la Vega and his colleagues were actually being optimistic! We will exceed the maximum Piacenzian CO2 level before 2025.

I am not saying, and don't believe, the climate effects will occur immediately - although they might do so, with a very low probability, but they are inevitable, unless we remove the excess CO2 from the atmosphere. Just stopping adding CO2 to the atmosphere, once we've reached the 428 ppm level, will not be enough, or indeed anything like enough. We will need negative emissions.

It ought to go without saying that we have to stop extracting and burning fossil fuels immediately - ten years' time is too late, five years' time is too late! We also have to stop all deforestation and destruction of wetlands immediately, and start reforestation and restoration of those wetlands.

Of course this will have a cost! It is no use pretending, as the World Bank does, that you can 'solve' the Climate Emergency with no sacrifice and without cost! And, if there is to be any Climate Justice, as people, especially in the developing countries, rightly demand there should be, then the vast majority of that sacrifice should be borne by those most able to bear it - namely, the people in the rich world: the 'Global North', who are the cause of the problem in the first place!

Whether this is 'politically possible' is, in my judgement, very doubtful. Neither the politicians nor the voters in democratic countries are likely to swallow the kind of sacrifice in material standards of living and economic growth that will be needed.

The result is likely to be that nature will take its course, and the climate impacts will take effect as predicted, with enormous loss of life, running into billions. The future will be sacrificed for the sake of the present, proving, if nothing else, that sacrifices are unavoidable: it's just a question of which sacrifices people choose to make.

Note (added 29th June 2023). The Sun would have been less luminous than it is today during the Mid-Piacenzian Warm Period:  3.35 million years ago, it would have been ~0.03045% less luminous than now; 3.15 million years ago, it would have been ~0.02864% less luminous than now. The Sun gains in luminosity by 0.01% every 1.1 million years; by 0.1% every 11 million years; 1% every 110 million years; and 10% every 1.1 billion years (Schröder and Smith, 2008). Its current luminosity is 3.828 × 10^26 W (382.8 YW = Yottawatts).

The 10% gain in solar luminosity in 1.1 billion years' time will render Earth uninhabitable to all life, because it will cause all the liquid water on the planet's surface to turn into steam, and - water vapour being a greenhouse gas - this will cause a runaway greenhouse effect, causing temperatures to soar beyond any tolerable limit, even for viruses or bacteria. Our remote descendants, if there are any, will have had to evacuate the planet by then.