This article first appeared on The Globalist.
The history of dramatic global warming is being repeated.
Timorous leaders of the three largest greenhouse gas emitters — China, India and the United States — will be held accountable by history for Earth’s great coastal cities permanently submerged under feet of water this century.
The indifference of China, India and the United States to pleas for action at the COP25 Madrid environmental summit and elsewhere raise the prospects for a calamitous development to near certainty: Global coastlines – including Amsterdam, the southeast of England, southern Florida, the Mekong, Mumbai, New York, Shanghai, Tokyo and the like – will suffer levels of inundation that will require massive permanent evacuations later this century.
Preventing sea levels tens of feet higher thereafter hinges on the rapid adoption globally of net zero emissions and on devising/maturing technologies for utility-scale direct carbon removal from the atmosphere.
Your grandchildren will wonder what you were thinking
Greenhouse gas (ghg) emissions have continued to rise. Capping global temperatures is inconceivable under current feeble climate policies despite a rapid decline in renewable energy hardware costs.
Indeed, public subsidies in the G-20 nations for coal alone totals $64 billion annually. This easily outstrips support for renewables, e-cars and carbon price programs. Led by China, investments in global clean energy declined in 2018 and especially in 2019.
The Trump administration is hostile to emission suppression and no senior official attended COP25. Emission pledges have been abandoned by OECD members South Korea and the United States.
The acceleration in global temperatures newly projected in recent months from rising atmospheric ghg concentrations has not occasioned the policy upgrades it warrants. Evidence from the most recent analogous period to today of comparable concentrations — the Pliocene millions of years ago — informs the unfolding climate consequences.
The Pliocene history threatens to be destiny
Without the greenhouse effect from atmospheric ghg, Earth’s surface temperature would be a deep freeze, a Martian-like -18 degrees centigrade (C). With planet temperatures determined by these gasses, maintaining an atmospheric concentration compatible with human life is essential to civilization.
Carbon dioxide (CO2) comprises 75% of ghg. With natural emissions in the pre-industrial era (PIE) of about 200 million tons of CO2 annually, its atmospheric concentration was at or below 285 parts per million (ppm) for much of the previous several million years, an accommodative range for humankind to emerge.
CO2 emissions have rocketed since the pre-industrial era, driven by industrialization, to a level of 37.5 billion tons (2018), with no end in sight. Atmospheric ghg concentrations have risen apace, reaching 410 ppm in 2019, and also relentlessly rising.
Including the non-CO2 ghg (methane, nitrous oxide and the hyper-dangerous fluoride gases), the CO2-equivalent concentration exceeds 450 ppm. The immediate previous period of comparably high atmospheric concentrations was the Pliocene 3 to 5 million years ago.
Some 3.6 million years ago, for instance, CO2 concentrations like today ranged between 380-450 ppm. The next previous such period was the Eocene 35 to 55 million years ago. Ghg concentrations were 680 ppm and above, producing global temperatures sufficiently high that glaciers and polar ice sheets were nonexistent.
The planet and civilization we know is certain to be stunningly degraded even if CO2 concentrations are miraculously stabilized at 400-450 ppm. Earth’s equilibrium at 400 ppm during this Pliocene era was a temperature 2.8C warmer with sea levels ranging from 32 to 65 feet higher than today.
The U.S. National Oceanic and Atmospheric Administration’s (NOAA) Pliocene sea level figure is 50-80 feet higher than in the pre-industrial era.
Avoiding this destiny requires zeroing-out net emissions and harnessing mankind’s ingenuity to actually reduce atmospheric concentrations of ghg by nearly half – and the clock is ticking.