[Reprinted with permission from Truthout.]
In 2017, scientists for the first time spelled out what it will take for civilization to survive global warming. Simply ending the use of fossil fuels isn't going to do it; we must also extract billions of tons of carbon dioxide (CO2) out of the atmosphere and store it somewhere forever. The world has been edging toward this momentous conclusion for a long time, but in 2017, scientists finally laid out the details.
At least as early as 2001, a few scientists started saying atmospheric CO2 could not safely exceed 350 parts per million for very long. The world snoozed. Then, in October 2009, huge, noisy crowds of young people jammed the streets in 4,300 synchronized demonstrations in 188 countries, to publicize 350 parts per million (ppm) as a climate goal. The world began to wake up.
Now, thanks to climate activists (and many scientists), the 350 goal is firmly fixed on the global agenda. However, few people still have any real idea what it will take to achieve 350. In 2017, though, climate godfather James Hansen and his colleagues laid it out for us.
From 1981 to 2013, Hansen was director and chief scientist for the National Aeronautics and Space Administration's Goddard Institute for Space Studies . In 1988, it was Hansen who first told Congress that global warming was upon us. Some scientists scoffed , but today all the world's major scientific organizations acknowledge that he was right . After another 20 years studying global warming, in 2008, Hansen published his disturbing conclusion that global warming promises "irreversible catastrophic effects" if we allow CO2 to exceed 350 ppm past the end of this century.
The natural amount of CO2 in the air is 280 ppm, but by 2016, it had risen to a dangerous 404 ppm because of humans burning coal, oil and natural gas. It's now rising a bit more than 2 ppm each year and the rate of increase is accelerating . As everyone now knows, CO2 acts like a blanket in the air, warming the planet and changing the climate.
Why It Matters
Hansen is a physicist, and his argument is based on physical evidence from Earth's rocks and ice, which contain a record of past CO2 levels, temperature, climate and sea levels. We are now living in a warm period between ice ages -- a balmy epoch known as the Holocene, which began about 11,700 years ago. During this warm period, humans invented agriculture, formed villages and towns, then cities, creating modern civilization.
Today, everyone on the planet is dependent upon Holocene conditions -- moderate temperatures, steady sea levels, abundant sea life, manageable storms, predictable patterns of rain, snow, snow-melt and river flows, plus plenty of food thanks to regular seasons, abundant pollinators, ample fresh water and moist, temperate soils. If those things change -- especially if they change rapidly, as they are now doing -- hundreds of millions of people will find themselves short of food, fresh water or tolerable temperatures , and will migrate into someone else's territory, creating conflict, war and social upheaval. If present warming trends continue, the foundations of civilization will crumble.
The Science of 350
Hansen's argument goes like this : In the last warm period before the Holocene (in an epoch called the Eemian ) the global average temperature peaked about 1.8 degrees Fahrenheit warmer than the Holocene average, and two things were hugely different from today: 1) sea level was 20 to 30 feet higher, and 2) coastal storms were much larger , producing waves that could push 1,000-ton boulders out of the sea onto the land.
Global average temperature today is already warmer than it was during the Eemian. If it remains so for long, polar ice will melt away, sea level will reach Eemian levels, and the world's coasts will be swamped. Since 1750, the global average temperature has risen about 2.07 degreesF and additional warming of about 1 degreesF is "in the pipeline ," meaning the heat has already entered the ocean and will be warming the atmosphere in the next several decades, no matter what we do. In sum, we have already overshot safe CO2 limits and polar ice is already melting faster than most scientists thought possible.
The Speed of Melting Matters
From the geologic record, we learn that sea-level rise can occur abruptly -- 13 feet to 15 feet in a century . Because of the unprecedented speed of recent warming, Hansen believes a 20- to 30-foot rise could occur within 50 to 150 years. Even the more optimistic estimate -- a 20-foot rise in 150 years -- would average 16 inches every decade, which even wealthy, low-lying cities could not accommodate for long. "The economic and social cost of losing functionality of all coastal cities is practically incalculable," Hansen writes .
How Many People Live on Low-Lying Coasts?