We are gathered here this week in Belize for the 15th annual permaculture design course at the Maya Mountain Research Farm. I have blogged in past years from this place, set upon an ancient city ruin from the Classic Maya Era, surrounded today by a multi-strata agroforestry example of the human potential for antifragile, harmonious living with élan in the uncertain and ominous Anthropocene. I’ll not do that again just now. Instead I want to mention something I delved into during our first day of class — a bit of climate science confusion that needs to be corrected and nipped in the bud.
The ecologist Walter Jehne is particularly guilty of spreading this particular point of misinformation, and while I like Jehne and his work in general, he does the world a disservice when he tries to opine on atmospheric science.
Jehne correctly reports that humans — primarily by land use change — have altered Earth’s water cycle in some very profound ways. He also correctly observes that the single largest greenhouse gas, by a sizeable margin, is water vapor. He then draws the conclusion that by restoring hydrological health to the land surface of the planet we will rapidly restore the natural climate that existed before the industrial age. This is a logical error in which coincidence is confused with causality, something we humans have a neurological propensity towards and that leads us to all manner of ills.
Yes, the water cycle is out of kilter. As are the nitrogen cycle, the carbon cycle, the potassium cycle, and much more. We humans are great disruptors. You could say, and I do in this permaculture class, that disturbance is our ecological niche, and we do our damage on the same scale as super-volcanoes or asteroid impacts, using mere biological means.
Searching for a metaphor to explain Jehne’s error, I have taken to comparing Earth’s atmosphere to mega rock concerts. If you look at that towering rack of amplifiers bathing an acre of audience in decibels of sound, you could call that water vapor in the atmosphere. Jehne, in my analogy, would tell us confidently that we can repair Earth’s climate by starting to remove some of those amplifiers from the tower. He is right, as far as he goes, but there are a lot of amplifiers up there, they are pretty heavy, and it is a very high tower.
Instead, we could look more closely at the electric guitar of the lead musician. Just below that jewel-studded ring on his pinky finger there is this little round knob. It is known as “gain” and maybe it has some markings on it like the numbers 1 to 5 or 1 to 10. Or 1 to 11 if the band is Spinal Tap. When the musician reaches down and gives that knob a tiny twist, the decibels in the entire amphitheater elevate (or diminish) exponentially. Gain is a control knob for volume.
In Earth’s climate system the gain knob is carbon.
In 1957, during the International Geophysical Year, the First Russian Antarctic Expedition founded Vostok Station, literally, “Station East” at the southern Pole of Cold, on the East Antarctic Ice Sheet, with the lowest reliably measured natural temperature on Earth of −89.2 °C (−128.6 °F; 184.0 K). It is also one of the driest places on earth with only 26 days of precipitation, on average. In the summer season of 1983–1984, a building was constructed by Professor Boris Kudryashov and ancient ice core samples were obtained.
I reprinted his core data chart in my 1990 book, Climate in Crisis. At that time, the chart looked back 800,000 years, and Kudryashov was able to reliably extract CO2 bubbles and to correlate the carbon content of the atmosphere across the ages to known temperatures, globally averaged, taken from various other data sources.
It’s true that water vapor is the largest contributor to the Earth’s greenhouse effect. On average, it probably accounts for about 60% of warming. However, water vapor does not control the Earth’s temperature, but is instead controlled by the temperature. Warmer temperatures evaporate more water.
From 2002 to 2009, an infrared sounder aboard NASA’s Aqua satellite measured the atmospheric concentration of water vapor. Combined with a radiative transfer model, Gordon et al. used these observations to determine the strength of the water vapor feedback. According to their calculations, atmospheric water vapor amplifies warming by 2.2 plus or minus 0.4 watts per square meter per degree short-term and 1.9 to 2.8 watts per square meter per degree long-term.
However, we have seen from these kinds of measurements that atmospheric water vapor concentration is not correlated to temperature rise the way carbon dioxide is.
What rightfully concerns climate scientists is what that Vostok ice core is telling us about our immediate future.
We are now at 414 parts per million CO2 by volume in the atmosphere and adding 2–3 more ppm each year. We know from the geological record that at 325 ppm, which is about where we were when I wrote Climate in Crisis, the equilibrium temperature should be 5 degrees above normal (“normal” being the average across the comfortable Holocene epoch in which mammals evolved into us). And yet, when that book came out, we were only 0.9 degrees above normal. How could that be?
Slowing that 5 degree temperature increase is a huge heat sink that covers 70% of the surface of Earth — the ocean. Deeper in places than Everest is tall, most of it far out of the reach of sunlight, the ocean warms or cools only very slowly, taking thousands of years to catch up to the rest of the biosphere.
We should all be very thankful for that, because all that water buys us a little time.
Whether humans will go extinct at 3 degrees, 5 degrees, or warmer is an open scientific question. We will not be able to function well out-of-doors once ambient temperatures go above the capacity of our sweat glands to maintain evaporative cooling for our bodies. This effect is already being observed in places that have never experienced the kinds of heat extremes they are now seeing.
Even if the US rejoins the Paris Agreement and nations accelerate their ambitions to curb the threat, it seems unlikely we will arrest the growth of CO2 before we reach 450 to 500 ppm, and that would imply, from the Vostok record, global atmosphere and oceanic temperature equilibrium will rise well into the double digits above normal, and with that rise will come certain extinction of most terrestrial lifeforms, ourselves included.
No amount of afforestation or changed grazing patterns would produce a water vapor change rapidly enough to succeed with Walter Jehne’s prescriptive pathway.
However, thanks to the time lag afforded by the oceans, if negative emissions technology can ramp up quickly enough in the next few decades, it is yet possible to turn the gain knob back to 350, 300, 250 and below and perhaps avoid our otherwise certain fate. That is my hope, and I am clinging to it.
Here in Belize we are training people to do exactly what will be needed, and what can be effective, in producing real-world changes in the short time remaining. I love this place, these people, and the great adventure upon which we have embarked.
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