Recently researchers have noticed several areas where large amounts of methane are bubbling to the surface of the Arctic Ocean. The press has quoted one of the observers as saying that this is “terrifying.” Perhaps.
How unusual is this? Circumstantial evidence indicates that this is pretty scary, but it needs to be put in the context of overall emissions from the Arctic biome. We need comprehensive inventories of these lands and waters to understand the extent to which these one-off events are truly cause for alarm. There is little doubt that the tundra is rapidly becoming a net source of carbon, and there have been a distressing number of discoveries of such large gas eruptions in Siberia.
Make note of the Paleocene-Eocene Thermal Maximum (PETM). This was a spike of 5-8˚C in the atmospheric temperature about 55.5 mya. Officially the academic community does not know what caused the PETM, but increasing evidence from stable isotopes is compelling that it was caused by pulses of CO2 and massive releases of methane. The short duration of about 200,000 years is perhaps consistent with the short lifespan of methane in the atmosphere and with methane’s intrinsically high forcing capacity.
There is a lot published on the ecosystem disruptions in the oceans and on land that occurred during the PETM, and it is a model for what is unfolding as we warm our atmosphere during this century. The impacts of the PETM did not result in one of the five mass extinctions, but many species went extinct and there was wholesale disruption of the Earth’s ecosystems.
We live in interesting times. What continues to amaze me is that as a species we can quantify and understand in explicit detail how we are destroying the Earth’s ability to support the civilization that has made this awareness possible. It is almost surreal.
Even stranger is the magic of CO2. Carbon dioxide is necessary for life and over billions of years the Earth has developed a dynamic flux of carbon among atmosphere, rocks, and living systems. This is part of the rhythms of our planet in which changes occurring over millennial timescales drive the evolution of species and ecosystems.
Without anthropogenic influences during the modern era, CO2 should exist in our atmosphere well below 300 ppm. We are at 415 ppm as I write this. The last time our atmosphere contained ~400 ppm was the Pliocene, about 3 mya, and sea level was at least 6 meters higher than it is now. It is a rare gas that nourishes us all, yet if there is too much of it, it can disrupt the climate that made possible the development of civilization.
CO2 and the other non-condensing greenhouse gases are responsible for the radiant energy structure of the atmosphere that makes the overall temperature of the Earth consistent with life. If CO2 were suddenly zeroed out, that structure would collapse and the Earth would become icebound with an average temperature below -20˚C. It is true that water vapor, a condensing greenhouse gas, is responsible for about 70% of the greenhouse effect, but only if CO2 provides the radiant energy structure of the atmosphere to allow sufficient capture of heat in the layer of air where we live.
The bottomline is that CO2 is the master thermostat for our planet and it has a rather narrow range of setpoints that are consistent with our needs. All of civilization and agriculture developed during the last 8,000 years, the stable period known as the Holocene, aka The Goldilocks Climate because it was neither too cold nor too hot.
Amazingly, we understand these things about our planet even as we wreck it. My mind has been blown by these little facts for about 30 years.