Comparing volcanic CO2 emissions to human-made emissions

There's a terrific article by T. Gerlach in last week's issue of AGU's EOS newspaper [PDF]. Gerlach is apparently a volcanologist, not a climate scientist. The article compares estimates of CO2 emission by volcanic sources to human-made emissions. There is a common misconception (I'm not sure how common) about the relative contributions of volcanos and humans to the emission of CO2.

So, which do you think is the larger source of CO2, global volcanos or human-made sources (includes land-use change, cement production, transport, energy, etc)?


The answer is that humans produce (as of 2010) about 135 times more CO2 than all the volcanoes in the world. The numbers are something like humans emitting about 35 billion tons versus volcanoes emitting 260 million tons. There doesn't appear to be any tricky business going on, and all kinds of volcanoes (including underwater volcanoes) are included. In fact, Gerlach goes on to make lots of interesting comparisons: one good one is that human activities produce the same amount of CO2 emissions as the global volcanic annual source every 12.5 hours.

Gerlach also accounts for the explosive volcanic eruptions like Mount St. Helens and Pinatubo, which are called paroxysms. These can suddenly emit a lot of CO2, but they are rare. While these paroxysms are happening, their emission rate might be as large as all of humanity's. The catch is that they only last a few hours, and wind up contributing very little to the global CO2 emissions.

Really nailing the coffin shut, Gerlach also considers what it would mean for volcanism if the emission rate did match the human-made CO2 emissions of  about 135 Gigatons per year. It sounds like it would mean that we would need one (or more) supereruptions per year. Supereruptions are huge volcanic eruptions, like when Yellowstone blew up 2 million years ago, and they are rare even for geologists, happening only every 100,000-200,000 years or so.

The only weakness of the article is that Gerlach forgets to address the obvious climate change denial argument that humans are not emitting as much CO2 as claimed. There are hints of how to deal with this, however, as Gerlach mentions that the total volcanic emission is equal to that of about two dozen large coal-fired power plants. The volcanic number is so small that we can easily eliminate huge amounts of human-made emissions and still have more human-made emissions than volcanic emissions by more than an order of magnitude. So I think this presentation is a great place to point to really come to terms with this comparison, and the vast difference in the volcanic versus human-made emissions means that there can be no dispute.

Also see another Gerlach article at EARTH Magazine [LINK].

Iceland Eruption and risk to airplanes

If you are looking for the best pictures of the ash plume flowing away from Iceland, then check out the NASA page [LINK].

Air traffic has been pretty badly impacted by the safety precautions, with a blanket ban on flights over much of northern Europe over the past five days. Things look to be getting back on track now, with the UK, France, and Germany opening their airspace starting today [LINK].

A troubling aspect of the ban on air traffic is a backlash against it [LINK]. Apparently there are a number of voices saying that grounding the flights is too cautions, including some airlines. These dissenters say that the precautions aren't based on this volcanic eruption, but on "theoretical" approach.

This line of thinking strikes a familiar chord, I think. It seems that there is a general pattern for science-based decisions, which tend toward being conservative, to be questioned by interested parties. Of course, in this case "interested parties" is a euphemism for people/corporations/industries/governments who have a financial or personal stake in the situation. The usual argument goes something like, these scientists are overly cautious (or alarmist) and the problem isn't that bad, and we should be making decisions based on what is really happening and not what some fancy computer model says.

Let us be quite honest in saying that the science-based findings will be conservative. Decision making based on science follows that. This is best summed up by the old phrase, "better safe than sorry." I think this is the right way to go. There are times when calculated risk is the right approach, but when the choice is between people perchance dying in plane crashes (and airlines making tons of money) or people NOT DYING but being stuck somewhere for a couple of days (and airlines losing some money), what is the right approach? Well, I am betting that there would certainly be some questions if planes started falling out of the sky. Better safe than sorry.

Another aspect of this story is that the decision-making process would certainly be better served with better real-time data. There's no doubt that if we had better in situ observations of the volcanic ash plume, then we would have a better idea of whether it would be safe for airplanes to fly. But guess what? There's really no money for these kinds of observations. Not in Europe and not in the USA. Sure, you can turn to the NASA satellites and get a lot of information. But the real-time information that can be gleaned from the satellites is limited, both because of the satellite coverage and technology, and also because of limited personnel who have the ability to analyze the data. I'm guessing a good amount of real science will come from this eruption, but it will take months (and years) to be done. Better observations could be collected by using balloons, mobile observing platforms, and aircraft. These all require the proverbial boots on the ground. There have to be scientists/technicians on the ready, with the equipment ready to go, a way to get to the site, and personnel to ingest the data and provide analysis to decision-makers. There's no doubt the capabilities exist, and there are scientists who would be willing to do the work (and excited to do it), but there aren't usually resources for that kind of science.

So for those who say that we shouldn't rely on models and statistics for decision-making, I think this is a false dichotomy. It is either that or nothing at this point, but the better way to go is to choose both models and statistics along with real-time observations. I'd also be willing to wager that many of those on that side of the debate would not want to put the money on the table for the kinds of observational networks and responses that they are calling for. In the end, isn't the existence of the risk enough to warrant a response? Isn't it better to be safe than sorry? Given the available resources and the collected knowledge about the risk, I can not see any other recourse.