Tag Archives: methane

North Atlantic sea surface temperature anomaly

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This year’s ocean temperatures are being described as “unprecedented”, “off the charts”, and “beyond extreme”. I have to stare at this plot for awhile to get it, but basically the 0 line is the long-term average, presumably over 50 years or so. Then each individual line shows the difference between actual temperature and that average, for one year, over the course of the year. So not only is the departure of more than 1.5 C in June 2023 way above the average, it is way above any other extremes seen over the last 50 years.

Daily sea surface temperature anomaly (°C) averaged over the northeastern Atlantic region during 2023 (black line) and for previous years from 1979 to 2022 (red and blue lines). Data source: ERA5. Credit: Copernicus Climate Change Service/ECMWF.  

The article gives physical explanations, including El Nino, changes in ocean currents, and changes in wind currents. It says climate change is a factor but doesn’t really reach conclusions on how much of a factor. I think it almost certainly has to be a factor. But the important question to me is whether this is an extreme fluctuation the likes of which we are going to start seeing occasionally, or the start of some runaway trend we are going to start seeing frequently and may even get worse? The article does not suggest anything like the latter. Tipping points concern me – could this be an early warning that we have hit some tipping point in terms of runaway methane release for example? The article doesn’t suggest that. Let’s hope not. If it is, it would be an “unprecedented” planetary emergency and we would need to pull out the stops and try any and all of those risky geoengineering ideas we have been hearing about, because “risky” is by definition less risky than “certain doom”. Let’s hope not. The fluctuation does appear to be subsiding, so we can see where we are next year around this time.

tipping points

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A new article from Proceedings of the National Academy of Sciences goes through eight climate change tipping points that have studied, and tries to assign an economic impact to each. I’ll list them here in order of highest to lowest impact according to this study (see Table 2). They use the change in social cost of carbon as their key metric.

Two tipping points have major potential impacts and represent over 80% of the total risk from the eight, according to this study:

  • ocean methane hydrates
  • permafrost carbon feedback

Four tipping points have relatively modest expected impacts, at least modest compared to the truly existential threats represented by the top two:

  • West Antarctic Ice Sheet
  • Greenland Ice Sheet disintegration
  • Indian Summer Monsoon
  • Amazon dieback

Finally, two actually have small positive impacts on the (human) economy according to these authors:

  • Atlantic Meridional Overturning Circulation slowdown (AMOC)
  • Arctic sea ice / Surface Albedo Feedback

They don’t include “nonmarket effects”, so if you just feel that the death of the Amazon forest is profoundly sad, that is not reflected here. The authors are explicit about this so I guess it is okay.

These results are mismatched with my impressions, which are most likely driven by the amount of media coverage given to tipping points. I have probably read the most about ice sheets, the AMOC, and the Amazon, and these somewhat surprisingly do not make the top of the list. I feel like I have some basic grasp of the scientific concepts on each of these other than the methane hydrates. I understand why releasing massive amounts of methane would raise temperatures. I just don’t yet understand the feedback loop that would cause it to happen, whereas with the permafrost thawing it is pretty clear. Are the methane hydrates just frozen and expected to melt? I suppose in that case they are very similar to methane under the permafrost, with the difference being land and water. So the release of vast amounts of trapped methane is by far the biggest impact identified by this paper. For the most part though, the solutions to address any of these tipping points are going to be the same – drastic greenhouse gas emissions reductions and/or drastic geoengineering. Nothing else is going to reduce the amount of heat and solar energy melting ice, thawing permafrost and undersea frozen methane hydrates, and affecting ocean currents across vast chunks of the planet.