Someone just pointed out this video (60 minutes Australia) about the problem of Methane released from melting arctic permafrost. Just curious if EN-ROADS accounts for this? I suspect so but didn't notice anything specifically in the info on Methane.
It does seem to be in there. You can adjust the En-ROADS sensitivity to permafrost methane in the model assumptions - upper right menu, Simulation > Assumptions > Climate system sensitivities, the last two sliders. Default setting is that permafrost starts releasing methane above 1C warming - that is, it's happening now.
Oops, "upper right menu" should be "upper left menu"
Actually, a follow-up question on this. The setting "Effect of temperature on methane emissions from permafrost and clathrates" has a default value of 0, defined as" "no temperature feedback and thus no additional release." Does this mean that the model assumes no feedback loop, where more methane means higher temperature which in turn means even more methane released?
Hi Kendra, Good question. Currently we do not include feedback loops from methane release from permafrost in the model due to the uncertainty around this. You can read more about this here: https://support.climateinteractive.org/support/solutions/articles/47001143457-does-en-roads-include-climate-tipping-points-such-as-large-scale-methane-release-from-permafrost-
One thing to note is that the methane (and CO2) emitted by the permafrost model in En-ROADS does not show up in any of the "Left Graphs" (e.g., the CH4 Emissions graph) since it is not under human cause/control -- it is just part of the climate system. Its GHG additions, however, are included in the Right Graphs, Impacts: CO2 Concentration and Greenhouse Gas Concentration, and, of course, it affects the Temperature Change.
"Tipping point" sounds very dramatic so we might expect that adding the permafrost would suddenly cause the simulation to blowup and show very large temperatures. Well, it's not quite that dramatic... But one way to do a demonstration that shows a tipping nature is to start with the "seven click 2.1C model" (From baseline click on: max Carbon Price, max Efficiencies and Electrifications, min Deforestation, max Afforestation). This shows a temperature of 2.1 at 2100 and it seems leveled off, maybe it will even bend down in the 2100s.
To include permafrost, go to the Assumptions, Climate Sensitivity, and set the last one, "Temp threshold", to a high value like 3 C, this keeps the permafrost off. Then set the one above it, "Effect of temp..." to its max of 2.5. So permafrost will kick in at 3 C of warming, and/but we have stayed under that so it hasn't affected things.
To demonstrate hitting the tipping point, move the Threshold down to 1.4 C which will cause permafrost to 'tip' and start contributing in 2030. Oops: now the temp in 2100 is 2.4 and it's increasing at about 0.1 degree per decade -- the nice leveling off is gone and instead we may hit 3.5 C by 2200. Crossing the tipping point has given us more to deal with...
P.S. It also matters how far past the tipping point we were going. In the example above the "2.1 C' model had its trajectory substantially changed by the 1.4 C tipping, heading to 3.5 C in 2200. On the other hand, if I add that same "x2.5, 1.4 C" permafrost tipping to this 1.7 C model , the 2100 temp increases to 1.9 C but has very low growth, maybe only getting to 2.1 C in 2200.