365 Days of Climate Awareness 93 – Tipping Points

A longstanding concern in climate change research has been the concept of “tipping points”, a transition between two stable energy states within the atmosphere, depending on factors such as atmospheric composition and continental structure. A lot of effort in recent years has been invested in looking for evidence of rapid transitions between fairly stable climate states, and for the possible occurrence of such an event now.

A side note: the illustrations now and for some time to come will be drawn from the IPCC AR6 volume 1, The Physical Science Basis. I’m abusing fair use a bit in posting these images because the report states that it is not meant for redistribution. However, these graphs are the approved draft for the initial public release and for use by governments around the world. I do think it’s in the public interest to promote awareness of the report’s contents, though the released copy is not the finalized version. The writing and illustrations have been intensely reviewed already, and I’m not taking any personal profit from these posts, so I think defying the no-redistribution caveat is called for in this case.

Also: the report is gigantic and I couldn’t find the system response time plots I’d originally intended to base this post on, so I switched topics. Please bear with your faithful pilot who’s going by VFR. 😋

When two or more possible energy states exist within a system, there are a few mechanisms by which it might make the transition from one to another. One is noise-based, where random variations of sufficient energy will cause the shift.  In the illustration’s top row, [a] shows the noisy variations of a system parameter—global mean temperature, in this case—becoming strong enough to lead to a jump to the higher energy level. Plot [b] shows this transition with the vertical axis representing system stability, and the horizontal axis being energy state. The local minimum shows how durable that state is, with the peak between them being the tipping point.

Types of tipping points.

Another is “bifurcation”, where the system’s energy state diverges from the earlier, stable point due to a driving influence. System variability—noise—might remain small but a very strong trend drives the energy state up or down (plot [c]). On the stability plot [d], the system driver is displayed as the elimination of one local minimum, forcing the system’s transition to the alternate energy state.

A number of data streams have generated significant concern in recent years about the likelihood of our climate system bifurcating into a hotter new overall state, with factors such as methane trapped in permafrost (both terrestrial and marine) posing a significant threat.

Tomorrow: global mean surface temperature, comparing the IPCC’s last two assessments.

Be brave, and be well.