Uncertainty in complex systems


Complex systems often exhibit feedback loops, as a change in one part of the system leads to (often unanticipated changes) in another part. Conceptual sketch of the climate system, IPCC AR4, WG1, FAQ 1.2 2007

The largest uncertainty in climate models

Nowadays, there is one factor which is involved in many of the most important feedback loops in Earth's climate system which

  • may be the most important,
  • the least well understood,
  • the hardest to predict,

It involves the response of this part of the system to changes:

What will the humans do??


(Human) tipping points

This (human!) part of the system has exhibited many non-linear tipping points in the past,which were not foreshadowed at all in the time dependence of the data (translation: fast changes with little warning ahead of time).

Industrial *Learning curves*

Consider this graph of what fraction of the U.S. population owned these kinds of things:

These curves are often exponential when a new product enters the market:

  • Scaling up: A company's first product may be crude. But once they start selling, profits combined with competition often result in improvements, and price drops.
  • Social effects Some things... like telephones, are moree attractive the more people that are using them.

    Sometimes, people hear or see new devices of friends and neighbors Solar power is contagious - The neighbor effect.
  • Learning curves apply primarily to Manufactured goods:
    • A tipping point: The momentum of the solar energy transition
      We find that... a global irreversible solar tipping point may have passed where solar energy gradually comes to dominate global electricity markets, without any further climate policies.

      This has been happening with renewables:
      CarbonTracker

    • In contrast, houses are built "in the field" (not in a factory), as are nuclear power plants, and their prices have not historically dropped. In fact, as the cumulative nuclear power installed in France has increased...

      nuclear energy has gotten *more* expensive. ["negative learning" according to the authors.]

    It is now 'Cheaper to save the planet than to ruin it"!
    CarbonTracker: Gain not pain summarized in their Political tipping point graphic.

    Katharine Hayhoe: Two (very) human feedback cycles

    Katharine Hayhoe is a curious climate communicator. She is also a Canadian, evangelical, climate scientist, UN "Champion of the Earth", professor at Texas Tech of Political Science and director of the Climate Center and more...

    She points out two feedback loops related to how we process information on climate change.

    [Which one is a positive feedback loop and which is negative?]

    Fear and anxiety

    Pro-climate social feedback loop

    Instead, when we talk about climate change, two most important things to focus on are: (1) how climate change is affecting things, people and places we care about, and (2) what we can do - individually, collectively, and globally - to FIX it.

    Your research paper

    The theme for your research paper will be Climate change solutions.

    We basically have three choices, mitigation, adaptation, and suffering. We're going to do some of each.

    The question is what the mix is going to be. The more mitigation we do, the less adaptation will be required, and the less suffering there will be.

    -John Holdren, 2007, Director of the White House Office of Science and Technology Policy, Assistant to the President [Obama] for Science and Technology


    Mitigation ...means addressing the roots of a problem.

    Mitigation includes:

    • Reducing greenhouse gas emissions.
    • Investing in new energy-generation technology.
    • Conservation.
    • Training for jobs in longer-term sustainable industries.

    The general outlines of what needs to be done is well summarized in Gain not pain (CarbonTracker).