Research Areas

  • 1. Aims
  • 2. Strategy

1. Aims

Ecosystems and societies in the North Atlantic region greatly profit from the warmth that the North Atlantic Current carries to them. Climate models and data from the past show that the thermohaline circulation (THC) in the oceans, of which the North Atlantic Current is one branch, may abruptly weaken or even shut down altogether. INTEGRATION explores the possibilities and consequences of future changes of the THC, addressing the following guiding questions:

  • How likely is a weakening or a breakdown of the THC?
  • What are the potential impacts of THC changes, on ecosystems, economy, and society?
  • What are possible strategies to reduce the risk of changes of the THC?

2. Strategy

The approach to answer the guiding questions is an Integrated Assessment, which comprises the following components:

  • Climate scenarios.Several climate models (Climber-2, Climber-3a and others) are driven with greenhouse gas emission scenarios for the next three centuries. This long time scale reflects the thermal inertia of the oceanic water masses.
  • The impacts on ecosystems and societyare explored along two impact chains (marine and terrestrial), using various impact models. While a large part of the marine impact chain is studied by the external project partners, the terrestrial and socio-economic impacts are dealt with at PIK. Some of the models used here are: AEZ for crop yield, LPJ for general impact on vegetation an the carbon cycle, 4C for tree vegetation dynamics of specific stands, EFISCEN for impacts on forestry in the economic sense. In addition, the impacts of an additional sea level rise are explored.
  • An expert elicitation collects the current knowledge about the THC and its risks, addressing questions like the driving mechanisms of the THC, future research needs to reduce uncertainties, or the feasibility of an early warning system for the THC. An important outcome of the interviews are experts' subjective probability estimates for essential climate parameters.
  • A dialogue with stakeholders explores their judgments and their risk aversion, using subjective probabilities. Especially the question of the potential dangerousness of a THC breakdown (in the sense of Art. 2 UNFCCC) is discussed here.
  • An uncertainty analysis addresses some of the many dimensions of uncertainty. Parameter uncertainty is studied in Climber-2 as well as Climber-3alpha. The propagation of this type of uncertainty through the impact chain is explored in some cases (e.g. for agriculture). Within Climber-3alpha, structural uncertainty is another focus. The uncertainty analysis aims at an likelihood estimate for a THC breakdown.
  • An integrated assessment model (IAM) is employed to outline mitigation options reducing the risk of a THC breakdown using the Tolerable Windows Approach. With the inclusion of a model of endogenous technical change more detailed socio-economic guardrails can be formulated.

Link to the INTEGRATION Model Overview