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Climate Dynamics: Facing the Harsh Realities of Now

Climate Sensitivity, Target Temperature & the Carbon Budget: Guidelines for Strategic Action – David Wasdell (Director of the Apollo-Gaia Project)

September 2015

Executive Summary

The value of Climate Sensitivity is the fundamental parameter governing all strategic policymaking in response to Climate Change. This presentation summarises 10 years of work under the auspices of the Apollo-Gaia Project, dedicated to providing the most robust answer to the question: “By how much does the Earth System amplify the effects of anthropogenic emissions of greenhouse gasses?”

Current computer estimates of Climate Sensitivity are shown to be dangerously low. They are based on inadequate treatment of the amplifying feedback system that multiplies the effect of human disturbance of atmospheric composition. Detailed analysis of historical planetary response to change in concentration of carbon dioxide, reveals an eight-fold amplification of CO2 forcing (in contrast to the three-fold amplification predicted by the IPCC climate modelling computer ensemble). Applying the corrected value of Climate Sensitivity multiplies previously predicted temperature rise by more than 21⁄2 times in response to any given change in CO2 concentration.

One immediate consequence is the collapse of the “available carbon budget” and the recognition that all future emissions add to the overshoot of atmospheric greenhouse gasses. Major reduction in the present stock of CO2e is an imperative element in the limiting of increase in global temperature to 2°C. Moreover, advances in understanding of implicit sea-level rise and the dynamic response of global climate to small changes in average surface temperature, demonstrate conclusively that the 2°C target temperature limit is set far too high. It has to be reduced to below 1°C if we are to avoid catastrophic climate change. Implications of the new analysis are spelled out for the set of emissions reduction pledges currently offered prior to COP21, as well as to the persistent high emissions scenario of “business as usual”.

Recognition of the dynamic inertia of the global system highlights the major time-lag between cause and effect, between human intervention and full manifestation of consequences. While this is significant in the case of temperature change, it is even more apparent with respect to rise in sea level, which is itself an extremely inert response to observed change in temperature. Introduction of the concept of “Implicit Change” collapses the time dimension and allows policymakers to develop strategies that are coherent with the total consequences of human action, rather than in response to minor changes in observed behaviour of the global climate. Planetary inertia also provides a time window of opportunity in which to achieve effective strategic intervention – perhaps the only remaining ground of realistic hope for the achievement of climate stabilisation at a level consistent with the terms of the UNFCCC.

Guidelines for Strategic Action

Strategy can no longer be driven by what is considered politically or economically feasible, but by the harsh reality of planetary dynamics. Response will have to be collective, collaborative and global. The current one-dimensional approach of emissions reduction and establishment of a “low-carbon economy” is completely inadequate. Effective strategy demands three concurrent lines of approach:

1: Stop making the problem worse.

Eliminate all activity that increases the energy imbalance of the Planet, or that profits therefrom.

2: Solve the problem we already have.

Engage an aggressive and effective carbon draw-down program to reduce the current concentration of greenhouse gasses.

3: Reduce target temperature increase to less than 1°C.

Contain disruption of climate behaviour, limit rise in sea-level, abort the extinction event and minimise risk of feedback-driven runaway change.

Concluding Caveat

The value of Climate Sensitivity, on which this presentation is based, was derived from historical conditions in which change was slow, close to equilibrium and in response to which natural systems had time to adapt. Those conditions no longer apply. Anthropogenic change is at least 100 times faster than at any time in the Paleo record. The system has been driven far from equilibrium and smooth natural adaptation is no longer possible. In this situation many factors combine to drive a higher and increasing value for Climate Sensitivity. That will inevitably require even more urgent and stringent strategic intervention than has been outlined above.

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