RISK ASSESSMENT AND ADAPTING STRATEGIES FOR POST-TIPPING POINT CLIMATE DISRUPTIONS: LESSONS FROM THE MIDDLE MIOCENE

Global climate change has emerged as the defining issue of our times with the rate and scale of the change and its far-reaching impacts not seen by humanity in its entirety. Given the current rate of greenhouse emissions, the lack of viable sequestration, low carbon technologies, and political will to effectively reduce atmospheric CO₂, according to the recently released IPCC Sixth Assessment Report, low Shared Socio-economic Pathways (SSP1-2) leading to scenarios with low or very low greenhouse gas emissions (Representative Concentration Pathway, RCP1.9-3.4) become increasingly unlikely. Based upon our current understanding of the process, sensitivity, and response of the climate system from paleoclimate evidence, low-likelihood outcomes, such as reaching a climate tipping point within decades, cannot be ruled out. Therefore, a better understanding of the time and scale, physical climate manifestation, and consequences of the post-tipping point disruptions is critical for long-term risk assessment and adaptation strategies.

The current level and rapid increasing rate of CO₂ emissions will soon exceed that of Pliocene and approach the middle Miocene levels, making the Miocene Climate Optimum (MCO) a suitable analog for near-future climate of the coming decades. Shedding light on of cryospheric, hydrologic, and biological responses before, during, and post MCO will expand the human-experienced climate baseline and provide the scientific base for long-term strategies and policy decisions under high RCP projections. Our research focuses on precisely-dated and annually-resolved middle Miocene lacustrine deposits in Clarkia, northern Idaho. Decadal scale CO₂ and temperature records reconstructed within a 1,000 years’ time window during the MCO in Clarkia capture novel climate behaviors that can be compared with near-future human societal time scale with high CO₂ concentrations. Middle Miocene geologic records display an Earth system and its disruptions that humanity will likely encounter after the climate tipping point. Our analyses raise serious concerns about adaptive capacity and call for reconsidering adaptation strategies ranging from design of infrastructure to mitigating natural hazard risk in order to combat the existential threat of climate change.