Holocene hurricanes: extending data and models to earlier millennia

How do tropical cyclones respond to climate changes? This question has been difficult to assess using observations largely because the records are short and subjective. Moreover, the response to changes of the scale predicted by 2100 cannot be assessed using past records, as surface temperatures in the tropics have changed only a fraction of a degree Celsius during the satellite era for which global records are considered complete. Thus, the response to climate changes has largely been studied using computer simulations, assessing both how the large-scale conditions that favor cyclogenesis change as well as how characteristics of modeled storms evolve.

The thermodynamic factors related to tropical cyclone genesis are examined in simulations modeling the climate of the last 10,000 years, during which time the precession of Earth's orbit altered the seasonal distribution of solar radiation. The thermodynamic properties most crucial for genesis undergo a shift in their seasonal cycle that responds to, but does not follow linearly from, the change in solar radiation. We examine how this change in seasonality interacts with the transient changes in environmental conditions that accompany El Nino to affect genesis potential over the past several millennia. These findings are compared with proxies of Atlantic hurricane activity recorded in sedimentary cores around the basin.