High CO2 climate

Project Leader: Chris Hollis

Mead Stream, Clarence Valley

The Mead Stream gorge in the northern Clarence River valley provides a spectacular record of ocean sediment accumulation over 40 million years. Photo: Chris Hollis

This project aims to identify the global causes and regional consequences for biological and physical systems of extreme climatic events in the greenhouse world of the early Cenozoic and Late Cretaceous (30 to 100 million years ago) in which greenhouse gases were at least two times higher than present (i.e. >1000 ppm CO2 equivalent).

The research aims to advance understanding of the regional impacts of climate change under a greenhouse climate, focusing on better understanding the nature, rates and magnitude of changes through climate transitions and in extreme climate states. We compare local terrestrial and continental margin records with regional and global records and with climate models as part of an international effort to refine model-based predictions of global warming impacts.

An important component of our research is providing the underpinning time framework for understanding past climate events, as well as for dating subsurface strata drilled during exploration for hydrocarbons, coal, mineral and water resources, and mapping the structure and geological history of the country. This involves developing the New Zealand Geological Timescale and its correlation with the International Geological Timescale, using biostratigraphy and other geochronologic methods.

Southwest Pacific ocean temperature history

A new marine temperature history for the Southwest Pacific ocean based on the paleo-calibration for the TEX86 sea surface temperature proxy described by Hollis et al. (2012)

Recent updates and outputs

  • A review of marine paleotemperature data for the southwest Pacific during the early Paleogene (60 to 40 million years ago) indicates that warm subtropical climatic conditions in the early Eocene (~50 million years ago) can be reconciled with climate models if (i) very high CO2 forcing is assumed for the models, (ii) proxy-sea surface temperatures at this latitude have a bias towards summer temperatures, (iii) poleward heat transport is increased by strengthening flow of a proto-East Australian Current, and (iv) inherent errors in paleotemperature proxies are taken into account.

See Outputs and Outcomes for our latest publications.