Climate Change: The Long View

By Bryan Walker 14/09/2011


Professor Tim Naish, Director of the Antarctic Research Centre, Victoria University of Wellington, and Principal Scientist, GNS Science, is giving a lecture tomorrow, Thursday 15 September, from 12.30-1.30 at VUW’s Pipitea Campus, Railway West Wing 501. It’s part of the NZ Climate Change Research Institute’s Seminar Series. Recommended to Wellingtonians, and worth attention from the rest of us for its sobering content indicated below.

Climate Change: The Long View

Computer models can now reliably reconstruct Earth’s climate over the last 150 years, including the rise in average global temperature of 0.7º C in the last century. When they are used to project Earth’s climate to 2100 under a range of greenhouse gas emissions scenarios they indicate average global temperature increase will likely be between 2 and 5ºC. Even at the low end, which requires an aggressive reduction in emissions, this is higher than at any time in the last million years, based on well established paleo-temperature records.

The last time Earth experienced such a climate was 3-5 million years ago. During this  period known as the warm Pliocene Epoch, atmospheric carbon dioxide was near present day levels and average surface temperature was  ~3°C warmer, but sea-level was up to ~20m higher, largely from ice sheet melt. In the last 50 years the polar regions have warmed at almost twice the global average, and the last decade the ice sheets have begun to melt. One of the key questions being addressed by the scientific community for the IPCC 5th Assessment Report is improving estimates of future sea level. This talk will outline progress in the use of past temperature, ice sheet reconstructions and sea level records in addressing this issue.