Victoria scientists profile state of the world’s climate

Professor David Frame, Professor Tim Naish and Associate Professor James Renwick are lead authors on Working Group One of the Intergovernmental Panel for Climate Change's (IPCC) Fifth Assessment Report (AR5), released in Sweden.

Climate Change 2013: The Physical Science Basis, confirms and strengthens many of the findings from the Fourth Assessment Report published in 2007, on observed changes in the global climate and the underlying causes.

The latest report documents global temperature increases of the atmosphere and oceans, decreases in the volume and cover of snow and ice, as well as an average rise in sea level of 19 centimetres between 1901 and 2010.

It also documents the continued increase in concentration of greenhouse gases in the Earth's atmosphere, caused primarily by the burning of fossil fuels and land use changes, and a related trend towards ocean acidification.

The report outlines four possible future greenhouse gas concentration scenarios to the end of this century and beyond, ranging from one in which emissions are substantially reduced, to one with continuing high emission rates. Corresponding estimates for global surface temperature increases range from between 0.3 and 1.7 ºC, to between 2.6 and 4.8 ºC by the year 2100.

Professor Frame, Professor Naish and Dr Renwick will speak about their contributions to the report at a free stakeholder workshop in Wellington on Friday 11 October, hosted by the Royal Society of New Zealand. For more information about the workshop, visit www.royalsociety.org.nz/ipcc.

The summary can be viewed online at www.climatechange2013.org, with the final draft of the full Working Group One report available from 30 September. The remainder of the AR5 report will be released in stages over the coming year.

Commentary from the three Victoria University scientists follows:

Professor David Frame

Professor Frame, Director of the New Zealand Climate Change Research Institute at Victoria University, says the report largely consolidates the findings of the previous 2007 report, due to improvements in climate modelling and observational records.

"Thousands of recent scientific research papers have been assessed by the panel of more than 250 scientists, and the resulting report is the world's most comprehensive evaluation of the science of climate change.

"The upshot is that globally, we expect further change in coming decades, consistent with the rate of change we've observed over the last thirty or forty years," he says.

Professor Tim Naish

The report also describes the changes observed to some of the world's largest ice sheets in Greenland and Antarctica. Professor Tim Naish, Director of Victoria's Antarctic Research Centre, says the report shows carbon dioxide concentrations are now at levels unprecedented in at least the last 800,000 years.

"It is very likely the Arctic sea ice cover will continue to shrink and thin as the region is expected to warm more rapidly than other areas of the world.

"In addition, the volume of the polar ice sheets and glaciers globally will continue to decrease, contributing to a global mean sea-level rise between 26-82 centimetres by the end of the century, depending on the greenhouse gas concentration pathway we end up following," he says.

"The report cautions that only the collapse of marine-based sectors of the Antarctic Ice Sheet, if initiated, could cause sea-level to rise substantially above these 'likely' ranges during the 21st century."

Dr James Renwick

In addition, the report gives a number of predictions for long-term changes in global weather patterns and climate. Dr James Renwick, a Southern hemisphere climate expert, says that climate change will be ongoing this century and will bring significant changes to New Zealand and the Pacific.

"By the end of this century, extreme heavy rainfalls are likely to become more intense and more frequent in many places, while at the same time the risk of drought is set to increase substantially, notably in the east and north of New Zealand.

"An increased frequency of high temperature extremes and fewer cold extremes is virtually certain almost everywhere."

Provided by Victoria University