Climate change talks heat up

Scientists behind the latest report from the Intergovernmental Panel on Climate Change (IPCC) are gathering in Hobart this week to review and update the latest draft of the body’s fifth assessment report, due out later this year.

The IPCC is considered the world’s leading body for the assessment of climate change, and their reports - published every six years - detail the current state of knowledge on climate change. The Hobart meeting is supported by the Australian Government Department of Climate Change and Energy Efficiency, the Tasmanian Climate Change Office, the government of Switzerland and the IPCC trust fund.

The meeting brings together the scientists who are chairing the first section of the IPCC report, known as ‘Working Group 1: Climate Change 2013: The Physical Science’. This section examines the latest science of climate change, building on past research and using data gathered over the last six years to estimate how our climate may change in the future. The group includes 255 scientists from 39 countries.

On 15 January, representatives attended a media briefing which addressed various issues surrounding the report, such as the topics it covers and the controversial leak of a draft version late last year. The panel included four coordinating lead authors from Working Group 1 - Drs John Church, Scott Power, Steve Rintoul and Nathaniel Bindoff - and co-chairs Professors Thomas Stocker and Qin Dahe.

Professor Stocker stressed that the leaked version of the assessment was a draft and the document was still being reviewed - which was the reason it had been distributed to experts in the first place. Eight hundred international experts have signed up to review the second draft, who are, according to Professor Stocker, “among the top scientists and experts in their respective fields”.

Dr Church’s focus is on sea level, which has a much stronger presence in this report than the last one. Dr Church said that in the last report there was “insufficient understanding of the ice sheets to be able to make robust projections of the dynamic response” - since then, there have been many advances in this field.

When informed of a story in The Australian that claimed there was no link between rising sea levels and human-induced climate change, Dr Church was quick to say otherwise.

“Sea level clearly is linked to climate change,” he said. “It is linked to increases in greenhouse gases, and that’s actually in the paper which was quoted by The Australian. So the quote is inaccurate.

“The sea level has already increased in the rate of rise from the 18th to 19th century; the instrumental record would indicate an acceleration during the 20th century, and the projections indicate a further acceleration during the 21st century.”

Another addition to the report is the area of detection attribution, covered by Dr Bindoff, which investigates the causes of climate change - both human-induced and natural. Dr Bindoff said the chapter is “all about understanding the role of greenhouse gases and aerosols on a climate system, and identifying the sources of those changes”.

“We identified the oceans as an emerging element,” he said. “We’ve got increased measurement systems around changes in ocean salinity, and those are now being assessed.”

The role of the oceans is further investigated by Dr Rintoul, who noted that the oceans play an important role in climate - particularly the Southern Ocean, “because it plays a big role in determining how much heat and carbon the ocean stores, and that in turn determines the rate at which climate change evolves”.

Dr Power, who addressed the issue of Australia’s recent heatwaves, noted that while extreme temperatures and bushfires are “part and parcel of living in Australia during summer”, climate change will increase the likelihood of these events - and their intensity.

“So far in Australia, we’ve seen warming of about 0.9°C since 1910, and that’s projected to be much higher if emissions aren’t brought down over the coming decades. So these sorts of events will become increasingly more common and the temperature records that are set will tend to go up with each passing decade,” he said.

Professor Stocker added that the five hottest European summers in the past 500 years have all occurred after 2001.

“It’s clear that Australia’s warmed up, the world’s warmed up, coastal sea levels have warmed up, global sea levels have warmed up,” said Dr Power.

“That’s not to say that every now and then we won’t set some cold temperature records in certain regions, and that’s because the climate system’s not wholly determined by the impacts of humans. It always comes wrapped in this enormous amount of natural variability, and I think that’s going to remain the way in coming decades.”

Professor Stocker concluded the briefing by addressing any possible errors in the report.

“Of course there are errors in a human endeavour,” he said.

“Right from day one when we released our report in 2007, we carried an errata page on the internet to actually list all the minute errors and details … these errors are typographical errors, missing elements in a table for example, things like that, that are all openly documented.

“Fortunately, through this very elaborate expert review, which is multiple-staged … we could avoid errors indeed in the top-level documents.”

The review is certainly in-depth, with the first draft gathering 24,400 comments worldwide and the second collecting 31,422.

“We want to get this right, and therefore there is this very sophisticated process of multiple reviews,” said Professor Stocker.

The report will be discussed and approved by the intergovernmental panel on climate change during an approval session which will take place at the end of September in Stockholm.