Expect more ‘complete surprises’ from climate change: NASA’s Schmidt
The Canberra Times, 12 February 2018
The eruption of pine bark beetles that has devastated millions of hectares of forests in North America is an example of the surprises yet to come as the planet warms, says Gavin Schmidt, head of NASA’s Goddard Institute for Space Studies. The tiny beetles, which have infested forests from Colorado to Alaska, develop a type of anti-freeze as winter arrives. With fewer cold snaps before the insects are “cold hardened”, more of them are making it through to spring.
“We just don’t understand ecosystems to the extent we understand the physical climate systems,” Dr Schmidt told Fairfax Media during a visit to Sydney. “We will see over the next few decades more and more thresholds being crossed.”
However, that’s not to say the physical climate is fully understood either.
Carbon dioxide levels are now the highest in about three and a million years when the Earth had a “very, very different climate”, Dr Schmidt said, adding it was inevitable more “unknown unknowns” would emerge.
The southern hemisphere, especially Antarctica, is of particular interest to NASA and other global organisations trying to understand how the build-up of additional heat will affect planetary processes, he said.
“There’s a tonne of extra energy that’s going into the south – in fact there’s more energy going into the sourthern ocean than the north,” Dr Schmidt said. “But that isn’t necessarily being seen at the surface.”
Scientists’ understanding of Antarctica continues to be limited by the short observational record, with much of the data compiled only since the late 1950s.
Satellites and argo floats are also not very helpful in gauging changes under the sea ice and ice shelves.
The region is already throwing up surprises. Dr Schmidt cited the Mertz Glacier Tongue, which used to protrude about 80 kilometres into the Southern Ocean until it was cut in two by an iceberg in 2010.
“It seemed very, very stable…but the whole thing got taken out by an iceberg and now it’s totally disappeared,” he said.
Research is focused on places such as the Totten ice sheet “where people think there is the greatest amount of potential change in the East Antarctic ice shelf”, Dr Schmidt said.
A study out last year in Science Advances estimated Totten itself had the potential to lift global sea levels by 3.5 metres if it melted entirely.
The east Antarctic ice shelves, though thought to be mostly stable, “are big enough that should anything start to happen there, these will be noticeable increases to the rate of sea level rise,” Dr Schmidt said. “So that makes them interesting.”
Sea ice cover around Antarctica is close to record low levels – set just a year earlier – as the region approaches its summer minimum extent.
Antarctica is also home to another scientific surprise: the ozone hole that was detected over the contenent in the mid-1980s.
While the class of chemicals – mostly chlorofluoro carbons – were relatively well known, their potential to destroy the crucial ozone layer that helps keep out cancer-causing ultraviolet light was not.
“It was a massive shock to the system – it hadn’t been predicted by anyone,” Dr Schmidt told a public talk last week.