Poles apart: Climate change at the ends of the earth
“The last time carbon dioxide levels in the atmosphere were this high was 3 million years ago, and sea levels were 20 metres higher than today.”
24 June 2015
That’s according to Victoria University of Wellington Professor James Renwick, whose sobering comment comes ahead of his upcoming inaugural lecture—a public address to mark his professorial promotion.
By primarily drawing comparisons between the two poles, Professor Renwick’s address, entitled A Tale of Two Hemispheres, will marry the science of man-made climate change with known natural occurrences in earth systems.
The focus will be on factors such as polar geography, the ozone hole, wave patterns and natural climate variations to show that, while the planet is warming overall, the impact will affect regions differently.
“Climate change doesn’t happen at the same rate everywhere or in the same way,” says Professor Renwick.
“We’re already observing obvious changes in climate in some parts of the world. Alaska, for instance, has experienced its warmest May ever, with large tracts of land having no snow¬—a remarkable thing for the area at any time of year.
“New Zealand, on the other hand, isn’t expected to feel the sharp end of climate change until much later in the century.”
He says the differences are most apparent at the earth’s poles, due primarily to different geographic profiles.
“In the case of the Arctic, there is almost no land mass north of latitude 70 degrees, meaning a relatively thin ice layer over the ocean. Antarctica, on the other hand, is a very large land mass, with ice up to 4 kilometres thick in some places.
“While the sea ice is very obviously diminishing in the Arctic, what we’re observing around Antarctica are increasing levels of sea ice.
“At first glance, this might seem to contradict the global warming story, but our satellite data suggests that this is likely due, in part, to the billions of tonnes of melted continent ice refreezing as sea ice.”
Global weather systems interacting with each pole’s unique geography also influences ice development, with Professor Renwick particularly interested in the impact of La Niña and El Niño on sea ice.
He is also looking at how ocean waves, which are a product of weather, might influence sea ice development.
“In understanding future sea levels, it’s the ice sheets on the continent that are important.
“What’s worrying is that a lot of land ice is grounded below sea level, inland from the coast. If warming ocean water can penetrate under the ice sheets, there’s the potential to cause massive ice loss at a very rapid rate.”
Professor Renwick’s inaugural lecture is open for the public to attend.
When: 6pm, Tuesday 30 June, 2015.
Where: Memorial Theatre, Student Union Building, Kelburn Campus, Victoria University of Wellington
RSVP by Friday 26 June. Phone 04-463 6300 or email with ‘Renwick’ in the subject line.