Jamie Morton

Jamie Morton is science reporter at the NZ Herald.

Tackling global warming head on

This week, we preview five developments that are poised to shake up the science landscape this year. Today, Jamie Morton looks at the most authoritative report on climate change to date, and its projections.

Changes would be like shifting New Zealand several hundred kilometres closer to the tropics, and frosts would not be found anywhere except in the mountains. Photo / Sarah Ivey
Changes would be like shifting New Zealand several hundred kilometres closer to the tropics, and frosts would not be found anywhere except in the mountains. Photo / Sarah Ivey

If there was any doubt that climate change is the biggest crisis facing mankind, the global groundswell of science being poured into the mother of all research efforts should confirm it.

The United Nations Inter-governmental Panel on Climate Change's Fifth Assessment Report, better known as the AR5, will provide policymakers around the world with the most comprehensive document on the issue to date.

"I think in terms of coming up with a carefully considered assessment of all the research that's been done in the past five years, this is the most up-to-date and authoritative document," said Niwa's chief climate scientist, Dr David Wratt, a vice-chairman of one of the IPCC's working groups.

The AR5 has been noted for its analysis of geo-engineering - large-scale concepts of combating global warming through physical intervention, rather than just the generally accepted need to slash greenhouse emissions.

Such ideas have included sucking carbon dioxide from the atmosphere and deflecting sunlight. One bold concept suggested mass amounts of sulphate particles could be injected into the stratosphere, simulating the sun-blocking fallout of a major eruption and cooling the Earth.

Victoria University climate scientist Dr Jim Renwick, a lead author contributing to the AR5, said the current forecast of 4C of warming for the planet within the next century held large and frightening ramifications.

"We're already just under a quarter of the way there at the moment.

"The governments of the world pledged in Copenhagen to limit the global warming to two degrees - that's a very laudable goal, but nobody's doing anything about it.

"To actually get to that now, given the way greenhouse gas emissions have gone in the last decade, would require massive cuts."

Countries such as New Zealand would need to slash emissions by at least half this decade and bring them down to zero by the end of the century.

Comparatively, New Zealand was better off than other areas on Earth under the 4C scenario.

"While it might mean 10C of warming for the Arctic, it was likely to be closer to 3C here, where our ocean surrounds and proximity to Antarctica kept the atmosphere cooler, said Dr Renwick.

"But even so, 3C of warming over New Zealand would put the climate of the country in many ways outside of anything it's experienced for a very long time."

Temperature-wise, he said, it would be like shifting the country several hundred kilometres closer to the tropics.

The climate of the North Island would be closer to Queensland's while the South Island would have that of the North Island. Frosts would not be found anywhere except in the mountains. In eastern regions, the frequency of droughts would double, as would rainfall on the wetter west coast.

"You could expect a change of maybe plus or minus 20 per cent or 25 per cent in average rainfall - that might not sound like much, but a long-term change of even 10 per cent in rainfall can be the difference between a climate suitable for growing crops and one that's too dry to do very much."

A high sea level would also directly affect many of our coastal centres, especially when combined with king tides and storm events.

Elsewhere, the dry centre of Australia would expand southward, areas closer to the tropics would become far wetter, and the east coast of the United States would become even more threatened by storm events and higher sea levels.

Dr Renwick said the AR5 was a "huge undertaking, because such a big problem requires this kind of effort".

But being a document that was policy-relevant, rather than policy-prescriptive, it stopped short of making decisions.

"When most political leaders talk about climate change, they usually talk about how important it is - whether that translates into action is another story.

"I appreciate it's one thing to recognise the problem, but it's another thing entirely to see a way forward that everyone will buy into."


The series

Monday: New look at mental disorders

Tuesday: Early warning for earthquakes

Yesterday: Graphene - super material

Today: Assessing climate change

Tomorrow: Future of the Ross Sea

- NZ Herald

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