Editorial: If this is global warming, we're all in it together

People flock to Bondi Beach to cool off in Sydney, Australia. Record temperatures were reached as high as 43 degrees around Sydney. Photo / Getty Images

Heat waves in Australia and NZ may not be a symptom of climate change ... but it might be an idea to keep working on ways of beating it.

The bush fires raging in Australia this week have been brought closer to home for New Zealanders than perhaps any previously. The heat over the country last weekend was said to have been an air current circulating southward around the Tasman, and the scrub fires in Canterbury late in the week, engulfing three homes, were a taste of what spontaneous combustion can do.

The speed of a flame-front fanned by strong winds is hard to believe for anyone who has never seen a fire spread through dry grass. Australia's inland heat is also hard to describe to those who have not ventured far from the coastal cities and found themselves running for shade.

In Australia, these dangers are well known. It is also now accepted there that regular fires are a natural and healthy feature of the native vegetation. In fact, it is recognised that suppressing natural summer fires might do more harm than good, enabling undergrowth to thicken abnormally and make a fire hotter and more destructive when it does break out.

Perhaps that realisation is the reason this week's outbreaks, though more extensive than any in memory, have not caused the destruction of some previously. Communications and evacuation procedures have been improved as a result of a royal commission into the 2009 Victorian bush fires.

The lessons were applied fairly successfully in Tasmania this week. A township was engulfed but not before its residents had left, or in at least one family's case, taking refuge in water beneath their pier.

Australians now know how close their houses can safely be to bush - about 700m, experience would suggest. About 85 per cent of houses lost to fires since 1967 have been within 100m of the trees. Any home within 10m of bushland in Victoria four years ago had an 80 to 90 per cent likelihood of being caught by the flames.

With Australia having its two hottest days on record this week, and New Zealand enjoying a hot summer, it feels like climate change has arrived. But most scientists are wary about attributing any particular weather to global warming. To cite this summer as evidence would enable sceptics to recall last January's washout.

In a review of climate study this week, we reported that New Zealand might fare quite well under the predicted 4C increase in average global temperatures. Here the expected rise is 3C.

Victoria University's Dr Jim Renwick, a lead author of the United Nations Intergovernmental Panel's next report, said the North Island's climate would be closer to Queensland's and the South Island would have the North Island's conditions. It does not sound so bad.

Melting polar ice caps would raise sea levels a metre, and droughts would be more frequent in eastern regions of New Zealand.

It remains wiser to contribute what we can to international efforts that might reduce or at least slow the rate of warming.

The next IPCC report will examine engineering responses to climate change, such as extracting carbon dioxide from the atmosphere and sending sun-reflecting particles into the stratosphere.

It is something to ponder as we bask in another hot, sunny weekend. And spare a thought for Australia where temperatures are predicted to set records this weekend.

If this is a symptom of global warming we are all in it together.