Extreme is the new normal

JIM SALINGER

OPINION: As I watch from my summer subtropical perch in Brisbane, Queensland, the somewhat unprecedented rains that deluged parts of Australia during the summer of 2010/11 have been replaced by sizzling heat waves this summer. These raise some pertinent lessons on climate and risk management for New Zealand.

Firstly, let's look at some figures and ask the question of what are the climate mechanisms behind the heat waves.

Figures from Australia's Bureau of Meteorology figures show that the highest temperatures of 2011 occurred in the third Australian heat wave of the year. This affected the Pilbara region in the north west of Western Australia. Multiple sites broke the previous Western Australian December record of 48.8 degrees Celsius.

This month incessant heat has struck the interior with daytime highs soaring to the mid forties. As I pen this there are a few more days of this heat wave left with temperatures averaging between 35C and 40C in central Australia. Places have been recording daily lows of 30C and daily highs of close to 45C. Mean temperatures have been running over 6C above average.

Meteorologists measure the warmth of the air lying above one spot as the 500-1000 hPa thickness. The "thickness" is a measure of how warm or cold a layer of the atmosphere is. High values mean warm air, and low values mean cold air. Summer 500-1000 hPa thickness values lie between 5600 and 5700 metres over Australia. It was values of around 5760 metres that brought New Zealand's highest temperatures, in the low forties, in February 1973.

And what has been happening in late December and early January? An incredibly hot blob of air has sat over parts of inland Australia with thickness values of 5850 metres or more.

It is a simple law of physics that with more greenhouse gases in a layer of atmosphere the warmer surface temperatures get. Atmospheric concentrations of CO2 now are at 392 parts per million compared with 280ppm in 1750. This means that the lower atmosphere is thicker and retains more warmth, as more CO2 in the atmosphere traps extra heat. The consequence is that global warming leads to an increase in the magnitude and incidence of heat waves.

The first lesson from the sizzling continental heat wave is that global warming has arrived for some time now, and the climate has warmed. Global warming is no longer a theory based on abstract calculations of what the climate is very likely to do in future decades. In 2007 the Intergovernmental Panel on Climate Change concluded: "It is very likely that hot extremes, heat waves and heavy precipitation events will continue to become more frequent."

The second lesson - the canary in the coal mine - is that because of global warming, the frequency of these extreme weather events will increase. Thus the century old high temperature extremes will be exceeded more often in the future.

The third lesson is that there needs to be better preparation for these events by civil society. Heat waves can have debilitating effects on the elderly who are not so healthy. The 2003 European heat wave caused at least 40,000 deaths and the 2010 western Russian heat wave 55,000 deaths. Heat waves also increase the fire risk when there is little rain, as occurred in the Black Saturday heat wave and bushfires in February 2009 in Victoria.

At least New Zealand is the lucky country in this respect, surrounded by oceans which dampen down any high temperatures. However Niwa future climate scenarios show a large increase in days above 30C and 35C in eastern districts with more frequent very hot nor'westers as the 21st century progresses.

Global warming is here, now - and not a phenomenon for future generations to deal with. We must embark on a course of emissions reductions targets as soon as possible. If we do not act now the severity of such heat waves and the subsequent damage to life and property will increase. There is no time like the present to invest in our future wellbeing.

Former Niwa scientist Jim Salinger is resident for the summer as a research fellow at the National Climate Change Adaptation Research Facility at Griffiths University, Queensland.

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