Northland drought is a harbinger of the future

A warming climate will ensure another dry summer will never be too far away, write Te Herenga Waka—Victoria University of Wellington's Dr Luke Harrington and Professor Dave Frame.

The transition period between February and March is a crucial time for drought in New Zealand.

We will soon know whether the severe dryness already witnessed in Auckland and Northland becomes a truly unprecedented event, or if some welcome rain might finally fall in the right places.

The chances rise as the tropical cyclone season peaks in the south-west Pacific over the coming weeks, but ex-tropical cyclone pathways remain notoriously unpredictable; if rain does come, it may come as too much of a good thing.

There are many similarities between the dryness we’ve seen in the northern North Island over the past several months and the drought in 2013.

The 2013 event was both record-breaking and devastating, but only really emerged over a 10-week period between January and March.

In the years since, we have studied the physical nuances of that drought in detail. We now know climate change is already making droughts like it both more likely to occur and more intense when they do.

Changes in the atmosphere that accompany human-induced warming are allowing the large blocking high-pressure systems typical of the New Zealand summertime to become a little more intense and thus a little bit harder to move

Unfortunately, our research found these seemingly small changes were enough to nearly double the odds of experiencing an exceptionally dry summer over the North Island in any given year. A report commissioned by the New Zealand Treasury translates this to an extra $300 million in economic losses from the 2013 drought alone, because of climate change.

Of course, we know the impacts of drought are by no means just economic. As we’ve already seen over the past fortnight, rural communities reliant on rainwater to keep their tanks full can find themselves particularly vulnerable to these extreme swings in our summer weather.

Decision-makers across the community will need to take heed of these impacts emerging after only six weeks of no rain—the questions for the next decade will be how to enable communities to prepare for dry spells that could exceed eight, 10 or even 12 weeks.

Scientists also have a part to play. While we now understand the pathways by which a warming planet can affect our weather systems in the summer, there remain important knowledge gaps.

These include quantifying how fast things will change as global temperatures continue to accelerate, understanding the complex effects of a recovering ozone hole over Antarctica, and identifying whether land surface feedbacks can worsen the local impacts of drought in New Zealand.

A multi-million-dollar research programme funded by the Ministry of Business, Innovation and Employment, and announced last year, will aim to answer precisely these questions.

While we hope for a favourable forecast and some welcome rain over the Northland region in the coming days, a warming climate will ensure another dry summer will never be too far away.

As the world transitions into this ‘new normal’, decision-makers—private as well as public—will need to work quickly with their communities to prepare for and adapt to the changes we cannot avoid.

Meanwhile, if we are to avoid a scale of change we cannot adapt to, reducing global carbon dioxide emissions to net zero within the next 30–50 years is nothing short of essential.

Dr Luke Harrington is a Research Fellow in Climate Extremes in the Environmental Change Institute at the University of Oxford in the United Kingdom and a Visiting Researcher in the New Zealand Climate Change Research Institute at Te Herenga Waka—Victoria University of Wellington; Dave Frame is Professor of Climate Change and Director of the New Zealand Climate Change Research Institute at Te Herenga Waka—Victoria University of Wellington.

Read the original article on Newsroom.