Warmer winters could cut the national peak electricity demand by 1 to 2 per cent for each degree of warming, and make hydro-electricity more secure, the United Nations Intergovernmental Panel on Climate Change's fifth report says in a chapter covering New Zealand..
Victoria University associate professor James Renwick said climate change could benefit the power supply, and power companies were aware of the implications.
Hydro lakes, mainly in the South Island, supply more than 50 per cent of New Zealand's electricity, but are vulnerable to dry periods. In a warming climate, more rain would fall instead of snow in the mountains and flow into the lakes.
An increase of 5 per cent to 10 per cent in water flow could reduce the risk of drought affecting electricity supply and prices, the IPCC says.
However, the effect of climate change could cut both ways. With less mountain snow in winter, there would be less meltwater flowing into the lakes in spring and summer.
This could match supply of water, and hydroelectricity, more effectively with demand.
"It should mean more reliable supply of hydro," Dr Renwick said. "The supply and demand will line up a bit better."
In present conditions, the lakes were lowest when demand was highest - in winter - as snow fell in the mountains and was "locked in" until it melted during spring, he said.
While power demand in winter might fall as a result of climate change, demand in summer could increase, mainly for power to run irrigation pumps in the drier, hotter east.
"The demand on electricity in Canterbury for driving irrigation pumps is getting to be a big fraction of total use at times [already]," Dr Renwick said.
Whether this would lead to lower electricity prices was debatable. "It would be very nice if increased reliability resulted in a decrease in the price of electricity.
"[But] I haven't noticed electricity prices going down for the last 20 years."
Despite stabilising hydro-electricity production, climate change could cause more problems than it solved, as droughts and floods became more common and agriculture came under stress. "There are more minuses than pluses," Dr Renwick said. "There is going to have to be quite a lot of adaptation."
Niwa scientists who worked on the report refused to comment until the formal publication on March 31.
WHAT IS THE IPCC?
The United Nations Intergovernmental Panel on Climate Change was set up in 1988 to monitor the effects of climate change and advise governments how to deal with them.
It has published four assessment reports, taking a global look at scientific matters in climate change and making predictions based on observation.
Its fifth report will be published on March 31, but leaked copies of chapters have been circulating for several weeks.
One chapter covers the effect of climate change on New Zealand and Australia and gives predictions for possible changes during the next century.
Predictions are graded from "low confidence" to "very high confidence".
More than 300 scientists from around the world are lead authors of the report.
They assessed more than 9000 peer-reviewed papers to compile it.
- The Dominion Post
Is this the best summer ever?Related story: Wellington sizzles in January heat