“Dangerously unpredictable” weather will worsen unless global action taken, New Zealand-led research shows

Extreme and unpredictable weather seen around the world in 2019 will get worse as ice sheets in Greenland and Antarctica continue to melt, according to an international research collaboration published in Nature today—and researchers say global government policy needs urgent review to prevent dangerous consequences.

The collaboration, led by Associate Professor Nick Golledge from Victoria University of Wellington’s Antarctic Research Centre and involving scientists at GNS Science and from Canada, the UK, Germany and the US, used climate models to simulate what might happen when water from melting ice sheets enters Earth’s oceans.

Last week it was colder in Chicago than at the North Pole, while wildfires raged in Australia as temperatures in Adelaide hit 47 degrees.

Despite the cold snap in the US, overall temperatures are warming and under current policy settings the Earth’s temperature will increase by 3 to 4 degrees by 2100, Associate Professor Golledge says.

“With this level of warming, a significant amount of melt water from the Greenland and Antarctic Ice Sheets will enter Earth’s oceans,” he says.

“According to our models, this melt water will cause significant disruption to ocean currents and change climate around the world.”

The model predictions of Associate Professor Golledge and his colleagues show that in some areas of the world these ocean changes will lead to more extreme weather events and greater year-to-year variation in temperatures.

The study also found that in the North Atlantic Ocean the influx of meltwater will lead to significant weakening of deep Atlantic circulation, which affects coastal ocean currents such as the Gulf Stream. This will lead to warmer air temperatures in Central America, Eastern Canada, and the high Arctic, but reduced warming over north-western Europe on the other side of the Atlantic.

“We will start to see more of this recent extreme weather, both hot and cold—with incredibly disruptive effects for agriculture, infrastructure, and human life itself. This is not accounted for in current global climate policies,” Associate Professor Golledge says.

“New Zealand is making a great effort, with the Zero Carbon Bill and attempts to find a cross-party solution—but globally policy is lagging far behind the science.”

This study is the first to use highly detailed models of both the Antarctic and Greenland ice sheets combined with observations of recent ice sheet changes from satellites, which creates more reliable and accurate predictions than achieved previously, Associate Professor Golledge says.

“Using the satellite data gives us confidence that the models are performing reliably, and the amounts of ice sheet melt we predict for the future are justified.”

The study also calculated the effect melting ice sheets will have on sea level.

“Sea level rise from ice sheet melt is already happening and has accelerated in recent years. Our new experiments show that this will continue to some extent even if Earth’s climate is stabilised, but they also show that if we drastically reduce emissions we can limit future impacts,” says Dr Liz Keller from GNS, co-author of the paper.

Developments in research methods have led this paper and another published in the same issue of Nature to conclude sea level rise by 2100 may be significantly less than was predicted in a high-profile 2016 study, Associate Professor Golledge says.

Dr Tamsin Edwards, a researcher from King’s College London and lead author of the second study, says, “The close agreement between the two new studies is really encouraging—it highlights how much progress is being made in this area”.