Warming signs

First published in The Listener, 10th April, 2014

Whenever there’s a major storm, heat wave or drought these days, people speculate over whether it’s because of global warming and climate change. The latest Intergovernmental Panel on Climate Change (IPCC) report, issued on March 31, suggests the frequency of these extreme events is on the increase.“Climate Change 2014: Impacts, Adaptation, and Vulnerability” reveals that the effects of climate change on New Zealand are likely to be more floods, storms, landslides and droughts – alongside the well-established impacts of higher temperatures and rising sea levels.

We already seem to be experiencing some of these extremes – the start of 2013 saw a summer drought affect much of the North Island, with an average of almost 80 days without rain. This unusually dry summer was followed by the warmest winter on record.

In parts of Australia, a record-breaking heat wave saw summer temperatures exceed 48°C. But how can we know if the likelihood of extreme events like these is changing as a result of human-caused climate change?

That’s what Weather@Home ANZ, a crowd-sourced climate modelling experiment just launched by Niwa and its Australian and British partners, hopes to find out. This project is already using thousands of crowd-sourced personal computers to provide the massive computing power required to run thousands of weather simulations.

The present experiment is simulating weather conditions for 2013, says Niwa climate scientist and project leader Suzanne Rosier. Although 2013 has been and gone, what this project is doing is modelling what “2013 might have been like if we hadn’t emitted greenhouse gases”.

By comparing our actual anthropogenic 2013 with a “natural” 2013, scientists will be able to find out if the risk of heat waves or droughts, like those we experienced last year, has increased, decreased or been unaffected by human influence on climate.

Simulations will also be performed for other years, allowing scientists to assess the possible role of climate change in such events as the record rainfall in Golden Bay in 2011 and the Black Saturday bush fires in Australia in 2009.

One of the things Weather@Home ANZ can do that other climate modelling programs can’t is put some hard numbers on how the risks of extreme events might be changing with climate change. “Because our models are sufficiently detailed and run enough times, we have the chance of capturing very rare weather events that other modelling programs would miss,” Rosier says.

Weather@Home ANZ is the local version of climateprediction.net, a project started in Oxford in 2003 and already running experiments focused on Europe, southern Africa and the western US. If you would like your PC to contribute to the Australia and New Zealand part of the project, got to climateprediction.net to get started.

Once you’ve joined, you can sit back and let your computer do the work, or you can follow the progress as the simulation unfolds on your computer. “The more people who participate, the more science we can do,” says Rosier.

The frequency and severity of future extreme weather events will depend to some extent on how much greenhouse gas we add to – or remove from – the atmosphere over the coming decades.

The latest IPCC report makes it clear that if we want to avoid climate-related population displacement, economic collapse, starvation, disease and war, we need to scale up our efforts to move towards a low-carbon world, and we need to do it now.

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About Rebecca Priestley

I have a PhD in the history & philosophy of science and I write about science and science history. I live in New Zealand.
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