By Kirsty MacLeod
The climate may be changing for the worse, but the models we use to predict its change are getting better, say experts speaking ahead of the release of the new IPCC report, due out next month.
Scientists often refer to climate models, systems of equations that take into account environmental factors like ocean currents and chemistry, and human actions like deforestation and greenhouse gas emission. Run on large computers, the output of these models can be used to predict how these factors will affect certain parameters in the future, including temperature and sea level. But how good are these models at predicting climate change? And how are they improving?
“Climate is one of the biggest, most complex systems that we study,” says Professor Peter Challenor, a mathematician and statistician from the University of Exeter. He stresses the need to understand that statistical models used to predict climate change contain an inherent degree of uncertainty due to this complexity - as do all statistical models. Understanding this uncertainty is important when trying to interpret models and making decisions based on these interpretations.
Dr Vicky Pope is the Head of Climate Change Predictions at the Met Office Hadley Centre for Climate Change. In the same way that now we can predict the weather days in advance as accurately as we were once able to forecast today’s weather, she says the way we model climate change is improving with time. Newer models look at biological processes at a smaller scale, meaning that the models are increasing in resolution. This, she says, will in future allow better predictions of the more localised weather impacts of climate change, such as droughts and floods.
The predictions of the new IPCC report will also be more accurate than before. This time, says Pope, the panel have been able to include data on permafrost, which has previously not been available for inclusion in climate models. Permafrost is permanently frozen land, and covers around a fifth of the world’s surface. As it melts, it releases stored soil carbon into the atmosphere.
“An understanding of how the permafrost will behave has been lacking,” says Pope. “We still don’t know how much gas it will release, or the gas composition. But we do now know more about how it is melting.” These data have been included in the latest IPCC climate models. Pope compares this information to “half of a jigsaw piece” – a powerful analogy for the unfinished picture of the effects of climate change on our future.