Climate Change Models Be Producing Inaccurate Results, Study of Ice Age Warns

When two scientists set about researching rainfall patterns across during the last ice age, they didn’t plan on the making the discovery they did: almost none of the climate models they tested were able to reproduce their results.

Together, Jessica Tierney of Woods Hole Oceanographic Institution and Pedro DiNezio of the University of Hawaii investigated preserved geological clues including charcoal from fires, evidence of more sand dune activity, desiccated lakes and seafloor sediments containing preserved shells of dead marine organisms in order to determine just how much it rained over the tropical and Pacific regions between 26,000 and 19,000 years ago.

The latter was especially telling given that higher or lower isotopes of oxygen found in the specimens were like diaries into the history of the ocean’s salinity, with high salinity meaning less rain and low salinity meaning more rain.

Conclusively, they came to their answer: conditions over the Indo-Pacific, a vast region of warm ocean waters and the main source of heat and moisture to Earth’s atmosphere, was dryer during the last ice age, with wetter conditions prevailing on either side of it.

They then compared these findings with 12 different mathematical climate models that simulate Earth’s climate using basic laws of physics, chemistry and fluid dynamics surrounding air-sea-land-ice interactions.

The idea, according to the scientists, was that the ice age provided a perfect way “to evaluate numerical models’ ability to simulate climate radically different from the present one,” they said in a press release.

However, only one model – that developed by the Hadley Centre for Climate Prediction and Research in England - reproduced their results.

According to the researchers, the likely reason for this is the models' limited ability to simulate the vertical air motions that lift humid air into the atmosphere, also known as convection.

However, Tierney said she hasn’t lost faith, yet.

“The good news is, the Hadley model combined with the geological evidence show a pathway to improve our ability to simulate and predict tropical rainfall in the future,” she said. “The more we study the mechanisms that governed tropical climate in the past, the better we can predict the climate changes that will affect the billions of people that live in the vast region of the world.”