Weather-wise, 2019 was a crazy way to end a decade. Fires spread through much of southeast Australia, fuelled by dry vegetation from the ongoing drought and fanned by hot, windy fire weather.
On the other side of the Indian Ocean, torrential rainfall and flooding devastated parts of eastern Africa. Communities there now face a locust plague and food shortages.
These intense events can partly be blamed on the extreme positive Indian Ocean Dipole, a climate phenomenon that unfolded in the second half of 2019.
The Indian Ocean Dipole refers to the difference in sea surface temperature on either side of the Indian Ocean, which alters rainfall patterns in Australia and other nations in the region. The dipole is a lesser-known relative of the Pacific Ocean’s El Niño.
Climate drivers, such as the Indian Ocean Dipole, are an entirely natural phenomenon, but climate change is modifying the behaviour of these climate modes.
In research published today in Nature, we reconstructed Indian Ocean Dipole variability over the last millennium. We found “extreme positive” Indian Ocean Dipole events like last year’s are historically very rare, but becoming more common due to human-caused climate change. This is big news for a planet already struggling to contain global warming.
So what does this new side-effect of climate change mean for the future?