Extreme wildfires in Australia have been raging for months, with bushfires breaking out as early as July. As a result, smoke from the wildfires is circulating around the globe, heavily affecting areas like New Zealand but also moving across the Southern Pacific and the Southern Ocean to affect South America and passing over the southern tip of Africa before looping back to Australia once again. NASA video of aerosol circulation suggests that this circumnavigation takes about two weeks, with New Zealand also being affected by smoke that does not circulate globally.
This year's fire season in Australia has been particularly bad due to Australia being in a drought. Temperatures have also been unusually high, with December having a record heat wave. Finally, strong winds have aided the spread of these fires. In addition to fires caused naturally by lightning strikes, there were some cases of human-set fires.
Video of aerosol circulation: https://youtu.be/uKfPbgPk1-0 (skip to about 1:50 to see most extreme smoke from Australia fires)
Sources:
- https://climate.nasa.gov/climate_resources/202/global-transport-of-australian-bushfire-smoke/
- https://www.washingtonpost.com/weather/2020/01/02/ash-covered-glaciers-toxic-amber-skies-australia-bushfire-smoke-spills-over-new-zealand/
- https://www.sbs.com.au/news/bushfire-smoke-will-circle-around-the-globe-and-return-to-australia-nasa-says
- https://www.cnn.com/2020/01/01/australia/australia-fires-explainer-intl-hnk-scli/index.html