Summer-like heat is scorching the Southern Hemisphere – in winter

These are some of the most extreme figures in a month of extremes for the land down under, which has been reeling under a prolonged winter heatwave that threatens to break the country's record for average winter temperatures - a record set just last year. In 2023, Australia's average winter temperature was 1.53°C above the long-term average of 14.96°C from 1961 to 1990, and the highest since records began in 1910.

Globally, average nighttime temperatures are rising even faster than daytime temperatures, a phenomenon scientists call "asymmetric warming." That nighttime warming is a big factor in pushing the planet's average temperature up, contributing to its 14-month record heat streak.SN: 19.8.24).

Australia is not the only region in the southern hemisphere that is drowning. Brazil's vast Pantanal wetlands, bordering Bolivia and Paraguay, are on fire — literally — thanks to a spate or two of severe droughts and unseasonably warm temperatures. Raging megafires have burned over 700,000 hectares of the Pantanal this year.

Winters in the past have brought dry and mild weather to the Pantanal. But that has changed. And in fact, the Southern Hemisphere has become increasingly drier over the past two decades, researchers reported in Science in 2023. The natural climate phenomenon El Niño is a major contributor; Climate change may also intensify the rains and droughts associated with El Niño, particularly in the Southern Hemisphere (SN: 7/19/23)

These warmer winters can have negative impacts on food security, water supplies and insect populations. Reader Judy Dobles asked about the effect of heat on the ability to grow food. Warmer winters can change when plants germinate and when they set fruit. For example, in the United States, where average winter temperatures are also rising, this change prompted the US Department of Agriculture in 2023 to release a new plant hardiness zone map used to recommend that which plants will thrive in certain regions and when is best to plant them.

"How do growers (agriculture and horticulture) plan for future production in a changing climate?" asks reader Brian Hesketh. Many efforts are being made to breed heat-tolerant plants, such as an apple bred to thrive in temperatures as low as 40°C (104°F) (SN: 22.8.24).

Warmer winters can also mean less snow to feed rivers and recharge groundwater. And the cool weather helps keep insect-borne diseases such as dengue in check (SN: 26.8.24).

As always, please continue to send in your questions about Earth's extreme climate data. thank you!