What are the impacts of an ‘unseasonably’ warm Autumn?
As we all basked in September and early October’s ‘unseasonably’ warm weather, a term that no longer holds any meaning, I began to wonder what are the impacts of a warm Autumn.
We are all mostly familiar with the problems of an early spring; trees and plants starting to grow and blossoming early before a late cold snap can kill all the blossom and new growth leading to a harvest free year, but are there equivalents in Autumn, and how should we be planning to respond to them?
While the impacts from a warm autumn are not as linear or necessarily dramatic, they can still be highly significant.
A warm autumn followed by a sharp cold snap can impact tree and plant health. Trees prepare gradually for hibernation; taking in the nutrients from their shrivelling leaves and expelling toxins. If this is delayed due to a long summer, and then there is a hard frost the leaves may fall before all the nutrients have been absorbed impacting their ability to grow the following spring.
Aside from this linear impact the effects are more systemic – exacerbating the impacts of extreme weather events. We are now seeing ‘unusually’ strong autumn storms. This September was the hottest on record globally and across Europe, as many countries experienced an increased number of Autumn storms, with Greece being hit by two massive storms, Storm Daniel and Storm Elias, within three weeks of each other. While these events cannot be directly attributed to climate change, the extended summer maintains high sea temperatures and strengthens these storms. Storm Daniel, for example, was classified as a ‘Mediterranean tropical-like cyclone’, events that are becoming more frequent due to climate change. And when these storms fall on drought hardened land, or burnt forest, the impact of the flooding is likely to be exacerbated.
A less dramatic, but potentially more deadly, impact is the worsened air pollution that is generally associated with heatwaves. Fires and dust will worsen air quality, but the lack of wind causes air pollution to build up.
The extended summer also obviously exacerbates drought conditions, with water tables falling across Europe and exacerbating glacier loss. Shorter periods of cold, and particularly freezing temperatures, can also make it easier for pests to survive the winter. Both these issues will impact food production. Summer extending into Autumn will have an impact on plant and ecosystem health, with knock-on effects on food production, flood resistance and urban livability.
In the run-up to COP28, we’re reviewing all the local government climate strategies, which aim to both mitigate carbon emissions as well as increase resilience. If this Autumn is anything to go by these strategies will need to include nature based solutions for cooling, food production, and flood protection. We will try and find the best examples of these approaches and share them widely.