Warm winters may sound good, but they can cause problems later

Not surprisingly, this has given spring blossoms and leaves a jump start for much of the country. From the Central Plains to the Middle Atlantic, the first leaves of spring are showing up two to three weeks ahead of schedule.

This also means blooms are showing up earlier, and with them, pollen. The same carbon dioxide that is driving the warming climate is also a key component of plant photosynthesis, the process in which plants use carbon dioxide along with sunlight, water and chlorophyll to make food.

As a result, the growing season over the last half century has increased an average of two weeks across the United States.

This means that allergy season is starting earlier, and its intensity is also getting worse as the concentration of pollen in the air has also risen. In addition, evidence from both oak and ragweed pollens indicate that the higher carbon dioxide concentration leads to stronger allergens within the pollen, compounding the problem.

A 2021 study examined pollen counts for 60 sites across North America since 1990, and the majority of locations saw their pollen seasons trending earlier in the year, along with a higher total amount of airborne pollen during the course of the season.

Beyond these health effects, the warmer winter also presents problems for agriculture, especially fruit trees. Warm winters disrupt the natural dormancy of trees during the winter, as the cold weather gives them the break they need before blossoming in the spring and producing fruit toward the summer.

The disruption causes the trees to flower prematurely, well before normal. If there is a brief freeze, even one that is close to the normal time of year, there can be tremendous damage to a fruit crop.

In both South Carolina and Georgia, the 2022-23 winter was the sixth warmest on record. This allowed a brief mid-March freeze to decimate the 2023 peach crop. In South Carolina, production was down 66 percent compared to 2022. In Georgia, it was down 78 percent.

So far this month, most areas east of the Rockies are having one of their 20 warmest starts to March. From the Midwest to the Northeast, it has been among the five warmest. But very cold air has been hovering in Canada, and most of the data suggest one or two more surges of cold air will reach as far south as Alabama, Georgia and Mississippi before the last week of the month.

Warmer winters may sound good, but we may have to pay the price for them during spring and summer in the decades to come.

Sean Sublette is the chief meteorologist for the Richmond Times-Dispatch in Virginia.