This opinion article was written by Penny Beames.
Has there ever been a wilder year to pay attention to the weather? We’ve just lived through the planet’s hottest three-month stretch on record. Droughts helped propel the deadly Lahaina fire and the Canadian wildfires that left millions outside Canada breathing smoke. Intense storms and flooding affected eight countries in the first twelve days of September.
The US has already experienced a record number of billion-dollar disasters, and there are still three months left in 2023.
A changing climate is making these extremes more likely. But according to Michael Wysession, Professor of Earth, Environmental, and Planetary Sciences at Washington University in St. Louis, this alone doesn’t explain this year’s intensity.
Rather, there are three other phenomena at play that have upped the ante, so to speak.
The El Niño Southern Oscillation essentially borrows heat from warm Pacific waters off the coast of Peru and spreads it around the globe. The weak El Niño in 2019/2020 contributed to 2020 being one of the hottest on record. The current El Niño is likely to be a strong one, and we’re already feeling its heat and storm activity.
To us, the sun is constant. But the earth is more sensitive to its fluxes. The sun’s energy output peaks and declines on an 11-year cycle, and we’re moving toward this cycle’s peak. Though the Earth only warms by about 0.05ºC during a solar maximum, that fraction is still meaningful, especially when combined with the warming from El Niño.
The Hunga Tonga-Hunga Ha’apai eruption
Normally, the stratosphere doesn’t hold much water vapor, but it certainly holds more now. The January 2022 underwater explosion sent a staggering 100 Tg (100 million tons) of this powerful greenhouse gas into the strats and we’re dealing with the effects.
Land eruptions typically reduce the Earth’s temperature because the sulfate aerosols they release tend to block radiative sunlight. But the Hunga released comparatively low amounts of sulfur dioxide. As such, we’re left with the warming effects of the water.
Honorable mention: shipping fuel changes
Speaking of sulfur, in 2020, new international regulations came into effect to reduce air pollution associated with marine fuels. But it’s possible that, by reducing the sulfur content in these fuels, we’re also reducing that sulfur’s capacity to reflect sunlight out of the Earth’s atmosphere.
What does all this mean?
Higher land and sea surface temperatures make for more heat waves, forest fires, flash floods, and other extremes like the ones we’ve witnessed this year. That’s because, generally, global warming makes dry areas drier and wet areas wetter. Droughts become more intense and dry vegetation fuels more fires. Rain, when it does come, falls in bursts.
The three phenomena outlined above will persist into the next year or so at least. So if you think 2023 has been a wild year for weather, buckle up for 2024. We’ll do our best to keep you informed.