If you’re confused by the weather right now, you’re in the company of millions of other Americans. The weather used to be fairly predictable. We live our lives by it.
From the clothes we wear in the morning to what produce we grow out of the ground, it’s all affected by what we know about the weather. When those patterns change quickly, it affects so many parts of society - transport, communications, and infrastructure, as well as being a matter of life and death. Extreme heat and cold can kill, while flash flooding can destroy communities and critical infrastructure.
But if you’re starting to feel like so-called freak weather occurrences are becoming more frequent, you’re right. Flooding and drought are occurring in places they didn’t use to. Hurricanes are stronger and more frequent. Ten of the hottest years on record have occurred since 1998.
Over the weekend, Southern California got hit by a freezing snow blizzard, bringing temperatures down to the 40s and causing flooding and power outages. At the same time, the East Coast and the South saw record-breaking winter temperatures in the upper 80s. Atlanta saw the mercury hit 81 degrees, the highest in February and the warmest ever during the winter. Washington D.C. broke its February heat record, while Nashville saw record-equalling temperatures. Orlando and Charlotte were a single degree short of February records.
Did the weather switch coasts? Not quite. But there is a lot of science involved in why that happened and it’s not exactly simple to understand. In short, it’s all a bit confusing.
So, who better to simplify it than Alecia M. Spooner, a former science professor and author of Environmental Science for Dummies.
Q: The weather seems so confusing right now. Why is it snowing in Southern California?
A: In simplest terms: It is snowing because warm, moisture-filled air from the Pacific Ocean near the equator is meeting freezing arctic air from the North Pacific just off the coast of California and Oregon (it has not hit Washington as hard). This moist air is not uncommon on the west coast during the winter (especially during an El Nino cycle), but historically, the temperatures along the U.S. west coast are not this cold at this time of year.
Q: Why is it so unseasonably warm on the East coast?
A: Scientists are saying that the East coast’s warm temperatures are a result of an El Nino cycle (yes, the same one sending warm moisture-filled air to California) along with something called the Arctic Oscillation. El Nino is when the Pacific Ocean near the equator warms up, and it affects climate and weather patterns all over the globe. The Arctic Oscillation is a pattern of shifting high and low air pressure over the arctic. Generally speaking, low air pressure draws in cold air and the Arctic Oscillation has been in a phase of low pressure, keeping cold air in the arctic. But it should be shifting to a negative phase pretty soon, with high pressure over the arctic, which will push that cold air across the U.S.
Q. Has this freak coastal weather switch ever happened before?
A: It’s important to understand that the east and west coasts of North America haven’t ‘switched weather.’ While global climate is all related, regional weather is dominated by regional effects, including bodies of water and mountain ranges. For example, on the west coast right now, El Nino is sending warm, moisture-filled air up from the equator, and cold air from the North Pacific is moving south due to variations in pressure cells in that region. This is separate from the low-pressure region over the arctic that is keeping cold air from moving down the east coast. But the El Nino warming at the Pacific equator does affect global wind patterns and, thus, the movement of heat around the globe, so the El Nino, as well as Atlantic Ocean circulation and Arctic Oscillation, are creating the weather on the east coast.
Q: Why has our weather been so seemingly unpredictable these past few years?
A: The weather has become more difficult to predict because humans have changed the global chemistry of the atmosphere by burning carbon-based fuels. The global climate is a complicated system of interactions between the oceans and the atmosphere (and living things, mountain ranges, and rocks – it’s quite complicated!). In the most general terms, much of the planet’s heat enters the Earth at the equator from direct sunlight, and it is moved around the planet, towards the cold poles, by ocean currents and wind currents.
A key factor in this system is the greenhouse effect – a layer of molecules that helps trap heat inside Earth’s atmosphere. Without greenhouse gases, the surface of the Earth would be very cold, like Mars. So, one of the important molecules in this greenhouse layer is carbon dioxide (others include methane and ozone). Around 100 years ago, humans started burning coal – which added carbon dioxide to the atmosphere. This continues today as we burn fossil fuels.
Essentially we have made the blanket of greenhouse gasses heavier and thicker so that even more of the sun’s heat is kept in the atmosphere than it used to be. But it doesn’t just stay in the atmosphere. Both the carbon and the heat move into the oceans as well – the carbon changes the seawater chemistry – which affects whether shell-building animals can build their shells. And the heat leads to warmer sea surface temperatures, which leads to more evaporation, which leads to more moisture in the atmosphere for storms, as well as more heat to drive storm movement.
Q: Does it have anything to do with climate change?
A: Yes, everything! Now, I don’t know if this week’s weather patterns have anything directly to do with climate change – that is a difficult thing to pin down with all the interacting variables. I do know that when you add more heat to any system – that system moves faster and with more chaos, in other words, with less predictability.
Until humans started burning fossil fuels, the global climate was fairly stable, predictable, and, frankly, comfortable. For the entirety of human evolution, we have existed in a moderate and seasonal climate in the mid-latitudes. Clearly, we humans got used to the idea that climate was a long-lasting and unchangeable thing. That time in Earth’s history is over.
The new normal will be one where we can’t look at the Farmers Almanac to know when to plant each year. When “freak” weather is just a thing that happens, in its own freaky way, all over the place. The only constant now is change.”