Can you guess how crazy last year’s weather was? Try this game.
The pollsters here at The Washington Post recently asked 1,404 random Americans: “Do you think human activity is or is not causing changes to the world’s climate, including an increase in average temperature?” Would you have said yes? If so, three-quarters of the people we polled agree with you, as does every scientist I’ve ever asked about it. As do I.
So sure, human-caused global warming is happening. But there are harder questions. How fast is it warming, exactly? Is the ocean warming faster than the rest of the planet? How has warming affected other parts of the environment, like sea ice?
Below, you’ll see a few charts showing monthly climate data over the past 40 years. Here’s the game: Draw your guess for each month of 2023. When you’re done drawing, you can compare your guess to the real data.
Last year was the warmest since people started to keep regular temperature records in the 1800s, and perhaps even the warmest of the last 125,000 years. The average global temperature topped the previous year’s by about 0.5 degrees Celsius (nearly 1 degree Fahrenheit), more than ten times the annual rate of warming between 1982 and 2022.
That kind of temperature spike could not have happened only because of global warming — the long-term but relatively gradual rise in temperature that happens as humans add carbon dioxide, methane and other heat-trapping gases to the atmosphere.
So why was 2023 so hot? The most likely culprit was this spring’s shift in weather patterns from a three-year La Niña to a new El Niño, in which unusually warm Pacific Ocean water near the equator drives extra heat into the atmosphere. El Niño is expected to continue into next year, so 2024 could be a hot one too.
El Niño was also likely to blame for last year’s off-the-charts sea surface temperature. In each month from April onward, 2023 set a new sea surface temperature record.
Dialing up the heat on the ocean surface is like tossing handfuls of quarters from an airplane — damage is inevitable, but the specifics are hard to predict. A warmer sea surface generates more water vapor over the ocean, which can fuel storms. In October, before Hurricane Otis slammed into Acapulco as a Category 5, the storm passed through 88-degree surface waters and intensified faster than any tropical cyclone ever observed in the eastern Pacific.
Warmer seas also alter the migration patterns of fish, posing challenges to the seafood industry upon which billions of people rely for animal protein. And while migratory species can adapt to higher temperatures, “some vegetation, like coral reefs, cannot move,” said NOAA oceanographer Boyin Huang. “The impact is, they will die.”
Did I trick you? This year did not, in fact, break the record of least Arctic sea ice. Even as global warming has triggered a long-term trend of shrinking sea ice, seasonal randomness still nudges the numbers up and down from year to year.
Sea ice is whiter than water, so an icy Arctic cools the atmosphere by reflecting more sunlight back to space than open ocean does. As ice disappears, its cooling effect wanes. That causes more global warming, which in turn causes more ice loss, and on and on. The feedback loop helps explain why the Arctic is warming faster than the rest of the planet, a phenomenon called “Arctic amplification.”
Sea ice floats on water, so when it melts, it does not raise the level of the ocean. But Arctic amplification is hastening the retreat of the nearby Greenland ice sheet, which is based on land and so does contribute to sea level rise as it melts by the ton.
Sea ice loss has other negative consequences, not least for the creatures like polar bears and seals — and human beings — who depend on it. But where some see environmental catastrophe, others see economic opportunity. At the current rate of retreat, Arctic summers will be free of ice by mid- to late-century, exposing new shipping lanes and, perhaps, a rush for freshly accessible natural resources, including oil and gas.
Could the Arctic ever be completely ice-free? “I probably don’t even want to think about that. That could be centuries from now or longer than that,” said Mark Serreze, director of the National Snow and Ice Data Center. “It depends on what humans do. Are we going to go on a ‘burn, baby, burn’ scenario of greenhouse gas emissions? Or take a more modest emissions scenario? In many ways, the future is up to us.”
Check my work
The datasets used in this column are from meteorologist Ryan Maue via the Japan Meteorological Agency’s JRA-55 dataset; Climate Reanalyzer via the NOAA’s OISST version 2.1; and the National Snow and Ice Data Center.
The code I wrote to analyze the data and make the charts for this article is available in computational notebooks: global mean surface air temperature, global mean sea surface temperature and Arctic sea ice extent.
You can use the code and data to produce your own analyses and charts — and to make sure mine are accurate. If you do, email at harry.stevens@washpost.com, and I might share your work in my next column.