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TCB quick hit: Is El Niño making the U.S. heat wave worse?
it depends on where you live, but maybe not
Most climate change is what is known as “forced,” meaning it is a response to an imposed energy imbalance on the planet. For example, if the Sun gets a bit brighter, that will increase energy in for the planet, resulting in warming.
El Niño is an example of “unforced” climate change, meaning it is not a response to a forcing, like variations in the Sun or the addition of greenhouse gases to the atmosphere. Instead, El Niño is part of a larger climatic cycle known as the El Niño-Southern Oscillation (ENSO), which oscillates between El Niño, neutral, and La Niña phases. It arises due to coupled ocean-atmosphere interactions:
El Niño-La Nina cycles have big impacts on the planet’s climate. You can see this in this plot of global average temperatures, where El Niño periods are colored red and La Nina periods are blue. During El Niño, the global warms up a lot, while during it’s opposite, La Nina, the globe cools off.
We’re in an El Niño right now and we’re also seeing scorching temperatures in the U.S. Are these connected?
People often talk about El Niño as if it were a short-term version of the long-term global warming that humans are causing. But the patterns of warming are different for these two climate variations. Under long-term global warming, just about everywhere warms up.
But during an El Niño event, that’s not true. The plot below shows that, during the northern hemisphere summer, much of the U.S. cools off during an El Niño.
The exception is the Western U.S., which is heated by the warm Pacific. Overall, though, the impact of El Niño is relatively minor over the U.S., modifying summertime temperatures on average by less half a degree Celsius.
So for those living in the U.S., don’t blame El Nino for the scorching heat you’re experiencing. Instead, blame the oil companies.
If you want a deeper dive on the global impacts of ENSO, and to look at other regions, take a look at my colleague R. Saravanan’s deep dive into the climate impacts of El Niño. His post includes interactive plots and google code so you can work with the data yourself.
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