I live in the Arizona White Mountains where it is usually in the 60s (Fahrenheit) by mid October and it’s still in the mid 80s/high 70s. I know seasons are caused by the tilt of Earth on its axis and as it travels around the sun it gets more/less intense sun. But if we are still tilted and at the same place around the sun as we are every year, what causes an unusually warm Autumn season?
In: Planetary Science
The main determinant of winter weather in the US west is the La Nina/El Nino cycle. That cycle is determined by how hot water in the Eastern Pacific Ocean is, which also determines wind patterns over the Western US.
La Nina causes cold air to blow from the Arctic Circle to the US Southwest, which cools the region.
El Nino causes air from the Eastern Pacific to blow to the US Southwest. This air is warm, but is still relatively cool.
Right now we’re in a “neutral” year where there is no La Nina or El Nino effect. During neutral years, the wind blows air from near the equator to the US Southwest. That air is *hot* and results in the weather than you’re seeing now.
The answer in this case is that decades of greenhouse gas production have led to more heat being retained by the atmosphere, causing the weather to be more intense and generally more hot.
In short, global warming is real.
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