Tropical convection, oscillations and cyclone climatology

5 problems

• What sets the number of tropical cyclones Earth has each year?

  Open

  Earth has about 80 to 90 hurricanes and typhoons a year, and this number has stayed roughly steady for decades. No theory explains why it is this number and not 10 or 1000, or how it will change with warming.

• How will El Nino-Southern Oscillation change as the climate warms?

  Contested

  El Nino and La Nina are swings in Pacific temperatures that shift weather worldwide. Climate models disagree on whether these swings will grow or shrink with warming, and the observed Pacific pattern has evolved differently from most models.

• What physical mechanism drives the Madden-Julian oscillation?

  Contested

  The Madden-Julian oscillation is a giant cluster of storms that moves slowly eastward around the tropics every 30 to 90 days, affecting weather worldwide. There is still no agreed theory of why it exists and moves at its speed.

• Why was the quasi-biennial oscillation disrupted in 2016 and 2020?

  Partially resolved

  High above the equator, stratospheric winds flip between east and west roughly every 28 months, a pattern so regular it was used for forecasting. This rhythm broke unexpectedly in 2016 and again in 2020, and the reason and future frequency of such breaks are unclear.

• Does convective self-aggregation operate in Earth's real atmosphere?

  Open

  In computer models with uniform warm oceans, thunderstorms spontaneously gather into one cluster surrounded by dry air, which changes how much heat Earth sheds to space. Whether this clumping happens in reality and matters for climate is unclear.