ENSO

• La Nina are typically colder years as the surface temp of the sea is relatively cooler
• El Nino typically warmer as the surface temperature tends to increase
• uncertain over the impacts of climate change on Enso because it can take up to a decade to switch between cycles and there is large variability between phases
• the warmer equatorial current moves from E to W and the colder equatorial undercurrent moves from West to East
• 2016 - El Nino year there was heavy coral bleaching
• during La Nina in 05-06 it brought relief to Australian farmers after years of drought
• El Nino can lead to forest fire and drought in Australia. This will reduce air quality and causes respiratory diseases such as bronchial disease
• Indonesia saw increased toxic air pollution following the most recent El Nino phase in 2023
• El Nino - opposite phase - trade winds weaken - warmer water drifts back to the east - increases convectional rainfall in Peru - increase risk of flooding and mass movement in South America. Australia has increased risk of drought and wildfire
• La Nina - amplified phase - trade winds strengthen - more rainfall in Australia - warmer water is pushed in greater quantities - Peru sees risk of drought but lots of fish stock
• climate change can increase the intensity of ENSO as there is more energy in the system
• increase greenhouse gases - upper layers of ocean become much warmer than deep ocean - increased precipitation - increased stratification of upper ocean - more sensitive to wind forcing
• climate change can increase the frequency of cycles
• every 1C increase the air can hold 7% more moisture
• 2023 was the hottest year on record and was boosted by El Nino conditions
• during El Nino events warmer water pushes the Pacific jet stream's strong air currents further to the south and the east - brings wetter conditions to USA
• El Nino means there more tropical storms in the tropical pacific
• The droughts and flooding caused by the extreme 2015-16 El Niño event affected the food security of more than 60 million people
• Global temperatures typically increase during an El Niño episode, and fall during La Niña.
• El Niño means warmer water spreads further, and stays closer to the surface. This releases more heat into the atmosphere, creating wetter and warmer air.

  But the regional effects are complicated, and some places may be both warmer and cooler than expected at different points in the year.
• El Nino - more precipitation to California and Peru, higher level of surface run off, increased possibility of flood events as river flow exceed capacity
• when talking about the hydrological cycle talk about flows, stores, inputs i.e., the different processes