1. Global Warming: EL NIÑO & LA NIÑA
Dr. Manish Semwal
Niño“Christ Child” “The Boy” “The Little One” Cf: La Niña “The Girl”

2. NINO4 region NINO3 region :2009/10 El Nino
Anomalous SST (Jan-Mar 2010)
Base period: , Data source: NCEP, EMC

4. The Southern Oscillation Index
Darwin
Tahiti
Mean pressure is lower at Darwin than Tahiti
The term “Southern Oscillation” was also coined by Gilbert Walker
The SOI measures the strength of the Pacific Walker circulation

5. The phenomenon is called SOUTHERN OSCILLATION…
Thus, “EL NIÑO” is a condition in the central and eastern equatorial Pacific Ocean where unusual warming is occurring. (Note that the formation/development of El Niño is very far from the country.. )
Then, why is it affecting the philippines..

6. What is El Niño Warming of sea surface waters in the central
and eastern tropical Pacific Ocean.
El Niño: the ocean part: Warm phase of ENSO:
El Niño - Southern Oscillation
Southern Oscillation: the atmospheric part;
a global wave pattern
La Niña: is the cold phase of ENSO:
Cool sea temperatures in tropical Pacific
EN events occur about every 3-7 years

8. Initial results of diagnostic and statistical studies on general influences of ENSO on Philippine climate
During El Niño Episode
During La Niña Episode
·              
Weak monsoon activity
Moderate to strong monsoon activity
- delayed onset of the rainy season
- early termination of the rainy season
- increased cloudiness and widespread rains
- occurrence of isolated heavy rainfall in short duration
- near normal to early onset of the rainy season
Weak tropical cyclones activity
Moderate to Strong tropical cyclones activity
- tropical cyclones follow tracks further off the Philippines
- near normal cyclone tracks (near and/or crossing the country)
- less number of tropical cyclones entering the Philippine Area of Responsibility (PAR)
- near-to-above normal cyclone occurrences in the PAR
- rain-effective cyclones
Below normal rainfall
Above normal rainfall
Above normal air temperatures
Near-to-below normal air temperatures
Drier weather conditions
Wetter weather conditions

9. Top: normal Bottom: El Niño condition
Eastern boundary
Shallow thermocline
Cold, nutrient-rich water
Mixing depth shallower than critical depth
High NPP
Deep thermocline
Warm, nutrient-poor water
Mixing depth not as much shallower than critical depth
Lower NPP
Normal
El Nino
Open University, 1998

10. El Niño
La Niña
Equatorial upwelling
Much weaker
Much stronger
California Current upwelling
Weaker
Stronger
California Current temperature
Warmer
Cooler
California Current thermocline
Deeper
Shallower
West Pacific warm pool
Spreads east across equator
Compressed in western Pacific

11. Central America /Mexico
Region
Period
Impact
Indonesia
Life of event
Drier
Northeast Brazil
March-May
Central America /Mexico
May-October
West Coast
South America
Wetter
Central South America
June-December
Southeast Africa
December-February

12. Understand EL Nino & La Nina

13. Rainfall in thunderstorms and organized convection gives rise to latent heat release in the atmosphere, which determines atmospheric heating patterns.
The heating patterns set up low level convergence and upper level divergence that drives Rossby waves in the atmosphere.
These propagate to other regions (teleconnections) and determine the atmospheric circulation locally.

14. Different flavors of El Niño
Events come in different “flavors”
El Niño refers to a warming of the tropical Pacific but this does
not take account of surrounding areas and character of event.
Tropical winds and rainfall
respond to total SSTs and
so depend on time of year
and details. Surface wind
convergence is in vicinity
of warmest water, not
anomaly.
Small changes in SST can
change region of warmest
water by 1000 km or more!

15. El Niño and Global warming
1998 warmest year on record, 2001 second warmest
El Niño contributes to global warming
There is a pattern of more and bigger El Niños in past 20 years
El Niño years
La Niña years
Is global warming contributing to changes in El Niño?
Likely, yes, to some extent.
Which part is natural variability?

16. Global warming  Heating  Temperature  & Evaporation 
water holding capacity  
atmospheric moisture 
 
greenhouse effect  & rain intensity 
Droughts & Flood

17. How will El Niño events change with global warming?
El Niño involves a build up and depletion of heat as well as major redistribution of heat in the ocean and the atmosphere during the course of events.
Because GHGs trap heat, they interfere.
Possibly expand the Pacific Warm Pool.
Enhance rate of recharge of heat losses.
More warming at surface: enhanced thermocline  enhanced swings
More frequent El Niños?
Some models more El Niño-like with increased GHGs.
But models do not simulate El Niño well
Nor do they agree
The hydrological cycle is expected to speed up with increased GHGs. Increased evaporation enhances the moisture content of the atmosphere which makes more moisture available for rainfall. ENSO-related droughts are apt to be more severe and last longer, while floods are likely to be enhanced.

18. Main effects of climate oscillations on pelagic species
Changes in temperature/nutrients affect primary production and food web
Higher trophic levels affected by changes in food availability
Changes in temperature affect rates of growth/survival
Fish/nekton with limited temperature range can move to water of preferred temperature, leading to range shifts

20. Central Case: Rising Temperatures and Seas May Take the Maldives Under
80% of this island nation’s land is <1 m above water.
Globally warming temperatures are causing sea levels to rise worldwide, endangering many island nations.
The 2004 tsunami (tidal wave) hit the Maldives hard.

21. Some Reading

22. Bibliography